®
Note
This manual applies to SN 6560XXX and higher.
HYDRA
2620A Data Acquisition Unit
2625A Data Logger
2635A Data Bucket
Service Manual
PN 202231
February 1997
© 1997 Fluke Corporation, All rights reserved. Printed in U.S.A.
All product names are trademarks of their respective companies.
LIMITED WARRANTY & LIMITATION OF LIABILITY
Each Fluke product is warranted to be free from defects in material and workmanship
under normal use and service. The warranty period is one year and begins on the date
of shipment. Parts, product repairs and services are warranted for 90 days. This
warranty extends only to the original buyer or end-user customer of a Fluke authorized
reseller, and does not apply to fuses, disposable batteries or to any product which, in
Fluke’s opinion, has been misused, altered, neglected or damaged by accident or
abnormal conditions of operation or handling. Fluke warrants that software will operate
substantially in accordance with its functional specifications for 90 days and that it has
been properly recorded on non-defective media. Fluke does not warrant that software
will be error free or operate without interruption.
Fluke authorized resellers shall extend this warranty on new and unused products to
end-user customers only but have no authority to extend a greater or different warranty
on behalf of Fluke. Warranty support is available if product is purchased through a Fluke
authorized sales outlet or Buyer has paid the applicable international price. Fluke
reserves the right to invoice Buyer for importation costs of repair/replacement parts
when product purchased in one country is submitted for repair in another country.
Fluke’s warranty obligation is limited, at Fluke’s option, to refund of the purchase price,
free of charge repair, or replacement of a defective product which is returned to a Fluke
authorized service center within the warranty period.
To obtain warranty service, contact your nearest Fluke authorized service center or
send the product, with a description of the difficulty, postage and insurance prepaid
(FOB Destination), to the nearest Fluke authorized service center. Fluke assumes no
risk for damage in transit. Following warranty repair, the product will be returned to
Buyer, transportation prepaid (FOB Destination). If Fluke determines that the failure
was caused by misuse, alteration, accident or abnormal condition of operation or
handling, Fluke will provide an estimate of repair costs and obtain authorization before
commencing the work. Following repair, the product will be returned to the Buyer
transportation prepaid and the Buyer will be billed for the repair and return transportation
charges (FOB Shipping Point).
THIS WARRANTY IS BUYER’S SOLE AND EXCLUSIVE REMEDY AND IS IN LIEU OF
ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
TO ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE. FLUKE SHALL NOT BE LIABLE FOR ANY SPECIAL,
INDIRECT, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSSES,
INCLUDING LOSS OF DATA, WHETHER ARISING FROM BREACH OF WARRANTY
OR BASED ON CONTRACT, TORT, RELIANCE OR ANY OTHER THEORY.
Since some countries or states do not allow limitation of the term of an implied warranty,
or exclusion or limitation of incidental or consequential damages, the limitations and
exclusions of this warranty may not apply to every buyer. If any provision of this
Warranty is held invalid or unenforceable by a court of competent jurisdiction, such
holding will not affect the validity or enforceability of any other provision.
Fluke Corporation
P.O. Box 9090
Everett, WA 98206-9090
U.S.A.
5/94
Fluke Europe B.V.
P.O. Box 1186
5602 BD Eindhoven
The Netherlands
Caution
This is an IEC Safety Class 1 product. Before using, the ground
wire in the line cord or the rear panel binding post must be
connected for safety.
Interference Information
This equipment generates and uses radio frequency energy and if not installed and used in strict
accordance with the manufacturer’s instructions, may cause interference to radio and television
reception. It has been type tested and found to comply with the limits for a Class B computing
device in accordance with the specifications of Part 15 of FCC Rules, which are designed to
provide reasonable protection against such interference in a residential installation.
Operation is subject to the following two conditions:
•
This device may not cause harmful interference.
•
This device must accept any interference received, including interference that may cause
undesired operation.
There is no guarantee that interference will not occur in a particular installation. If this equipment
does cause interference to radio or television reception, which can be determined by turning the
equipment off and on, the user is encouraged to try to correct the interference by one of more of
the following measures:
•
Reorient the receiving antenna
•
Relocate the equipment with respect to the receiver
•
Move the equipment away from the receiver
•
Plug the equipment into a different outlet so that the computer and receiver are on different
branch circuits
If necessary, the user should consult the dealer or an experienced radio/television technician for
additional suggestions. The user may find the following booklet prepared by the Federal
Communications Commission helpful: How to Identify and Resolve Radio-TV Interference
Problems. This booklet is available from the U.S. Government Printing Office, Washington, D.C.
20402. Stock No. 004-000-00345-4.
Declaration of the Manufacturer or Importer
We hereby certify that the Fluke Models 2625A Data Logger, 2620A Data Acquisition Unit and
2635A Data Bucket are in compliance with BMPT Vfg 243/1991 and is RFI suppressed. The
normal operation of some equipment (e.g. signal generators) may be subject to specific
restrictions. Please observe the notices in the users manual. The marketing and sales of the
equipment was reported to the Central Office for Telecommunication Permits (BZT). The right to
retest this equipment to verify compliance with the regulation was given to the BZT.
Bescheinigung des Herstellers/Importeurs
Hiermit wird bescheinigt, daβ Fluke Models 2625A Data Logger, 2620A Data Acquisition Unit und
2635A Data Bucket in Übereinstimung mit den Bestimmungen der BMPT-AmtsblVfg 243/1991
funk-entstört ist. Der vorschriftsmäßige Betrieb mancher Geräte (z.B. Meßsender) kann allerdings
gewissen Einschränkungen unterliegen. Beachten Sie deshalb die Hinweise in der
Bedienungsanleitung. Dem Bundesamt für Zulassungen in der Telekcommunikation wurde das
Inverkehrbringen dieses Gerätes angezeigt und die Berechtigung zur Überprüfung der Seire auf
Einhaltung der Bestimmungen eingeräumt.
Fluke Corporation
Safety Summary
Safety Terms in this Manual
This instrument has been designed and tested in accordance with IEC Publication 1010,
Safety Requirements for Electronical Measuring, Control and Laboratory Equipment. This
Service Manual contains information, warnings, and cautions that must be followed to
ensure safe operation and to maintain the instrument in a safe condition. Use of this
equipment in a manner mot specified herein may impair the protection by the equipment.
This meter is designed for IEC 64, Installation Category II use. It is not designed for use in
circuits rated over 48000VA.
Warning statements identify conditions or practices that could result in personal injury or
loss of life.
Caution statements identify conditions or practices that could result in damage to the
equipment.
Symbols Marked on Equipment
Danger - High voltage
Ground (Earth) Terminal
Protective ground (earth) terminal. Must be connected to safety earth ground
when the power cord is not used. See Section 2.
Attention — refer to the manual. This symbol indicates that information
about the use of a feature is contained in the manual. This symbol appears in
the following places on the rear panel:
1. Ground Binding Post (left of line power connector). Refer to “Using
External DC Power” in Section 2.
2. Alarm Ouputs/Digital I/O Connectors. Refer to Appendix A, Specifications.
AC Power Source
The instrument is intended to operate from a ac power source that will not apply more
than 264V ac rms between the supply conductors or between either supply conductor and
ground. A protective ground connection by way of the grounding conductor in the power
cord is required for safe operation.
DC Power Source
The instrument may also be operated from a 9 to 16V dc power source when either the
rear panel ground binding post or the power cord grounding conductor is properly
connected.
Use the Proper Fuse
To avoid fire hazard, use only a fuse identical in type, voltage rating, and current rating
as specified on the rear panel fuse rating label.
Grounding the Standard
The instrument utilized controlled overvoltage techniques that require the instrument to
be grounded whenever normal mode or common mode ac voltage or transient voltages
may occur. The enclosure must be grounded through the grounding conductor of the
power cord, or if operated on battery with the power cord unplugged, through the rear
panel ground binding post.
Use the Proper Power Cord
Use only the power cord and connector appropriate for the voltage and plug
configuration in your country.
Use only a power cord that is in good condition.
Refer cord and connector changes to qualified service personnel.
Do Not Operate in Explosive Atmospheres
To avoid explosion, do not operate the instrument in an atmosphere of explosive gas.
Do Not Remove Cover
To avoid personal injury or death, do not remove the instrument cover. Do not operate
the instrument without the cover properly installed. Normal calibration is accomplished
with the cover closed, and there are no user-serviceable parts inside the instrument, so
there is no need for the operator to ever remove the cover. Access procedures and the
warnings for such procedures are contained in the Service Manual. Service procedures
are for qualified service personnel only.
Do Not Attempt to Operate if Protection May be Impaired
If the instrument appears damaged or operates abnormally, protection may be impaired.
Do not attempt to operate it. When is doubt, have the instrument serviced.
Table of Contents
Chapter
1
Title
Introduction and Specifications........................................................ 1-1
1-1.
1-2.
1-3.
1-4.
1-5.
1-6.
2
Page
Introduction .........................................................................................
Options and Accessories .....................................................................
Operating Instructions .........................................................................
Organization of the Service Manual ...................................................
Conventions .........................................................................................
Specifications ......................................................................................
1-3
1-3
1-3
1-4
1-5
1-7
Theory of Operation (2620A/2625A).................................................. 2-1
2-1.
2-2.
2-3.
2-4.
2-5.
2-6.
2-7.
2-8.
2-9.
2-10.
2-11.
2-12.
2-13.
2-14.
2-15.
2-16.
2-17.
2-18.
2-19.
2-20.
2-21.
2-22.
2-23.
2-24.
Introduction ........................................................................................
Functional Block Description ..............................................................
Main PCA Circuitry ........................................................................
Power Supply ..............................................................................
Digital Kernel .............................................................................
Serial Communication (Guard Crossing) ...................................
Digital Inputs and Outputs ..........................................................
A/D Converter PCA ........................................................................
Analog Measurement Processor .................................................
Input Protection Circuitry ...........................................................
Input Signal Conditioning ..........................................................
Analog-to-Digital (A/D) Converter ............................................
Inguard Microcontroller Circuitry ..............................................
Channel Selection Circuitry .......................................................
Open Thermocouple Check Circuitry .........................................
Input Connector Assembly .............................................................
20 Channel Terminals .................................................................
Reference Junction Temperature ................................................
Display PCA ...................................................................................
Memory PCA (2625A Only) ...........................................................
IEEE-488 Option (-05) ...................................................................
Detailed Circuit Description ...............................................................
Main PCA .......................................................................................
Power Supply Circuit Description ..............................................
i
2-3
2-3
2-3
2-3
2-3
2-6
2-6
2-6
2-6
2-6
2-6
2-6
2-6
2-7
2-7
2-7
2-7
2-7
2-7
2-7
2-7
2-8
2-8
2-8
HYDRA
Service Manual
2-32.
2-43.
2-44.
2-45.
2-46.
2-47.
2-48.
2-49.
2-50.
2-51.
2-52.
2-58.
2-59.
2-60.
2-61.
2-62.
2-63.
2-64.
2-65.
2-66.
2-67.
2-68.
2-69.
2-70.
2-71.
2-72.
2-73.
2-74.
2-75.
2-76.
2-77.
2A
Digital Kernel .............................................................................
Digital I/O ...................................................................................
Digital Input Threshold ..............................................................
Digital Input Buffers ...................................................................
Digital and Alarm Output Drivers ..............................................
Totalizer Input ............................................................................
External Trigger Input Circuits ..................................................
A/D Converter PCA ........................................................................
Analog Measurement Processor .................................................
Input Protection ..........................................................................
Input Signal Conditioning ..........................................................
Passive and Active Filters ..........................................................
A/D Converter ............................................................................
Inguard Microcontroller Circuitry ..............................................
Channel Selection Circuitry .......................................................
Open Thermocouple Check ........................................................
Input Connector PCA ......................................................................
Display PCA ...................................................................................
Main PCA Connector .................................................................
Front Panel Switches ..................................................................
Display ........................................................................................
Beeper Drive Circuit ...................................................................
Watchdog Timer and Reset Circuit ............................................
Display Controller ......................................................................
Memory PCA (2625A Only) ...........................................................
Main PCA Connector .................................................................
Address Decoding .......................................................................
Page Register ..............................................................................
Byte Counter ...............................................................................
Nonvolatile Memory ...................................................................
IEEE-488 Interface (Option -05) ....................................................
2-10
2-14
2-15
2-15
2-15
2-16
2-16
2-16
2-17
2-17
2-20
2-25
2-26
2-27
2-27
2-28
2-28
2-29
2-29
2-29
2-30
2-30
2-30
2-31
2-33
2-33
2-33
2-34
2-34
2-34
2-34
Theory of Operation (2635A) ............................................................. 2A-1
2A-1. Introduction .......................................................................................... 2A-3
2A-2. Functional Block Description............................................................... 2A-3
2A-3.
Main PCA Circuitry......................................................................... 2A-3
2A-4.
Power Supply............................................................................... 2A-3
2A-5.
Digital Kernel .............................................................................. 2A-3
2A-6.
Serial Communication (Guard Crossing) .................................... 2A-6
2A-7.
Digital Inputs and Outputs........................................................... 2A-6
2A-8.
A/D Converter PCA ......................................................................... 2A-6
2A-9.
Analog Measurement Processor .................................................. 2A-6
2A-10.
Input Protection Circuitry............................................................ 2A-6
2A-11.
Input Signal Conditioning ........................................................... 2A-6
2A-12.
Analog-to-Digital (A/D) Converter ............................................. 2A-6
2A-13.
Inguard Microcontroller Circuitry............................................... 2A-6
2A-14.
Channel Selection Circuitry ........................................................ 2A-7
2A-15.
Open Thermocouple Check Circuitry.......................................... 2A-7
2A-16.
Input Connector Assembly .............................................................. 2A-7
2A-17.
20 Channel Terminals.................................................................. 2A-7
2A-18.
Reference Junction Temperature................................................. 2A-7
2A-19.
Display PCA .................................................................................... 2A-7
2A-20.
Memory Card Interface PCA ........................................................... 2A-7
2A-21. Detailed Circuit Description ................................................................ 2A-7
ii
Contents (continued)
2A-22.
2A-23.
2A-31.
2A-42.
2A-43.
2A-44.
2A-45.
2A-46.
2A-47.
2A-48.
2A-49.
2A-50.
2A-51.
2A-57.
2A-58.
2A-59.
2A-60.
2A-61.
2A-62.
2A-63.
2A-64.
2A-65.
2A-66.
2A-67.
2A-68.
2A-69.
2A-70.
2A-71.
2A-72.
2A-73.
2A-74.
3
Main PCA ........................................................................................
Power Supply Circuit Description...............................................
Digital Kernel ..............................................................................
Digital I/O....................................................................................
Digital Input Threshold ...............................................................
Digital Input Buffers....................................................................
Digital and Alarm Output Drivers ...............................................
Totalizer Input .............................................................................
External Trigger Input Circuits ...................................................
A/D Converter PCA .........................................................................
Analog Measurement Processor ..................................................
Input Protection ...........................................................................
Input Signal Conditioning ...........................................................
Passive and Active Filters ...........................................................
A/D Converter .............................................................................
Inguard Microcontroller Circuitry...............................................
Channel Selection Circuitry ........................................................
Open Thermocouple Check .........................................................
Input Connector PCA.......................................................................
Display PCA ....................................................................................
Main PCA Connector ..................................................................
Front Panel Switches ...................................................................
Display.........................................................................................
Beeper Drive Circuit....................................................................
Watchdog Timer and Reset Circuit .............................................
Display Controller .......................................................................
Memory Card Interface PCA ...........................................................
Main PCA Connector ..................................................................
Microprocessor Interface.............................................................
Memory Card Controller .............................................................
PCMCIA Memory Card Connector.............................................
2A-7
2A-8
2A-10
2A-18
2A-19
2A-19
2A-19
2A-19
2A-20
2A-20
2A-20
2A-23
2A-24
2A-29
2A-29
2A-31
2A-31
2A-31
2A-32
2A-32
2A-32
2A-33
2A-33
2A-33
2A-34
2A-34
2A-37
2A-37
2A-37
2A-37
2A-39
General Maintenance ......................................................................... 3-1
3-1.
3-2.
3-3.
3-4.
3-5.
3-6.
3-7.
3-8.
3-9.
3-10.
3-11.
3-12.
3-13.
3-14.
3-15.
3-16.
3-17.
3-18.
3-19.
3-20.
3-21.
Introduction ........................................................................................
Warranty Repairs and Shipping ..........................................................
General Maintenance ...........................................................................
Required Equipment .......................................................................
Power Requirements .......................................................................
Static Safe Handling .......................................................................
Servicing Surface-Mount Assemblies ............................................
Cleaning ...............................................................................................
Line Fuse Replacement .......................................................................
Disassembly Procedures ......................................................................
Remove the Instrument Case ..........................................................
Remove Handle and Mounting Brackets ........................................
Remove the Front Panel Assembly .................................................
Remove the Display PCA ...............................................................
Remove the IEEE-488 Option (2620A Only) .................................
Remove the Memory PCA (2625A Only) ......................................
Remove the Memory Card I/F PCA (2635A Only) ........................
Remove the Main PCA ...................................................................
Remove the A/D Converter PCA ....................................................
Disconnect Miscellaneous Chassis Components ............................
Assembly Procedures ..........................................................................
iii
3-3
3-3
3-3
3-3
3-3
3-3
3-4
3-4
3-5
3-5
3-6
3-6
3-6
3-6
3-11
3-11
3-11
3-12
3-12
3-13
3-13
HYDRA
Service Manual
3-22.
3-23.
3-24.
3-25.
3-26.
3-27.
3-28.
3-29.
3-30.
3-31.
4
3-13
3-13
3-14
3-14
3-14
3-15
3-15
3-15
3-15
3-15
Performance Testing and Calibration............................................... 4-1
4-1.
4-2.
4-3.
4-4.
4-5.
4-6.
4-7
4-8.
4-9.
4-10.
4-11.
4-12.
4-13.
4-14.
4-15.
4-16.
4-17.
4-18.
4-19.
4-20.
4-21.
4-22.
4-23.
4-24.
4-25.
4-26.
4-28.
4-29.
4-30.
4-31.
4-32.
4-33.
4-34.
5
Install Miscellaneous Chassis Components ....................................
Install the A/D Converter PCA .......................................................
Install the Main PCA ......................................................................
Install the IEEE-488 Option (2620A Only) ....................................
Install the Memory PCA (2625A Only) ..........................................
Install the Memory Card I/F PCA (2635A Only) ...........................
Assemble the Front Panel Assembly ..............................................
Install the Front Panel Assembly ....................................................
Install the Handle and Mounting Brackets .....................................
Install the Instrument Case .............................................................
Introduction ........................................................................................
Required Equipment ............................................................................
Performance Tests ...............................................................................
Accuracy Verification Test .............................................................
Channel Integrity Test .....................................................................
Thermocouple Measurement Range Accuracy Test .......................
4-Terminal Resistance Test. ............................................................
Thermocouple Temperature Accuracy Test ...................................
Open Thermocouple Response Test ...............................................
RTD Temperature Accuracy Test ...................................................
RTD Temperature Accuracy Test (Using Decade Resistance
Source) ........................................................................................
RTD Temperature Accuracy Test (Using DIN/IEC 751) ...........
Digital Input/Output Verification Tests ..........................................
Digital Output Test .....................................................................
Digital Input Test ........................................................................
Totalizer Test ..............................................................................
Totalizer Sensitivity Test ............................................................
Dedicated Alarm Output Test .........................................................
External Trigger Input Test .............................................................
Calibration ...........................................................................................
Using Hydra Starter Calibration Software ......................................
Setup Procedure Using Starter ....................................................
Calibration Procedure Using Starter ...........................................
Using a Terminal .............................................................................
Setup Procedure Using a Terminal .............................................
Calibration Procedure Using a Terminal ....................................
Reference Junction Calibration .......................................................
Concluding Calibration ...................................................................
Updating 2635A Data Bucket Embedded Instrument Firmware ........
Using the PC Compatible Firmware Loader Software ...................
Setup Procedure for Firmware Download ..................................
Default Instrument Firmware Download Procedure ..................
Using LD2635 Firmware Loader Directly .................................
4-3
4-3
4-4
4-4
4-4
4-6
4-7
4-8
4-11
4-11
4-11
4-12
4-13
4-13
4-14
4-14
4-15
4-16
4-18
4-18
4-20
4-20
4-21
4-22
4-22
4-22
4-24
4-25
4-27
4-28
4-29
4-29
4-30
Diagnostic Testing and Troubleshooting (2620A/2625A)................ 5-1
5-1.
5-2.
5-3.
5-4.
5-5.
5-6.
Introduction ........................................................................................
Servicing Surface-Mount Assemblies .................................................
Error Codes ..........................................................................................
General Troubleshooting Procedures ..................................................
Power Supply Troubleshooting ...........................................................
Raw DC Supply ..............................................................................
iv
5-3
5-3
5-4
5-6
5-8
5-8
Contents (continued)
5-7.
5-8.
5-9.
5-10.
5-11.
5-12.
5-13.
5-14.
5-15.
5-16.
5-17.
5-18.
5-19.
5-20.
5-21.
5-22.
5-23.
5-24.
5-25.
5-26.
5-27.
5-28.
5-29.
5A
Power Fail Detection .......................................................................
5-Volt Switching Supply..................................................................
Inverter ............................................................................................
Analog Troubleshooting ......................................................................
DC Volts Troubleshooting ..............................................................
AC Volts Troubleshooting ..............................................................
Ohms Troubleshooting ....................................................................
Digital Kernel Troubleshooting ..........................................................
Digital and Alarm Output Troubleshooting ........................................
Digital Input Troubleshooting .............................................................
Totalizer Troubleshooting ...................................................................
Display Assembly Troubleshooting ....................................................
Variations in the Display .....................................................................
Calibration Failures .............................................................................
Introduction .....................................................................................
Calibration-Related Components ....................................................
Retrieving Calibration Constants ....................................................
Replacing the EEPROM (A1U1) ....................................................
IEEE-488 Interface PCA (A5) Troubleshooting .................................
Memory PCA (A6) Troubleshooting ..................................................
Power-Up Problems ........................................................................
Failure to Detect Memory PCA ..................................................
Failure to Store Data ...................................................................
5-8
5-8
5-9
5-12
5-17
5-17
5-18
5-19
5-21
5-21
5-21
5-23
5-25
5-26
5-26
5-26
5-28
5-28
5-29
5-29
5-29
5-29
5-29
Diagnostic Testing and Troubleshooting (2635A) ........................... 5A-1
5A-1.
5A-2.
5A-3.
5A-4.
5A-5.
5A-6.
5A-7.
5A-8.
5A-9.
5A-10.
5A-11.
5A-12.
5A-13.
5A-14.
5A-15.
5A-16.
5A-17.
5A-18.
5A-19.
5A-20.
5A-21.
5A-22.
5A-23.
5A-24.
5A-25.
5A-26.
5A-27.
5A-28.
5A-29.
Introduction ..........................................................................................
Servicing Surface-Mount Assemblies..................................................
Error Codes...........................................................................................
General Troubleshooting Procedures ...................................................
Power Supply Troubleshooting............................................................
Raw DC Supply ...............................................................................
Power Fail Detection........................................................................
5A-Volt Switching Supply...............................................................
Inverter .............................................................................................
Analog Troubleshooting.......................................................................
DC Volts Troubleshooting...............................................................
AC Volts Troubleshooting...............................................................
Ohms Troubleshooting.....................................................................
Digital Kernel Troubleshooting ...........................................................
Digital and Alarm Output Troubleshooting .........................................
Digital Input Troubleshooting..............................................................
Totalizer Troubleshooting ....................................................................
Display Assembly Troubleshooting .....................................................
Variations in the Display......................................................................
Calibration Failures ..............................................................................
Introduction......................................................................................
Calibration-Related Components.....................................................
Retrieving Calibration Constants.....................................................
Replacing the Flash Memory (A1U14 and A1U16) ........................
Memory Card I/F PCA (A6) Troubleshooting.....................................
Power-Up Problems .........................................................................
Failure to Detect Memory Card I/F PCA ....................................
Failure to Detect Insertion of Memory Card ...............................
Failure to Power Card / Illuminate the Busy Led........................
v
5A-3
5A-3
5A-4
5A-6
5A-8
5A-8
5A-8
5A-8
5A-9
5A-11
5A-16
5A-17
5A-17
5A-18
5A-21
5A-21
5A-23
5A-23
5A-26
5A-27
5A-27
5A-27
5A-29
5A-29
5A-30
5A-30
5A-30
5A-31
5A-31
HYDRA
Service Manual
5A-30.
5A-31.
5A-32.
6
List of Replaceable Parts .................................................................. 6-1
6-1.
6-2.
6-3.
6-4.
6-5.
7
Failure to Illuminate the Battery Led .......................................... 5A-31
Failure to Write to Memory Card................................................ 5A-32
Write/Read Memory Card Test (Destructive) ............................. 5A-32
Introduction ........................................................................................
How to Obtain Parts ............................................................................
Manual Status Information ..................................................................
Newer Instruments ..............................................................................
Service Centers ....................................................................................
6-3
6-3
6-3
6-4
6-4
IEEE-488 Option -05........................................................................... 7-1
7-1.
7-2.
7-3.
7-4.
7-5.
7-6.
7-7.
7-8.
7-9.
7-10.
7-11.
7-12.
7-13.
7-14.
7-15.
7-16.
7-17.
7-18.
7-19.
7-20.
7-21.
7-22.
7-23.
Introduction ........................................................................................
Theory of Operation ............................................................................
Functional Block Description .........................................................
IEEE-488 PCA Detailed Circuit Description (2620A Only) ..............
Main PCA Connector ......................................................................
IEEE-488 Controller .......................................................................
IEEE-488 Transceivers/Connector .................................................
General Maintenance ...........................................................................
Removing the IEEE-488 Option .....................................................
Installing the IEEE-488 Option ......................................................
Performance Testing ...........................................................................
Troubleshooting ..................................................................................
Power-Up Problems ........................................................................
Communication Problems ...............................................................
Failure to Select IEEE-488 Option .............................................
Failure to Handshake on IEEE-488 Bus .....................................
Failure to Enter Remote ..............................................................
Failure to Receive Multiple Character Commands ....................
Failure to Transmit Query Responses ........................................
Failure to Generate an End or Identify (EOI) .............................
Failure to Generate a Service Request (SRQ) ............................
List of Replaceable Parts .....................................................................
Schematic Diagram .............................................................................
7-3
7-3
7-3
7-3
7-4
7-4
7-5
7-5
7-5
7-7
7-7
7-8
7-8
7-8
7-8
7-8
7-8
7-9
7-9
7-9
7-9
7-9
7-9
8
Schematic Diagrams.......................................................................... 8-1
9
Hydra Starter Calibration Software................................................... 9-1
Introduction ....................................................................................................... 9-3
vi
List of Tables
Table
1-1.
1-2.
1-3.
1-4.
2-1.
2-2.
2-3.
2-4.
2-5.
2-6.
2-7.
2-8.
2A-1.
2A-2.
2A-3.
2A-4.
2A-5.
2A-6.
2A-7.
2A-8.
4-1.
4-2.
4-3.
4-4.
4-5.
4-6.
4-7.
4-8.
4-9.
4-10.
4-11.
4-12.
4-13.
5-1.
5-2.
Title
Page
Hydra Features......................................................................................................... 1-6
Accessories ............................................................................................................ 1-7
2620A/2625A Specifications................................................................................. 1-8
2635A Specifications............................................................................................. 1-20
Microprocessor Memory Map ............................................................................... 2-11
Option Type Sensing ............................................................................................. 2-14
Programmable Input Threshold Levels ................................................................. 2-15
Analog Measurement Processor Pin Descriptions ................................................ 2-19
Function Relay States ............................................................................................ 2-21
AC Volts Input Signal Dividers............................................................................. 2-25
Front Panel Switch Scanning................................................................................. 2-29
Display Initialization Modes ................................................................................. 2-32
Microprocessor Interrupt Sources (2635A)........................................................... 2A-12
Booting Microprocessor Memory Map (2635A)................................................... 2A-13
Instrument Microprocessor Memory Map (2635A) .............................................. 2A-13
Analog Measurement Processor Pin Descriptions (2635A) .................................. 2A-22
Function Relay States (2635A).............................................................................. 2A-24
AC Volts Input Signal Dividers (2635A) .............................................................. 2A-28
Front Panel Switch Scanning (2635A) .................................................................. 2A-33
Display Initialization Modes (2635A)................................................................... 2A-36
Recommended Test Equipment............................................................................. 4-3
Performance Tests (Voltage, Resistane, and Frequency) ...................................... 4-5
Thermocouplt Information .................................................................................... 4-10
Performance Tests for Thermocouple Temperature Function............................... 4-10
Performance Tests for RTD Temperature Function (Resistance Source) ............. 4-12
Performance Tests for RTD Temperature Function (DIN/IEC 751)..................... 4-13
Digital Input Values............................................................................................... 4-14
Calibration Mode Computer Interface Commands ............................................... 4-20
DC Volts Calibration ............................................................................................. 4-23
AC Volts Calibration ............................................................................................. 4-24
4-Wire Ohms Calibration (Fixed Resistor) ........................................................... 4-27
4-Wire Ohms Calibration (5700A)........................................................................ 4-28
Frequency Calibration ........................................................................................... 4-29
Error Codes ............................................................................................................ 5-5
Preregulated Power Supplies ................................................................................. 5-6
vii
HYDRA
Service Manual
5-3.
5-4.
5-5.
5-6.
5-7.
5-8.
5-9.
5-10.
5A-1.
5A-2.
5A-3.
5A-4.
5A-5.
5A-6.
5A-7.
5A-8.
5A-9.
6-1.
6-2.
6-3.
6-4.
6-5.
6-6.
6-7.
6-9.
6-10.
7-1.
7-2.
Power Supply Troubleshooting Guide...................................................................
DC Volts HI Troubleshooting ...............................................................................
AC Volts HI Troubleshooting ...............................................................................
Ohms Open-Circuit Voltage ..................................................................................
Ohms HI Troubleshooting .....................................................................................
Display Initialization .............................................................................................
Calibration Faults (for software versions 5.4 and above)......................................
Calibration Faults (for sotware versions lower than 5.4) ......................................
Error Codes (2635A) .............................................................................................
Preregulated Power Supplies (2635A) ..................................................................
Power Supply Troubleshooting Guide (2635A) ....................................................
DC Volts HI Troubleshooting (2635A).................................................................
AC Volts HI Troubleshooting (2635A).................................................................
Ohms Open-Circuit Voltage (2635A) ...................................................................
Ohms HI Troubleshooting (2635A).......................................................................
Display Initialization (2635A)...............................................................................
Calibration Faults (for software versions 5.4 and above) (2635A) .......................
2620A/2625A Final Assembly ..............................................................................
2635A Final Assembly ..........................................................................................
2620A/2625A A1 Main PCA ................................................................................
2635A A1 Main PCA ............................................................................................
A2 Display PCA ....................................................................................................
A3 A/D Converter PCA.........................................................................................
A4 Analog Input PCA............................................................................................
2625A A6 Memory PCA .......................................................................................
2635A A6 Memory Card I/F PCA.........................................................................
A5U1 Pin Differences............................................................................................
IEEE-488 Transceiver Control ..............................................................................
viii
5-13
5-17
5-18
5-18
5-18
5-23
5-27
5-28
5A-5
5A-6
5A-13
5A-18
5A-18
5A-19
5A-19
5A-26
5A-29
6-5
6-11
6-17
6-21
6-25
6-27
6-30
6-34
6-36
7-3
7-5
List of Figures
Figure
2-1.
2-2.
2-3.
2-5.
2-6.
2-7.
2-8.
2-9.
2-10.
2A-1.
2A-2.
2A-3.
2A-4.
2A-5.
2A-6.
2A-7.
2A-8.
2A-9.
2A-10.
3-1.
3-3.
3-3.
3-5.
3-5.
4-1.
4-2.
4-3.
4-4.
4-5.
4-6.
5-1.
5-2.
5-3.
5-5.
5-5.
Title
Page
Interconnect Diagram ............................................................................................
Overall Functional Block Diagram........................................................................
Analog Simplified Schematic Diagram.................................................................
Ohms Simplified Schematic ..................................................................................
AC Buffer Simplified Schematic...........................................................................
A/D Converter Simplified Schematic....................................................................
Command Byte Transfer Waveforms....................................................................
Grid Control Signal Timing...................................................................................
Grid-Anode Timing Relationships ........................................................................
Interconnect Diagram (2635A)..............................................................................
Overall Functional Block Diagram (2635A) .........................................................
Analog Simplified SchematicDiagram (2635A) ...................................................
DC Volts 300V Range Simplified Schematic (2635A).........................................
Ohms Simplified Schematic (2635A)....................................................................
AC Buffer Simplified Schematic (2635A) ............................................................
A/D Converter Simplified Schematic (2635A) .....................................................
Command Byte Transfer Waveforms (2635A) .....................................................
Grid Control Signal Timing (2635A) ....................................................................
Grid-Anode Timing Relationships (2635A)..........................................................
Replacing the Line Fuse ........................................................................................
Removing the Handle and Handle Mounting Brackets .........................................
Removing the Case ................................................................................................
2635A Assembly Details .......................................................................................
2620A and 2625A Assembly Details ....................................................................
Input Module .........................................................................................................
2T and 4T Connections..........................................................................................
Dedicated Alarms Test ..........................................................................................
External Trigger Test.............................................................................................
4-Terminal Connections to Decade Resistance Source.........................................
4-Terminal Connections to the 5700A ..................................................................
Test Point Locator, Main PCA (A1)......................................................................
5-Volt Switching Supply .......................................................................................
Inverter FET Drive Signals....................................................................................
Test Points, A/D Converter PCA (A3, A3U9) ......................................................
Test Points, A/D Converter PCA (A3, A3U9) ......................................................
ix
2-4
2-5
2-18
2-23
2-24
2-26
2-31
2-32
2-33
2A-4
2A-5
2A-21
2A-25
2A-26
2A-28
2A-30
2A-35
2A-37
2A-37
3-5
3-8
3-8
3-10
3-10
4-8
4-9
4-17
4-18
4-25
4-26
5-7
5-9
5-11
5-16
5-17
HYDRA
Service Manual
5-6.
5-7.
5-8.
5-9.
5-10.
5-11.
5A-1.
5A-2.
5A-3.
5A-4.
5A-5.
5A-5.
5A-6.
5A-7.
5A-8.
5A-9.
5A-10.
5A-11.
6-1.
6-2.
6-3.
6-4.
6-5.
6-6.
6-7.
6-8.
6-9.
6-10.
7-1.
8-1.
8-2.
8-3.
8-4.
8-5.
8-6.
8-7.
8-8.
Integrator Output ...................................................................................................
Microprocessor Timing .........................................................................................
Test Points, Display PCA (A2)..............................................................................
Display Controller to Microprocessor Signals ......................................................
Display Test Pattern #1..........................................................................................
Display Test Pattern #2..........................................................................................
Test Point Locator, Main PCA (A1) (2635A) .......................................................
5-Volt Switching Supply (2635A).........................................................................
Inverter FET Drive Signals (2635A) .....................................................................
Test Points, A/D Converter PCA (A3, A3U8) (2635A) ........................................
Test Points, A/D Converter PCA (A3U9) (2635A)...............................................
Test Points, A/D Converter PCA (A3, A3U8) (2635A) ........................................
Integrator Output (2635A).....................................................................................
Microprocessor Timing (2635A)...........................................................................
Test Points, Display PCA (A2) (2635A) ...............................................................
Display Controller to Microprocessor Signals (2635A)........................................
Display Test Pattern #1 (2635A) ...........................................................................
Display Test Pattern #2 (2635A) ...........................................................................
2620A/2625A Final Assembly ..............................................................................
2635A Final Assembly ..........................................................................................
2620A/2625A A1 Main PCA ................................................................................
2635A A1 Main PCA ............................................................................................
A2 Display PCA ....................................................................................................
A3 A/D Converter PCA........................................................................................
A4 Analog Input PCA............................................................................................
A5 IEEE-488 Interface PCA (Option -05) ............................................................
2625A A6 Memory PCA .......................................................................................
2635A A6 Memory Card I/F PCA.........................................................................
Installation .............................................................................................................
A1 Main PCA (2620A/2625A)..............................................................................
A1 Main PCA (2635A)..........................................................................................
A2 Display PCA ....................................................................................................
A3 A/D Converter PCA.........................................................................................
A4 Analog Input PCA............................................................................................
A5 (Option -05) IEEE-488 Interface PCA ............................................................
A6 Memory PCA (2625A) ....................................................................................
A6 Memory Card I/F PCA (2635A) ......................................................................
x
5-17
5-20
5-22
5-23
5-24
5-24
5A-7
5A-10
5A-11
5A-15
5A-16
5A-16
5A-17
5A-23
5A-25
5A-26
5A-26
5A-26
6-7
6-13
6-20
6-24
6-26
6-29
6-31
6-33
6-35
6-37
7-6
8-3
8-8
8-14
8-16
8-20
8-22
8-24
8-26
Chapter 1
Introduction and Specifications
Title
1-1.
1-2.
1-3.
1-4.
1-5.
1-6.
Introduction ..........................................................................................
Options and Accessories ......................................................................
Operating Instructions ..........................................................................
Organization of the Service Manual.....................................................
Conventions..........................................................................................
Specifications .......................................................................................
Page
1-3
1-3
1-3
1-4
1-5
1-7
1-1
HYDRA
Service Manual
1-2
Introduction and Specifications
Introduction
1
1-1. Introduction
Hydra measures analog inputs of dc and ac volts, thermocouple and RTD temperatures,
resistance, and frequency. It features 21 measurement input channels. In addition, it
contains eight digital input/output lines, one totalizing input, one external scan trigger
input, and four alarm output lines. Hydra is fully portable and can be ac or dc powered.
An RS-232 computer interface is standard. An optional IEEE-488 computer interface is
available for the Hydra Data Acquisition Unit (2620A) only.
The Hydra Data Logger (2625A) adds substantial measurement memory capabilities.
The RS-232 computer interface is standard, but IEEE-488 capability is not available for
the Hydra Data Logger.
The Hydra Data Bucket (2635A) adds more flexible storage for instrument setups and
measurement data by adding a PCMCIA memory card and interface. The amount of
storage can be easily changed by selecting a memory card of the appropriate size for the
job.
The Hydra instruments share many features and functions. The term "instrument" is used
to refer to all three instruments. The model number (2620A, 2625A, or 2635A) is used
when discussing features unique to one instrument.
The instrument is designed for bench-top, field service, and system applications. A dual
vacuum-fluorescent display uses combinations of alphanumeric characters and
descriptive annunciators to provide prompting and measurement information during
setup and operation modes.
Some features provided by the instrument are listed in Table 1-1.
1-2. Options and Accessories
The following items can be installed either at the factory or in the field:
•
Option 2620A-05K (IEEE-488 Interface Kit) consists of a printedcircuit assembly,
connecting cable, and mounting hardware. Thisfield-installable kit gives the 2620A
Hydra Data Acquisition UnitIEEE-488 interface capabilities. IEEE-488 computer
interfacecommands are virtually identical to RS-232 interface commands.
(The2625A and 2635A cannot be equipped with an IEEE-488 Interface.)
•
Accessory 2620A-100 (Connector Kit).
The instrument can be mounted in a standard 19-inch rack panel on either the right-hand
or left-hand side using the Fluke M00-200-634 Rackmount Kit.
Accessories are listed in Table 1-2.
1-3. Operating Instructions
Full operating instructions are provided in the Hydra User Manual (2620A or 2625A)
and in the Hydra Data Bucket User Manual (2635A). Refer to the User Manual as
necessary during the maintenance and repair procedures presented in this Service
Manual.
1-3
HYDRA
Service Manual
1-4. Organization of the Service Manual
This manual focuses on performance tests, calibration procedures, and component-level
repair of each of the instruments. To that end, manual sections are often interdependent;
effective troubleshooting may require not only reference to the troubleshooting
procedures in Section 5, but also some understanding of the detailed Theory of
Operation in Section 2 and some tracing of circuit operation in the Schematic Diagrams
presented in Section 8.
Often, scanning the table of contents will yield an appropriate place to start using the
manual. A comprehensive table of contents is presented at the front of the manual; local
tables of contents are also presented at the beginning of each chapter for ease of
reference. If you know the topic name, the index at the end of the manual is probably a
good place to start.
The following chapter descriptions serve to introduce the manual:
Chapter 1. Introduction and Specifications
Introduces the instrument, describing its features, options, and accessories. This chapter
also discusses use of the Service Manual and the various conventions used in describing
the circuitry. Finally, a complete set of specifications is presented.
Chapter 2. Theory of Operation (2620A and 2625A)
This chapter first categorizes these instrument’s circuitry into functional blocks, with a
description of each block’s role in overall operation. A detailed circuit description is then
given for each block. These descriptions explore operation to the component level and
fully support troubleshooting procedures defined in Chapter 5.
Chapter 2A. Theory of Operation (2635A)
This chapter first categorizes the instrument’s circuitry into functional blocks, with a
description of each block’s role in overall operation. A detailed circuit description is then
given for each block. These descriptions explore operation to the component level and
fully support troubleshooting procedures defined in Chapter 5A.
Chapter 3. General Maintenance
Provides maintenance information covering handling, cleaning, and fuse replacement.
Access and reassembly procedures are also explained in this chapter.
Chapter 4. Performance Testing and Calibration
This chapter provides performance verification procedures, which relate to the
specifications presented in Chapter 1. To maintain these specifications, a full calibration
procedure is also presented.
Chapter 5. Diagnostic Testing and Troubleshooting (2620A and 2625A)
The troubleshooting procedures presented in this chapter rely closely on both the Theory
of Operation presented in Chapter 2, the Schematic Diagrams shown in Chapter 8, and
the access information provided in Chapter 3.
Chapter 5A. Diagnostic Testing and Troubleshooting (2635A)
The troubleshooting procedures presented in this chapter rely closely on both the Theory
of Operation presented in Chapter 2A, the Schematic Diagrams shown in Chapter 8, and
the access information provided in Chapter 3.
Chapter 6. List of Replaceable Parts
Includes parts lists for all standard assemblies. Information on how and where to order
parts is also provided.
1-4
Introduction and Specifications
Conventions
1
Chapter 7. IEEE-488 Option (2620A only)
This chapter describes the IEEE-488 option. Included are specifications, theory of
operation, maintenance, and a list of replaceable parts. Schematic diagrams for this
option are included at the end of the overall Service Manual (Chapter 8).
Chapter 8. Schematic Diagrams
Includes schematic diagrams for all standard and optional assemblies. A list of
mnemonic definitions is also included to aid in identifying signal name abbreviations.
Chapter 9. HYDRA Starter Calibration Software
This chapter provides an extened tutorial that demostrates how to perform a series of
operations. These operations introduce you to the menu structure of the Starter with cal
software, explain what the menu items do, and teach you how to use them.
1-5. Conventions
Throughout the manual set, certain notational conventions are used. A summary of these
conventions follows:
• Instrument Reference
The Hydra Data Acquisition Unit (Model 2620A), the Hydra Data Logger(Model
2625A), and the Hydra Data Bucket (Model 2635A) share manyfeatures and
functions. The term Hydra refers to any of theseinstruments. The model number
(e.g., 2620A, 2625A, or 2635A) isused when features unique to one instrument are
being described.
• Printed Circuit Assembly
The term "pca" is used to represent a printed circuit board and itsattached parts.
• Signal Logic Polarity
On schematic diagrams, a signal name followed by a "*" is active (orasserted) low.
Signals not so marked are active high.
• Circuit Nodes
Individual pins or connections on a component are specified with adash (-) following
the assembly and component reference designators.For example, pin 19 of U30 on
assembly A1 would be A1U30-19.
• User Notation
For front panel operation,
XXXAn uppercase word or symbol without parentheses indicates a button to be
pressed by the user. Buttons can be pressed in four ways:
1. Press a single button to select a function or operation.
2. Press a combination of buttons, one after the other.
3. Press and hold down a button, then press another button.
4. Press multiple buttons simultaneously.
For computer interface operation,
XXX
An uppercase word without parentheses identifies a command byname.
<XXX>
Angle brackets around all uppercase letters mean press the<XXX> key.
(xxx)
When associated with a keyword, a lowercase word inparentheses
indicates an input required by the user.
1-5
HYDRA
Service Manual
Table 1-1. Hydra Features
• Channel Scanning
Can be continuous scanning, scanning at an interval time, single scans, or triggered (internal or external)
scans.
• Channel Monitoring
Make measurements on a single channel and view these measurements on the display.
• Channel Scanning and Monitoring
View measurements made for the monitor channel while scanning of all active channels continues.
• Multi-Function Display
Left (numeric) display shows measurement readings; also used when setting numeric parameters.
Right (alphanumeric) display used for numeric entries, channel number selection and display, status
information, and operator prompts.
• Front-Panel Operation
Almost all operations can be readily controlled with the buttons on the front panel.
• Measurement Input Function and Range
Volts dc (VDC), volts ac (VAC), frequency (Hz), and resistance (Ω) inputs can be specified in a fixed
measurement range. Autoranging, which allows the instrument to use the measurement range providing
the optimum resolution, can also be selected.
• Temperature Measurement
Thermocouple types J, K, E, T, N, R, S, B, and Hoskins Engineering Co. type C are supported.Also,
DIN/IEC 751 (Pt 385) Platinum RTDs are supported.
• Totalize Events on the Totalizing Input
• Alarms Limits and Digital Output Alarm Indication
• 4-Terminal Resistance Measurements (Ch. 1 .. 10)
• RS-232 Computer Interface Operation
• Measurement Rate Selection
• Nonvolatile Memory
Storage of minimum, maximum, and most recent measurements for all scanned channels.
Storage of Computer Interface setup, channel configurations, and calibration values.
• Features unique to the 2625A Data Logger.
Storage of measurement data: storage for 2047 scans of up to 21 channels, representing up to 42,987
readings.
• Features unique to the 2635A Data Bucket.
Internal storage of measurement data for 100 scans of up to 21 channels, representing up to 2,100
readings.
Memory card storage of instrument setup configurations so that instrument may be quickly set up to do
different tasks.
Memory card storage of measurement data for up to 4,800 scans of 10 channels on a 256K-byte card or
up to 19,800 scans of 10 channels on a 1M-byte memory card.
Enhanced RS-232 interface with higher baud rates and hardware flow control using the Clear to Send
modem control signal.
1-6
Introduction and Specifications
Specifications
1
Table 1-2. Accessories
Model
80i-410
Description
Clamp-On DC/AC Current Probes
80i-1010
80J-10
Current Shunt
2620A-05K
Field-installable IEEE-488 Option kit (Hydra Data Acquisition Unit only.)
2620A-100
Extra I/O Connector Set: Includes Universal Input Module, Digital I/O and Alarm Output
Connectors.
262XA-801
Diconix(R) 80-column serial printer.
263XA-803
Memory Card Reader for IBM-PC or compatible personal computer. Card reader is external
to the PC and connects to a PC parallel port (LPT1, LPT2, etc.). (2635A Data Bucket only).
263XA-804
256K-Byte Memory Card (2635A Data Bucket only). (This card is supplied with the
instrument.)
263XA-805
1M-Byte Memory Card (2635A Data Bucket only).
26XXA-901
Hydra Logger Applications Package (Version 3.0)
C40
Soft carrying case. Provides padded protection for the instrument. Includes a pocket for the
manual and pouch for the line cord.
M00-200-634
Rackmount Kit. Provides standard 19-inch rack mounting for one instrument (right or left
side.)
PM 8922
Switchable X1, X10 passive probe.
RS40
Shielded RS-232 terminal interface cable. Connects the instrument to any terminal or
printer with properly configured DTE connector (DB-25 socket), including an IBM PC(R),
IBM PC/XT(R) or IBM PS/2 (models 25, 30, 50, P60, 70, and 80).
RS41
Shielded RS-232 modem cable. Connects the instrument to a modem with properly
configured DB-25 male pin connector. Use an RS40 and an RS41 cable in series to
connect with an IBM PC/AT(R).
RS42
Shielded serial printer cable. Contact Fluke for list of compatible printers.
TL20
Industrial test lead set.
TL70A
Test lead set (one set is supplied with the instrument).
Y8021
Shielded IEEE-488 one-meter (39.4 inches) cable, with plug and jack at each end.
Y8022
Shielded IEEE-488 two-meter (78.8 inches) cable, with plug and jack at each end.
Y8023
Shielded IEEE-488 four-meter (13 feet) cable, with plug and jack at each end.
Y9109
Binding post to BNC plug.
Footnote:
IBM PC, IBM PC/XT, and IBM PC/AT are registered trademarks of International Business Machines
1-6. Specifications
Table 1-3 contains the specifications for the 2620A and 2625A.
Table 1-4 contains the specifications for the 2635A.
1-7
HYDRA
Service Manual
Table 1-3. 2620A/2625A Specifications
The instrument specifications presented here are applicable within the conditions listed in the
Environmental portion of this specification.
The specifications state total instrument accuracy following calibration, including:
• A/D errors
• Linearization conformity
• Initial calibration errors
• Isothermality errors
• Relay thermal emf’s
• Reference junction conformity
• Temperature coefficients
• Humidity errors
Sensor inaccuracies are not included in the accuracy figures.
Accuracies at Temperatures Other Than Specified
To determine typical accuracies at temperatures intermediate to those listed in the specification
tables, linearly interpolate between the applicable 0oC to 60oC and 18oC to 28oC accuracy
specifications.
Response Times
Refer to Typical Scanning Rate and Maximum Autoranging Time later in this table.
DC Voltage Inputs
Resolution
Range
Slow
Fast
300 mV
10 µV
0.1 mV
3V
0.1 mV
1 mV
30V
1 mV
10 mV
300V
10 mV
0.1V
Accuracy ±(% ±V)
Range
18°C to 28°C
90 Days, Slow
300 mV
0.026% + 20 µV
1 Year, Slow
0.031% + 20 µV
0°C to 60°C
1 Year, Fast
0.047% + 0.2 mV
1 Year, Slow
0.070% + 20 µV
1 Year, Fast
0.087% + 0.2 mV
3V
0.028% + 0.2 mV
0.033% + 0.2 mV
0.050% + 2 mV
0.072% + 0.2 mV
0.089% + 2 mV
30V
0.024% + 2 mV
0.029% + 2 mV
0.046% + 20 mV
0.090% + 2 mV
0.107% + 20 mV
300V
0.023% + 20 mV
0.028% + 20 mV
0.045% + 0.2V
0.090% + 20 mV
0.107% + 0.2V
Input Impedance
100 MΩ minimum in parallel with 150 pF maximum for all ranges 3V and below 10 MΩ in parallel
with 100 pF maximum for the 30V and 300V ranges.
Normal Mode Rejection
53 dB minimum at 60 Hz ±0.1%, slow rate
47 dB minimum at 50 Hz ±0.1%, slow rate
Common Mode Rejection
120 dB minimum at dc, 1 kΩ imbalance, slow rate
120 dB minimum at 50 or 60 Hz ±0.1%, 1 kΩ imbalance, slow rate
Maximum Input
300V dc or ac rms on any range for channels 0, 1, and 11
150V dc or ac rms for channels 2 to 10 and 12 to 20
Voltage ratings between channels must not be exceeded
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
1-8
Introduction and Specifications
Specifications
1
Table 1-3. 2620A/2625A Specifications (cont)
Thermocouple Inputs
Accuracy (±°C)*
Thermocouple
18°C to 28°C
90 Days
Slow
1 Year
Slow
1 Year
Fast
1 Year
Slow
1 Year
Fast
-100.00
0.00
760.00
0.49
0.38
0.49
0.53
0.40
0.54
1.00
0.77
0.97
0.73
0.53
0.91
1.22
0.91
1.35
-100.00
0.00
1000.00
1372.00
0.57
0.42
0.73
0.95
0.60
0.44
0.80
1.05
1.20
0.88
1.46
1.89
0.82
0.57
1.36
1.85
1.43
1.02
2.03
2.70
-100.00
0.00
400.00
1300.00
0.66
0.51
0.46
0.75
0.69
0.53
0.49
0.83
1.48
1.14
0.99
1.53
0.90
0.66
0.72
1.45
1.70
1.29
1.23
2.16
-100.00
0.00
500.00
1000.00
0.50
0.36
0.40
0.58
0.53
0.38
0.43
0.65
0.99
0.72
0.77
1.11
0.75
0.52
0.71
1.16
1.22
0.86
1.05
1.63
T
-150.00
0.00
400.00
0.79
0.42
0.37
0.84
0.45
0.40
1.66
0.89
0.74
1.16
0.58
0.61
1.99
1.04
0.97
R
250.00
1000.00
1767.00
0.96
0.86
1.14
0.98
0.91
1.24
2.48
2.10
2.65
1.14
1.29
1.96
2.65
2.48
3.38
S
250.00
1000.00
1767.00
1.01
0.97
1.29
1.03
1.02
1.39
2.62
2.37
3.02
1.20
1.42
2.17
2.80
2.77
3.80
B
600.00
1000.00
1820.00
1.26
0.92
0.97
1.28
0.95
1.03
3.52
2.48
2.41
1.40
1.16
1.51
3.64
2.69
2.89
C
0.00
500.00
1000.00
1850.00
2316.00
0.76
0.66
0.85
1.47
2.30
0.78
0.69
0.91
1.61
2.53
1.87
1.53
1.90
3.18
4.93
0.92
0.96
1.41
2.70
4.35
2.01
1.81
2.41
4.29
6.77
Type
J
K
N
E
Temperature
(°C)
0°C to 60°C
* Sensor inaccuracies are not included.
1-9
HYDRA
Service Manual
Table 1-3. 2620A/2625A Specifications (cont)
Thermocouple Inputs (cont)
Input Impedance
100 MΩ minimum in parallel with 150 pF maximum
Common Mode and Normal Mode Rejection
See Specifications, DC Voltage Inputs
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
Open Thermocouple Detect
Small ac signal injection and detection scheme before each measurement detects greater than 1
to 4 kΩ as open. Performed on each channel unless defeated by computer command.
RTD Inputs
Type
DIN/IEC 751, 100Ω Platinum
1 Year, 4-Wire Accuracy (±°C)
RTD
Temperature
Resolution
18°C to 28°C
(°C)
Slow
Fast
Slow
Fast
Slow
Fast
-200.00
0.02
0.01
0.08
0.49
0.12
0.54
0.00
0.02
0.01
0.21
0.67
0.50
0.96
100.00
0.02
0.01
0.27
0.75
0.69
1.17
300.00
0.02
0.01
0.41
0.92
1.10
1.60
600.00
0.02
0.01
0.65
1.21
1.77
2.33
2-Wire Accuracy
Not specified
Maximum Current Through Sensor
1 mA
Typical Full Scale Voltage
0.22V
Maximum Open Circuit Voltage
3.2V
Maximum Sensor Temperature
600°C nominal
999.99°F is the maximum that can be displayed when using °F.
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
1-10
0°C to 60°C
Introduction and Specifications
Specifications
1
Table 1-3. 2620A/2625A Specifications (cont)
AC Voltage Inputs (True RMS AC Voltage, AC-Coupled Inputs)
Resolution
Range
Slow
Fast
Minimum Input for
Rated Accuracy
300 mV
10 µV
100 µV
20 mV
3V
100 µV
1 mV
200 mV
30V
1 mV
10 mV
2V
300V
10 mV
100 mV
20V
1 Year Accuracy ±(%±V)
Frequency
18°C to 28°C
SLow
0°C to 60°C
Fast
Slow
Fast
1.43% + 0.25 mV
0.30% + 0.25 mV
0.17% + 0.25 mV
0.37% + 0.25 mV
1.9% + 0.30 mV
5.0% + 0.50 mV
1.43% + 0.4 mV
0.30% + 0.4 mV
0.17% + 0.4mV
0.37% + 0.4mV
1.9% + 0.5 mV
5.0% + 1.0 mV
1.54% + 0.25 mV
0.41% + 0.25 mV
0.28% + 0.25 mV
0.68% + 0.25 mV
3.0% + 0.30 mV
7.0% + 0.50 mV
1.54% + 0.4 mV
0.41% + 0.4 mV
0.28% + 0.4 mV
0.68% + 0.4 mV
3.0% + 0.5 mV
7.0% + 1.0 mV
1.42% + 2.5 mV
0.29% + 2.5 mV
0.14% + 2.5 mV
0.22% + 2.5 mV
0.6% + 3.0 mV
1.0% + 5.0 mV
1.42% + 4 mV
0.29% + 4 mV
0.14% + 4 mV
0.22% + 4 mV
0.6% + 5 mV
1.0% + 10 mV
1.53% + 2.5 mV
0.40% + 2.5 mV
0.25% + 2.5 mV
0.35% + 2.5 mV
0.9% + 3.0 mV
1.4% + 5.0 mV
1.53% + 4 mV
0.40% + 4 mV
0.25% + 4 mV
0.35% + 4 mV
0.9% + 5 mV
1.4% + 10 mV
1.43% + 25 mV
0.29% + 25 mV
0.15% + 25 mV
0.22% + 25 mV
0.9% + 30 mV
2.0% + 50 mV
1.43% + 40 mV
0.29% + 40 mV
0.15% + 40 mV
0.22% + 40 mV
0.9% + 50 mV
2.0% + 100 mV
1.58% + 25 mV
0.45% + 25 mV
0.30% + 25 mV
0.40% + 25 mV
1.1% + 30 mV
2.2% + 50 mV
1.58% + 40 mV
0.45% + 40 mV
0.30% + 40 mV
0.40% + 40 mV
1.1% + 50 mV
2.2% + 100 mV
300 mV Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
3V Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
30V Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
300V Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
1.42% + 0.25V
0.29% + 0.25V
0.14% + 0.25V
0.22% + 0.25V
0.9% + 0.30V
2.5% + 0.50V
1.42% + 0.4V
0.29% + 0.4V
0.14% + 0.4V
0.22% + 0.4V
0.9% + 0.5V
2.5% + 1.0V
1.57% + 0.25V
0.44% + 0.25V
0.29% + 0.25V
0.38% + 0.25V
1.0% + 0.30V
2.6% + 0.50V
1.57% + 0.4V
0.44% + 0.4V
0.29% + 0.4V
0.38% + 0.4V
1.0% + 0.5V
2.6% + 1.0V
1-11
HYDRA
Service Manual
Table 1-3. 2620A/2625A Specifications (cont)
AC Voltage Inputs (True RMS AC Voltage, AC-Coupled Inputs) (cont)
Maximum Frequency
Input at Upper Frequency
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
300V rms
300V rms
200V rms
100V rms
40V rms
20V rms
Input Impedance
1 MΩ in parallel with 100 pF maximum
Maximum Crest Factor
3.0 maximum
2.0 for rated accuracy
Crest Factor Error
Non-sinusoidal input signals with crest factors between 2 and 3 and pulse widths 100 µs and
longer add 0.2% to the accuracy specifications.
Common Mode Rejection
80 dB minimum at 50 or 60 Hz ±0.1%, 1 kΩ imbalance, slow rate
Maximum AC Input
300V rms or 424V peak on channels 0, 1, and 11
150V rms or 212V peak on channels 2 to 10 and 12 to 20
Voltage ratings between channels must not be exceeded
6
2 x 10 Volt-Hertz product on any range, normal mode input
6
1 x 10 Volt-Hertz product on any range, common mode input
DC Component Error
SCAN and first MONitor measurements will be incorrect if the dc signal component exceeds 60
counts in slow rate or 10 counts in fast rate. To measure ac with a dc component present,
MONitor the input and wait 5 seconds before recording the measurement.
Using Channel 0
When measuring voltages above 100V rms, the rear Input Module must be installed to obtain the
rated accuracy.
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
1-12
Introduction and Specifications
Specifications
1
Table 1-3. 2620A/2625A Specifications (cont)
Ohms Input
Resolution
Range
Slow
Typical Full
Scale Voltage
Fast
Maximum Current
Through Unknown
Maximum Open
Circuit Voltage
300Ω
10 mΩ
0.1Ω
0.22V
1 mA
3.2V
3 kΩ
0.1Ω
1Ω
0.25V
110 µA
1.5V
30 kΩ
1Ω
10Ω
0.29V
13 µA
1.5V
300 kΩ
10Ω
100Ω
0.68V
3.2 µA
3.2V
3 MΩ
100Ω
1 kΩ
2.25V
3.2 µA
3.2V
10 MΩ
1 kΩ
10 kΩ
2.72V
3.2 µA
3.2V
4-Wire Accuracy ±(% ± Ω)
18°C to 28°C
Range
0°C to 60°C
90 Days, Slow
1 Year, Fast
1 Year, Fast
1 Year, Fast
1 Year, Fast
300Ω
0.056% + 20 mΩ
0.060% + 20 mΩ
0.060% + 0.2Ω
0.175% + 20 mΩ 0.175% + 0.2Ω
3 kΩ
0.053% + 0.2Ω
0.057% + 0.2Ω
0.057% + 2Ω
0.172% + 0.2Ω
0.172% + 2Ω
30 kΩ
0.055% + 2Ω
0.059% + 2Ω
0.059% + 20Ω
0.176% + 2Ω
0.176% + 20Ω
300 kΩ
0.053% + 20Ω
0.057% + 20Ω
0.057% + 200Ω
0.184% + 20Ω
0.184% + 200Ω
3 MΩ
0.059% + 200Ω
0.063% + 200Ω
0.063% + 2 kΩ
0.203% + 200Ω
0.203% + 2 kΩ
10 MΩ
0.115% + 2 kΩ
0.120% + 2 kΩ
0.200% + 30 kΩ
0.423% + 2 kΩ
0.423% + 30 kΩ
2-wire Accuracy
Not specified
Input Protection
300V dc or ac rms on all ranges
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
Frequency Inputs
Frequency Range
15 Hz to greater than 1 MHz
Range
15 Hz - 900 Hz
9 kHz
90 kHz
900 kHz
1 MHz
Accuracy ±(% ± Hz)
Resolution
Slow
Fast
0.01 Hz
0.1 Hz
1 Hz
10 Hz
100 Hz
0.1 Hz
1 Hz
10 Hz
100 Hz
1 Hz
Slow
0.05% + 0.02 Hz
0.05% + 0.1 Hz
0.05% + 1 Hz
0.05% + 10 Hz
0.05% + 100 Hz
Fast
0.05% + 0.2 Hz
0.05% + 1 Hz
0.05% + 10 Hz
0.05% + 100 Hz
0.05% + 1 kHz
1-13
HYDRA
Service Manual
Table 1-3. 2620A/2625A Specifications (cont)
Frequency Inputs (cont)
Sensitivity
Frequency
Level (sine Wave)
100 mV rms
150 mV rms
2V rms
NotSpecified
15 Hz - 100 kHz
100 kHz - 300 kHz
300 kHz - 1 MHz
Above 1 MHz
Maximum AC Input
300V rms or 424V peak on channels 0, 1, and 11
150V rms or 212V peak on channels 2 to 10 and 12 to 20
Voltage ratings between channels must not be exceeded
6
2 x 10 Volt-Hertz product on any range, normal mode input
6
1 x 10 Volt-Hertz product on any range, common mode input
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
Typical Scanning Rate
(Channels per Second, for 1, 10, and 20 Channel Scans with Shorted Inputs)
Function
Range
Channels:
1-14
Slow
Fast
1
10
20
1
10
20
VDC
300 mV
1.7
3.6
3.8
2.2
10.3
12.9
VDC
3V
1.7
3.6
3.8
2.2
10.3
12.9
VDC
30V
1.7
3.6
3.8
2.2
10.3
12.9
VDC
150/300V
1.7
3.5
3.8
2.2
10.2
12.8
VDC
AUTO
1.0
3.4
3.6
2.2
8.9
10.7
Temperature
J
1.5
3.1
3.5
1.9
9.5
12.1
Temperature
PT
1.0
2.5
2.6
1.7
4.2
4.5
VAC
300 mV
1.0
1.5
1.5
1.3
2.3
2.4
VAC
3V
1.0
1.5
1.5
1.3
2.3
2.4
VAC
30V
1.0
1.5
1.5
1.3
2.3
2.4
VAC
150/300V
1.0
1.5
1.5
1.3
2.3
2.4
VAC
AUTO
1.0
1.4
1.5
1.3
2.3
2.4
Ohms
300Ω
1.5
2.5
2.6
1.8
4.2
4.5
Ohms
3 kΩ
1.5
2.5
2.6
1.7
4.2
4.5
Ohms
30 kΩ
1.5
2.5
2.6
1.7
4.2
4.5
Ohms
300 kΩ
1.0
1.5
1.5
1.4
2.8
2.9
Ohms
3 MΩ
1.0
1.5
1.5
1.4
2.7
2.9
Ohms
10 MΩ
1.0
1.5
1.5
1.4
2.7
2.9
Ohms
AUTO
1.5
2.5
2.6
1.7
4.2
4.5
Frequency
any
0.5
0.6
0.7
0.6
0.7
0.7
Introduction and Specifications
Specifications
1
Table 1-3. 2620A/2625A Specifications (cont)
Maximum Autoranging Time (Seconds per Channel)
Function
VDC
VAC
Ohms
Range Change
Slow
Fast
300 mV to 150V
0.25
0.19
150V to 300 mV
0.25
0.18
300 mV to 150V
1.40
1.10
150V to 300 mV
1.40
1.10
300Ω to 10.0 MΩ
1.70
0.75
10.0 MΩ to 300Ω
1.70
0.60
Totalizing Inputs
Input Voltage
30V maximum
-4V minimum
2V peak minimum signal
Isolation
None
dc-coupled
Threshold
1.4V
Hysteresis
500 mV
Input Debouncing
None or 1.66 ms
Rate
0 to 5 kHz with debouncing off
Maximum Count
65,535
Digital Inputs
Input Voltage
30V maximum
-4V minimum
Isolation
None
dc-coupled
Threshold
1.4V
Hysteresis
500 mV
Trigger Inputs
Input Voltages
contact closure and TTL compatible
"high" = 2.0V min, 7.0V max
"low" = -0.6V min, 0.8V max
Isolation
None
dc-coupled
Minimum Pulse Width
5 µs
Maximum Frequency
5 Hz
Specified Conditions
The instrument must be in the quiescent state, with no interval scans in
process, no commands in the queue, no RS-232 or IEEE interface activity,
and no front panel activity if the latency and repeatability performance is to
be achieved. For additional information, refer to Section 5.
Maximum Latency
Latency is measured from the edge of the trigger input to the start of the first
channel measurement for the Specified Conditions (above).
480 ms for fast rate, scanning DCV, ACV, ohms, and frequency only
550 ms for fast rate, scanning any thermocouple or 100 mV dc channels
440 ms for slow rate, scanning DCV, ACV, ohms, and frequency only
890 ms for slow rate, scanning any thermocouple or 100 mV dc channels
Repeatability
3 ms for the Specified Conditions (above)
1-15
HYDRA
Service Manual
Table 1-3. 2620A/2625A Specifications (cont)
Digital and Alarm Outputs
Output Logic Levels
Logical "zero":
Logical "one":
0.8V max for an Iout of -1.0 mA (1 LSTTL load)
3.8V min for an Iout of 0.05 mA (1 LSTTL load)
For non-TTL loads:
Logical "zero":
Isolation
1.8V max for an Iout of -20 mA
3.25V max for an Iout of -50 mA
None
Real-Time Clock and Calendar
Accuracy
Within 1 minute per month for 0°C to 50°C range
Battery Life
10 years minimum for Operating Temperature range
Environmental
Warmup Time
1 hour to rated specifications
15 minutes when relative humidity is kept below 50% (non-condensing)
Operating Temperature
0°C to 60°C (32°F to 140°F)
Storage Temperature
-40°C to +75°C (-40°F to +167°F)
Instrument storage at low temperature extremes may necessitate adding
up to 0.008% to the dc voltage and ac voltage accuracy specifications.
Alternatively, any resulting shift can be compensated for by recalibrating
the instrument.
Relative Humidity
(Non-Condensing)
90% maximum for 0°C to 28°C (32°F to 82.4°F),
75% maximum for 28°C to 35°C (82.4°F to 95°F),
50% maximum for 35°C to 60°C (95°F to 140°F),
(Except 70% maximum for 0°C to 35°C (32°F to 95°F) for the 300 kΩ,
3 MΩ, and 10 MΩ ranges.)
Altitude
Operating:
Non-operating:
3,050m (10,000 ft) maximum
12,200m (40,000 ft) maximum
Vibration
0.7g at 15 Hz
1.3g at 25 Hz
3g at 55 Hz
Shock
30g half sine per Mil-T-28800
Bench handling per Mil-T-28800
General
Channel Capacity
21 Analog Inputs
4 Alarm Outputs
8 Digital I/O (Inputs/Outputs)
Measurement Speed
Slow rate:
Fast rate:
4 readings/second nominal
17 readings/second nominal
1.5 readings/second nominal for ACV and high-Ω inputs
For additional information, refer to Typical Scanning Rate and Maximum Autoranging Time.
1-16
Introduction and Specifications
Specifications
1
Table 1-3. 2620A/2625A Specifications (cont)
Memory Life
10 years minimum over Operating Temperature range Stores: real-time
clock, set-up configuration, and measurement data
Common Mode Voltage
300V dc or ac rms maximum from any analog input(channel) to earth
provided that channel to channel maximum voltage ratings are observed.
Voltage Ratings
Channels 0, 1, and 11 are rated at 300V dc or ac rms maximum from a
channel terminal to earth and from a channel terminal to any other
channel terminal.
Channels 2 to 10 and 12 to 20 are rated at 150V dc or ac rms maximum
from a channel terminal to any other channel terminal within channels 2
to 10 and 12 to 20.
Size
9.3 cm high, 21.6 cm wide, 31.2 cm deep
(3.67 in high, 8.5 in wide, 12.28 in deep)
Weight
Net, 2.95 kg (6.5 lbs)
Shipping, 4.0 kg (8.7 lbs)
Power
90 to 264V ac (no switching required), 50 and 60 Hz, 10 VA maximum 9V
dc to 16V dc, 10W maximum
If both sources are applied simultaneously, ac is used if it exceeds
approximately 8.3 times dc.
Automatic switchover occurs between ac and dc without interruption.(At
120V ac the equivalent dc voltage is ~14.5V.)
Standards
Complies with IEC 1010, UL 1244 and CSA Bulletin 556B.
Complies with ANSI/ISA-S82.01-1988 and CSA C22.2 No. 231 when
common mode voltages and channel 0, 1, and 11 inputs are restricted to
250V dc or ac rms maximum.
Complies with VDE 0871B when shielded cables are used.
Complies with FCC-15B, at the Class A level when shielded cables are
used.
RS-232-C
Connector:
9 pin male (DB-9P)
Signals:
TX, RX, DTR, GND
Modem Control:
full duplex
Baud rates:
300, 600, 1200, 2400, 4800, and 9600
Data format:
8 data bits, no parity bit, one stop bit, or
7 data bits, one parity bit (odd or even), one stop bit
Flow control:
XON/XOFF
Echo:
on/off
2625A Data Storage
Storage
2047 Scans
Each scan includes:
•
•
•
•
•
Time stamp
Readings for all defined analog input channels
Status of the four alarm outputs
Status of the eight digital I/O
Totalizer count
Memory
Battery-backed static RAM
Memory life:
5 years minimum at 25°C
1-17
HYDRA
Service Manual
Table 1-3. 2620A/2625A Specifications (cont)
2620A Options
IEEE-488 (Option -05K)
Capability codes:SH1, AH1, T5, L4, SR1, RL1, PP0, DC1, DT1, E1, TE0, LE0 and C0
Complies with IEEE-488.1 standard
Crosstalk Rejection
AC signals can have effects on other channels(crosstalk). These effects are discussed here by
measurement function. These numbers should only be considered as references. Since crosstalk
can be introduced into a measurement system in many places, each setup must be considered
individually.
The effect of crosstalk could be much better than shown for "Typical"; in extreme cases, the effect
could be worse than the "Worst Case" numbers.In general, the "Worst Case" information assumes
that none of the guidelines for minimizing crosstalk(Section 5) have been followed; the "Typical"
information assumes that the guidelines have been followed where reasonable.
These numbers assume that input L (low) is tied to earth ground; refer to "Using Shielded Wiring"
in Section 5. For dc volts and thermocouple temperature measurements, a source impedance of 1
kΩ in series with the H (high) input is assumed (except where otherwise noted.)
AC Signal Crosstalk in a DC Voltage Channel
 VDC (error ) 
DCV Error Tatio (CTRR) = 

 VAC rms 
Frequency
Worst case
50, 60 Hz, ±0.1%:
1.1 x 10
-7
Other Frequencies:
3.8 x 10
-6
Typical
2.0 x 10
-8
8.6 x 10
-7
For example, to find the typical effect of a 300V ac signal at 60 Hz on another channel for the 300
-8
mV range, you would calculate: 300 X 2.0 X 10 = 0.01 mV.
AC Signal Crosstalk into an AC Voltage Channel

VAC rms (error )

ACV Error Ratio = 

 VAC rms (crosstalk ) x Frequency (crosstalk ) 
Range
Ratio (worst case)
-8

V

-7

V

-6

V

-5

V

300.00 mV
4.8 x 10 

 V x Hz 
3.0000V
1.1 x 10 

 V x Hz 
30.000V
1.2 x 10 

 V x Hz 
150.00/300.00V
1.2 x 10 

 V x Hz 
Ratio (typical)
-8

V

-8

V

-7

V

-6

V

1.4 x 10 

 V x Hz 
3.0 x 10 

 V x Hz 
2.6 x 10 

 V x Hz 
3.4 x 10 

 V x Hz 
For example, to find the typical effect of a 60 Hz, 220V ac signal on another channel for the the 300
-8
mV range, you would calculate: 220 X 60 X 1.4 X 10 = 0.18 mV.
1-18
Introduction and Specifications
Specifications
1
Table 1-3. 2620A/2625A Specifications (cont)
AC Signal Crosstalk into an Ohms Channel
AC Frequency = 50, 60 Hz, ±0.1%

Ohmss (error )

OHMS Error Ratio = 

 VAC rms (crosstalk ) 
Range
Ratio (worst case)
-5
 Ohms 
-6
 kOhms 
-4
 kOhms 
-3
 kOhms 
-4
 MOhms 
-3
 MOhms 
300.00Ω
3.3 x 10 

 VAC rms 
3.000 kΩ
2.4 x 10 

 VAC rms 
30.000 kΩ
3.1 x 10 

 VAC rms 
300.00 kΩ
5.6 x 10 

 VAC rms 
3.0000 MΩ
3.8 x 10 

 VAC rms 
10.000 MΩ
1.4 x 10 

 VAC rms 
Ratio (typical)
No Effect
-7
 kOhms 
-5
 kOhms 
-3
 kOhms 
-5
 MOhms 
-4
 MOhms 
6.7 x 10 

 VAC rms 
8.4 x 10 

 VAC rms 
3.7 x 10 

 VAC rms 
3.8 x 10 

 VAC rms 
4.3 x 10 

 VAC rms 
For example, to find the typical effect of a 60 Hz, 100V ac signal on another channel for the 30 kΩ
-5
range, you would calculate: 100 X 8.4 X 10 = 0.008 kΩ.
AC Signal Crosstalk into a Temperature Channel
Frequency = 50, 60 Hz

° C (error )

Temperature Error Ratio = 

 VAC rms (crosstalk ) 
Type
Worst case
Typical
-3

°C

-2

°C

-5

°C

Types J, K, E, T, N:
2.7 x 10 

 VAC rms 
Types R, S, B, C:
1.1 x 10 

 VAC rms 
Type PT (RTD):
8.6 x 10 

 VAC rms 
-4

°C

-3

°C

5.0 x 10 

 VAC rms 
2.0 x 10 

 VAC rms 
No Effect
AC Signal Crosstalk into a Frequency Channel
Frequency measurements are unaffected by crosstalk as long as the voltage-frequency product is kept
below the following limits:
V x Hz Product Limit
1
Worst Case
Typical
4
1.0 x 10 (V x Hz)
3.7 x 10 (V x Hz)
6
These valkues assu;me no more than 1000 pF of capacitance between either end of the resistor (HI and LOW) and earth groung.
1-19
HYDRA
Service Manual
Table 1-4. 2635A Specifications
The instrument specifications presented here are applicable within the conditions listed in the
Environmental portion of this specification.
The specifications state total instrument accuracy following calibration, including:
• A/D errors
• Linearization conformity
• Initial calibration errors
• Isothermality errors
• Relay thermal emf’s
• Reference junction conformity
• Temperature coefficients
• Humidity errors
Sensor inaccuracies are not included in the accuracy figures.
Accuracies at Temperatures Other Than Specified
To determine typical accuracies at temperatures intermediate to those listed in the specification
tables, linearly interpolate between the applicable 0°C to 60°C and 18°C to 28°C accuracy
specifications.
Response Times
Refer to Typical Scanning Rate and Maximum Autoranging Time later in this table.
DC Voltage Inputs
Resolution
Range
Slow
Fast
90 mV*
1 µV
10 µV
300 mV
10 µV
0.1 mV
3V
0.1 mV
1 mV
30V
1 mV
10 mV
150/300V
10 mV
0.1V
900V* **
10 µV
0.1 mV
Accuracy ±(% ±V)
Range
18°C to 28°C
90 Days, Slow
90 mV*
0.29% + 7µV
0°C to 60°C
1 Year, Slow
0.034% + 7 µV
1 Year, Fast
0.054% + 20 µV
0.074% + 7 µV
1 Year, Fast
0.094% + 20 µV
300 mV
0.026% + 20 µV
0.031% + 20 µV
0.047% + 0.2 mV
0.070% + 20 µV
0.087% + 0.2 mV
3V
0.028% + 0.2 mV
0.033% + 0.2 mV
0.050% + 2 mV
0.072% + 0.2 mV
0.089% + 2 mV
30V
0.024% + 2 mV
0.029% + 2 mV
0.046% + 20 mV
0.090% + 2 mV
0.107% + 20 mV
150/300V 0.023% + 20 mV
0.028% + 20 mV
0.045% + 0.2V
0.090% + 20 mV
0.107% + 0.2V
0.026% + 20 µV
0.031% + 21 µV
0.047% + 0.2 mV
0.070% + 20 µV
0.087% +0.2 mV
900 mV
* Not used in Autoranging.
** Computer interface only (see FUNC command).
1-20
1 Year, Slow
Introduction and Specifications
Specifications
1
Table 1-4. 2635A Specifications (cont)
Input Impedance
100 MΩ minimum in parallel with 150 pF maximum for all ranges 3V and below 10 MΩ in parallel
with 100 pF maximum for the 30V and 300V ranges.
Normal Mode Rejection
53 dB minimum at 60 Hz ±0.1%, slow rate
47 dB minimum at 50 Hz ±0.1%, slow rate
Common Mode Rejection
120 dB minimum at dc, 1 kΩ imbalance, slow rate
120 dB minimum at 50 or 60 Hz ±0.1%, 1 kΩ imbalance, slow rate
Maximum Input
300V dc or ac rms on any range for channels 0, 1, and 11
150V dc or ac rms for channels 2 to 10 and 12 to 20
Voltage ratings between channels must not be exceeded
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of Table 1-3.
1-21
HYDRA
Service Manual
Table 1-4. 2635A Specifications (cont)
Thermocouple Inputs
Temperature Measurements - Accuracy (Thermocouples) (IPTS-68)
Accuracy (±°C)*
Thermocouple
18°C to 28°C
Type
Temperature
(°C)
90 Days
Slow
1 Year
Slow
1 Year
Fast
1 Year
Slow
1 Year
Fast
J
-100 to -30
-30 to 150
150 to 760
0.44
0.40
0.52
0.45
0.42
0.56
0.87
0.78
0.99
0.54
0.58
0.92
1.05
1.00
1.39
-100 to -25
-25 to 120
120 to 1000
1000 to 1372
0.53
0.46
0.94
1.24
0.54
0.47
1.00
1.34
1.08
0.92
1.66
2.16
0.64
0.63
1.54
2.11
1.27
1.14
2.27
3.01
-100 to -25
-25 to 120
120 to 410
410 to 1372
0.65
0.57
0.54
1.16
0.66
0.58
0.56
1.23
1.39
1.20
1.10
1.93
0.75
0.70
0.77
1.83
1.57
1.37
1.32
2.58
-100 to -25
-25 to 350
350 to 650
650 to 1000
0.44
0.43
0.49
0.78
0.46
0.45
0.53
0.85
0.86
0.76
0.89
1.31
0.55
0.66
0.85
1.34
1.05
1.02
1.27
1.85
T
-150 to 0
0 to 120
120 to 400
0.72
0.48
0.45
0.73
0.49
0.48
1.46
0.93
0.82
0.83
0.60
0.68
1.68
1.11
1.07
R
250 to 400
400 to 1000
1000 to 1767
1.02
1.09
1.60
1.04
1.13
1.69
2.54
2.37
3.08
1.17
1.49
2.39
2.71
2.71
3.80
S
250 to 1000
1000 to 1400
1400 to 1767
1.19
1.43
1.78
1.24
1.49
1.88
2.70
2.86
3.48
1.26
2.01
2.61
3.00
3.40
4.25
B
600 to 1200
1200 to 1550
1550 to 1820
1.42
1.36
1.62
1.43
1.40
1.68
3.67
2.70
3.06
1.57
1.78
2.17
3.82
3.09
3.55
C
0 t 150
150 to 650
650 to 1000
1000 to 1800
1800 to 2316
0.81
0.81
1.05
2.04
3.29
0.82
0.85
1.11
2.17
3.51
1.90
1.71
2.10
3.69
5.87
0.93
1.16
1.59
3.19
5.26
2.08
2.07
2.63
4.78
7.72
K
N
E
* Sensor inaccuracies are not included.
1-22
0°C to 60°C
Introduction and Specifications
Specifications
1
Table 1-4. 2635A Specifications (cont)
Thermocouple Inputs
Temperature Measurements - Accuracy (Thermocouples) (ITS-90)
Accuracy (±°C)*
Thermocouple
18°C to 28°C
0°C to 60°C
Type
Temperature
(°C)
90 Days
Slow
1 Year
Slow
1 Year
Fast
1 Year
Slow
1 Year
Fast
J
-100 to -30
-30 to 150
150 to 760
0.44
0.41
0.51
0.45
0.43
0.55
0.88
0.79
0.98
0.54
0.59
0.91
1.06
1.01
1.39
-100 to -25
-25 to 120
120 to 1000
1000 to 1372
0.54
0.47
0.75
1.11
0.55
0.49
0.82
1.21
1.10
0.94
1.47
2.03
0.65
0.65
1.35
1.98
1.28
1.16
2.08
2.88
-100 to -25
-25 to 120
120 to 410
410 to 1300
0.66
0.57
0.51
0.81
0.67
0.58
0.53
0.88
1.41
1.20
1.07
1.58
0.77
0.69
0.67
1.48
1.58
1.37
1.27
2.23
-100 to -25
-25 to 350
350 to 650
650 to 1000
0.46
0.40
0.49
0.59
0.47
0.41
0.53
0.65
0.87
0.75
0.89
1.11
0.57
0.62
0.86
1.34
1.06
0.98
1.27
1.65
T
-150 to 0
0 to 120
120 to 400
0.70
0.48
0.40
0.72
0.49
0.43
1.45
0.93
0.78
0.82
0.60
0.63
1.67
1.11
1.02
R
250 to 400
400 to 1000
1000 to 1767
0.96
0.92
1.17
0.98
0.94
1.26
2.48
2.32
2.69
1.13
1.27
1.98
2.66
2.54
3.43
S
250 to 1000
1000 to 1400
1400 to 1767
1.01
1.03
1.32
1.03
1.09
1.41
2.61
2.45
3.06
1.39
1.61
2.17
2.80
3.00
3.85
B
600 to 1200
1200 to 1550
1550 to 1820
1.30
0.90
1.01
1.31
0.94
1.07
3.56
2.32
2.44
1.45
1.31
1.56
3.71
2.62
2.94
C
0 t 150
150 to 650
650 to 1000
1000 to 1800
1800 to 2316
0.80
0.71
0.86
1.42
2.34
0.81
0.75
0.92
1.55
2.56
1.89
1.62
1.90
3.07
4.92
0.92
1.06
1.39
2.57
4.32
2.07
1.97
2.43
4.16
6.78
K
N
E
* Sensor inaccuracies are not included.
1-23
HYDRA
Service Manual
Table 1-4. 2635A Specifications (cont)
Thermocouple Inputs (cont)
Input Impedance
100 MΩ minimum in parallel with 150 pF maximum
Common Mode and Normal Mode Rejection
See Specifications, DC Voltage Inputs
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of Table 1-3.
Open Thermocouple Detect
Small ac signal injection and detection scheme before each measurement detects greater than 1
to 4 kΩ as open. Performed on each channel unless defeated by computer command.
RTD Inputs
Type
DIN/IEC 751, 100Ω Platinum
1 Year, 4-Wire Accuracy (±°C)
RTD
Temperature
Resolution
18°C to 28°C
(°C)
Slow
Fast
Slow
Fast
Slow
Fast
-200.00
0.02
0.01
0.08
0.49
0.12
0.54
0.00
0.02
0.01
0.21
0.67
0.50
0.96
100.00
0.02
0.01
0.27
0.75
0.69
1.17
300.00
0.02
0.01
0.41
0.92
1.10
1.60
600.00
0.02
0.01
0.65
1.21
1.77
2.33
2-Wire Accuracy
Not specified
Maximum Current Through Sensor
1 mA
Typical Full Scale Voltage
0.22V
Maximum Open Circuit Voltage
3.2V
Maximum Sensor Temperature
600°C nominal
999.99°F is the maximum that can be displayed when using °F.
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
1-24
0°C to 60°C
Introduction and Specifications
Specifications
1
Table 1-4. 2635A Specifications (cont)
AC Voltage Inputs (True RMS AC Voltage, AC-Coupled Inputs)
Resolution
Range
Slow
Fast
Minimum Input for
Rated Accuracy
300 mV
10 µV
100 µV
20 mV
3V
100 µV
1 mV
200 mV
30V
1 mV
10 mV
2V
150/300V
10 mV
100 mV
20V
1 Year Accuracy ±(%±V)
Frequency
18°C to 28°C
SLow
0°C to 60°C
Fast
Slow
Fast
1.43% + 0.25 mV
0.30% + 0.25 mV
0.17% + 0.25 mV
0.37% + 0.25 mV
1.9% + 0.30 mV
5.0% + 0.50 mV
1.43% + 0.4 mV
0.30% + 0.4 mV
0.17% + 0.4mV
0.37% + 0.4mV
1.9% + 0.5 mV
5.0% + 1.0 mV
1.54% + 0.25 mV
0.41% + 0.25 mV
0.28% + 0.25 mV
0.68% + 0.25 mV
3.0% + 0.30 mV
7.0% + 0.50 mV
1.54% + 0.4 mV
0.41% + 0.4 mV
0.28% + 0.4 mV
0.68% + 0.4 mV
3.0% + 0.5 mV
7.0% + 1.0 mV
1.42% + 2.5 mV
0.29% + 2.5 mV
0.14% + 2.5 mV
0.22% + 2.5 mV
0.6% + 3.0 mV
1.0% + 5.0 mV
1.42% + 4 mV
0.29% + 4 mV
0.14% + 4 mV
0.22% + 4 mV
0.6% + 5 mV
1.0% + 10 mV
1.53% + 2.5 mV
0.40% + 2.5 mV
0.25% + 2.5 mV
0.35% + 2.5 mV
0.9% + 3.0 mV
1.4% + 5.0 mV
1.53% + 4 mV
0.40% + 4 mV
0.25% + 4 mV
0.35% + 4 mV
0.9% + 5 mV
1.4% + 10 mV
1.43% + 25 mV
0.29% + 25 mV
0.15% + 25 mV
0.22% + 25 mV
0.9% + 30 mV
2.0% + 50 mV
1.43% + 40 mV
0.29% + 40 mV
0.15% + 40 mV
0.22% + 40 mV
0.9% + 50 mV
2.0% + 100 mV
1.58% + 25 mV
0.45% + 25 mV
0.30% + 25 mV
0.40% + 25 mV
1.1% + 30 mV
2.2% + 50 mV
1.58% + 40 mV
0.45% + 40 mV
0.30% + 40 mV
0.40% + 40 mV
1.1% + 50 mV
2.2% + 100 mV
300 mV Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
3V Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
30V Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
300V Range
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
1.42% + 0.25V
0.29% + 0.25V
0.14% + 0.25V
0.22% + 0.25V
0.9% + 0.30V
2.5% + 0.50V
1.42% + 0.4V
0.29% + 0.4V
0.14% + 0.4V
0.22% + 0.4V
0.9% + 0.5V
2.5% + 1.0V
1.57% + 0.25V
0.44% + 0.25V
0.29% + 0.25V
0.38% + 0.25V
1.0% + 0.30V
2.6% + 0.50V
1.57% + 0.4V
0.44% + 0.4V
0.29% + 0.4V
0.38% + 0.4V
1.0% + 0.5V
2.6% + 1.0V
1-25
HYDRA
Service Manual
Table 1-4. 2635A Specifications (cont)
AC Voltage Inputs (True RMS AC Voltage, AC-Coupled Inputs) (cont)
Maximum Frequency
Input at Upper Frequency
20 Hz - 50 Hz
50 Hz - 100 Hz
100 Hz - 10 kHz
10 kHz - 20 kHz
20 kHz - 50 kHz
50 kHz - 100 kHz
300V rms
300V rms
200V rms
100V rms
40V rms
20V rms
Input Impedance
1 MΩ in parallel with 100 pF maximum
Maximum Crest Factor
3.0 maximum
2.0 for rated accuracy
Crest Factor Error
Non-sinusoidal input signals with crest factors between 2 and 3 and pulse widths 100 µs and
longer add 0.2% to the accuracy specifications.
Common Mode Rejection
80 dB minimum at 50 or 60 Hz ±0.1%, 1 kΩ imbalance, slow rate
Maximum AC Input
300V rms or 424V peak on channels 0, 1, and 11
150V rms or 212V peak on channels 2 to 10 and 12 to 20
Voltage ratings between channels must not be exceeded
6
2 x 10 Volt-Hertz product on any range, normal mode input
6
1 x 10 Volt-Hertz product on any range, common mode input
DC Component Error
SCAN and first MONitor measurements will be incorrect if the dc signal component exceeds 60
counts in slow rate or 10 counts in fast rate. To measure ac with a dc component present,
MONitor the input and wait 5 seconds before recording the measurement.
Using Channel 0
When measuring voltages above 100V rms, the rear Input Module must be installed to obtain the
rated accuracy.
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of Table 1-3.
1-26
Introduction and Specifications
Specifications
1
Table 1-4. 2635A Specifications (cont)
Ohms Input
Resolution
Range
Slow
Typical Full
Scale Voltage
Fast
Maximum Current
Through Unknown
Maximum Open
Circuit Voltage
300Ω
10 mΩ
0.1Ω
0.22V
1 mA
3.2V
3 kΩ
0.1Ω
1Ω
0.25V
110 µA
1.5V
30 kΩ
1Ω
10Ω
0.29V
13 µA
1.5V
300 kΩ
10Ω
100Ω
0.68V
3.2 µA
3.2V
3 MΩ
100Ω
1 kΩ
2.25V
3.2 µA
3.2V
10 MΩ
1 kΩ
10 kΩ
2.72V
3.2 µA
3.2V
4-Wire Accuracy ±(% ± Ω)
18°C to 28°C
Range
0°C to 60°C
90 Days, Slow
1 Year, Fast
1 Year, Fast
1 Year, Fast
1 Year, Fast
300Ω
0.056% + 20 mΩ
0.060% + 20 mΩ
0.060% + 0.2Ω
0.175% + 20 mΩ 0.175% + 0.2Ω
3 kΩ
0.053% + 0.2Ω
0.057% + 0.2Ω
0.057% + 2Ω
0.172% + 0.2Ω
0.172% + 2Ω
30 kΩ
0.055% + 2Ω
0.059% + 2Ω
0.059% + 20Ω
0.176% + 2Ω
0.176% + 20Ω
300 kΩ
0.053% + 20Ω
0.057% + 20Ω
0.057% + 200Ω
0.184% + 20Ω
0.184% + 200Ω
3 MΩ
0.059% + 200Ω
0.063% + 200Ω
0.063% + 2 kΩ
0.203% + 200Ω
0.203% + 2 kΩ
10 MΩ
0.115% + 2 kΩ
0.120% + 2 kΩ
0.200% + 30 kΩ
0.423% + 2 kΩ
0.423% + 30 kΩ
2-wire Accuracy
Not specified
Input Protection
300V dc or ac rms on all ranges
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of Table 1-3.
Frequency Inputs
Frequency Range
15 Hz to greater than 1 MHz
Range
15 Hz - 900 Hz
9 kHz
90 kHz
900 kHz
1 MHz
Accuracy ±(% ± Hz)
Resolution
Slow
Fast
0.01 Hz
0.1 Hz
1 Hz
10 Hz
100 Hz
0.1 Hz
1 Hz
10 Hz
100 Hz
1 Hz
Slow
0.05% + 0.02 Hz
0.05% + 0.1 Hz
0.05% + 1 Hz
0.05% + 10 Hz
0.05% + 100 Hz
Fast
0.05% + 0.2 Hz
0.05% + 1 Hz
0.05% + 10 Hz
0.05% + 100 Hz
0.05% + 1 kHz
1-27
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Service Manual
Table 1-4. 2635A Specifications (cont)
Frequency Inputs (cont)
Sensitivity
Frequency
Level (sine Wave)
100 mV rms
150 mV rms
2V rms
NotSpecified
15 Hz - 100 kHz
100 kHz - 300 kHz
300 kHz - 1 MHz
Above 1 MHz
Maximum AC Input
300V rms or 424V peak on channels 0, 1, and 11
150V rms or 212V peak on channels 2 to 10 and 12 to 20
Voltage ratings between channels must not be exceeded
6
2 x 10 Volt-Hertz product on any range, normal mode input
6
1 x 10 Volt-Hertz product on any range, common mode input
Crosstalk Rejection
Refer to "Crosstalk Rejection" at the end of this table.
Typical Scanning Rate
Function
Range
Channels:
1-28
Slow
Fast
1
10
20
1
10
20
VDC
300 mV
1.7
3.6
3.8
2.2
10.3
12.9
VDC
3V
1.7
3.6
3.8
2.2
10.3
12.9
VDC
30V
1.7
3.6
3.8
2.2
10.3
12.9
VDC
150/300V
1.7
3.5
3.8
2.2
10.2
12.8
VDC
AUTO
1.0
3.4
3.6
2.2
8.9
10.7
Temperature
J
1.5
3.1
3.5
1.9
9.5
12.1
Temperature
PT
1.0
2.5
2.6
1.7
4.2
4.5
VAC
300 mV
1.0
1.5
1.5
1.3
2.3
2.4
VAC
3V
1.0
1.5
1.5
1.3
2.3
2.4
VAC
30V
1.0
1.5
1.5
1.3
2.3
2.4
VAC
150/300V
1.0
1.5
1.5
1.3
2.3
2.4
VAC
AUTO
1.0
1.4
1.5
1.3
2.3
2.4
Ohms
300Ω
1.5
2.5
2.6
1.8
4.2
4.5
Ohms
3 kΩ
1.5
2.5
2.6
1.7
4.2
4.5
Ohms
30 kΩ
1.5
2.5
2.6
1.7
4.2
4.5
Ohms
300 kΩ
1.0
1.5
1.5
1.4
2.8
2.9
Ohms
3 MΩ
1.0
1.5
1.5
1.4
2.7
2.9
Ohms
10 MΩ
1.0
1.5
1.5
1.4
2.7
2.9
Ohms
AUTO
1.5
2.5
2.6
1.7
4.2
4.5
Frequency
any
0.5
0.6
0.7
0.6
0.7
0.7
Introduction and Specifications
Specifications
1
Table 1-4. 2635A Specifications (cont)
Maximum Autoranging Time (Seconds per Channel)
Function
VDC
VAC
Ohms
Range Change
Slow
Fast
300 mV to 150V
0.25
0.19
150V to 300 mV
0.25
0.18
300 mV to 150V
1.40
1.10
150V to 300 mV
1.40
1.10
300Ω to 10.0 MΩ
1.70
0.75
10.0 MΩ to 300Ω
1.50
0.60
Totalizing Inputs
Input Voltage
30V maximum
-4V minimum
2V peak minimum signal
Isolation
None
dc-coupled
Threshold
1.4V
Hysteresis
500 mV
Input Debouncing
None or 1.75 ms
Rate
0 to 5 kHz with debouncing off
Maximum Count
65,535
Digital Inputs
Input Voltage
30V maximum
-4V minimum
Isolation
None
dc-coupled
Threshold
1.4V
Hysteresis
500 mV
Trigger Inputs
Input Voltages
contact closure and TTL compatible
"high" = 2.0V min, 7.0V max
"low" = -0.6V min, 0.8V max
Isolation
None
dc-coupled
Minimum Pulse Width
5 µs
Maximum Frequency
5 Hz
Specified Conditions
The instrument must be in the quiescent state, with no interval scans in
process, no commands in the queue, no RS-232 or IEEE interface activity,
and no front panel activity if the latency and repeatability performance is to
be achieved. For additional information, refer to Section 5.
Maximum Latency
Latency is measured from the edge of the trigger input to the start of the first
channel measurement for the Specified Conditions (above).
540 ms for fast rate, scanning DCV, ACV, ohms, and frequency only
610 ms for fast rate, scanning any thermocouple or 100 mV dc channels
500 ms for slow rate, scanning DCV, ACV, ohms, and frequency only
950 ms for slow rate, scanning any thermocouple or 100 mV dc channels
Repeatability
3 ms for the Specified Conditions (above)
1-29
HYDRA
Service Manual
Table 1-4. 2635A Specifications (cont)
Digital and Alarm Outputs
Output Logic Levels
Logical "zero":
Logical "one":
0.8V max for an Iout of -1.0 mA (1 LSTTL load)
3.8V min for an Iout of 0.05 mA (1 LSTTL load)
For non-TTL loads:
Logical "zero":
Isolation
1.8V max for an Iout of -20 mA
3.25V max for an Iout of -50 mA
None
Real-Time Clock and Calendar
Accuracy
Within 1 minute per month for 0°C to 50°C range
Battery Life
>10 unpowered instrument years for 0°C to 28°C (32°F to 82.4°F).
>3 unpowered instrument years for 0°C to 50°C (32°F to 122°F).
>2 unpowered instrument years for 50°C to 70°C (122°F to 158°F).
Environmental
Warmup Time
1 hour to rated specifications
15 minutes when relative humidity is kept below 50% (non-condensing)
Operating Temperature
0°C to 60°C (32°F to 140°F)
Storage Temperature
-40°C to +70°C (-40°F to +158°F)
Instrument storage at low temperature extremes may necessitate adding
up to 0.008% to the dc voltage and ac voltage accuracy specifications.
Alternatively, any resulting shift can be compensated for by recalibrating
the instrument.
Relative Humidity
(Non-Condensing)
90% maximum for 0°C to 28°C (32°F to 82.4°F),
75% maximum for 28°C to 35°C (82.4°F to 95°F),
50% maximum for 35°C to 60°C (95°F to 140°F),
(Except 70% maximum for 0°C to 35°C (32°F to 95°F) for the 300 kΩ,
3 MΩ, and 10 MΩ ranges.)
Altitude
Operating:
Non-operating:
1-30
3,050m (10,000 ft) maximum
12,200m (40,000 ft) maximum
Vibration
0.7g at 15 Hz
1.3g at 25 Hz
3g at 55 Hz
Shock
30g half sine per Mil-T-28800
Bench handling per Mil-T-28800
Introduction and Specifications
Specifications
1
Table 1-4. 2635A Specifications (cont)
General
Channel Capacity
21 Analog Inputs
4 Alarm Outputs
8 Digital I/O (Inputs/Outputs)
Measurement Speed
Slow rate:
Fast rate:
4 readings/second nominal
17 readings/second nominal
1.5 readings/second nominal for ACV and high-Ω inputs
For additional information, refer to Typical Scanning Rate and Maximum Autoranging Time.
Nonvolatile Memory Life
>10 unpowered instrument years for 0°C to 28°C (32°F to 82.4°F).
>3 unpowered instrument years for 0°C to 50°C (32°F to 122°F).
>2 unpowered instrument years for 50°C to 70°C (122°F to 158°F).
Common Mode Voltage
300V dc or ac rms maximum from any analog input(channel) to earth
provided that channel to channel maximum voltage ratings are observed.
Voltage Ratings
Channels 0, 1, and 11 are rated at 300V dc or ac rms maximum from a
channel terminal to earth and from a channel terminal to any other
channel terminal.
Channels 2 to 10 and 12 to 20 are rated at 150V dc or ac rms maximum
from a channel terminal to any other channel terminal within channels 2
to 10 and 12 to 20.
Size
9.3 cm high, 21.6 cm wide, 31.2 cm deep
(3.67 in high, 8.5 in wide, 12.28 in deep)
Weight
Net, 2.95 kg (6.5 lbs)
Shipping, 4.0 kg (8.7 lbs)
Power
90 to 264V ac (no switching required), 50 and 60 Hz, 10 VA maximum 9V
dc to 16V dc, 10W maximum
If both sources are applied simultaneously, ac is used if it exceeds
approximately 8.3 times dc.
Automatic switchover occurs between ac and dc without interruption.(At
120V ac the equivalent dc voltage is ~14.5V.)
Standards
Complies with IEC 1010, UL 1244 and CSA Bulletin 556B.
Complies with ANSI/ISA-S82.01-1988 and CSA C22.2 No. 231 when
common mode voltages and channel 0, 1, and 11 inputs are restricted to
250V dc or ac rms maximum.
Complies with VDE 0871B when shielded cables are used.
Complies with FCC-15B, at the Class A level when shielded cables are
used.
RS-232-C
Connector:
9 pin male (DB-9P)
Signals:
TX, RX, DTR, DSR, RTS, CTS, GND
Modem Control:
full duplex
Baud rates:
300, 600, 1200, 2400, 4800, 9600, 19200, AND 38400
Data format:
8 data bits, no parity bit, one stop bit, or
7 data bits, one parity bit (odd or even), one stop bit
Flow control:
XON/XOFF (Software) and CTS (Hardware)
Echo:
on/off
1-31
HYDRA
Service Manual
1-32
Chapter 2
Theory of Operation (2620A/2625A)
Title
2-1.
2-2.
2-3.
2-4.
2-5.
2-6.
2-7.
2-8.
2-9.
2-10.
2-11.
2-12.
2-13.
2-14.
2-15.
2-16.
2-17.
2-18.
2-19.
2-20.
2-21.
2-22.
2-23.
2-24.
2-32.
2-43.
2-44.
2-45.
2-46.
Introduction ..........................................................................................
Functional Block Description...............................................................
Main PCA Circuitry.........................................................................
Power Supply...............................................................................
Digital Kernel ..............................................................................
Serial Communication (Guard Crossing) ....................................
Digital Inputs and Outputs...........................................................
A/D Converter PCA .........................................................................
Analog Measurement Processor ..................................................
Input Protection Circuitry............................................................
Input Signal Conditioning............................................................
Analog-to-Digital (A/D) Converter .............................................
Inguard Microcontroller Circuitry ...............................................
Channel Selection Circuitry.........................................................
Open Thermocouple Check Circuitry..........................................
Input Connector Assembly...............................................................
20 Channel Terminals..................................................................
Reference Junction Temperature.................................................
Display PCA ....................................................................................
Memory PCA (2625A Only)............................................................
IEEE-488 Option (-05).....................................................................
Detailed Circuit Description ................................................................
Main PCA ........................................................................................
Power Supply Circuit Description...............................................
Digital Kernel ..............................................................................
Digital I/O....................................................................................
Digital Input Threshold 2-1. ........................................................
Digital Input Buffers....................................................................
Digital and Alarm Output Drivers ...............................................
Page
2-3
2-3
2-3
2-3
2-3
2-6
2-6
2-6
2-6
2-6
2-6
2-6
2-6
2-7
2-7
2-7
2-7
2-7
2-7
2-7
2-7
2-7
2-7
2-8
2-10
2-14
2-15
2-15
2-15
2-1
HYDRA
Service Manual
2-47.
2-48.
2-49.
2-50.
2-51.
2-52.
2-58.
2-59.
2-60.
2-61.
2-62.
2-63.
2-64.
2-65.
2-66.
2-67.
2-68.
2-69.
2-70.
2-71.
2-72.
2-73.
2-74.
2-75.
2-76.
2-77.
2-2
Totalizer Input .............................................................................
External Trigger Input Circuits....................................................
A/D Converter PCA .........................................................................
Analog Measurement Processor ..................................................
Input Protection ...........................................................................
Input Signal Conditioning............................................................
Passive and Active Filters............................................................
A/D Converter .............................................................................
Inguard Microcontroller Circuitry ...............................................
Channel Selection Circuitry.........................................................
Open Thermocouple Check .........................................................
Input Connector PCA.......................................................................
Display PCA ....................................................................................
Main PCA Connector ..................................................................
Front Panel Switches ...................................................................
Display.........................................................................................
Beeper Drive Circuit....................................................................
Watchdog Timer and Reset Circuit .............................................
Display Controller .......................................................................
Memory PCA (2625A Only)............................................................
Main PCA Connector ..................................................................
Address Decoding........................................................................
Page Register ...............................................................................
Byte Counter................................................................................
Nonvolatile Memory....................................................................
IEEE-488 Interface (Option -05)......................................................
2-16
2-16
2-16
2-16
2-17
2-20
2-25
2-26
2-27
2-27
2-28
2-28
2-29
2-29
2-29
2-30
2-30
2-30
2-31
2-33
2-33
2-33
2-33
2-34
2-34
2-34
Theory of Operation (2620A/2625A)
Introduction
2
2-1. Introduction
The theory of operation begins with a general overview of the instrument and progresses
to a detailed description of the circuits of each pca.
The instrument is first described in general terms with a Functional Block Description.
Then, each block is detailed further (often to the component level) with Detailed Circuit
Descriptions. Refer to Section 8 of this manual for full schematic diagrams. The
Interconnect Diagram in this section (Figure 2-1) illustrates physical connections among
pca’s.
Signal names followed by a ’*’ are active (asserted) low. All other signals are active high.
2-2. Functional Block Description
Refer to Figure 2-2, Overall Functional Block Diagram, during the following functional
block descriptions.
2-3.
Main PCA Circuitry
The following paragraphs describe the major circuit blocks on the Main PCA.
2-4.
Power Supply
The Power Supply functional block provides voltages required by the vacuumfluorescent display (-30V dc, -5.0V dc, and filament voltage of 5.4V ac), the inguard
circuitry (-5.4V dc VSS, +5.3V dc VDD, and +5.6V dc VDDR), and outguard digital
circuitry of +5.1V dc (VCC).
Within the Power Supply, the Raw DC Supply converts ac line voltage to dc levels. The
5V Switching Supply converts this raw dc to 5.1V ±0.25V dc, which is used by the
Inverter in generating the above-mentioned outputs. The Power Fail Detector monitors
the Raw DC Supply and provides a power supply status signal to the Microprocessor in
the Digital Kernel.
2-5.
Digital Kernel
The Digital Kernel functional block is responsible for the coordination of all activities
within the instrument. This block requires power supply voltages from the Power Supply
and reset signals from the Display Assembly.
Specifically, the Digital Kernel Microprocessor performs the following functions:
• Executes the instructions in ROM.
• Stores temporary data in RAM.
• Stores instrument configuration and calibration data in nonvolatileRAM and
EEPROM.
• Communicates with the microcontroller on the A/D Converter PCA viathe Serial
Communication (Guard Crossing) block.
• Communicates with the Display Controller to display readings and userinterface
information.
• Scans the user interface keyboard found on the Display Assembly.
• Communicates via the RS-232 interface and optional IEEE-488interfaces.
• Reads digital inputs and changes digital and alarm outputs.
2-3
HYDRA
Service Manual
DIGITAL I/O AND
TOTALIZE INPUT
ALARM OUTPUTS
SCAN TRIGGER INPUT
AC IN
RS-232
J4
J1
DISPLAY
J6
J5
J3
J2
MAIN
MEMORY
P1
2625A
ONLY
P1
2620A
ONLY
J1
REAR
PANEL
IEEE
P10
CHANNEL 0
CHANNELS 11…20
J10
TB1
TB2
ANALOG
INPUT
CONNECTOR
P1
J1
A/D
CONVERTER
P2
J2
CHANNELS 1…10
S1F.EPS
Figure 2-1. Interconnect Diagram
2-4
Theory of Operation (2620A/2625A)
Functional Block Description
2
ANALOG INPUT CONNECTOR
INPUT MULTIPLEXING
INPUT PROTECTION
INPUT SIGNAL
CONDITIONING
ANALOG
MEASUREMENT
PROCESSOR
(A/D CONVERTER)
MICRO CONTROLLER
INGUARD
SERIAL
OUTGUARD
COMMUNICATION
A/D CONVERTER
PCA
GUARD
CROSSING
DIGITAL
I/O
VACUUM FLUORESCENT
DISPLAY
RS-232
DISPLAY CONTROLLER
µP
RAM
ROM
IEEE-488
OPTION -05
(2620A ONLY)
CALENDAR
CLOCK
FRONT PANEL
SWITCHES
EEPROM
CALIBRATION
CONSTANTS
DISPLAY ASSEMBLY
MEMORY
(2625A ONLY)
DIGITAL KERNEL
POWER
SUPPLY
+5.6 Vdc (Vddr)
–5.4 Vdc (Vss)
+5.3Vdc (Vdd)
INGUARD
–30 Vdc
MAIN PCA ASSEMBLY
+5.1 Vdc (Vcc)
–5 Vdc
OUTGUARD
5.4 Vac
s2f.eps
Figure 2-2. Overall Functional Block Diagram
2-5
HYDRA
Service Manual
2-6.
Serial Communication (Guard Crossing)
This functional block provides a high isolation voltage communication path between the
Digital Kernel of the Main PCA and the microcontroller on the A/D Converter PCA.
This bidirectional communication circuit requires power supply voltages from the Power
Supply block.
2-7.
Digital Inputs and Outputs
This functional block contains the Totalizer, Totalizer Debouncer, eight bidirectional
Digital I/O channels, four Alarm Outputs, and the Input Threshold control circuits. These
circuits require power supply voltages from the Power Supply, a reset signal from the
Display PCA, and signals from the Digital Kernel.
2-8.
A/D Converter PCA
The following paragraphs describe the major blocks of circuitry on the A/D Converter
PCA.
2-9.
Analog Measurement Processor
The Analog Measurement Processor (A3U8) provides input signal conditioning, ranging,
a/d conversion, and frequency measurement. This custom chip is controlled by the A/D
Microcontroller (A3U9). The A/D Microcontroller communicates with the Main PCA
processor (A1U4) over a custom serial interface.
2-10. Input Protection Circuitry
This circuitry protects the instrument measurement circuits during overvoltage
conditions.
2-11. Input Signal Conditioning
Here, each input is conditioned and/or scaled to a dc voltage for measurement by the a/d
converter. DC voltage levels greater than 3V are attenuated. To measure resistance, a dc
voltage is applied across a series connection of the input resistance and a reference
resistance to develop dc voltages that can be ratioed. DC volts and ohms measurements
are filtered by a passive filter. AC voltages are first scaled by an ac buffer, converted to a
representative dc voltage by an rms converter, and then filtered by an active filter.
2-12. Analog-to-Digital (A/D) Converter
The dc voltage output from the signal conditioning circuits is applied to a
buffer/integrator which charges a capacitor for an exact amount of time. The time
required to discharge this capacitor, which is proportional to the level of the unknown
input signal, is then measured by the digital counter circuits in the Analog Measurement
Processor.
2-13. Inguard Microcontroller Circuitry
This microcontroller (and associated circuitry) controls all functions on the A/D
Converter PCA and communicates with the digital kernel on the Main PCA. Upon
request by the Main PCA, the inguard microcontroller selects the input channel to be
measured through the channel selection circuitry, sets up the input signal conditioning,
commands the Analog Measurement Processor to begin a conversion, stops the
measurement, and then fetches the measurement result. The inguard microcontroller
manipulates the result mathematically and transmits the reading to the digital kernel.
2-6
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
2-14. Channel Selection Circuitry
This circuitry consists of a set of relays and relay-control drivers. The relays form a tree
that routes the input channels to the measurement circuitry. Two of the relays are also
used to switch between 2-wire and 4-wire operation.
2-15. Open Thermocouple Check Circuitry
Under control of the Inguard Microcontroller, the open thermocouple check circuit
applies a small ac signal to a thermocouple input before each measurement. If an
excessive resistance is encountered, an open thermocouple input condition is reported.
2-16. Input Connector Assembly
The following paragraphs briefly describe the major sections of the Input Connector
PCA, which is used for connecting most of the analog inputs to the instrument.
2-17. 20 Channel Terminals
Twenty HI and LO terminal blocks are provided in two rows, one for channels 1 through
10 and one for channels 11 through 20. The terminals can accommodate a wide range of
wire sizes. The two rows of terminal blocks are maintained very close to the same
temperature for accurate thermocouple measurements.
2-18. Reference Junction Temperature
A semiconductor junction is used to sense the temperature of the thermocouple input
terminals. The resulting dc output voltage is proportional to the block temperature and is
sent to the A/D Converter PCA for measurement.
2-19. Display PCA
The Display Assembly controller communicates with the main Microprocessor over a
three-wire communication channel. Commands from the Microprocessor inform the
Display Controller how to modify its internal display memory. The Display Controller
then drives the grid and anode signals to illuminate the required segments on the
Display. The A2 Display Assembly requires power supply voltages from the Power
Supply and a clock signal from the A1U4 Microprocessor.
2-20. Memory PCA (2625A Only)
The Memory PCA is used by the Digital Kernel to store nonvolatile measurement data.
This block requires power supply voltages from the Power Supply, a reset signal from
the Display PCA, and signals from the Digital Kernel.
2-21. IEEE-488 Option (-05)
Theory of operation for the IEEE-488 Option (-05) is presented in Section 7 of this
manual. The related schematic diagram is found in Section 8.
2-22. Detailed Circuit Description
2-23. Main PCA
The following paragraphs describe the operation of the circuits on the Main PCA. The
schematic for this pca is located in Section 8.
2-7
HYDRA
Service Manual
2-24. Power Supply Circuit Description
The Hydra power supply consists of three major sections:
•
Raw DC Supply
The raw dc supply converts line voltage (90V to 264V ac) to a dcoutput of 7.5V to
35V.
•
5V Switcher Supply
The 5V switching supply regulates the 7.5 to 35V dc input to anominal 5.1V ±0.25V
dc (VCC).
•
Inverter
Using the 5V switching supply output, the inverter generates the -30Vdc, -5V dc,
and 5.4V ac supply levels needed for thevacuum-fluorescent display and the RS-232
Interface. The inverteralso provides isolated +5.3V (VDD), +5.6V (VDDR), and 5.4V (VSS)outputs for the inguard circuitry.
2-25. Raw DC Supply
The raw dc supply circuitry receives input from power transformer T401, which operates
on an input ranging from 90V to 264V ac. The power transformer is energized whenever
the power cord is plugged into the ac line; there is no on/off switch on the primary side
of the transformer. The transformer has an internal 275V ac metal-oxide varistor (MOV)
to clamp line transients. The MOV normally acts as an open circuit. When the peak
voltage exceeds approximately 400V, the line impedance in series with the line fuse
limits transients to approximately 450V. All line voltages use a slow blow 0.125 A,
250V fuse.
On the secondary side of the transformer, rectifiers A1CR2, A1CR3, and capacitor A1C7
rectify and filter the output. When it is ON, switch A1S1 (the front panel POWER
switch) connects the output of the rectifiers to the filter capacitor and the rest of the
instrument. Depending on line voltage, the output of the rectifiers is between 7.5 and
35V dc. Capacitor A1C2 helps to meet electromagnetic interference (EMI) and
electromagnetic compatibility (EMC) requirements.
When external dc power is used, the power switch connects the external dc source to
power the instrument. The external dc input uses thermistor A1RT1 (for overcurrent
protection) and diode A1CR1 (for reverse input voltage protection.) Capacitor A1C59
helps meet EMI/EMC requirements. Resistor A1R48, capacitors A1C2 and A1C39 also
ensure that the instrument meets EMI/EMC performance requirements.
2-26. Auxiliary 6V Supply
Three-terminal regulator A1U19, voltage-setting resistors A1R44 and A1R46, and
capacitor A1C34 make up the auxiliary 6-volt supply. This supply is used for the inverter
oscillator, inverter driver, and the power fail detection circuits.
2-27. 5V Switcher
The 5V switcher supply uses a switcher supply controller/switch device A1U9 and
related circuitry.The 7.5V dc to35V dc input is regulated to 5.1V dc (VCC) through
pulse-width modulation at a nominal switching frequency of 100 kHz.
The output voltage of the switcher supply is controlled by varying the duty cycle (ON
time) of the switching transistor in the controller/switch device A1U9. A1U9 contains
the supply reference, oscillator, switch transistor, pulse-width modulator comparator,
switch drive circuit, current-limit comparator, current-limit reference, and thermal limit.
2-8
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
Dual inductor A1T2 regulates the current that flows from the raw supply to the load as
the switching transistor in A1U9 is turned on and off. Complementary switch A1CR10
conducts when the switching transistor is off.
The pulse-width modulator comparator in A1U9 compares the output to the reference
and sets the ON-time/OFF-time ratio to regulate the output to 5.1V dc. A1C26 is the
input filter capacitor, and A1C14 is the output filter capacitor. Proper inductor and
capacitor values set the filter frequency response to ensure best overall system stability.
Circuitry consisting of A1R26, A1C21, and A1C18 ensure that the switcher supply
remains stable and operating in the continuous mode. Resistors A1R30 and A1R31 set
the output voltage to within 5% of 5.1V.Capacitor A1C21 sets the operating frequency
of the switcher at approximately 100 kHz.
Resistors A1R30 and A1R31 form a voltage divider that operates in conjunction with
amplifier A1U31, which is configured as a voltage follower.A1U31-5 samples the 5.1V
dc output, while A1U31-6 is the voltage divider input.The effect is to maintain the
junction of R30 and R31 at 5.1V dc, resulting in an A1U31-7 output level of 6.34V dc,
or 1.24V dc above the output.This feedback voltage is applied to A1U9-2, which A1U9
interprets as 1.24V dc because A1U9-3 (ground) is connected to the 5.1V dc output.
2-28. Inverter
The inverter supply uses a two transistor driven push-pull configuration. The center tap
of transformer A1T1 primary is connected to the 5.1V dc VCC supply, and each side is
alternately connected to common through transistors A1Q7 and A1Q8. A1R38 may be
removed to disable the inverter supply for troubleshooting purposes. A1Q7 and A1Q8
are driven by the outputs of D flip-flop A1U22. Resistors A1R34 and A1R28, and diodes
A1CR11 and A1CR12 shape the input drive signals to properly drive the gate of the
transistors. D flip-flop A1U22 is wired as a divide-by-two counter driven by a 110-kHz
square wave. The 110-kHz square wave is generated by hex inverter A1U23, which is
connected as an oscillator with a frequency determined by the values of resistors A1R40
and A1R47 and capacitor A1C35. The resulting ac voltage produced across the
secondary of A1T1 is rectified to provide the input to the inverter inguard and outguard
supplies.
2-29. Inverter Outguard Supply
The inverter outguard supply provides three outputs: 5.4V ac, -30V dc, and -5V dc.
These voltages are required by the display and RS-232 drivers and receiver. The 5.4V ac
supply comes off the secondary windings (pins 6 and 7) on transformer T1, and it is
biased at -24V dc with zener diode A1VR3 and resistor A1R22. Dual diodes A1CR8 and
A1CR9 and capacitor A1C17 are for the -30V dc supply. Capacitors A1C30 and A1C31,
and dual diodes A1CR13 form a voltage doubler circuit that generates -12 volts. Threeterminal regulator A1U18 then regulates this voltage down to -5V for the RS-232 circuit.
Capacitor A1C32 is needed for transient response performance of the three-terminal
regulator.
2-30. Inverter Inguard Supply
The inverter inguard supply provides three outputs: +5.3V dc (VDD) and -5.4V dc
(VSS) for the inguard analog and digital circuitry, and +5.6V dc (VDDR) for the relays.
Diodes A1CR5 and A1CR6, and capacitor A1C12 are for the +9.5 volt source, and
diodes A1CR7 and capacitor A1C13 are for the -9.5V source.
Three-terminal regulator A1U6 regulates the 9.5V source to 5.6V for the relays. A1R5
and A1R6 set the output voltage at 5.6V. A1C6 is required for transient performance.
The +5.3V regulator circuit uses A1Q2 for the series-pass element and A1Q4 as the error
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amplifier. A1VR2 is the reference for the positive supply. A1R14 provides the current to
bias the reference zener. A1C4 is the output filter, and A1C9 provides frequency
compensation of the regulator circuit. Transistor A1Q1 and resistor A1R13 make up the
current-limit circuit.
When the voltage across A1R13 increases enough to turn on A1Q1, output current is
limited by removing the base drive to A1Q2.
The -5.4 volt regulator operates like the +5.3 volt regulator, except that the NPN
transistors in the positive supply are PNP transistors in the negative supply, and the PNP
transistors in the positive supply are NPN transistors in the negative supply. If a VDDto-VSS short circuit occurs, diode A1CR4 ensures that current limit occurs at the limit
set for the -5.4V dc or +5.3V dc supply, whichever is lower.
2-31. Power Fail Detection
The power fail detection circuit generates a signal to warn the Microprocessor that the
power supply is going down. Comparator A1U24 compares the divided-down raw
supply voltage and the band-gap generated reference voltage. When the raw supply
voltage is greater than about 8V dc, the output of A1U24 is "high" and when the raw
supply falls below 8V dc, the output goes "low". Resistors A1R39 and A1R41 make up
the divider, and resistor A1R43 provides bias for the band-gap reference. Resistor
A1R42 is a pull up resistor for the comparator output, and resistor A1R45 provides
positive feedback to provide the comparator with some hysteresis.
2-32. Digital Kernel
The Digital Kernel is composed of the following eight functional circuit blocks: the
Microprocessor, the ROM (Read-Only Memory), the NVRAM/Clock (Nonvolatile
Random Access Memory and Real-Time Clock), the EEPROM (Electrically Erasable
Programmable Read-Only Memory), the Counter/Timer, the RS-232 Interface, and the
Option Interface.
2-33. Microprocessor
The Microprocessor uses an eight-bit data bus and a sixteen-bit address bus to access
memory locations in the ROM (A1U8), the NVRAM/Clock (A1U3), the Counter/Timer
(A1U2), the Digital I/O Registers (A1U13, A1U16, A1U26), the Memory PCA (A6),
and the IEEE-488 PCA (A5).
The Microprocessor oscillator operates at a 4.9152-MHz frequency determined by
crystal A1Y1. The A1U4-68 system clock signal (the Microprocessor oscillator
frequency divided by four) is a square wave with a frequency of 1.2288 MHz. This
system clock also determines the memory cycle time of 0.813 microseconds. The system
clock is also used by the Display Assembly and the IEEE-488 option assembly after
being damped by series resistor A1R19 to minimize the EMI generated by this signal’s
sharp edges.
When the address bus is stable, the Microprocessor enables either the reading of memory
(by driving RD*, A1U4-67, low) or writing of memory (by driving WR*, A1U4-66,
low.)
The Microprocessor uses a three-wire synchronous communication interface to store and
retrieve instrument communication configuration and calibration information in the
EEPROM (A1U1). See the EEPROM description for more detailed information.
The Microprocessor communicates to the Display Controller using another synchronous,
three-wire communication interface described in detail in the Display Controller Theory
of Operation in this section.
2-10
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
The Microprocessor communicates to the Microcontroller on the A/D Converter PCA
(via the Serial Communication circuit) using an asynchronous communication protocol
at 4800 baud. Communication to the Microcontroller (A3U9) originates at A1U4-11.
Communication from the A/D’s Microcontroller to the Microprocessor appears at A1U410. When there is no communication in progress between the Microprocessor and the
Microcontroller, both of these signals are low.
2-34. Address Decoding
The upper three bits of the address bus are decoded by A1U10-3,4,5 to generate the
ROM* chip select signal for the ROM (A1U10-6).
The NVRAM/Clock chip select signal (A1U21-6 going low) is generated when the
ROM* and RESET* signals are high and any one of address bits 9 through 12 is high.
To avoid spurious write cycles during power cycling, the INT* output of the NVRAM
(A1U3-1) is used to discharge the reset circuit on the Display PCA through resistor
A1R63 when the power supply level at A1U3-28 is too low (less than approximately
4.65V dc) to allow memory operations to the NVRAM.
The miscellaneous I/O chip select (hexadecimal addresses 0000 through 01FF) is
decoded using the ROM* signal and address bits 9 through 12 by A1U15 and A1U21.
When ROM* is high and all four of the address bits are low, the I/O* signal (A1U21-8)
is low. The I/O* signal and address bits 3 through 8 are then used by A1U10 and A1U11
to generate the CNTR*, DIO*, IEEE*, and MEM* chip select signals.
Table 2-1 shows a memory map for the Microprocessor.
Table 2-1. Microprocessor Memory Map
Hexadecimal Address
Device Selected
2000 - FFFF
ROM (A1U8)
1FF8 - 1FFF
Real-Time Clock (A1U3)
0200 - 1FF7
NVRAM (A1U3)
0040 - 013F
Microprocessor Internal RAM
0038 - 003F
Counter/Timer (A1U2)
0032 (Read Only)
Digital Inputs (A1U13)
0032 (Write Only)
Digital Outputs (A1U26)
0035 (Write Only)
Alarm Outputs (A1U16)
0028 - 002F
IEEE-488 Option (2620A Only)
0005 - 0006 (Write Only)
Memory Page (2625A Only)
0004
Memory Data (2625A Only)
2-35. Serial Communication (Guard Crossing)
The transmission of information from the Microprocessor (A1U4) to the Microcontroller
(A3U9) is accomplished via the circuit made up of A1U15, A1U7, A1R8, A1R16, and
A3R8. The transmit output from the Microprocessor (A1U4-11) is inverted by A1U15,
which drives the optocoupler LED (A1U7-2). Resistor A1R8 limits the current through
the LED.
The phototransistor in A1U7 responds to the light emitted by the LED when A1U7-2 is
driven low (the collector of the phototransistor (A1U7-5) goes low.) The phototransistor
collector is pulled up by A3R8 on the A/D Converter PCA. When turning off, the
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phototransistor base discharges through A1R16. With this arrangement, the rise and fall
times of the phototransistor collector signal are nearly symmetrical.
The transmission of data from the Microcontroller (A3U9) to the Microprocessor
(A1U4) is accomplished via the circuit made up of A3Q1, A3R7, A1U5, A1R7, and
A1R3. The transmit output from the Microcontroller (A3U9-14) is inverted by A3Q1,
which drives the optocoupler LED (A1U5-2) through resistor A3R7. The current through
the LED is limited by resistor A3R7. The phototransistor in A1U5 responds to the light
emitted by the LED when A1U5-2 is driven low; the emitter of the phototransistor
(A1U5-4) goes high. The phototransistor collector (A1U5-5) is pulled up by VCC, and
the emitter is pulled down by resistor A1R3. When turning off, the phototransistor base
discharges through A1R7. With this arrangement, the rise and fall times of the
phototransistor collector signal are nearly symmetrical.
2-36. Display/Keyboard Interface
The Microcontroller sends information to the Display Processor via a three-wire
synchronous communication interface. The detailed description of the DISTX, DISRX,
and DSCLK signals may be found in the detailed description of the Display PCA. Note
that the DISRX signal is pulled down by resistor A1R1 so that Microprocessor input
A1U4-15 is not floating at any time. The Display PCA also provides the system reset
circuitry and watchdog timer.
The Keyboard interface is made up of six bidirectional port lines from the
Microcontroller. SWR1 through SWR6 (A1U4-21 through A1U4-26, respectively) are
pulled up by A2Z1 on the Display PCA. The detailed description of the Display PCA
describes how the Microprocessor interfaces to the Keyboard.
2-37. ROM
The ROM provides the instruction storage for the Microprocessor. The chip select for
this device (A1U8-20) goes low for any memory cycle between hexadecimal addresses
2000 and FFFF (accessing 56 kbytes). Whenever this device is chip selected for read, the
instruction in the addressed location is output to the data bus and read by the
Microprocessor.
2-38. NVRAM/Clock
The NVRAM/Clock (A1U3) provides the data storage and real-time clock for the
instrument. A lithium battery, a crystal, and an automatic power-fail control circuit are
also integrated into this single package. When the RAM* chip select signal (A1U3-20) is
low, the Microprocessor is accessing one of the 8192 bytes in the NVRAM/Clock. The
RD* (A1U3-22) and WR* (A1U3-27) signals go low to indicate a read or write cycle,
respectively.
The internal power-fail control circuit disables access to this device and drives the INT*
output (A1U3-1) low when the VCC power supply is below approximately +4.5V dc.
This action keeps locations in the NVRAM/Clock from being modified while the
instrument is powering up and down. When the INT* output is low, the reset circuit on
the Display PCA is discharged, and a system reset occurs. Therefore, the Microprocessor
is reset on power failure as soon as it can no longer access the NVRAM/Clock.
The NVRAM contains 8184 bytes of nonvolatile data storage. The nonvolatile
instrument configuration information, the nonvolatile measurement data, and the
Microprocessor temporary data are stored in this area.
The Clock is composed of 8-byte wide registers that allow access to the real-time clock
counters. The Microprocessor accesses these registers in the same way as the NVRAM.
2-12
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
2-39. EEPROM
The EEPROM contains 64 registers, each of which is 16 bits long. These registers are
used to provide nonvolatile storage of some of the instrument configuration information
and all of the calibration information. When the Microprocessor is communicating to the
EEPROM, Chip Select input (A1U1-1) is driven high to enable the EEPROM interface.
When the Microprocessor is reading data from the EEPROM, the data bits are serially
shifted out on the Data Out signal (A1U1-4) with each one-to-zero transition of the
Serial Clock (A1U1-2).
When the Microprocessor is writing commands and data to the EEPROM, the bits are
serially shifted into the EEPROM on the Data In signal (A1U1-3) with each zero-to-one
transition of the Serial Clock (A1U1-2). When the last data bit for an erase or write
operation is shifted into the EEPROM, the Microprocessor pulses the Chip Select input
(A1U1-1) low to start the operation. The EEPROM will then drive the Data Out signal
(A1U1-4) low to indicate that it is busy writing the register. The Data Out signal goes
high when the operation is complete. Since the Microprocessor waits for this signal to go
high before doing anything else, an EEPROM failing to drive this signal high causes the
Microprocessor to wait until the Watchdog Timer on the Display PCA resets the
instrument.
The Chip Select input (A1U1-1) is always set low at the end of each EEPROM
operation.
2-40. Counter/Timer
The Counter/Timer IC (A1U2) has three 16-bit counters that are used both to implement
the Totalizer function and to provide a periodic 50-millisecond interrupt used for interval
time operation.
The output from the Totalizer Input circuit (A1U28-3) provides the clock input for
Counter 2. Counter 2 operates as a 16-bit pre-loadable down counter for the Totalizer
function. This counter causes the IRQ1* interrupt (A1U2-9) to go low, interrupting the
Microprocessor when the counter value changes from hexadecimal 0000 to FFFF. The
Counter 2 Gate input (A1U2-2) must be low for the Totalizer to operate correctly.
Counter 3 is used as a periodic 50.0-millisecond interrupt source. This counter divides
the E clock input (A1U2-17) by 61440. The IRQ1* interrupt (A1U2-9) goes low
(interrupting the Microprocessor) at the end of each 50.0-millisecond period. The
Counter 3 Gate input (A1U2-5) and the Counter 3 Clock input (A1U2-7) should both be
low for this counter to operate correctly. The 10-Hz square wave signal observed on the
Counter 3 Output pin (A1U2-6) changes state every 50.0 milliseconds.
Counter 1 is not used in the instrument, but its Clock and Output pins have been
connected to available pins on the Option Interface.
2-41. RS-232 Interface
The RS-232 interface is composed of connector A1J4, RS-232 Driver/Receiver A1U25,
and the hardware serial communication interface (SCI) in Microprocessor A1U4.
The SCI transmit signal (A1U4-14) goes to the RS-232 driver (A1U25-12), where it is
inverted and level shifted so that the RS-232 transmit signal transitions between
approximately +5.0 and -5.0V dc. When the instrument is not transmitting, the driver
output A1U25-5 is approximately -5.0V dc. The RS-232 receive signal from A1J4 goes
to the RS-232 receiver A1U25-4, which inverts and level shifts the signal so that the
input to the SCI transitions between 0 and +5.0V dc. When nothing is being transmitted
to the instrument, the receiver output (A1U25-13) is +5.0V dc.
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Data Terminal Ready (DTR) is a modem control signal controlled by the
Microprocessor. When the instrument is powered up, the Microprocessor port pin
(A1U4-32) goes high, which results in the RS-232 driver output (A1U25-7) going to 5.0V dc. When the instrument has initialized the SCI and is ready to receive and
transmit, A1U4-32 will go low, resulting in the RS-232 DTR signal (A1U25-7) going to
+5.0V dc. The RS-232 DTR signal remains at +5.0V dc until the instrument is powered
down.
2-42. Option Interface
The interconnection to the option slot is implemented by J1 on the Main PCA. This
connector (A1J1) routes the outguard logic power supply (VCC and GND), the eight-bit
data bus, RD*, WR*, E, RESET*, IEEE*, MEM*, and the lower three bits of the address
bus to the option installed in the option slot. This connector also routes an interrupt
signal from the IEEE-488 option to the IRQ2* input of the Microprocessor.
An option sense signal from the installed option allows the Microprocessor to identify
the type of option. When the instrument is powered up, the type of PCA installed in the
option slot is determined by the Microprocessor by driving the IRQ2* signal (A1U4-20)
and sensing the activity on the OPS* signal (A1U4-29). The Microprocessor first sets
IRQ2* low and samples the OPS* input, then sets IRQ2* high and samples the OPS*
input again. Table 2-2 describes how this information is used to determine what
hardware is installed in the option slot.
Table 2-2. Option Type Sensing
State of *OPS Input for PCA:
IRQ2* Output
None Installed
IEEE-488
Memory
0
1
0
0
1
1
0
1
2-43. Digital I/O
The following paragraphs describe the Digital Input Threshold, Digital Input Buffers,
Digital and Alarm Output Drivers, Totalizer Input, and External Trigger Input circuits.
2-14
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
2-44. Digital Input Threshold
2-1.
The Digital Input Threshold circuit sets the input threshold level for the Digital Input
Buffers and the Totalizer Input. A software programmable voltage divider (A1U17,
A1R35, A1R36, A1R37) and a unity gain buffer amplifier (A1AR1) are the main
components in this circuit. The Microprocessor sets outputs A1U16-15 and A1U16-12 to
select one of four input threshold levels. These outputs control the resistive divider
(A1R35, A1R36, A1R37) via two drivers with open-collector outputs in A1U17. The
voltage from the divider is then buffered by A1AR1 which sets the input threshold.
Capacitor A1C29 filters the divider voltage at the input of A1AR1. Table 2-3 defines the
programmable input threshold levels.
The instrument selects the +1.4V dc threshold level at power-up initialization.
Table 2-3. Programmable Input Threshold Levels
A1U16-15
A1U16-12
Input Threshold Voltage
0
0
+2.5V dc
0
1
+0.7V dc
1
0
+1.4V dc
1
1
+0.7V dc
2-45. Digital Input Buffers
Since the eight Digital Input Buffers are identical in design, only components used for
Digital Input 0 are referenced in this description. If the Digital Output Driver (A1U2716) is off, the input to the Digital Input Buffer is determined by the voltage level at
A1J5-10. If the Digital Output Driver is on, the input of the Digital Input Buffer is the
voltage at the output of the Digital Output Driver.
The Digital Input Threshold circuit and resistor network A1Z1 determine the input
threshold voltage and hysteresis for inverting comparator A1AR2. The inverting input of
the comparator (A1AR2-2) is protected by a series resistor (A1Z3) and diode A1CR14.
A negative input clamp circuit (A1Q9, A1Z2, and A1CR17) sets a clamp voltage of
approximately +0.7V dc for the protection diodes of all Digital Input Buffers. A negative
input voltage at A1J5-10 causes A1CR14 to conduct current, clamping the comparator
input A1AR2-2 at approximately 0V dc.
The input threshold of +1.4V dc and a hysteresis of +0.5V dc are used for all Digital
Input Buffers. When the input of the Digital Input Buffer is greater than approximately
+1.65V dc, the output of the inverting comparator is low. When the input then drops
below about +1.15V dc, the output of the inverting comparator goes high.
2-46. Digital and Alarm Output Drivers
Since the 12 Digital Output and Alarm Output Drivers are identical in design, the
following example description references only the components that are used for Alarm
Output Driver 0.
The Microprocessor controls the state of Alarm Output Driver 0 by writing to latch
output A1U16-2. When A1U16-2 is set high, the output of the open-collector Darlington
driver (A1U17-15) sinks current through current limiting resistor A1R62. When A1U162 is set low, the driver output turns off and is pulled up by A1Z2 and/or the voltage of
the external device that the output is driving. If the driver output is driving an external
inductive load, the internal flyback diode (A1U17-9) conducts the energy into MOV
A1RV1 to keep the driver output from being damaged by excessive voltage. Capacitor
A1C58 ensures that the instrument meets electromagnetic interference (EMI) and
electromagnetic compatibility (EMC) performance requirements.
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2-47. Totalizer Input
The Totalizer Input circuit consists of Input Protection, a Digital Input Buffer circuit,
and a Totalizer Debouncer circuit. The Digital Input Buffer for the totalizer is protected
from electrostatic discharge (ESD) damage by A1R49 and A1C43. Refer to the detailed
description of the Digital Input Buffer circuit for more information.
The Totalizer Debounce circuit allows the Microprocessor to select totalizing of either
the input signal or the debounced input signal. Latch output A1U16-16 is set low by
A1U4 to totalize the unmodified input signal or high to totalize the debounced input
signal. This totalizer clock control is provided by A1U28; output A1U28-3 drives the
totalizer counter clock input (A1U2-4).
The actual debouncing of the input signal is accomplished by A1U14, A1U20, and
A1U29. An EXOR gate compares the input signal (A1U14-13) and the output of an
eight-bit shift register (A1U29-9). If these signals differ, EXOR gate output A1U14-11
goes high, enabling counter A1U20 and shift register A1U29. The counter divides the
system clock of 1.2288 MHz (A1U20-10) by 256 to yield a 4.8-kHz clock (A1U20-13).
This signal clocks the eight-bit shift register. After approximately 1.5625 milliseconds,
the input signal will have been shifted from the serial input (A1U29-10) through to the
eighth output bit (A1U29-9). This forces the counter and shift register to stop. If the
input signal changes state before 1.5625 milliseconds have elapsed, the counter is
cleared and the shift register is preloaded again. Therefore, the input signal must remain
stable for greater than 1.5625 milliseconds before that transition changes the state of the
clock input of the totalizer counter (A1U2-4).
2-48. External Trigger Input Circuits
The External Trigger Input circuit can be configured by the Microprocessor to interrupt
on a rising or falling edge of the XT* input (A1J6-2) or to not interrupt on any
transitions of the XT* input.
The Microprocessor sets latch output A1U16-19 high for falling edge detection and low
for rising edge detection of the XT* input. The Microprocessor can enable the external
trigger interrupt by setting port pin A1U4-28 high or disable the interrupt by setting it
low. Microprocessor port pin A1U4-28 should only be high if the instrument trigger
mode of "ON" has been selected. Resistor A1R20 pulls NAND gate input A1U13 low
during power-up to ensure that the external trigger interrupt input (A1U4-9) is high.
When the EXOR gate output (A1U14-3) goes high, and NAND gate input A1U12-13 is
high, the output of the NAND gate (A1U12-11) goes low to interrupt the
Microprocessor. The Microprocessor can also determine the state of the XT* input by
reading the TRIG signal on port pin A1U4-27.
The XT* input is pulled up to +5V dc by A1Z2 and is protected from damage by ESD by
A1R58, A1C54, A1Z3, and A1CR15. Capacitor A1C54 helps ensure that the instrument
meets EMI/EMC performance requirements.
2-49. A/D Converter PCA
The following paragraphs describe the operation of the circuits on the A/D Converter
PCA. The schematic for this pca is located in Section 8.
2-50. Analog Measurement Processor
Refer to Figure 2-3 for an overall picture of the Analog Measurement Processor chip and
its peripheral circuits. Table 2-4 describes Analog Measurement Processor chip signal
names.
2-16
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
The Analog Measurement Processor (A3U8) is a 68-pin CMOS device that, under
control of the A/D Microcontroller (A3U9), performs the following functions:
• Input signal routing
• Input signal conditioning
• Range switching
• Passive filtering of dc voltage and resistance measurements
• Active filtering of ac voltage measurements
• A/D conversion
• Support for direct volts, true rms ac volts, temperature, resistance,and frequency
measurements
Two separate signal paths are used, one for dc/ohms/temperature and one for ac. The
volts dc (3V range and below) and temperature voltages are coupled directly to the a/d
converter, while higher voltages are attenuated first. For ohms, the dc circuitry is
augmented with an internal ohms source voltage regulator controlled through an extra set
of switches. For volts ac, inputs are routed through the ac buffer, which uses the gain
selected by the Measurement Processor (A3U8).
The a/d converter uses a modified dual-slope minor cycle method. The basic
measurement unit, a minor cycle, consists of a fixed time integrate period for the
unknown input, a variable time reference integrate period, a variable time hold period,
and various short transition periods. A minor cycle period lasts for 25 ms or until a new
minor cycle is begun, whichever comes first.
2-51. Input Protection
The instrument measurement circuits are protected when overvoltages are applied
through the following comprehensive means:
• Any voltage transients on channel 0 HI or LO terminals areimmediately clamped to
a peak of about 1800V or less by MOVs A3RV1and A3RV2. (This is much lower
than the 2500V peaks that can beexpected on 240 VAC, IEC 664 Installation
Category II, ac mains.)
• Fusible resistors A3R10 and A3R11 protect the measurement circuitryin all
measurement modes by limiting currents.
• A3Q11 clamps voltages exceeding 0.7V below and approximately 6.0Vabove analog
common (LO) or LO SENSE, with A3R35 limiting the inputcurrent.
• A3Q10 clamps voltages during ohms measurements with A3RT1, A3R34,A3R10,
and A3Z4 limiting the input current. With large overloads,thermistor A3RT1 will
heat up and increase in resistance.
• A3U8 also clamps voltages on its measurement input pins that exceedthe VDD and
VSS supply rails. Resistors A3R42, A3R11, A3R10, A3RT1,A3Z4, A3R35, and
A3R34 limit any input currents.
• Any excessive voltages that are clamped through A3U8 to VDD or VSS,are then
also clamped by zener diodes A3VR3 and A3VR2.
• The open thermocouple detect circuitry is protected against voltagetransient damage
by A3Q14 and A3Q15.
• When measuring ac volts, the ac buffer is protected by dual-diodeclamp A3CR1 and
resistor network A3Z3.
• Switching induced transients are also clamped by dual-diodeA3CR4 and capacitor
A3C33, and limited by resistor A3R33.
2-17
2-18
LO
SENSE
LO
SOURCE
HI
SENSE
HI
SOURCE
REFERENCE
JUNCTION
R43
R11
R10
K16
C31
Figure 2-3. Analog Simplified Schematic Diagram
K17
Z4
R34
R35
R32
TO U9
300V
300Ω
15
14
19
R42
S16
7 6 5
OHMS
VOLTAGE
SOURCE
TO
REFERENCE
RESISTOR
2
TO U9
28 29 30 31 32 33
S2
S3
TO OHMS
SOURCE &
RRS HI
DIVIDER
SWITCHING
LOW
8
36
3.84 MHz
37
U8 ANALOG
MEASUREMENT
PROCESSOR*
RRS LOW
DC HI
S18
S19
FREQUENCY
COUNTER
RRS
LOW
RRS HI
S42
RMS
CONVERTER
REFER TO THE SCHEMATIC DIAGRAM IN SECTION 8.
* NOT ALL U8 SWITCHES ARE SHOWN HERE.
25
23
30 VDC 21
300 VDC
30 KΩ
30V
3 KΩ
300 KΩ 16
3 MΩ, 10 MΩ
OPEN
THERMOCOUPLE
DETECT
10M
100K
1M
10K
1K
13
11
10
GAIN CONTROL
V LO/RRS LO
Ω LO
AC BUFFER
RRS = REFERENCE RESISTOR SENSE
3 VDC/300 MVDC/TC/Ω
Ω
K15
ACV
DIGITAL
SECTION
A/D HI
+
–
ACTIVE
FILTER
AMP
TO U9
39 40 41 42
A/D
A/D LO
S81
61
ACTIVE
ACV
FILTER
52
1.05V
51
57
56
58
59
60
C12
A/D
REF
Z2
PASSIVE
DC
FILTERS
VR1
VDD
HYDRA
Service Manual
s3f.eps
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
Table 2-4. Analog Measurement Processor Pin Descriptions
Pin
Name
Description
1
2
3
4
5
VDD
ACBO
AIN
AGND2
ACR4
+5.4V supply
AC buffer output
(not used)
Analog ground
AC buffer range 4 (300V)
6
7
8
9
10
ACR3
ACR2
ACR1
VSSA
REFJ
AC buffer range 3 (30V)
AC buffer range 2 (3V)
AC buffer range 1 (300 mV)
-5.4V supply for AC ranging
Reference junction input
11
12
13
14
15
DCV
LOW
GRD
RRS
V4
V3
A/D converter low input
Driven guard
Reference resistor sense for ohms
Tap #4 on the DCV input divider/ohms reference network
Tap #3 on the DCV input divider/ohms reference network
16
17
18
19
20
V1
GRD
V2F
V2
GRD
Tap #1 on the DCV input divider/ohms reference network
Driven guard
Tap #2 input on the DCV input divider/ohms reference network
Tap #2 on the DCV input divider/ohms reference network
Driven guard
21
22
23
24
25
V0
GRD
OVS
GRD
AGND1
Tap #0 on the DCV input divider/ohms reference network
Driven guard
Ohms and volts sense input
Guard
Analog ground
26
27
28
29
30
DGND
FC0
FC1
FC2
(not used)
Analog ground
Function control #0
Function control #1
Function control #2
31
32
33
34
35
FC3
FC4
FC5
FC6
FC7
Function control #3
(not used)
(not used)
Function control #6
Function control #7
36
37
38
39
40
XIN
XOUT
MRST
AS
AR
Crystal oscillator input
Crystal oscillator output
Master reset
Analog send
Analog receive
41
42
43
44
45
SK
CS
BRS
VSS
INT
Serial clock
Chip select
(not used)
-5.4V dc
Integrator output
2-19
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Service Manual
Table 2-4. Analog Measurement Processor Pin Descriptions (cont)
Pin
Name
Description
46
47
48
49
50
SUM
B.1
B.32
B1
B3.2
Integrator summing node
Buffer output, 100 mV range
Buffer output, 300 mV range
Buffer output, 1000 mV range
Buffer output, 3V range
51
52
53
54
55
VREF+
VREFRAO
RA+
RA-
A/D voltage reference plus
A/D voltage reference minus
A/D reference amplifier output
A/D reference amplifier noninverting input
A/D reference amplifier inverting input
56
57
58
59
60
AFO
MOF
AFI
FAI
FAO
Passive filter 2
Passive filter 1 plus resistance
Passive filter 1
Filter amplifier inverting input
Filter amplifier output
61
62
63
64
65
RMSF
AGND3
RMSG
2
RMSO
CAVG
RMS output, filtered
(not used, connected to filtered -5.4V dc)
(not used)
RMS converter output
(not used)
66
67
68
VSSR
RMSG
1
RMSI
-5.4V dc, filtered
(not used, pulled to filtered -5.4V dc)
(not used)
2-52. Input Signal Conditioning
Each input is conditioned and/or scaled to a dc voltage appropriate for measurement by
the a/d converter. DC voltage applied to the a/d converter can be handled on internal
ranges of 0.1V, 0.3V, 1V, or 3V. Therefore, high-voltage dc inputs are scaled, and ohms
inputs are converted to a dc voltage. Line voltage level ac inputs are first scaled and then
converted to a dc voltage. Noise rejection is provided by passive and active filters.
2-53. Function Relays
Latching relays A3K15, A3K16, and A3K17 route the input signal to the proper circuit
blocks to implement the desired measurement function. These relays are switched when
a 6-millisecond pulse is applied to the appropriate reset or set coil by the NPN
Darlington drivers in IC A3U10. The A/D Microcontroller A3U9 controls the relay drive
pulses by setting the outputs of port 6. Since the other end of the relay coil is connected
to the VDDR supply, a magnetic field is generated, causing the relay armature and
contacts to move to (or remain in) the desired position. Function relay states are defined
in Table 2-5.
2-20
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
Table 2-5. Function Relay States
Relay Position
Function
A3K17
A3K16
A3K15
DC mV, 3V,Thermocouples
Reset
Set
Set
DC 30V, 300V
Set
Set
Set
ACV
Set
Set
Reset
Ohms, RTDs
Reset
Reset
Set
Frequency
Set
Set
Reset
2-54. DC Volts and Thermocouples
For the 3V and lower ranges (including thermocouples), the HI input signal is applied
directly to the A3U8 analog processor through A3R11, A3K17, and A3R42. Capacitor
A3C27 filters this input, which the analog processor then routes through S2 and other
internal switches, through the passive filter, and to the internal a/d converter. The LO
SENSE signal is applied to A3U8 through A3R35 and routed through internal switch
A3U8-S19 to LO of the a/d converter.
Guard signals MGRD and RGRD are driven by an amplifier internal to A3U8 to a
voltage appropriate for preventing leakage from the input HI signal under high humidity
conditions.
For the 30V range, the HI signal is scaled by resistor network A3Z4. Here, the input is
applied to pin 1 of A3Z4 so that an approximate 100:1 divider is formed by the 10-MΩ
and 100.5-kΩ resistors in A3Z4 when analog processor switches S3 and S13 are closed.
The attenuated HI input is then sent through internal switch S12 to the passive filter and
the a/d converter. Input LO is sensed through analog processor switch S18 and resistor
A3R34.
For the 300V range (Figure 2-4), the HI signal is again scaled by A3Z4. The input is
applied to pin 1 of A3Z4, and a 1000:1 divider is formed by the 10-MΩ and 10.01-kΩ
resistors when switches S3 and S9 are closed in A3Z4. The attenuated HI input is then
sent through internal switch S10 to the passive filter and the a/d converter. LO is sensed
through analog processor switch S18 and resistor A3R34.
2-55. Ohms and RTDs
Resistance measurements are made using a ratio ohms technique, as shown in Figure 25. A stable voltage source is connected in series with the reference resistor in A3Z4 and
the unknown resistor. Since the same current flows through both resistors, the unknown
resistance can be determined by multiplying the ratio of the voltage drops across the
reference and the unknown resistors by the known reference resistor value.
For the RTD, 300Ω, 3-kΩ, and 30-kΩ ranges, the ratio technique is implemented by
integrating the voltage across the unknown resistance for a fixed period of time and then
integrating the negative of the voltage across the reference resistance for a variable time
period. In this way, each minor cycle result gives the ratio directly.
For the 300-kΩ, 3-MΩ, and 10-MΩ ranges, the ratio is determined by performing two
separate voltage measurements in order to improve noise rejection. One fixed-period
integration is performed on the voltage across the unknown resistance, and the second
integration is performed on the voltage across the reference resistance. The ratio of the
two fixed-period voltge measurements is then computed by Microcontroller A3U9. The
resistance measurement result is determined when A3U9 multiplies the ratio by the
reference resistance value.
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S2
A3R11
A3K17
INPUT HI
A3R10
A3Z4
10M
S3
S9
S10
A3Z4
10.01k
PASSIVE
FILTER
HIGH
A/D
A3R34
LOW
A3K16
INPUT LO
s4f.eps
Figure 2-4. DC Volts 300V Range Simplified Schematic
When an input is switched in for a measurement, the ohms source in Analog Processor
A3U8 is set to the correct voltage for the range selected and is connected to the
appropriate reference resistor in network A3Z4. A measurement current then flows
through A3Z4, relay A3K16, thermistor A3RT1, resistor A3R10, the unknown
resistance, A3R43, ground, and the ohms source.
The resulting voltage across the unknown resistance is integrated for a fixed period of
time by the A/D Converter through the HI SENSE path of A3R11, A3K17, A3R42 and
A3U8 switch S2, and the LO SENSE path of A3R35 and Analog Processor switch S19.
Passive filtering is provided by A3C34, A3C27, and portions or all of the DC Filter
block.
The voltage across the reference resistor for the 300Ω and RTD, 3-kΩ, and 30-kΩ
ranges (the 1-kΩ, 10.01-kΩ, and 100.5-kΩ resistances in A3Z4, respectively) is
integrated for a variable period of time until the voltage across the integrate capacitor
reaches zero. For the 300Ω and RTD range, the reference resistor voltage is switched in
through Analog Processor switch S6 and applied to the A/D Converter by switch S8. For
the 3-kΩ range, switches S9 and S11 perform these functions, respectively. For the 30kΩ range, switches S13 and S14 are used. For all ranges, the voltage is routed through
A3R34 to the RRS input.
2-22
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
OHMS
VOLTAGE
SOURCE
IX
LOW
+
VR REF
–
A/D
INTEGRATE
REFERENCE
A3Z4 R REF
REFERENCE
RESISTOR
A3R34
HIGH
A3K16
A3RT1 & A3R10
A3R11
HI
+
VR X
-
A3R42
A3K17
PASSIVE
FILTER
RX
UNKNOWN
RESISTOR
HIGH
A/D
INTEGRATE
UNKNOWN
LO
LOW
RX
IX•RX
VR X
=
=
IX•RREF
R REF
VR REF
s5f.eps
Figure 2-5. Ohms Simplified Schematic
The reference resistor for the 300-kΩ, 3-MΩ, and 10-MΩ ranges is the 1-MΩ resistor in
A3Z4, which is selected by S15. The voltage across this reference is integrated during its
own minor cycle(s) and is switched to a passive filter and the A/D Converter by switches
S1 and S18.
When 4-wire measurements are made on any of the six ranges, separate Source and
Sense signal paths are maintained to the point of the unknown resistance. The 4-wire
Source path measurement current is provided by the A3U8 ohms source through one of
the A3U8 internal switches (S6, S9, S13, or S15) and the appropriate reference resistor
in A3Z4. The current flows through relay A3K16, thermistor A3RT1, resistor A3R10,
the HI Source instrument relay contacts (A3K1 - A3K3, A3K5 - A3K14), and the HI
Source lead wire, to the unknown resistance to be measured. The current flows back
through the LO Source lead wire, the LO Source path of the instrument relays (A3K1 A3K3, A3K5 - A3K14), resistor A3R43, and analog ground, to the A3U8 ohms source.
The voltage that develops across the unknown resistance is sensed through the other 2
wires of the 4-wire set. HI is sensed through the HI Sense path made up of the users HI
Sense lead wire, the HI Sense contacts in the instrument relays, resistor A3R11, relay
A3K17, resistor A3R42, and Analog Processor A3U8 switch S2. LO is sensed through
the users LO Sense lead wire, the LO Sense contacts in the instrument relays, protection
resistor A3R35, and A3U8 switch S19.
2-23
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Since virtually no current flows through the sense path, no error voltages are developed
that would add to the voltage across the unknown resistance; this 4-wire measurement
technique eliminates user lead-wire and instrument relay contact and circuit board trace
resistance errors.
2-56. AC Volts
AC-coupled ac voltage inputs are scaled by the ac buffer, converted to dc by a true rms
ac-to-dc converter, filtered, and then sent to the a/d converter.
Refer to Figure 2-6. Input HI is switched to the ac buffer by dc-blocking capacitor
A3C31, protection resistor A3R11, and latching relay A3K15. Resistor A3R44 and
A3K15 act to discharge A3C31 between channel measurements. LO is switched to the
A3U8 A/D Converter through A3R34 and S18.
INPUT HI
A3R11
A3Z3
1.111M
A3K15
_
A3C31
A3U7
A3U6
RMS
COVERTER
+
A3Z3
2.776k
A3R44
A3Z3 FEEDBACK
RESISTOR
INPUT LO
A3C15
&
A3C16
A3Z3
115.7
A3R43
s6f.eps
Figure 2-6. AC Buffer Simplified Schematic
JFETs A3Q3 through A3Q9 select one of the four gain (or attenuation) ranges of the
buffer (wide-bandwidth op-amp A3U7.) The four JFET drive signals ACR1 through
ACR4 turn the JFETs on at 0V and off at -VAC. Only one line at a time will be set at 0
volts to select a range.
The input signal to the buffer is first divided by 10, 100, or 1000 for the 300 mV, 3V,
and 30V ranges, respectively. The resistance ratios used are summarized in Table 2-6.
Note that the 111.1-kΩ resistor is left in parallel with the smaller (higher attenuation)
resistors. The attenuated signal is then amplified by A3U7, which is set for a gain of 25
by the 2.776-kΩ and 115.7Ω resistors in A3Z3. Components A3R27 and A3C23
compensate high-frequency performance on the 300 mV range. For the 300V range,
overall buffer gain is determined by the ratio of the 2.776-kΩ feedback resistor to the
1.111-MΩ input resistor.
2-24
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
Table 2-6. AC Volts Input Signal Dividers
Range
Drive Signal
A3Z3 Divider
Resistor(s)
Overall Gain
300 mV
ACR1
111.1 kΩ
2.5
3V
ACR2
12.25 kΩ || 111.1 kΩ
0.25
30V
ACR3
1.013 kΩ || 111.1 kΩ
0.025
150/300V
ACR4
none
0.0025
The output of the buffer is ac-coupled by A3C15 and A3C16 to the true-rms ac-to-dc
converter A3U6. Discharge JFET A3Q13 is switched on to remove any excess charge
from the coupling capacitors A3C15 and A3C16 between channel measurements. A3C17
provides an averaging function for the converter, and resistor network A3Z1 divides the
output by 2.5 before sending the signal to the active ac volts filter. Analog processor
switch S81 connects the output of the active filter to HI of the A/D Converter.
Components A3R29, A3R30, A3C26, and A3C28 provide filtered power supplies
(+VAC and -VAC) for the ac buffer, the ac switch JFETs, and the rms converter.
2-57. Frequency
2-1.
After any dc component is blocked by capacitors A3C15, A3C16, and A3C31, the output
of the ac buffer is used to determine the input frequency. This signal is sent to the ACBO
pin of analog processor A3U8 and switched to the internal frequency comparator and
counter circuit by S42.
2-58. Passive and Active Filters
The passive filters are used for the dc voltage and ohms measurements. For most ranges,
capacitors A3C14 and A3C11 are switched into the measurement circuit in front of the
A3U8 A/D Converter by switches S86, S87, and S88. These capacitors act with the 100kΩ series resistance provided by A3R42 or A3Z4 to filter out high-frequency noise. For
the 300-kΩ range, only A3C14 is switched in by switches S86 and S85. For the 3-MΩ
and 10-MΩ ranges, A3C11 or A3C14 are not switched in to keep settling times
reasonably short.
Between channel measurements, the passive filters are discharged by JFET A3Q2 under
control of Microcontroller A3U9 through comparator A3U14. When the ZERO signal is
asserted, A3R14 pulls the gate of A3Q2 to ground, turning the JFET on and discharging
A3C11. At the same time, zeroing of filter capacitors A3C14 and A3C27 is
accomplished by having the Analog Processor turn on internal switches S2, S86, and
S87.
The active filter is only used for ac voltage measurements. This three-pole active filter
removes a significant portion of the ac ripple and noise present in the output of the rms
converter without introducing any additional dc errors. The active filter op-amp within
A3U8, resistors A3R20, A3R17, and A3R16, and capacitors A3C7, A3C10, and A3C6
form the filter circuit. This filter is referenced to the LO input to the a/d converter within
A3U8 by the op-amp. The input to the filter is available at the RMSO pin, and the output
is sent to the RMSF pin of A3U8. Switches S80 and S82, which are turned on prior to
each new channel measurement, cause the filter to quickly settle (pre-charge) to near the
proper dc output level.
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2-59. A/D Converter
Figure 2-7 shows the dual slope a/d converter used in the instrument. The unknown input
voltage is buffered and used to charge (integrate) a capacitor for an exact period of time.
This integrator capacitor is then discharged by the buffered output of a stable and
accurate reference voltage of opposite polarity. The capacitor discharge time, which is
proportional to the level of the unknown input signal, is measured by the digital circuits
in the Analog Measurement Processor. This time count becomes the conversion result.
+ REFERENCE
(– INPUT)
+
+
COUNTER
REFERENCE
_
_
A3C13
A/D
COMPARATOR
S77
–REFERENCE
(+ INPUT)
INTEGRATE
REFERENCE
+
A3Z2
_
_
INPUT HI
BUFFER
+
INTEGRATOR
INPUT LO
INTEGRATE
INPUT
s7f.eps
Figure 2-7. A/D Converter Simplified Schematic
In both the slow and fast measurement rates, the a/d converter uses its ±300 mV range
for most measurement functions and ranges. The primary exceptions are that the 3V dc
range is measured on the a/d converter 3V range, thermocouples are measured on the
±100 mV range, and the temperature reference is measured on the 1V a/d converter
range. The typical overload point on a slow rate 30000 count range is 32000 display
counts; the typical overload point on a fast rate 3000 count range is 3200 display counts.
During the integrate phase, the a/d buffer in the A3U8 Analog Measurement Processor
applies the signal to be measured to one of the four integrator input resistors in network
A3Z2. As shown on the A/D Converter schematic diagram in Section 8, the choice of
resistor selects the a/d converter range. Switch S69 connects the buffer output through
pin B.1 for the 100-mV range, S71 connects the output through B.32 for the 300 mV
range, S73 connects to pin B1 for the 1V range, and S75 sets up the 3V range through
pin B3.2.
2-26
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
The current through the selected integrator input resistor charges integrator capacitor
A3C13, with the current dependent on the buffer output voltage. After the integrate
phase, the buffer is connected to the opposite polarity reference voltage, and the
integrator integrates back toward zero capacitor voltage until the comparator trips. An
internal counter measures this variable integrate time. If the a/d converter input voltage
is too high, the integrator overloads and does not return to its starting point by the end of
the measurement phase. Switch S77 is then turned on to discharge integrate capacitor
A3C13.
The reference voltage used during the variable integrate period for voltage (and high
ohms) conversions is generated from zener reference diode A3VR1, which is time and
temperature stable. The reference amplifier in the Analog Measurement Processor, along
with resistors A3R15, A3R18, and A3R21, pulls approximately 2 mA of current through
the zener. Resistors in network A3Z2 divide the zener voltage down to the reference
1.05V required by the A/D Converter.
2-60. Inguard Microcontroller Circuitry
The Microcontroller, A3U9, with its internal program memory and RAM and associated
circuitry, controls measurement functions on the A/D Converter PCA and communicates
with the Main (outguard) processor.
The Microcontroller communicates directly with the A3U8 Analog Measurement
Processor using the CLK, CS, AR, and AS lines and can monitor the state of the analog
processor using the FC[0:7] lines. Filter zeroing is controlled by the ZERO signal. The
open thermocouple detect circuitry is controlled by the OTCCLK and OTCEN lines and
read by the OTC line. The Microcontroller also communicates with the Main (outguard)
processor serially using the IGDR line to receive and the IGDS line (driven by A3Q1) to
send.
The channel and function relays are driven to the desired measurement state by signals
sent out through microcontroller ports 1, 3, 4, 6, and 7.
On power up, the reset/break detect circuit made up of quad comparator A3U1,
capacitors A3C1 and A3C2, and resistors A3R1 through A3R6 and A3R8 resets the
Microcontroller through the RESET* line. When a break signal is received from the
outguard processor, the inguard A3U9 is again reset. Therefore, if Microcontroller
operation is interrupted by line transients, the outguard can regain control of the inguard
by resetting A3U9.
2-61. Channel Selection Circuitry
Measurement input channel selection is accomplished by a set of latching 4-form-C
relays organized in a tree structure. Relays A3K5, A3K6, and A3K8 through A3K14
select among channels 1 through 20. Relay A3K7 disconnects rear input channels 1
through 20 from the measurement circuitry between measurements. Relay A3K3
switches in the front panel channel 0 or the rear channels. Inductors A3L1 through
A3L24 reduce EMI and current transients.
Selection between 2-wire and 4-wire operation for ohms measurements is performed by
latching 2-form-C relays (A3K1 and A3K2.) These relays also serve to select a voltage
or thermocouple rear input channel from either channels 1 through 10 or channels 11
through 20.
2-27
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The coils for the relays are driven by the outputs of Darlington drivers A3U4, A3U5,
A3U10, A3U11, and A3U12. The relays are switched when a 6-millisecond pulse is
applied to the appropriate reset or set coil by the NPN Darlington drivers in these ICs.
When the port pin of Microcontroller A3U9 connected to the input of a driver is set high,
the output of the driver pulls one end of a relay set or reset coil low. Since the other end
of the relay coil is connected to the VDDR supply, a magnetic field is generated, causing
the relay armature and contacts to move to (or remain in) the desired position.
2-62. Open Thermocouple Check
Immediately before a thermocouple measurement, the open thermocouple check circuit
applies a small, ac-coupled signal to the thermocouple input. Microcontroller A3U9
initiates the test by asserting OTCEN, causing comparator A3U14/A3R40 to turn on
JFET A3Q12. Next, the Microcontroller sends a 78-kHz square wave out the OTCCLK
line through A3R41, A3Q12, and A3C32 to the thermocouple input. The resulting
waveform is detected by A3U13 and A3CR2, and a proportional level is stored on
capacitor A3C30. Op amp A3U13 compares this detected level with the VTH threshold
voltage set up by A3R37 and A3R36 and stored on A3C29. If the resistance at the input
is too large, the VTH level will be exceeded and the OTC (open thermocouple check)
line will be asserted. After a short delay, the Microcontroller analyzes this OTC signal,
determines whether the thermocouple should be reported as open, and deasserts OTCEN
and sets OTCCLK high, ending the test.
2-63. Input Connector PCA
The Input Connector assembly, which plugs into the A/D Converter PCA from the rear
of the instrument, provides 20 pairs of channel terminals for connecting measurement
sensors. This assembly also provides the reference junction temperature sensor circuitry
used when making thermocouple measurements.
Circuit connections between the Input Connector and A/D Converter PCAs are made via
connectors A4P1 and A4P2. Input channel and earth ground connections are made via
A4P1, while temperature sensor connections are made through A4P2.
Input connections to channels 1 through 20 are made through terminal blocks TB1 and
TB2. Channel 1 and 11 HI and LO terminals incorporate larger creepage and clearance
distances and each have a metal oxide varistor (MOV) to earth ground in order to clamp
voltage transients. MOVs A4RV1 through A4RV4 limit transient impulses to the more
reasonable level of approximately 1800V peak instead of the 2500V peak that can be
expected on 240 VAC, IEC 664 Installation Category II, ac mains. In this way, higher
voltage ratings can be applied to channels 1 and 11 than can be applied to the other rear
channels.
Strain relief for the user’s sensor wiring is provided both by the Connector PCA housing
and the two round pin headers. Each pin of the strain relief headers is electrically
isolated from all other pins and circuitry.
Temperature sensor transistor A4Q1 outputs a voltage inversely proportional to the
temperature of the input channel terminals. This voltage is 0.6V dc at 25ºC, increasing 2
mV with each degree decrease in temperature, or decreasing 2 mV with each degree
increase in temperature. For high accuracy, A4Q1 is physically centered within and
thermally linked to the 20 input terminals. Local voltage reference A4VR1 and resistors
A4R1 through A4R3 set the calibrated operating current of the temperature sensor.
Capacitor A4C1 shunts noise and EMI to ground.
2-28
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
2-64. Display PCA
Display Assembly operation is classified into six functional circuit blocks: the Main
PCA Connector, the Front Panel Switches, the Display, the Beeper Drive Circuit, the
Watchdog Timer/Reset Circuit, and the Display Controller. These blocks are described
in the following paragraphs.
2-65. Main PCA Connector
The 20-pin Main PCA Connector (A2J1) provides the interface between the Main PCA
and the other functional blocks on the Display PCA. Seven of the connector pins provide
the necessary connections to the four power supply voltages (-30V dc, -5V dc, +5.1V dc,
and 5.4V ac filament voltage). Six pins are used to provide the interface to the Front
Panel Switches (A2SWR1 through A2SWR6). The other seven signals interface the
Microprocessor (A1U4) to the Display Controller (A2U1) and pass the reset signals
between the assemblies.
2-66. Front Panel Switches
The Microprocessor scans the 19 Front Panel Switches (A2S1 through A2S18, and
A2S21) using only six interface signals (plus the ground connection already available
from the power supply). These six signals (SWR1 through SWR6) are connected to a
bidirectional I/O port on the microprocessor. Each successive column has one less
switch.
This arrangement allows the unused interface signals to function as strobe signals when
their respective column is driven by the Microprocessor. The Microprocessor cycles
through six steps to scan the complete Front Panel Switch matrix. Table 2-7 shows the
interface signal state and, if the signal state is an output, the switches that may be
detected as closed.
Table 2-7. Front Panel Switch Scanning
Interface Signal States or Key Sensed
Step
SWR6
SWR5
SWR4
SWR3
SWR2
SWR1
1
A2S8
A2S17
A2S10
A2S12
A2S18
A2S13
2
A2S1
A2S2
A2S3
A2S4
A2S11
0
3
A2S7
A2S9
A2S5
A2S6
0
Z
4
A2S14
A2S15
A2S16
0
Z
Z
5
NA
NA
0
Z
Z
Z
6
A2S21
0
Z
Z
Z
Z
A2Sn indicates switch closure sensed.
0 indicated strobe driven to logic 0
Z indicated high impedance input; state ignored.
In step 1, six port bits are set to input, and the interface signal values are read. In steps 2
through 6, the bit listed as O is set to output zero, the other bits are read, and bits
indicated by a Z are ignored.
Each of the interface signals is pulled up to the +5V dc supply by a 10-kΩ resistor in
network A2Z1. Normally, the resistance between any two of the interface signals is
2-29
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approximately 20 kΩ. Checking resistances between any two signals (SWR1 through
SWR6) verifies proper termination by resistor network A2Z1.
2-67. Display
The custom vacuum-fluorescent display (A2DS1) comprises a filament, 11 grids
(numbered 0 through 10 from right to left on the display), and up to 14 anodes under
each grid. The anodes make up the digits and annunciators for their respective area of the
display. The grids are positioned between the filament and the anodes.
A 5.4V ac signal, biased at a -24V dc level, drives the filament. When a grid is driven to
+5V dc, the electrons from the filament are accelerated toward the anodes that are under
that grid. Anodes under that grid that are also driven to +5V dc are illuminated, but the
anodes that are driven to -30V dc are not. Grids are driven to +5V dc one at a time,
sequencing from GRID(10) to GRID(0) (left to right, as the display is viewed.)
2-68. Beeper Drive Circuit
The Beeper Drive circuit drives the speaker (A2LS1) to provide an audible response to a
button press. A valid entry yields a short beep; an incorrect entry yields a longer beep.
The circuitry comprises a dual four-bit binary counter (A2U4) and a NAND gate (A2U6)
used as an inverter. One four-bit free-running counter (A2U4) divides the 1.2288-MHz
clock signal (E) from the microprocessor (A1U4) by 2 to generate the 614.4-kHz clock
(CLK1) used by the Display Controller. This counter also divides the 1.2288-MHz clock
by 16, generating the 76.8-kHz clock that drives the second four-bit binary counter
(A2U4).
The second four-bit counter is controlled by an open-drain output on the Display
Controller (A2U1-17) and pull-down resistor A2R1. When the beeper (A2LS1) is off,
A2U1-17 is pulled to ground by A2R1. This signal is then inverted by A2U6, with
A2U6-6 driving the CLR input high to hold the four-bit counter reset. Output A2U4-8 of
the four-bit counter drives the parallel combination of the beeper (A2LS1) and A2R10 to
ground to keep the beeper silent. When commanded by the Main Microprocessor, the
Display Controller drives A2U1-17 high, enabling the beeper and driving the CLR input
of the four-bit counter (A2U4-12) low. A 4.8-kHz square wave then appears at counter
output A2U4-8 and across the parallel combination of A2LS1 and A2R10, causing the
beeper to resonate.
2-69. Watchdog Timer and Reset Circuit
This circuit provides active high and active low reset signals to the rest of the system at a
power-up or system reset if the Microprocessor does not communicate with the Display
Processor for a 5-second period. The Watchdog Timer and Reset Circuit comprises dual
retriggerable monostable multivibrator A2U5, NAND gates A2U6, diode A2CR3, and
various resistive and capacitive timing components.
At power-up, capacitor A2C3 begins to charge up through resistor A2R3. The voltage
level on A2C3 is detected by an input of Schmitt-Trigger NAND gate A2U6-12. The
output of this gate (A2U6-11) then drives the active high reset signal (RESET) to the rest
of the system. When the voltage on A2C3 is below the input threshold (typically +2.5V
dc) of A2U6-12, A2U6-11 is high. As soon as A2C3 charges up to the threshold of
A2U6-12, A2U6-11 goes low. The RESET signal drives NAND gate inputs A2U6-1 and
A2U6-2 to generate the active low reset signal (RESET*) at A2U6-3.
When the RESET signal transitions from high to low (A2U5-1), the Watchdog Timer is
triggered initially, causing A2U5-13 to go high. This half of the dual retriggerable
monostable multivibrator uses timing components A2R2 and A2C2 to define a nominal
2-30
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
4.75-second watchdog timeout period. Each time a low-to-high transition of DISTX is
detected on A2U5-2, capacitor A2C2 is discharged to restart the timeout period. If there
are no low-to-high transitions on DISTX during the 4.75-second period, A2U5-13
transitions from high to low, triggers the other half of A2U5, and causes output A2U5-12
to go low. A2U5-12 is then inverted by A2U6 to drive the RESET signal high, causing a
system reset. The low duration of A2U5-12 is determined by timing components A2Z1
and A2C4 and is nominally 460 µs. When A2U5-12 goes high again, RESET goes low to
retrigger the Watchdog Timer.
2-70. Display Controller
The Display Controller is a four-bit, single-chip microcomputer with high-voltage
outputs that are capable of driving a vacuum-fluorescent display directly. The controller
receives commands over a three-wire communication channel from the Microprocessor
on the Main Assembly. Each command is transferred serially to the Display Controller
on the display transmit (DISTX) signal, with bits being clocked into the Display
Controller on the rising edges of the display clock signal (DSCLK). Responses from the
Display Controller are sent to the Microprocessor on the display receive signal (DISRX)
and are clocked out of the Display Controller on the falling edge of DSCLK.
Series resistor A2R11 isolates DSCLK from A2U1-40, preventing this output from
trying to drive A1U4-16 directly. Figure 2-8 shows the waveforms during a single
command byte transfer. Note that a high DISRX signal is used to hold off further
transfers until the Display Controller has processed the previously received byte of the
command.
DSCLK
BIT 7
DISTX
BIT 7
DISRX
CLEAR TO
RECEIVE
BIT 6
BIT 6
BIT 5
BIT 5
BIT 4
BIT 4
BIT 3
BIT 3
BIT 2
BIT 2
BIT 1
BIT 1
BIT 0
BIT 0
HOLD OFF
26 µs
CLEAR TO
RECEIVE
26 µs
s8f.eps
Figure 2-8. Command Byte Transfer Waveforms
Once reset, the Display Controller performs a series of self-tests, initializing display
memory and holding the DISRX signal high. After DISRX goes low, the Display
Controller is ready for communication; on the first command byte from the
Microprocessor, the Display Controller responds with a self-test results response. If all
self-tests pass, a response of 00000001 (binary) is returned. If any self-test fails, a
response of 01010101 (binary) is returned. The Display Controller initializes its display
memory to one of four display patterns depending on the states of the DTEST* (A2U141) and LTE* (A2U1-13) inputs. The DTEST* input is pulled up by A2Z1, but may be
pulled down by jumpering A2TP4 to A2TP3 (GND). The LTE* input is pulled down by
A2R12, but may be pulled up by jumpering A2TP5 to A2TP6 (VCC). The default
conditions of DTEST* and LTE* cause the Display Controller to turn all segments on
bright at power-up.
Table 2-8 defines the logic and the selection process for the four display initialization
modes.
The two display test patterns are a mixture of on and off segments forming a
recognizable pattern that allows for simple testing of display operation. Test patterns #1
and #2 are shown in Section 5 of this manual.
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Table 2-8. Display Initialization Modes
A2TP4
A2TP5
1
1
0
0
Power-Up Display Initialization
1
0
1
0
All Segments OFF
All Segments ON (default)
Display Test Pattern #1
Display Test Pattern #2
The Display Controller provides 11 grid control outputs and 15 anode control outputs
(only 14 anode control outputs are used). Each of these 26 high-voltage outputs provides
an active driver to the +5V dc supply and a passive 220-kΩ (nominal) pull-down to the 30V dc supply. These pull-down resistances are internal to the Display Controller.
The Display Controller provides multiplexed drive to the vacuum-fluorescent display by
strobing each grid while the segment data for that display area is present on the anode
outputs. Each grid is strobed for approximately 1.14 milliseconds every 13.8
milliseconds, resulting in each grid on the display being strobed about 72 times per
second. The grid strobing sequence is from GRID(10) to GRID(0), which results in leftto-right strobing of grid areas on the display. Figure 2-9 shows grid control signal
timing.
The single grid strobing process involves turning off the previously enabled grid,
outputting the anode data for the next grid, and then enabling the next grid. This
procedure ensures that there is some time between grid strobes so that no shadowing
occurs on the display. A grid is enabled only if one or more anodes are also enabled.
Thus, if all anodes under a grid are to be off, the grid is not turned on. Figure 2-10
describes the timing relationship between an individual grid control signal and the anode
control signals.
GRID TIMING
13.8 ms
0V
GRID(10)
1.14 ms
0V
GRID(9)
…
…
1.14 ms
0V
GRID(1)
1.14 ms
0V
GRID(0)
1.14 ms
116 µs
s9f.eps
Figure 2-9. Grid Control Signal Timing
2-32
Theory of Operation (2620A/2625A)
Detailed Circuit Description
2
GRID/ANODE TIMING
5V
0V
1.14 ms
GRID(X)
-30V
116 µs
5V
0V
ANODE(14..0)
-30V
19 µs
60 µs
56 µs
98 µs
5V
0V
GRID(X-1)
-30V
s10f.eps
Figure 2-10. Grid-Anode Timing Relationships
2-71. Memory PCA (2625A Only)
The Memory PCA is a serially-accessed, byte-wide, nonvolatile 256K-byte memory that
is capable of storing up to 2047 scans of data. The following paragraphs describe in
detail the Main PCA Connector, Address Decoding, Page Register, Byte Counter, and
Nonvolatile Memory blocks that make up this assembly.
2-72. Main PCA Connector
The Memory PCA interfaces to the Main PCA through a 26-pin, right angle connector
(A6J1). This connector routes the eight-bit data bus, the lower three bits of the address
bus, memory control and address decode signals from the Main PCA to the Memory
PCA. The Memory PCA is powered by the +5.1V dc power supply (VCC). The Memory
PCA is sensed by the Microprocessor on the Main PCA through the connection of A6J111 to the option sense signal OPS* (A6J1-22).
2-73. Address Decoding
Circuitry on the Main PCA decodes the Microprocessor address bus and provided the
MEM* select signal to the Memory PCA. The 3-line to 8-line decoder (A6U8) is used to
decode the three least significant address bits to get register select signals for
hexadecimal addresses 4, 5, and 6. When the MEM* signal drives A6U8-4 low and the
RESET* signal (A6U8-6) is high, the A0 through A2 address bits are decoded to get the
MEMORY, PAGEL, and PAGEH register select signals.Address decoding is disabled
when RESET* is low so that the Nonvolatile Memory cannot be accidentally modified
during power-up or power-down.
2-74. Page Register
The Page Register is an 11-bit register that is writable by the Microprocessor on the
Main PCA. The outputs of this register control the most significant address bits of the
nonvolatile memories (A6U6 and A6U7.) When register select PAGEL goes high and
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the WE* signal is low, NAND gate output A6U2-3 goes high to latch the data bus into
the lower part of the page register (A6U1).When register select PAGEH goes high and
the WE* signal is low, NAND gate output A6U2-8 goes high to latch the lower three bits
of the data bus into the high part of the page register (A6U4).
2-75. Byte Counter
The Byte Counter is a seven-bit ripple counter that controls the lower address bits of the
nonvolatile RAMs. This counter is cleared when a new value is written to the lower page
register. It automatically increments at the end of each read or write access to the
memory data register.
NAND gate output A6U2-3 goes high to write the lower page register and clear the Byte
Counter. When data is read from or written to the Non-Volatile Memory, NAND gate
output A6U2-6 goes high during the memory cycle, and then low at the end of the
memory cycle. The transition from high to low increments the Byte Counter so that the
next access to the memory data register will be for the next sequential byte in the NonVolatile Memory.
2-76. Nonvolatile Memory
The Non-Volatile Memory is made up of two 128K-byte static CMOS memories with
integrated lithium battery, power-fail detection, and battery switching circuitry. When
the VCC (+5.1V dc) power supply is above +4.5V dc, memories A6U6 and A6U7 are
fully operational. When VCC drops below approximately +4.25V dc, all access to the
memory are disabled by the internal power-fail detection circuit. When VCC drops
below about +3.0V dc, the battery switching circuitry disconnects VCC and connects the
lithium battery to the memory so that data is retained while the instrument power is off.
The most significant bit of the Page Register (A6U4-1,16) is gated with the MEMORY
register select signal by A6U5 to get the memory chip select signals (A6U5-6 and
A6U5-8). Memory pages 0 through 1023 are stored in memory device A6U7, and
memory pages 1024 through 2047 are stored in memory device A6U6. The WR* and
RD* control signals from the Microprocessor on the Main PCA are used to enable
writing of data to and reading data from the memory devices, respectively.
2-77. IEEE-488 Interface (Option -05)
Refer to Section 7 for detailed circuit description of this option.
2-34
Chapter 2A
Theory of Operation (2635A)
Title
Page
2A-1. Introduction ..........................................................................................2A-3
2A-2. Functional Block Description...............................................................2A-3
2A-3.
Main PCA Circuitry.........................................................................2A-3
2A-4.
Power Supply...............................................................................2A-3
2A-5.
Digital Kernel ..............................................................................2A-3
2A-6.
Serial Communication (Guard Crossing) ....................................2A-6
2A-7.
Digital Inputs and Outputs...........................................................2A-6
2A-8.
A/D Converter PCA .........................................................................2A-6
2A-9.
Analog Measurement Processor ..................................................2A-6
2A-10.
Input Protection Circuitry............................................................2A-6
2A-11.
Input Signal Conditioning............................................................2A-6
2A-12.
Analog-to-Digital (A/D) Converter .............................................2A-6
2A-13.
Inguard Microcontroller Circuitry ...............................................2A-6
2A-14.
Channel Selection Circuitry.........................................................2A-7
2A-15.
Open Thermocouple Check Circuitry..........................................2A-7
2A-16.
Input Connector Assembly...............................................................2A-7
2A-17.
20 Channel Terminals..................................................................2A-7
2A-18.
Reference Junction Temperature.................................................2A-7
2A-19.
Display PCA ....................................................................................2A-7
2A-20.
Memory Card Interface PCA ...........................................................2A-7
2A-21. Detailed Circuit Description ................................................................2A-7
2A-22.
Main PCA ........................................................................................2A-7
2A-23.
Power Supply Circuit Description...............................................2A-8
2A-31.
Digital Kernel ..............................................................................2A-10
2A-42.
Digital I/O....................................................................................2A-19
2A-43.
Digital Input Threshold ...............................................................2A-19
2A-44.
Digital Input Buffers....................................................................2A-19
2A-45.
Digital and Alarm Output Drivers ...............................................2A-19
2A-1
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2A-46.
2A-47.
2A-48.
2A-49.
2A-50.
2A-51.
2A-57.
2A-58.
2A-59.
2A-60.
2A-61.
2A-62.
2A-63.
2A-64.
2A-65.
2A-66.
2A-67.
2A-68.
2A-69.
2A-70.
2A-71.
2A-72.
2A-73.
2A-74.
2A-2
Totalizer Input .............................................................................2A-19
External Trigger Input Circuits....................................................2A-20
A/D Converter PCA .........................................................................2A-20
Analog Measurement Processor ..................................................2A-20
Input Protection ...........................................................................2A-24
Input Signal Conditioning............................................................2A-25
Passive and Active Filters............................................................2A-30
A/D Converter .............................................................................2A-30
Inguard Microcontroller Circuitry ...............................................2A-32
Channel Selection Circuitry.........................................................2A-32
Open Thermocouple Check .........................................................2A-32
Input Connector PCA.......................................................................2A-33
Display PCA ....................................................................................2A-33
Main PCA Connector ..................................................................2A-33
Front Panel Switches ...................................................................2A-34
Display.........................................................................................2A-34
Beeper Drive Circuit....................................................................2A-34
Watchdog Timer and Reset Circuit .............................................2A-35
Display Controller .......................................................................2A-35
Memory Card Interface PCA ...........................................................2A-37
Main PCA Connector ..................................................................2A-38
Microprocessor Interface.............................................................2A-38
Memory Card Controller .............................................................2A-38
PCMCIA Memory Card Connector .............................................2A-39
Theory of Operation (2635A)
Introduction
2A
2A-1. Introduction
The theory of operation begins with a general overview of the instrument and progresses
to a detailed description of the circuits of each pca.
The instrument is first described in general terms with a Functional Block Description.
Then, each block is detailed further (often to the component level) with Detailed Circuit
Descriptions. Refer to Section 8 of this manual for full schematic diagrams. The
Interconnect Diagram in this section (Figure 2A-1) illustrates physical connections
among pca’s.
Signal names followed by a ’*’ are active (asserted) low. All other signals are active high.
2A-2. Functional Block Description
Refer to Figure 2A-2, Overall Functional Block Diagram, during the following
functional block descriptions.
2A-3. Main PCA Circuitry
The following paragraphs describe the major circuit blocks on the Main PCA.
2A-4. Power Supply
The Power Supply functional block provides voltages required by the vacuumfluorescent display (-30V dc, -5.0V dc, and filament voltage of 5.4V ac), the inguard
circuitry (-5.4V dc VSS, +5.3V dc VDD, and +5.6V dc VDDR), and outguard digital
circuitry of +5.0V dc (VCC).
Within the Power Supply, the Raw DC Supply converts ac line voltage to dc levels. The
5V Switching Supply converts this raw dc to 5.0V ±0.25V dc, which is used by the
Inverter in generating the above-mentioned outputs. The Power Fail Detector monitors
the Raw DC Supply and provides a power supply status signal to the Microprocessor in
the Digital Kernel.
2A-5. Digital Kernel
The Digital Kernel functional block is responsible for the coordination of all activities
within the instrument. This block requires voltages from the Power Supply and signals
from the Power-on Reset circuit.
Specifically, the Digital Kernel Microprocessor performs the following functions:
• Executes the instructions stored in FLASH EPROM.
• Stores temporary data and nonvolatile instrument configuration datain NVRAM.
• Stores instrument calibration data in FLASH EPROM.
• Communicates with the microcontroller on the A/D Converter PCA viathe Serial
Communication (Guard Crossing) block.
• Communicates with the Display Controller to display readings and userinterface
information.
• Communicates with the Field Programmable Gate Array, which scans theuser
interface keyboard found on the Display Assembly and interfaceswith the Digital I/O
hardware.
• Communicates with a host computer via the RS-232 interface.
• Stores instrument setup and measurement data on a Static RAM memorycard
installed in the Memory Card Interface Assembly.
• Reads the digital inputs and changes digital and alarm outputs.
2A-3
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DIGITAL I/O AND
TOTALIZE INPUT
ALARM OUTPUTS
SCAN TRIGGER INPUT
AC IN
RS-232
J4
DISPLAY
J1
J6
J5
J3
J2
MAIN
MEMORY
CRAD
INTERFACE
P4
P2
P10
CHANNEL 0
CHANNELS 11…20
J10
TB1
TB2
ANALOG
INPUT
CONNECTOR
P1
J1
A/D
CONVERTER
P2
J2
CHANNELS 1…10
S11F.EPS
FIGURE 2A-1. InterconnectDiagram (2635A)
2A-4
Theory of Operation (2635A)
Functional Block Description
2A
ANALOG INPUT CONNECTOR
INPUT MULTIPLEXING
INPUT PROTECTION
INPUT SIGNAL
CONDITIONING
ANALOG
MEASUREMENT
PROCESSOR
(A/D CONVERTER)
MICRO CONTROLLER
INGUARD
A/D CONVERTER
PCA
SERIAL
COMMUNICATION
OUTGUARD
GUARD
CROSSING
RS-232
µP
FLASH
MEMORY
NVRAM &
REAL-TIME
CLOCK
MEMORY
CARD
INTERFACE
VACUUM FLUORESCENT
DISPLAY
ADDRESS
DECODING
DISPLAY CONTROLLER
FPGA
FRONT PANEL SWITCHES
OPTION
INTERFACE
RESET
CIRCUITS
DIGITAL I/O
DISPLAY ASSEMBLY
POWER
SUPPLY
+5.6 Vdc (VDDR)
–5.4 Vdc (VSS)
+5.3Vdc (VDD)
INGUARD
–30 Vdc (VLOAD)
MAIN PCA
+5.1 Vdc (VCC)
–5 Vdc (VEE)
5.4 Vac
OUTGUARD
s12f.eps
Figure 2A-2. Overall Functional Block Diagram (2635A)
2A-5
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2A-6. Serial Communication (Guard Crossing)
This functional block provides a high isolation voltage communication path between the
Digital Kernel of the Main PCA and the microcontroller on the A/D Converter PCA.
This bidirectional communication circuit requires power supply voltages from the Power
Supply block.
2A-7. Digital Inputs and Outputs
This functional block contains the Totalizer and External Trigger Input Buffers, eight
bidirectional Digital I/O channels, four Alarm Outputs, and the Input Threshold control
circuits. These circuits require power supply voltages from the Power Supply and signals
from the Digital Kernel.
2A-8. A/D Converter PCA
The following paragraphs describe the major blocks of circuitry on the A/D Converter
PCA.
2A-9. Analog Measurement Processor
The Analog Measurement Processor (A3U8) provides input signal conditioning, ranging,
a/d conversion, and frequency measurement. This custom chip is controlled by the A/D
Microcontroller (A3U9). The A/D Microcontroller communicates with the Main PCA
Microprocessor (A1U1) over a custom serial interface.
2A-10. Input Protection Circuitry
This circuitry protects the instrument measurement circuits during overvoltage
conditions.
2A-11. Input Signal Conditioning
Here, each input is conditioned and/or scaled to a dc voltage for measurement by the a/d
converter. DC voltage levels greater than 3V are attenuated. To measure resistance, a dc
voltage is applied across a series connection of the input resistance and a reference
resistance to develop dc voltages that can be ratioed. DC volts and ohms measurements
are filtered by a passive filter. AC voltages are first scaled by an ac buffer, converted to a
representative dc voltage by an rms converter, and then filtered by an active filter.
2A-12. Analog-to-Digital (A/D) Converter
The dc voltage output from the signal conditioning circuits is applied to a
buffer/integrator which charges a capacitor for an exact amount of time. The time
required to discharge this capacitor, which is proportional to the level of the unknown
input signal, is then measured by the digital counter circuits in the Analog Measurement
Processor.
2A-13. Inguard Microcontroller Circuitry
This microcontroller (and associated circuitry) controls all functions on the A/D
Converter PCA and communicates with the digital kernel on the Main PCA. Upon
request by the Main PCA, the inguard microcontroller selects the input channel to be
measured through the channel selection circuitry, sets up the input signal conditioning,
commands the Analog Measurement Processor to begin a conversion, stops the
measurement, and then fetches the measurement result. The inguard microcontroller
manipulates the result mathematically and transmits the reading to the digital kernel.
2A-6
Theory of Operation (2635A)
Detailed Circuit Description
2A
2A-14. Channel Selection Circuitry
This circuitry consists of a set of relays and relay-control drivers. The relays form a tree
that routes the input channels to the measurement circuitry. Two of the relays are also
used to switch between 2-wire and 4-wire operation.
2A-15. Open Thermocouple Check Circuitry
Under control of the Inguard Microcontroller, the open thermocouple check circuit
applies a small ac signal to a thermocouple input before each measurement. If an
excessive resistance is encountered, an open thermocouple input condition is reported.
2A-16.
Input Connector Assembly
The following paragraphs briefly describe the major sections of the Input Connector
PCA, which is used for connecting most of the analog inputs to the instrument.
2A-17. 20 Channel Terminals
Twenty HI and LO terminal blocks are provided in two rows, one for channels 1 through
10 and one for channels 11 through 20. The terminals can accommodate a wide range of
wire sizes. The two rows of terminal blocks are maintained very close to the same
temperature for accurate thermocouple measurements.
2A-18. Reference Junction Temperature
A semiconductor junction is used to sense the temperature of the thermocouple input
terminals. The resulting dc output voltage is proportional to the block temperature and is
sent to the A/D Converter PCA for measurement.
2A-19.
Display PCA
The Display Assembly controller communicates with the main Microprocessor over a
three-wire communication channel. Commands from the Microprocessor inform the
Display Controller how to modify its internal display memory. The Display Controller
then drives the grid and anode signals to illuminate the required segments on the
Display. The A2 Display Assembly requires power supply voltages from the Power
Supply, a reset signal from the Reset Circuit, and a clock signal from the Digital Kernel.
2A-20.
Memory Card Interface PCA
The Memory Card Interface PCA is used to access the memory on an industry standard
memory card installed through the slot in the front panel of the instrument. This
assembly allows management of the memory card power, adapts timing of accesses by
the Digital Kernel to the memory card, and provides visible indicators for low battery
voltage and memory card busy status.
2A-21. Detailed Circuit Description
2A-22.
Main PCA
>The following paragraphs describe the operation of the circuits on the Main PCA. The
schematic for this pca is located in Section 8.
2A-7
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2A-23. Power Supply Circuit Description
The Hydra power supply consists of three major sections:
•
Raw DC Supply
The raw dc supply converts line voltage (90V to 264V ac) to a dcoutput of 7.5V to
35V.
•
5V Switcher Supply
The 5V switching supply regulates the 7.5 to 35V dc input to anominal 5.0V ±0.25V
dc (VCC).
•
Inverter
Using the 5V switching supply output, the inverter generates the -30Vdc, -5V dc,
and 5.4V ac supply levels needed for thevacuum-fluorescent display and the RS-232
Interface. The inverteralso provides isolated +5.3V (VDD), +5.6V (VDDR), and 5.4V (VSS)outputs for the inguard circuitry.
2A-24. Raw DC Supply
The raw dc supply circuitry receives input from power transformer T401, which operates
on an input ranging from 90V to 264V ac. The power transformer is energized whenever
the power cord is plugged into the ac line; there is no on/off switch on the primary side
of the transformer. The transformer has an internal 275V ac metal-oxide varistor (MOV)
to clamp line transients. The MOV normally acts as an open circuit. When the peak
voltage exceeds approximately 400V, the line impedance in series with the line fuse
limits transients to approximately 450V. All line voltages use a slow blow 0.125 A,
250V fuse.
On the secondary side of the transformer, rectifiers A1CR2, A1CR3, and capacitor A1C7
rectify and filter the output. When it is ON, switch A1S1 (the front panel POWER
switch) connects the output of the rectifiers to the filter capacitor and the rest of the
instrument. Depending on line voltage, the output of the rectifiers is between 7.5 and
35V dc. Capacitor A1C2 helps to meet electromagnetic interference (EMI) and
electromagnetic compatibility (EMC) requirements.
When external dc power is used, the power switch connects the external dc source to
power the instrument. The external dc input uses thermistor A1RT1 (for overcurrent
protection) and diode A1CR1 (for reverse input voltage protection.) Capacitor A1C59
helps meet EMI/EMC requirements. Resistor A1R48, capacitors A1C2 and A1C39 also
ensure that the instrument meets EMI/EMC performance requirements.
2A-25. Auxiliary 6V Supply
Three-terminal regulator A1U19, voltage-setting resistors A1R44 and A1R46, and
capacitor A1C34 make up the auxiliary 6-volt supply. This supply is used for the inverter
oscillator, inverter driver, and the power fail detection circuits.
2A-26. 5V Switcher
The 5V switcher supply uses a switcher supply controller/switch device A1U9 and
related circuitry.The 7.5V dc to 35V dc input is regulated to 5.1V dc (VCC) through
pulse-width modulation at a nominal switching frequency of 100 kHz.
2A-8
Theory of Operation (2635A)
Detailed Circuit Description
2A
The output voltage of the switcher supply is controlled by varying the duty cycle (ON
time) of the switching transistor in the controller/switch device A1U9. A1U9 contains
the supply reference, oscillator, switch transistor, pulse-width modulator comparator,
switch drive circuit, current-limit comparator, current-limit reference, and thermal limit.
Dual inductor A1T2 regulates the current that flows from the raw supply to the load as
the switching transistor in A1U9 is turned on and off. Complementary switchA1CR10
conducts when the switching transistor is off.
The pulse-width modulator comparator in A1U9 compares the output to the reference
and sets the ON-time/OFF-time ratio to regulate the output to 5.1V dc. A1C26 is the
input filter capacitor, and A1C14 is the output filter capacitor. Proper inductor and
capacitor values set the filter frequency response to ensure best overall system stability.
Circuitry consisting of A1R26, A1C21, and A1C18 ensure that the switcher supply
remains stable and operating in the continuous mode. Resistors A1R30 and A1R31 set
the output voltage to within 5% of 5.1V.Capacitor A1C21 sets the operating frequency
of the switcher at approximately 100 kHz.
Resistors A1R30 and A1R31 form a voltage divider that operates in conjunction with
amplifier A1U28, which is configured as a voltage follower.A1U28-5 samples the 5.1V
dc output, while A1U28-6 is the voltage divider input.The effect is to maintain the
junction of R30 and R31 at 5.1V dc, resulting in an A1U28-7 output level of 6.34V dc,
or 1.24V dc above the output.This feedback voltage is applied to A1U9-2, which A1U9
interprets as 1.24V dc because A1U9-3 (ground) is connected to the 5.1V dc output.
A1U9 maintains the feedback and reference voltages at 1.24V dc and thus regulates the
5.1V dc source.
2A-27. Inverter
The inverter supply uses a two transistor driven push-pull configuration. The center tap
of transformer A1T1 primary is connected to the 5.0V dc VCC supply, and each side is
alternately connected to common through transistors A1Q7 and A1Q8. A1R38 may be
removed to disable the inverter supply for troubleshooting purposes. A1Q7 and A1Q8
are driven by the outputs of D flip-flop A1U22. Resistors A1R34 and A1R28, and diodes
A1CR11 and A1CR12 shape the input drive signals to properly drive the gate of the
transistors. D flip-flop A1U22 is wired as a divide-by-two counter driven by a 110-kHz
square wave. The 110-kHz square wave is generated by hex inverter A1U23, which is
connected as an oscillator with a frequency determined by the values of resistors A1R40
and A1R47 and capacitor A1C35. The resulting ac voltage produced across the
secondary of A1T1 is rectified to provide the input to the inverter inguard and outguard
supplies.
2A-28. Inverter Outguard Supply
The inverter outguard supply provides three outputs: 5.4V ac, -30V dc, and -5V dc.
These voltages are required by the display and RS-232 drivers and receiver. The 5.4V ac
supply comes off the secondary windings (pins 6 and 7) on transformer T1, and it is
biased at -24V dc with zener diode A1VR3 and resistor A1R22. Dual diodes A1CR8 and
A1CR9 and capacitor A1C17 are for the -30V dc supply. Capacitors A1C30 and A1C31,
and dual diodes A1CR13 form a voltage doubler circuit that generates -12 volts. Threeterminal regulator A1U18 then regulates this voltage down to -5V for the RS-232 circuit.
Capacitor A1C32 is needed for transient response performance of the three-terminal
regulator.
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2A-29. Inverter Inguard Supply
The inverter inguard supply provides three outputs: +5.3V dc (VDD) and -5.4V dc
(VSS) for the inguard analog and digital circuitry, and +5.6V dc (VDDR) for the relays.
Diodes A1CR5 and A1CR6, and capacitor A1C12 are for the +9.5 volt source, and
diodes A1CR7 and capacitor A1C13 are for the -9.5V source.
Three-terminal regulator A1U6 regulates the 9.5V source to 5.6V for the relays. A1R5
and A1R6 set the output voltage at 5.6V. A1C6 is required for transient performance.
The +5.3V regulator circuit uses A1Q2 for the series-pass element and A1Q4 as the error
amplifier. A1VR2 is the reference for the positive supply. A1R14 provides the current to
bias the reference zener. A1C4 is the output filter, and A1C9 provides frequency
compensation of the regulator circuit. Transistor A1Q1 and resistor A1R13 make up the
current-limit circuit.
When the voltage across A1R13 increases enough to turn on A1Q1, output current is
limited by removing the base drive to A1Q2.
The -5.4 volt regulator operates like the +5.3 volt regulator, except that the NPN
transistors in the positive supply are PNP transistors in the negative supply, and the PNP
transistors in the positive supply are NPN transistors in the negative supply. If a VDDto-VSS short circuit occurs, diode A1CR4 ensures that current limit occurs at the limit
set for the -5.4V dc or +5.3V dc supply, whichever is lower.
2A-30. Power Fail Detection
The power fail detection circuit generates a signal to warn the Microprocessor that the
power supply is going down. A comparator in A1U10 compares the divided-down raw
supply voltage to a voltage reference internal to A1U10. When the raw supply voltage is
greater than about 8V dc, the output of A1U10 is "high" and when the raw supply falls
below 8V dc, the output goes "low". Resistors A1R19 and A1R20 make up the divider,
and capacitor A1C74 provides filtering of high frequency noise at the comparator input.
The reference voltage internal to A1U10 is nominally 1.3 volts dc.
2A-31. Digital Kernel
The Digital Kernel is composed of the following nine functional circuit blocks: the Reset
Circuits, the Microprocessor, the Address Decoding, the Flash Memory, the Nonvolatile
Static RAM and Real-Time Clock, the FPGA (Field Programmable Gate Array), the
Serial Communication (Guard Crossing), the RS-232 Interface, and the Option Interface.
2A-32. Reset Circuits
The Power-On Reset signal (POR*, A1U10-7) is generated by the Microprocessor
Supervisor, which monitors the voltage of VCC at A1U10-2. If VCC is less than +4.65
volts, then A1U10-7 will be driven low. POR* drives the enable inputs of the four tristate buffers in A1U2, causing the HALT*, RESET*, ORST*, and DRST* signals to be
driven low when POR* is low. When POR* goes high, the tri-state buffer outputs
(A1U2) go to their high-impedance state and the pull-up resistors pull the outputs to a
high level.
When HALT* and RESET* are both driven low, the Microprocessor (A1U1) is reset and
will begin execution when they both go high. The Microprocessor may execute a "reset"
instruction during normal operation to drive A1U1-92 low for approximately 10
microseconds to reset all system hardware connected to the RESET* signal.
2A-10
Theory of Operation (2635A)
Detailed Circuit Description
2A
The Display Reset signal (DRST*) is driven low by A1U2-6 when POR* is low, or it
may be driven low by the Microprocessor (A1U1-56) if the instrument firmware needs to
reset only the display hardware. For example, the firmware resets the display hardware
after the FPGA is loaded at power-up and the Display Clock (DCLK) signal from the
FPGA begins normal operation. This ensures that the Display Processor is properly reset
while DCLK is active.
The Option Reset signal (ORST*) is driven low by A1U2-3 when POR* is low, or it may
be driven low by the Microprocessor (A1U1-58) if the instrument firmware needs to
reset only the Option Interface hardware. For example, the firmware resets any option
interface hardware after the FPGA is loaded at power-up and the Option Clock (OCLK)
signal from the FPGA begins normal operation. This ensures that any Option Interface
hardware is properly reset while OCLK is active.
2A-33. Microprocessor
The Microprocessor uses a 16-bit data bus and a 19-bit address bus to access locations in
the Flash Memory (A1U14 and A1U16), the Nonvolatile Static RAM (A1U20 and
A1U24), the Real-Time Clock (A1U12), the FPGA (A1U25), the Memory Card
Interface PCA (A6), and the Option Interface (A1J1). All of the data bus lines and the
lowest 12 address lines have series termination resistors located near the Microprocessor
(A1U1) to ensure that the instrument meets EMI/EMC performance requirements. When
a memory access is done to the upper half of the data bus (D15 through D8), the upper
data strobe (UDS*) goes low. When a memory access is done to the lower half of the
data bus (D7 through D0), the lower data strobe (LDS*) goes low. When a memory
access is a read cycle, R/W* must be high. Conversely for any write cycle, R/W* must
be low.
The Microprocessor is a variant of the popular Motorola 68000 processor and is
enhanced by including hardware support for clock generation, address decoding, timers,
parallel ports, synchronous and asynchronous serial communications, interrupt
controller, DMA (Direct Memory Access) controllers, and a watchdog timer.
The 12.288-MHz system clock signal (A1TP11) is generated by the oscillator circuit
composed of A1U1, A1Y1, A1R2, A1C3, and A1C8. This clock goes through a series
termination resistor (A1R107) to the FPGA (A1U25) and also through another series
termination resistor (A1R86) to the Memory Card Interface (A1P4). These resistors are
necessary to ensure that the instrument meets EMI/EMC performance requirements.
The Microprocessor has four software programmed address decoders that include wait
state control logic. These four outputs are used to enable external memory and I/O
components during read and write bus cycles. See "Address Decoding" for a complete
description.
One sixteen-bit timer in the Microprocessor is used to generate a regular interrupt every
53.333 milliseconds. This timer uses the 12.288-MHz system clock (A1TP11) as a clock
source. The timer changes the state of parallel port pin A1U1-113 each time that it
interrupts the Microprocessor. The signal at A1U1-113 should be a 9.375-Hz square
wave (period of 106.67 milliseconds).
Another 16-bit timer is used as the totalizer counter. The totalizer signal originating at
J5-2 goes through the totalizer input buffer, the FPGA, and then to the external clock
input for this timer in the Microprocessor (U1-114 and TP20). See the Totalizer part of
"Digital I/O" for a complete description.
The Microprocessor has two parallel ports. Many of the parallel port pins are either used
as software controlled signals or as inputs or outputs of timers and serial communication
channels. Port A has 16 bits and Port B has 12 bits.
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The Microprocessor communicates to the Display Controller using a synchronous, threewire communication interface controlled by hardware in the Microprocessor.
Information is communicated to the Display Controller to display user interface menus
and measurement data. Details of this communication are described in the Display
Controller Theory of Operation in this section.
The Microprocess communicated to the Microcontroller on the A/D Converter PCA (via
the Serial Communication circuit) using an asynchronous communication channel at
4800 baud. Communication to the Microcontroller (A3U9) originates at A1U1-54.
Communication from the A/D’s Microcontroller to the Microprocessor appears at A1U153. When there is no communication in progress between the Microprocessor and the
Microcontroller, both of these signals are high.
The Microprocessor uses another asynchronous communication channel to communicate
to external computing or modem equipment through the RS-232 interface. This interface
is described in detail in the RS-232 Interface Theory of Operation in this section.
The third asynchronous communication channel in the Microprocessor is connected to
the Option Interface (J1) but is not used in the instrument at this time.
The interrupt controller in the Microprocessor prioritizes interrupts received from
hardware devices both internal and external to the Microprocessor. Table 2A-1 lists
interrupt sources from highest to lowest priority.
Table 2A-1. Microprocessor Interrupt Sources (2635A)
Pin
Signal Name
Description
A1U1-95
XTINT*
External Trigger Interrupt (Highest Priority)
A1U1-96
CINT*
Real-Time Clock Interrupt; once per second
A1U1-121
KINT*
Keyboard Interrupt; interrupts on each debounced change of keyboard
conditions.
RS-232 Interface Interrupt; internal to the Microprocessor.
A/D Communication Interrupt; internal to the Microprocessor.
Timer Interrupt every 53.333 milliseconds; internal to the Microprocessor.
A1U1-119
MCINT*
Memory Card Interface Interrupt; interrupts when a memory card is inserted,
removed, powered up or powered down.
Totalizer Interrupt; internal to the Microprocessor. Interrupts on totalizer
overflow from a count of 65535 to 0.
A1U1-97
OINT*
Option Interface Interrupt; not currently used in this product.
The Microprocessor also has several internal DMA (Direct Memory Access) controllers
that are used by the serial communication channels. Each serial communication channel
has a DMA channel that handles character reception and another that handles character
transmission. The use of these DMA controllers is transparent to the external operation
of the Microprocessor, but it is important to understand that communication is handled at
hardware speeds without the need for an interrupt for each character being transferred.
A watchdog timer internal to the Microprocessor is programmed to have a 10-second
timeout interval. If the code executed by the Microprocessor fails to reinitialize the
watchdog timer every 10 seconds or less, then A1U1-117 (POR*) is driven low for 16
cycles of SCLK (approximately 1.3 microseconds). This results in a complete hardware
reset of the instrument, which restarts operation.
2A-12
Theory of Operation (2635A)
Detailed Circuit Description
2A
2A-34. Address Decoding
The four chip-select outputs on the Microprocessor are individual software programmed
elements that allow the Microprocessor to select the base address, the size, and the
number of wait states for the memory accessed by each output.
The FLASH* signal (A1U1-128) enables accesses to 128 kilobytes of Flash Memory
(A1U14 and A1U16). The FLASH* signal goes through jumper W3, which must always
be installed during normal instrument operation. W3 is removed only during the initial
programming of the Flash Memory during production at the factory. The SRAM* signal
enables the Nonvolatile Static RAM (A1U20 and A1U24), and the MCARD* signal goes
to the Memory Card Interface PCA (A6). The I/O* signal goes to the I/O Decoder
(A1U11), which decodes small areas of address space for I/O devices like the FPGA, the
Real-Time Clock, and the Option Interface. There are no wait states for accesses to
FLASH* and SRAM*, but two wait states are used for any access to I/O*. Each wait
state adds approximately 83 nanoseconds to the length of a memory read or write cycle.
The Memory Card Interface handles wait state timing for any accesses to MCARD*.
When the Microprocessor is starting up (also referred to as "booting"), the address
decoding maps the address space as shown in Table 2A-2.
Table 2A-2. Booting Microprocessor Memory Map (2635A)
Hexadecimal Address
000000 - 03FFFF
100000 - 13FFFF
300000 - 30007F
300080 - 3000FF
300100 - 30017F
310000 - 311FFF
400000 - 401000
Device Selected
Flash (A1U14 and A1U16)
NVRAM (A1U20 and A1U24)
FPGA Configuration (A1U25)
Real-Time Clock (A1U12)
Option Interface (A1J1)
Memory Card Interface (A1P4)
Microprocessor Internal
Just before beginning execution of the instrument code, the address decoding is changed
to map the address space as shown in Table 2A-3. This change switches the positions of
Flash Memory and Nonvolatile Static RAM within the address space of the
Microprocessor.
Table 2A-3. Instrument Microprocessor Memory Map (2635A)
Hexadecimal Address
000000 - 03FFFF
100000 - 13FFFF
300000 - 300007
300008 - 30000F
300010 - 300017
300018 - 30001F (Read Only)
300020 - 300027 (Read Only)
300080 - 3000FF
300100 - 30017F
310000 - 311FFF
400000 - 401000
Device Selected
NVRAM (A1U20 and A1U24)
Flash (A1U14 and A1U16)
FPGA Control / Status (A1U25)
Alarm Outputs (A1U25)
Digital Outputs (A1U25)
Digital Inputs (A1U25)
Keyboard Input (A1U25)
Real-Time Clock (A1U12)
Option Interface (A1J1)
Memory Card Interface (A1P4)
Microprocessor Internal
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2A-35. Flash EPROM
The Flash EPROM is an electrically erasable and programmable memory that provides
storage of instructions for the Microprocessor and measurement calibration data.
A switching power supply composed of A1U15, A1T3, A1CR21, and A1C66 through
A1C69 generates a nominal +12 volt programming power supply (VPP) when the
Microprocessor drives VPPEN high (A1U15-2). Resistor A1R35 pulls A1U15-2 to near
ground during power-up to ensure that A1U15 is not enabled while the Microprocessor
is being reset. When the power supply is not enabled, the output voltage (VPP) should be
about 0.1 volt less than the input voltage of the power supply (VCC).
The only time that the programming power supply is active is when new firmware is
being loaded or new calibration constants are being stored into the Flash EPROM. The
code executed immediately after power-up is stored in an area of the Flash EPROM
(known as the Boot Block) that is only eraseable and reprogrammable if BBVPP
(A1U14-30 and A1U16-30) is at a nominal +12 volts. This may be accomplished by
installing jumper A1W1, but this should only be done by a trained technican, and A1W1
should never be installed unless it is necessary to update the Boot firmware. In normal
operation, resistor A1R73 and diode A1CR20 pull BBVPP up to about 0.25 volts less
than VCC.
The FLASH* chip select (A1U1-128) for these devices goes low for any memory access
to A1U14 or A1U16. The FLASH* signal goes through jumper W3, which must always
be installed during normal instrument operation. W3 is removed only during the initial
programming of the Flash Memory during production at the factory. A1U14 is connected
to the high 8 bits of the data bus, so read accesses are enabled by the Read Upper
(RDU*) signal going low, and write accesses are enabled by the Write Upper (WRU*)
signal going low. A1U16 is connected to the low 8 bits of the data bus, so read accesses
are enabled by the Read Lower (RDL*) signal going low, and write accesses are enabled
by the Write Lower (WRL*) signal going low.
2A-36. NVRAM/Real-Time Clock
The Nonvolatile Static RAM (NVRAM) provides the storage of data and configuration
information for the instrument. The Real-Time Clock maintains time and calendar date
information for use by the instrument.
A nonvolatile power supply (VBB) biases A1U12, A1U20, A1U24, and A1U26. The
Microprocessor Supervisor (A1U10) monitors the voltage on VCC (A1U10-2). If VCC
is greater than the voltage of the lithium battery (A1U10-8), A1U10 switches VCC from
A1U10-2 to A1U10-1 (VBB). If VCC drops below the voltage of the lithium battery
(A1U10-8), A1U10 will switch voltage from lithium battery A1BT1 through currentlimiting resistor A1R98 to A1U10-1 (VBB). The nominal current required from the
lithium battery (A1BT1) at room temperature with the instrument powered down is
approximately 2 microamperes. This can be easily measured by checking the voltage
across A1R98.
2A-14
Theory of Operation (2635A)
Detailed Circuit Description
2A
The SRAM* address decode output (A1U1-127) for the 128 kilobytes of NVRAM goes
low for any memory access to A1U20 or A1U24. This signal must go through two
NAND gates in A1U26 to the NVRAM chip select inputs (A1U20-22 and A1U24-22).
This ensures that when the instrument is powered down and A1U10-7 is driven low,
A1U20-22 and A1U24-22 will be driven high so that the contents of the NVRAM cannot
be changed and the power dissipated by the NVRAM is minimized. Jumper A1W4 in
A<18> is not used in the current instrument; it should be installed only if more NVRAM
is needed in a future instrument that needs 512 kilobytes of NVRAM using the same
circuit board. A1U24 is connected to the high 8 bits of the data bus, so read accesses are
enabled by the Read Upper (RDU*;A1U24-24) signal going low, and write accesses are
enabled by the Write Upper (WRU*;A1U24-29) signal going low. A1U20 is connected
to the low 8 bits of the data bus, so read accesses are enabled by the Read Lower
(RDL*;A1U20-24) signal going low, and write accesses are enabled by the Write Lower
(WRL*;A1U20-29) signal going low.
Memory accesses to the Real-Time Clock (A1U12) are enabled by the RTC* address
decode output (A1U11-16). This signal must go through two NAND gates in A1U26 to
the Real-Time Clock chip select input (A1U12-18). This ensures that when the
instrument is powered down and A1U10-7 is driven low, A1U12-18 will be driven high
so that the contents of the Real-Time Clock cannot be changed, and the power dissipated
by the Real-Time Clock is minimized. A1U12 is connected to the low 8 bits of the data
bus, so read accesses are enabled by the Read Lower (RDL*;A1U12-19) signal going
low, and write accesses are enabled by the Write Lower (WRL*;A1U12-20) signal going
low. When the instrument is powered up, the accuracy of the timebase generated by the
internal crystal may be tested by measuring the frequency of the 1-Hz square wave
output (A1U12-4). The Real-Time Clock also has an interrupt output (A1U12-3) that is
used by the Microprocessor to time the interval between scans when a scan interval is set
in the instrument. There should be one interrupt per second from the Real-Time Clock.
2A-37. Serial Communication (Guard Crossing)
The transmission of information from the Microprocessor (A1U1) to the Microcontroller
(A3U9) is accomplished via the circuit made up of A1Q10, A1U7, A1R8, A1R16, and
A3R8. The transmit output from the Microprocessor (A1U1-54) is buffered by A1Q10,
which then switches current through optocoupler LED (A1U7-2). Resistor A1R8 limits
the current through the LED.
The phototransistor in A1U7 responds to the light emitted by the LED when A1U1-54 is
driven low. (The collector of the phototransistor, A1U7-5, goes low.) The phototransistor
collector is pulled up by A3R8 on the A/D Converter PCA. When turning off, the
phototransistor base discharges through A1R16. With this arrangement, the rise and fall
times of the phototransistor collector signal are nearly symmetrical.
The transmission of data from the Microcontroller (A3U9) to the Microprocessor
(A1U1) is accomplished via the circuit made up of A3Q1, A3R7, A1U5, A1R7, and
A1R3. The transmit output from the Microcontroller (A3U9-14) is inverted by A3Q1,
which drives the optocoupler LED (A1U5-2) through resistor A3R7. The current through
the LED is limited by resistor A3R7. The phototransistor in A1U5 responds to the light
emitted by the LED when A1U5-2 is driven low. (The collector of the phototransistor,
A1U5-4, goes low.) The phototransistor collector (A1U5-5) is pulled up by resistor
A1R3. When turning off, the phototransistor base discharges through A1R7. With this
arrangement, the rise and fall times of the phototransistor collector signal are nearly
symmetrical.
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2A-38. Display/Keyboard Interface
The Microprocessor sends information to the Display Processor via a three-wire
synchronous communication interface. The detailed description of the DISTX, DISRX,
and DSCLK signals may be found in the detailed description of the Display PCA. Note
that the DISRX signal is pulled down by resistor A1R1 so that Microprocessor inputs
A1U1-49 and A1U1-118 are not floating at any time.
The Display Clock (DCLK) is a 1.024-MHz clock that is generated by the FPGA. Series
resistor A1R85 is necessary to ensure that the instrument meets EMI/EMC performance
requirements. The Display Assembly is reset when the Display Reset (DRST*) signal is
driven low. The reset circuit on the Display Assembly is discharged through resistor
A1R21, which limits the peak current from A2C3. DRST* is driven low at power-up, or
it may be driven low by the Microprocessor (A1U1-56).
The Keyboard interface is made up of six bidirectional I/O lines from the Field
Programmable Gate Array (FPGA). SWR1 through SWR6 (A1U25-67, A1U25-68,
A1U25-71, A1U25-73, A1U25-70, A1U25-69, respectively) are pulled up by A2Z1 on
the Display PCA. Hardware in the FPGA scans the keyboard switch array, detects and
debounces switch changes, and interrupts the Microprocessor to indicate that a
debounced keypress is available. A detailed description of this may be found under the
following heading "Field Programmable Gate Array (FPGA)".
2A-39. Field Programmable Gate Array (FPGA)
The FPGA is a complex programmable logic device that contains the following six
functional elements after the Microprocessor has loaded the configuration into the
FPGA: Clock Dividers, Internal Register Address Decoding, Keyboard Scanner, Digital
I/O Buffers and Latches, Totalizer Debouncing and Mode Selection, and the External
Trigger Logic.
When the instrument is powered up, the FPGA clears its configuration memory and
waits until RESET* (A1U25-78) goes high. The FPGA then tests its mode pins and
should determine that it is in "peripheral" configuration mode (A1U25-54 high; A1U2552 low; A1U25-56 high). In this mode the Microprocessor must load the configuration
information into the FPGA before the FGPA logic can begin operation.
The Microprocessor first makes sure that the FPGA is ready to be configured by driving
XD/P* (A1U25-80) low and then pulsing the RESET* (A1U25-78) input low for about
10 microseconds. The Microprocessor then waits until the XINIT* (A1U25-65) output
goes high, indicating that the FPGA has been initialized and is ready for configuration.
The Microprocessor then writes a byte of configuration data to the FPGA by driving
PGA* (A1U25-88) low and latching the data on the data inputs (D<8> through D<15>)
by pulsing WRU* (A1U25-5) low and then back high. The XRDY (A1U25-99) output
then goes low to indicate that the FPGA is busy loading that configuration byte. The
Microprocessor will then wait until XRDY goes high again before loading the next
configuration byte, and the sequence is repeated until the last byte is loaded. While the
configuration data is being loaded, the FPGA drives the XD/P* signal (A1U25-80) low.
When the FPGA has been completely configured, the XD/P* signal is released and
pulled high by resistor A1R70. The Microprocessor will repeat the configuration
sequence if XD/P* (A1U25-80) does not go high when it is expected to.
2A-16
Theory of Operation (2635A)
Detailed Circuit Description
2A
Clock Dividers
The 12.288-MHz system clock (A1U25-30) is divided down by the Clock Dividers to
create the 3.072-MHz Option Clock (OCLK; A1U25-22) and 1.024-MHz Display Clock
(DCLK; A1U25-19). The Display Clock is not a square wave; it is low for 2/3 of a cycle
and high for the other 1/3. The Display Clock is also used internal to the FPGA to create
the 128-kHz Totalizer Debouncer Clock and the 4-kHz Keyboard Scanner Clock.
Internal Register Address Decoding
The FPGA logic decodes four bits of the address bus (A<3> through A<6>), the PGA*
chip select signal (A1U25-88), RDU* (A1U25-95), and WRU* (A1U25-5) to allow the
Microprocessor to read five registers and write to three registers implemented in the
FPGA logic. The absolute addresses are listed in Table 2A-1.
Keyboard Scanner
The Keyboard Scanner sequences through the array of switches on the Display Assembly
to detect and debounce switch closures. After a switch closure is detected, it must remain
closed for at least 16 milliseconds before the Microprocessor will be interrupted and the
Keyboard Input register will be read from the FPGA. When the keyboard interrupt
(KINT*, A1U25-62) goes low, the Keyboard Scanner stops scanning until the
Microprocessor reads the Keyboard Input register which automatically clears the
interrupt by driving KINT* high again. The FPGA will interrupt the Microprocessor
again when the switch on the Display Assembly is detected as open again. Actually the
Microprocessor will be interrupted once for each debounced change in the contents of
the Keyboard Input register. See also the information on "Front Panel Switches" in the
"Display PCA" section for this instrument.
The Microprocessor can enable or disable the Keyboard Scanner by changing the state of
a bit in the Control/Status register that is in the FPGA. The Keyboard Scanner is disabled
if the instrument is in either the RWLS or LWLS state (see User Manual; RWLS and
LWLS Computer Interface Commands).
Digital I/O Buffers and Latches
The FPGA logic implements internal registers for the eight Digital Outputs (DO<0>
through DO<7>) and the four Alarm Outputs (AO<0> through AO<3>). These registers
are both written and read by the Microprocessor. The FPGA logic also implements an
eight-bit input buffer so that the Microprocessor can read the eight Digital Input lines
(DI<0> through DI<7>). See also "Digital Input Buffers" and "Digital and Alarm Output
Drivers".
Totalizer Debouncing and Mode Selection
Logic internal to the FPGA lets the Microprocessor enable a debouncer in the Totalizer
input signal path. The detailed description of the Totalizer Debouncer and Mode
Selection may be found under the heading "Totalizer Input".
External Trigger Logic
Logic internal to the FPGA allows the Microprocessor to set up the External Trigger
Logic to interrupt on rising or falling edges of the XTI input to the FPGA. The detailed
2A-17
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description of the External Trigger operation may be found in the "External Trigger
Input Circuits" section.
2A-40. RS-232 Interface
The RS-232 interface is composed of connector A1J4, RS-232 Driver/Receiver A1U13,
and the serial communication hardware in Microprocessor A1U1.
The serial communication transmit signal (A1U1-80) goes to the RS-232 driver (A1U1314), where it is inverted and level shifted so that the RS-232 transmit signal transitions
between approximately +5.0 and -5.0V dc. When the instrument is not transmitting, the
driver output (TP13;A1U13-3) is approximately -5.0V dc. The RS-232 receive signal
from A1J4 goes to the RS-232 receiver A1U13-4, which inverts and level shifts the
signal so that the input to the serial communication hardware transitions between 0 and
+5.0V dc. When nothing is being transmitted to the instrument, the receiver output
(TP12;A1U13-13) is +5.0V dc.
Data Terminal Ready (DTR) and Request To Send (RTS) are modem control signals
controlled by the Microprocessor. When the instrument is powered up, the
Microprocessor initially sets DTR and RTS false by setting A1U1-61 and A1U1-79 high,
which results in the RS-232 driver outputs (A1U13-7 and A1U13-5 respectively) going
to -5.0V dc. When the instrument has initialized the RS-232 interface and is ready to
receive and transmit, A1U1-61 and A1U1-79 will go low, resulting in the RS-232 DTR
and RTS signals going to +5.0V dc. The RS-232 DTR and RTS signals will remain at
+5.0V dc until the instrument is powered down except for a short period of time when
the user changes RS-232 communication parameters from the front panel of the
instrument.
Clear To Send (CTS) and Data Set Ready (DSR) are modem control inputs from the
attached RS-232 equipment. Of these signals, only CTS is used when CTS flow control
is enabled when CTS is turned on via the RS-232 communication setup menu. The CTS
modem control signal from A1J4 goes to the RS-232 receiver A1U13-6, which inverts
and level shifts the signal so that the input to the Microprocessor (A1U1-51) transitions
between 0 and +5.0V dc. When the instrument is cleared to send characters to the RS232 interface, the receiver output (A1U13-11) is +5.0V dc. If the RS-232 CTS signal is
not driven by the attached RS-232 equipment, the receiver output (A1U13-11) is near 0V
dc.
2A-41. Option Interface
The interconnection to the option slot is implemented by J1 on the Main PCA. This
connector (A1J1) routes the outguard logic power supply (VCC and GND), eight bits of
the data bus (D<8> through D<15>), RDU*, WRU*, OCLK, RESET*, OPTE*, and the
lower three bits of the address bus to the hardware installed in the option slot. This
connector also routes an interrupt signal (OINT*) from the option hardware to the IRQ1*
input of the Microprocessor (A1U1-97). The OPTE*, RDU*, and WRU* signals pass
through series resistors that are necessary to ensure that the instrument meets EMI/EMC
performance requirements.
An option sense signal from the installed option allows the Microprocessor to detect
whether or not option hardware is installed. Currently there is no optional hardware
available for this instrument.
2A-18
Theory of Operation (2635A)
Detailed Circuit Description
2A
2A-42. Digital I/O
The following paragraphs describe the Digital Input Threshold, Digital Input Buffers,
Digital and Alarm Output Drivers, Totalizer Input, and External Trigger Input circuits.
2A-43. Digital Input Threshold
The Digital Input Threshold circuit sets the input threshold level for the Digital Input
Buffers and the Totalizer Input. A fixed value voltage divider (A1R36, A1R37) and a
unity gain buffer amplifier (A1U8) are the main components in this circuit. The voltage
from the divider (approximately +1.4V dc) is then buffered by A1U8, which sets the
input threshold. Capacitor A1C29 filters the divider voltage at the input of A1U8.
2A-44. Digital Input Buffers
Since the eight Digital Input Buffers are identical in design, only components used for
Digital Input 0 are referenced in this description. If the Digital Output Driver (A1U1712) is off, the input to the Digital Input Buffer is determined by the voltage level at
A1J5-10. If the Digital Output Driver is on, the input of the Digital Input Buffer is the
voltage at the output of the Digital Output Driver.
The Digital Input Threshold circuit and resistor network A1Z1 determine the input
threshold voltage and hysteresis for inverting comparator A1U3. The inverting input of
the comparator (A1U3-13) is protected by a series resistor (A1Z3) and diode A1CR14. A
negative input clamp circuit (A1Q9, A1Z2, and A1CR17) sets a clamp voltage of
approximately +0.7V dc for the protection diodes of all Digital Input Buffers. A negative
input voltage at A1J5-10 causes A1CR14 to conduct current, clamping the comparator
input A1U3-13 at approximately 0V dc.
The input threshold of +1.4V dc and a hysteresis of +0.5V dc are used for all Digital
Input Buffers. When the input of the Digital Input Buffer is greater than approximately
+1.25V dc, the output of the inverting comparator is low. When the input then drops
below about +0.75V dc, the output of the inverting comparator goes high.
2A-45. Digital and Alarm Output Drivers
Since the 12 Digital Output and Alarm Output Drivers are identical in design, the
following example description references only the components that are used for Alarm
Output Driver 0.
The Microprocessor controls the state of Alarm Output Driver 0 by writing to the Alarm
Output register in the FPGA (A1U25) to set the level of output A1U25-63. When
A1U25-63 is set high, the output of the open-collector Darlington driver (A1U17-16)
sinks current through current-limiting resistor A1R62. When A1U25-63 is set low, the
driver output turns off and is pulled up by A1Z2 and/or the voltage of the external device
that the output is driving. If the driver output is driving an external inductive load, the
internal flyback diode (A1U17-9) conducts the energy into MOV A1RV1 to keep the
driver output from being damaged by excessive voltage. Capacitor A1C58 ensures that
the instrument meets electromagnetic interference (EMI) and electromagnetic
compatibility (EMC) performance requirements.
2A-46. Totalizer Input
The Totalizer Input circuit consists of Input Protection, a Digital Input Buffer circuit,
and a Totalizer Debouncing circuit. The Digital Input Buffer for the totalizer is protected
from electrostatic discharge (ESD) damage by A1R49 and A1C43. Refer to the detailed
description of the Digital Input Buffer circuit for more information.
2A-19
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The Totalizer Debounce circuit in the FPGA (A1U25) allows the Microprocessor to
select totalizing of either the input signal or the debounced input signal. The buffered
Totalizer Input signal (TOTI*) goes into the FPGA at A1U25-12. Inside the FPGA, the
totalizer signal is routed to the Totalizer Output (TOTO, A1U25-8) which then goes to a
16-bit counter in the Microprocessor (A1U1-114; TP20).
The actual debouncing of the input signal is accomplished by A1U25. Counters divide
the 12.288-MHz system clock down to 128 kHz for the debouncing circuit. An EXOR
gate compares the input signal (TOTI*) and the latched output of the debouncer. If these
signals differ, the EXOR gate output goes high, enabling the debouncer. If the input
remains stable for 1.75 milliseconds, the totalizer output (TOTO, A1U25-8) changes
state. If the input does not remain stable for 1.75 milliseconds, the totalizer output does
not change state. For a stable totalizer input of +5V dc, the totalizer output (TOTO,
A1U25-8) will be 0.0V dc. For a stable totalizer input of +0.0V dc, the totalizer output
(TOTO, A1U25-8) will be +5V dc.
2A-47. External Trigger Input Circuits
The External Trigger Input circuit can be configured by the Microprocessor to interrupt
on a rising or falling edge of the XT* input (A1J6-2) or to not interrupt on any
transitions of the XT* input. The falling edge of the XT* input is used by the instrument
firmware as an indication to start scanning, and the rising edge is used as an indication to
stop scanning.
The External Trigger Input is pulled up to +5V dc by A1Z2 and is protected from
electrostatic discharge (ESD) damage by A1R58, A1C54, A1Z3, and A1CR15. Capacitor
A1C54 helps ensure that the instrument meets EMI/EMC performance requirements.
The input (XTI) is then routed to the FPGA (A1U25), which contains the External
Trigger control circuitry. The Microprocessor sets control register bits in the FPGA
(A1U25) to control the external trigger circuit. The External Trigger control circuit
output (A1U25-9) drives the non-maskable interrupt on the Microprocessor (A1U1-95).
If External Triggering is enabled (see User Manual), the Microprocessor sets FPGA
control register bits to allow a low level on the XT* input to cause the External Trigger
Interrupt (XTINT*; A1U25-9) to go low. The Microprocessor then changes the FPGA
control register bits to allow a high level on the XT* input to cause XTINT* (A1U25-9)
to go low. Thus the Microprocessor can detect both rising and falling edges on the XT*
input. Normally, the XTINT* output of the FPGA (A1U25-9) should be low only for a
few microseconds at any time. If it is held low constantly, the instrument will not be able
to operate. Resistor A1R64 pulls the XTINT* output high to ensure that it is high during
power-up.
2A-48.
A/D Converter PCA
The following paragraphs describe the operation of the circuits on the A/D Converter
PCA. The schematic for this pca is located in Section 8.
2A-49. Analog Measurement Processor
Refer to Figure 2A-3 for an overall picture of the Analog Measurement Processor chip
and its peripheral circuits. Table 2A-4 describes Analog Measurement Processor chip
signal names.
The Analog Measurement Processor (A3U8) is a 68-pin CMOS device that, under
control of the A/D Microcontroller (A3U9), performs the following functions:
• Input signal routing
• Input signal conditioning
• Range switching
2A-20
Theory of Operation (2635A)
Detailed Circuit Description
•
•
•
•
2A
Passive filtering of dc voltage and resistance measurements
Active filtering of ac voltage measurements
A/D conversion
Support for direct volts, true rms ac volts, temperature, resistance,and frequency
measurements
2A-21
2A-22
LO
SENSE
LO
SOURCE
HI
SENSE
HI
SOURCE
REFERENCE
JUNCTION
R43
R11
R10
K16
C31
Figure 2A-3. Analog Simplified SchematicDiagram (2635A)
K17
Z4
R34
R35
R32
TO U9
300V
300Ω
15
14
R42
30 VDC
300 VDC
30 KΩ
30V
S16
7 6 5
OHMS
VOLTAGE
SOURCE
TO
REFERENCE
RESISTOR
2
TO U9
28 29 30 31 32 33
S2
S3
TO OHMS
SOURCE &
RRS HI
DIVIDER
SWITCHING
LOW
8
RMS
36
3.84 MHz
37
U8 ANALOG
MEASUREMENT
PROCESSOR*
RRS LOW
DC HI
S18
S19
FREQUENCY
COUNTER
RRS
LOW
RRS HI
S42
CONVERTER
REFER TO THE SCHEMATIC DIAGRAM IN SECTION 8.
* NOT ALL U8 SWITCHES ARE SHOWN HERE.
25
23
21
19
3 KΩ
300 KΩ 16
3 MΩ, 10 MΩ
OPEN
THERMOCOUPLE
DETECT
10M
100K
1M
10K
1K
13
11
10
GAIN CONTROL
V LO/RRS LO
Ω LO
AC BUFFER
RRS = REFERENCE RESISTOR SENSE
3 VDC/300 MVDC/TC/Ω
Ω
K15
ACV
DIGITAL
SECTION
A/D HI
+
–
ACTIVE
FILTER
AMP
TO U9
39 40 41 42
A/D
A/D LO
S81
61
ACTIVE
ACV
FILTER
52
1.05V
51
57
56
58
59
60
C12
A/D
REF
Z2
PASSIVE
DC
FILTERS
VR1
VDD
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Service Manual
s13f.eps
Theory of Operation (2635A)
Detailed Circuit Description
2A
Table 2A-4. Analog Measurement Processor Pin Descriptions (2635A)
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Name
VDD
ACBO
AIN
AGND2
ACR4
ACR3
ACR2
ACR1
VSSA
REFJ
DCV
LOW
GRD
RRS
V4
V3
V1
GRD
V2F
V2
GRD
V0
GRD
OVS
GRD
AGND1
DGND
FC0
FC1
FC2
FC3
FC4
FC5
FC6
FC7
XIN
XOUT
MRST
AS
AR
SK
CS
BRS
VSS
INT
SUM
B.1
B.32
B1
B3.2
Description
+5.4V supply
AC buffer output
(not used)
Analog ground
AC buffer range 4 (300V)
AC buffer range 3 (30V)
AC buffer range 2 (3V)
AC buffer range 1 (300 mV)
-5.4V supply for AC ranging
Reference junction input
A/D converter low input
Driven guard
Reference resistor sense for ohms
Tap #4 on the DCV input divider/ohms reference network
Tap #3 on the DCV input divider/ohms reference network
Tap #1 on the DCV input divider/ohms reference network
Driven guard
Tap #2 input on the DCV input divider/ohms reference network
Tap #2 on the DCV input divider/ohms reference network
Driven guard
Tap #0 on the DCV input divider/ohms reference network
Driven guard
Ohms and volts sense input
Guard
Analog ground
(not used)
Analog ground
Function control #0
Function control #1
Function control #2
Function control #3
(not used)
(not used)
Function control #6
Function control #7
Crystal oscillator input
Crystal oscillator output
Master reset
Analog send
Analog receive
Serial clock
Chip select
(not used)
-5.4V dc
Integrator output
Integrator summing node
Buffer output, 100 mV range
Buffer output, 300 mV range
Buffer output, 1000 mV range
Buffer output, 3V range
2A-23
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Table 2A-4. Analog Measurement Processor Pin Descriptions (2635A) (cont)
Pin
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
Name
VREF+
VREFRAO
RA+
RAAFO
MOF
AFI
FAI
FAO
RMSF
AGND3
RMSG2
RMSO
CAVG
VSSR
RMSG1
RMSI
Description
A/D voltage reference plus
A/D voltage reference minus
A/D reference amplifier output
A/D reference amplifier noninverting input
A/D reference amplifier inverting input
Passive filter 2
Passive filter 1 plus resistance
Passive filter 1
Filter amplifier inverting input
Filter amplifier output
RMS output, filtered
(not used, connected to filtered -5.4V dc)
(not used)
RMS converter output
(not used)
-5.4V dc, filtered
(not used, pulled to filtered -5.4V dc)
(not used)
Two separate signal paths are used, one for dc/ohms/temperature and one for ac. The
volts dc (3V range and below) and temperature voltages are coupled directly to the a/d
converter, while higher voltages are attenuated first. For ohms, the dc circuitry is
augmented with an internal ohms source voltage regulator controlled through an extra set
of switches. For volts ac, inputs are routed through the ac buffer, which uses the gain
selected by the Measurement Processor (A3U8).
The a/d converter uses a modified dual-slope minor cycle method. The basic
measurement unit, a minor cycle, consists of a fixed time integrate period for the
unknown input, a variable time reference integrate period, a variable time hold period,
and various short transition periods. A minor cycle period lasts for 25 ms or until a new
minor cycle is begun, whichever comes first.
2A-50. Input Protection
The instrument measurement circuits are protected when overvoltages are applied
through the following comprehensive means:
• Any voltage transients on channel 0 HI or LO terminals areimmediately clamped to
a peak of about 1800V or less by MOVs A3RV1and A3RV2. (This is much lower
than the 2500V peaks that can beexpected on 240 VAC, IEC 664 Installation
Category II, ac mains.)
• Fusible resistors A3R10 and A3R11 protect the measurement circuitryin all
measurement modes by limiting currents.
• A3Q11 clamps voltages exceeding 0.7V below and approximately 6.0Vabove analog
common (LO) or LO SENSE, with A3R35 limiting the inputcurrent.
• A3Q10 clamps voltages during ohms measurements with A3RT1, A3R34,A3R10,
and A3Z4 limiting the input current. With large overloads,thermistor A3RT1 will
heat up and increase in resistance.
• A3U8 also clamps voltages on its measurement input pins that exceedthe VDD and
VSS supply rails. Resistors A3R42, A3R11, A3R10, A3RT1,A3Z4, A3R35, and
A3R34 limit any input currents.
• Any excessive voltages that are clamped through A3U8 to VDD or VSS,are then
also clamped by zener diodes A3VR3 and A3VR2.
2A-24
Theory of Operation (2635A)
Detailed Circuit Description
•
•
•
2A
The open thermocouple detect circuitry is protected against voltagetransient damage
by A3Q14 and A3Q15.
When measuring ac volts, the ac buffer is protected by dual-diodeclamp A3CR1 and
resistor network A3Z3.
Switching induced transients are also clamped by dual-diodeA3CR4 and capacitor
A3C33, and limited by resistor A3R33.
2A-51. Input Signal Conditioning
Each input is conditioned and/or scaled to a dc voltage appropriate for measurement by
the a/d converter. DC voltage applied to the a/d converter can be handled on internal
ranges of 0.1V, 0.3V, 1V, or 3V. Therefore, high-voltage dc inputs are scaled, and ohms
inputs are converted to a dc voltage. Line voltage level ac inputs are first scaled and then
converted to a dc voltage. Noise rejection is provided by passive and active filters.
2A-52. Function Relays
Latching relays A3K15, A3K16, and A3K17 route the input signal to the proper circuit
blocks to implement the desired measurement function. These relays are switched when
a 6-millisecond pulse is applied to the appropriate reset or set coil by the NPN
Darlington drivers in IC A3U10. The A/D Microcontroller A3U9 controls the relay drive
pulses by setting the outputs of port 6. Since the other end of the relay coil is connected
to the VDDR supply, a magnetic field is generated, causing the relay armature and
contacts to move to (or remain in) the desired position. Function relay states are defined
in Table 2A-5.
Table 2A-5. Function Relay States (2635A)
Relay Position
Function
A3K17
A3K16
A3K15
DC mV, 3V,Thermocouples
Reset
Set
Set
DC 30V, 300V
Set
Set
Set
ACV
Set
Set
Reset
Ohms, RTDs
Reset
Reset
Set
Frequency
Set
Set
Reset
2A-53. DC Volts and Thermocouples
For the 3V and lower ranges (including thermocouples), the HI input signal is applied
directly to the A3U8 analog processor through A3R11, A3K17, and A3R42. Capacitor
A3C27 filters this input, which the analog processor then routes through S2 and other
internal switches, through the passive filter, and to the internal a/d converter. The LO
SENSE signal is applied to A3U8 through A3R35 and routed through internal switch
A3U8-S19 to LO of the a/d converter.
Guard signals MGRD and RGRD are driven by an amplifier internal to A3U8 to a
voltage appropriate for preventing leakage from the input HI signal under high humidity
conditions.
For the 30V range, the HI signal is scaled by resistor network A3Z4. Here, the input is
applied to pin 1 of A3Z4 so that an approximate 100:1 divider is formed by the 10-MΩ
and 100.5-kΩ resistors in A3Z4 when analog processor switches S3 and S13 are closed.
The attenuated HI input is then sent through internal switch S12 to the passive filter and
the a/d converter. Input LO is sensed through analog processor switch S18 and resistor
A3R34.
2A-25
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Service Manual
For the 300V range (Figure 2A-4), the HI signal is again scaled by A3Z4. The input is
applied to pin 1 of A3Z4, and a 1000:1 divider is formed by the 10-MΩ and 10.01-kΩ
resistors when switches S3 and S9 are closed in A3Z4. The attenuated HI input is then
sent through internal switch S10 to the passive filter and the a/d converter. LO is sensed
through analog processor switch S18 and resistor A3R34.
S2
A3R11
A3K17
INPUT HI
A3R10
A3Z4
10M
S3
S9
S10
A3Z4
10.01k
PASSIVE
FILTER
HIGH
A/D
A3R34
LOW
A3K16
INPUT LO
s14f.eps
Figure 2A-4. DC Volts 300V Range Simplified Schematic (2635A)
2A-54. Ohms and RTDs
Resistance measurements are made using a ratio ohms technique, as shown in Figure
2A-5. A stable voltage source is connected in series with the reference resistor in A3Z4
and the unknown resistor. Since the same current flows through both resistors, the
unknown resistance can be determined by multiplying the ratio of the voltage drops
across the reference and the unknown resistors by the known reference resistor value.
2A-26
Theory of Operation (2635A)
Detailed Circuit Description
2A
OHMS
VOLTAGE
SOURCE
IX
LOW
+
VR REF
–
A/D
INTEGRATE
REFERENCE
A3Z4 R REF
REFERENCE
RESISTOR
A3R34
HIGH
A3K16
A3RT1 & A3R10
A3R11
HI
+
VR X
-
A3R42
A3K17
PASSIVE
FILTER
RX
UNKNOWN
RESISTOR
HIGH
A/D
INTEGRATE
UNKNOWN
LO
LOW
RX
IX•RX
VR X
=
=
IX•RREF
R REF
VR REF
s15f.eps
Figure 2A-5. Ohms Simplified Schematic (2635A)
For the RTD, 300Ω, 3-kΩ, and 30-kΩ ranges, the ratio technique is implemented by
integrating the voltage across the unknown resistance for a fixed period of time and then
integrating the negative of the voltage across the reference resistance for a variable time
period. In this way, each minor cycle result gives the ratio directly.
For the 300-kΩ, 3-MΩ, and 10-MΩ ranges, the ratio is determined by performing two
separate voltage measurements in order to improve noise rejection. One fixed-period
integration is performed on the voltage across the unknown resistance, and the second
integration is performed on the voltage across the reference resistance. The ratio of the
two fixed-period voltge measurements is then computed by Microcontroller A3U9. The
resistance measurement result is determined when A3U9 multiplies the ratio by the
reference resistance value.
When an input is switched in for a measurement, the ohms source in Analog Processor
A3U8 is set to the correct voltage for the range selected and is connected to the
appropriate reference resistor in network A3Z4. A measurement current then flows
through A3Z4, relay A3K16, thermistor A3RT1, resistor A3R10, the unknown
resistance, A3R43, ground, and the ohms source.
The resulting voltage across the unknown resistance is integrated for a fixed period of
time by the A/D Converter through the HI SENSE path of A3R11, A3K17, A3R42 and
2A-27
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Service Manual
A3U8 switch S2, and the LO SENSE path of A3R35 and Analog Processor switch S19.
Passive filtering is provided by A3C34, A3C27, and portions or all of the DC Filter
block.
The voltage across the reference resistor for the 300Ω and RTD, 3-kΩ, and 30-kΩ
ranges (the 1-kΩ, 10.01-kΩ, and 100.5-kΩ resistances in A3Z4, respectively) is
integrated for a variable period of time until the voltage across the integrate capacitor
reaches zero. For the 300Ω and RTD range, the reference resistor voltage is switched in
through Analog Processor switch S6 and applied to the A/D Converter by switch S8. For
the 3-kΩ range, switches S9 and S11 perform these functions, respectively. For the 30kΩ range, switches S13 and S14 are used. For all ranges, the voltage is routed through
A3R34 to the RRS input.
The reference resistor for the 300-kΩ, 3-MΩ, and 10-MΩ ranges is the 1-MΩ resistor in
A3Z4, which is selected by S15. The voltage across this reference is integrated during its
own minor cycle(s) and is switched to a passive filter and the A/D Converter by switches
S1 and S18.
When 4-wire measurements are made on any of the six ranges, separate Source and
Sense signal paths are maintained to the point of the unknown resistance. The 4-wire
Source path measurement current is provided by the A3U8 ohms source through one of
the A3U8 internal switches (S6, S9, S13, or S15) and the appropriate reference resistor
in A3Z4. The current flows through relay A3K16, thermistor A3RT1, resistor A3R10,
the HI Source instrument relay contacts (A3K1 - A3K3, A3K5 - A3K14), and the HI
Source lead wire, to the unknown resistance to be measured. The current flows back
through the LO Source lead wire, the LO Source path of the instrument relays (A3K1 A3K3, A3K5 - A3K14), resistor A3R43, and analog ground, to the A3U8 ohms source.
The voltage that develops across the unknown resistance is sensed through the other 2
wires of the 4-wire set. HI is sensed through the HI Sense path made up of the users HI
Sense lead wire, the HI Sense contacts in the instrument relays, resistor A3R11, relay
A3K17, resistor A3R42, and Analog Processor A3U8 switch S2. LO is sensed through
the users LO Sense lead wire, the LO Sense contacts in the instrument relays, protection
resistor A3R35, and A3U8 switch S19.
Since virtually no current flows through the sense path, no error voltages are developed
that would add to the voltage across the unknown resistance; this 4-wire measurement
technique eliminates user lead-wire and instrument relay contact and circuit board trace
resistance errors.
2A-55. AC Volts
AC-coupled ac voltage inputs are scaled by the ac buffer, converted to dc by a true rms
ac-to-dc converter, filtered, and then sent to the a/d converter.
Refer to Figure 2A-6. Input HI is switched to the ac buffer by dc-blocking capacitor
A3C31, protection resistor A3R11, and latching relay A3K15. Resistor A3R44 and
A3K15 act to discharge A3C31 between channel measurements. LO is switched to the
A3U8 A/D Converter through A3R34 and S18.
2A-28
Theory of Operation (2635A)
Detailed Circuit Description
INPUT HI
A3R11
A3Z3
1.111M
A3K15
_
A3C31
A3U7
A3U6
RMS
COVERTER
+
A3Z3
2.776k
A3R44
A3Z3 FEEDBACK
RESISTOR
INPUT LO
A3C15
&
A3C16
2A
A3Z3
115.7
A3R43
s16f.eps
Figure 2A-6. AC Buffer Simplified Schematic (2635A)
JFETs A3Q3 through A3Q9 select one of the four gain (or attenuation) ranges of the
buffer (wide-bandwidth op-amp A3U7.) The four JFET drive signals ACR1 through
ACR4 turn the JFETs on at 0V and off at -VAC. Only one line at a time will be set at 0
volts to select a range.
The input signal to the buffer is first divided by 10, 100, or 1000 for the 300 mV, 3V,
and 30V ranges, respectively. The resistance ratios used are summarized in Table 2A-6.
Note that the 111.1-kΩ resistor is left in parallel with the smaller (higher attenuation)
resistors. The attenuated signal is then amplified by A3U7, which is set for a gain of 25
by the 2.776-kΩ and 115.7Ω resistors in A3Z3. Components A3R27 and A3C23
compensate high-frequency performance on the 300 mV range. For the 300V range,
overall buffer gain is determined by the ratio of the 2.776-kΩ feedback resistor to the
1.111-MΩ input resistor.
Table 2A-6. AC Volts Input Signal Dividers (2635A)
Range
Drive Signal
A3Z3 Divider
Resistor(s)
Overall Gain
300 mV
ACR1
111.1 kΩ
2.5
3V
ACR2
12.25 kΩ || 111.1 kΩ
0.25
30V
ACR3
1.013 kΩ || 111.1 kΩ
0.025
150/300V
ACR4
none
0.0025
2A-29
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Service Manual
The output of the buffer is ac-coupled by A3C15 and A3C16 to the true-rms ac-to-dc
converter A3U6. Discharge JFET A3Q13 is switched on to remove any excess charge
from the coupling capacitors A3C15 and A3C16 between channel measurements. A3C17
provides an averaging function for the converter, and resistor network A3Z1 divides the
output by 2.5 before sending the signal to the active ac volts filter. Analog processor
switch S81 connects the output of the active filter to HI of the A/D Converter.
Components A3R29, A3R30, A3C26, and A3C28 provide filtered power supplies
(+VAC and -VAC) for the ac buffer, the ac switch JFETs, and the rms converter.
2A-56. Frequency
After any dc component is blocked by capacitors A3C15, A3C16, and A3C31, the output
of the ac buffer is used to determine the input frequency. This signal is sent to the ACBO
pin of analog processor A3U8 and switched to the internal frequency comparator and
counter circuit by S42.
2A-57. Passive and Active Filters
The passive filters are used for the dc voltage and ohms measurements. For most ranges,
capacitors A3C14 and A3C11 are switched into the measurement circuit in front of the
A3U8 A/D Converter by switches S86, S87, and S88. These capacitors act with the 100kΩ series resistance provided by A3R42 or A3Z4 to filter out high-frequency noise. For
the 300-kΩ range, only A3C14 is switched in by switches S86 and S85. For the 3-MΩ
and 10-MΩ ranges, A3C11 or A3C14 are not switched in to keep settling times
reasonably short.
Between channel measurements, the passive filters are discharged by JFET A3Q2 under
control of Microcontroller A3U9 through comparator A3U14. When the ZERO signal is
asserted, A3R14 pulls the gate of A3Q2 to ground, turning the JFET on and discharging
A3C11. At the same time, zeroing of filter capacitors A3C14 and A3C27 is
accomplished by having the Analog Processor turn on internal switches S2, S86, and
S87.
The active filter is only used for ac voltage measurements. This three-pole active filter
removes a significant portion of the ac ripple and noise present in the output of the rms
converter without introducing any additional dc errors. The active filter op-amp within
A3U8, resistors A3R20, A3R17, and A3R16, and capacitors A3C7, A3C10, and A3C6
form the filter circuit. This filter is referenced to the LO input to the a/d converter within
A3U8 by the op-amp. The input to the filter is available at the RMSO pin, and the output
is sent to the RMSF pin of A3U8. Switches S80 and S82, which are turned on prior to
each new channel measurement, cause the filter to quickly settle (pre-charge) to near the
proper dc output level.
2A-58. A/D Converter
Figure 2A-7 shows the dual slope a/d converter used in the instrument. The unknown
input voltage is buffered and used to charge (integrate) a capacitor for an exact period of
time. This integrator capacitor is then discharged by the buffered output of a stable and
accurate reference voltage of opposite polarity. The capacitor discharge time, which is
proportional to the level of the unknown input signal, is measured by the digital circuits
in the Analog Measurement Processor. This time count becomes the conversion result.
2A-30
Theory of Operation (2635A)
Detailed Circuit Description
2A
+ REFERENCE
(– INPUT)
+
+
COUNTER
REFERENCE
_
_
A3C13
A/D
COMPARATOR
S77
–REFERENCE
(+ INPUT)
INTEGRATE
REFERENCE
+
A3Z2
_
_
INPUT HI
BUFFER
+
INTEGRATOR
INPUT LO
INTEGRATE
INPUT
s17f.eps
Figure 2A-7. A/D Converter Simplified Schematic (2635A)
In both the slow and fast measurement rates, the a/d converter uses its ±300 mV range
for most measurement functions and ranges. The primary exceptions are that the 3V dc
range is measured on the a/d converter 3V range, thermocouples are measured on the
±100 mV range, and the temperature reference is measured on the 1V a/d converter
range. The typical overload point on a slow rate 30000 count range is 32000 display
counts; the typical overload point on a fast rate 3000 count range is 3200 display counts.
During the integrate phase, the a/d buffer in the A3U8 Analog Measurement Processor
applies the signal to be measured to one of the four integrator input resistors in network
A3Z2. As shown on the A/D Converter schematic diagram in Section 8, the choice of
resistor selects the a/d converter range. Switch S69 connects the buffer output through
pin B.1 for the 100-mV range, S71 connects the output through B.32 for the 300 mV
range, S73 connects to pin B1 for the 1V range, and S75 sets up the 3V range through
pin B3.2.
The current through the selected integrator input resistor charges integrator capacitor
A3C13, with the current dependent on the buffer output voltage. After the integrate
phase, the buffer is connected to the opposite polarity reference voltage, and the
integrator integrates back toward zero capacitor voltage until the comparator trips. An
internal counter measures this variable integrate time. If the a/d converter input voltage
is too high, the integrator overloads and does not return to its starting point by the end of
the measurement phase. Switch S77 is then turned on to discharge integrate capacitor
A3C13.
The reference voltage used during the variable integrate period for voltage (and high
ohms) conversions is generated from zener reference diode A3VR1, which is time and
temperature stable. The reference amplifier in the Analog Measurement Processor, along
with resistors A3R15, A3R18, and A3R21, pulls approximately 2 mA of current through
the zener. Resistors in network A3Z2 divide the zener voltage down to the reference
1.05V required by the A/D Converter.
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2A-59. Inguard Microcontroller Circuitry
The Microcontroller, A3U9, with its internal program memory and RAM and associated
circuitry, controls measurement functions on the A/D Converter PCA and communicates
with the Main (outguard) processor.
The Microcontroller communicates directly with the A3U8 Analog Measurement
Processor using the CLK, CS, AR, and AS lines and can monitor the state of the analog
processor using the FC[0:7] lines. Filter zeroing is controlled by the ZERO signal. The
open thermocouple detect circuitry is controlled by the OTCCLK and OTCEN lines and
read by the OTC line. The Microcontroller also communicates with the Main (outguard)
processor serially using the IGDR line to receive and the IGDS line (driven by A3Q1) to
send.
The channel and function relays are driven to the desired measurement state by signals
sent out through microcontroller ports 1, 3, 4, 6, and 7.
On power up, the reset/break detect circuit made up of quad comparator A3U1,
capacitors A3C1 and A3C2, and resistors A3R1 through A3R6 and A3R8 resets the
Microcontroller through the RESET* line. When a break signal is received from the
outguard processor, the inguard A3U9 is again reset. Therefore, if Microcontroller
operation is interrupted by line transients, the outguard can regain control of the inguard
by resetting A3U9.
2A-60. Channel Selection Circuitry
Measurement input channel selection is accomplished by a set of latching 4-form-C
relays organized in a tree structure. Relays A3K5, A3K6, and A3K8 through A3K14
select among channels 1 through 20. Relay A3K7 disconnects rear input channels 1
through 20 from the measurement circuitry between measurements. Relay A3K3
switches in the front panel channel 0 or the rear channels. Inductors A3L1 through
A3L24 reduce EMI and current transients.
Selection between 2-wire and 4-wire operation for ohms measurements is performed by
latching 2-form-C relays (A3K1 and A3K2.) These relays also serve to select a voltage
or thermocouple rear input channel from either channels 1 through 10 or channels 11
through 20.
The coils for the relays are driven by the outputs of Darlington drivers A3U4, A3U5,
A3U10, A3U11, and A3U12. The relays are switched when a 6-millisecond pulse is
applied to the appropriate reset or set coil by the NPN Darlington drivers in these ICs.
When the port pin of Microcontroller A3U9 connected to the input of a driver is set high,
the output of the driver pulls one end of a relay set or reset coil low. Since the other end
of the relay coil is connected to the VDDR supply, a magnetic field is generated, causing
the relay armature and contacts to move to (or remain in) the desired position.
2A-61. Open Thermocouple Check
Immediately before a thermocouple measurement, the open thermocouple check circuit
applies a small, ac-coupled signal to the thermocouple input. Microcontroller A3U9
initiates the test by asserting OTCEN, causing comparator A3U14/A3R40 to turn on
JFET A3Q12. Next, the Microcontroller sends a 78-kHz square wave out the OTCCLK
line through A3R41, A3Q12, and A3C32 to the thermocouple input. The resulting
waveform is detected by A3U13 and A3CR2, and a proportional level is stored on
capacitor A3C30. Op amp A3U13 compares this detected level with the VTH threshold
voltage set up by A3R37 and A3R36 and stored on A3C29. If the resistance at the input
is too large, the VTH level will be exceeded and the OTC (open thermocouple check)
line will be asserted. After a short delay, the Microcontroller analyzes this OTC signal,
determines whether the thermocouple should be reported as open, and deasserts OTCEN
and sets OTCCLK high, ending the test.
2A-32
Theory of Operation (2635A)
Detailed Circuit Description
2A-62.
2A
Input Connector PCA
The Input Connector assembly, which plugs into the A/D Converter PCA from the rear
of the instrument, provides 20 pairs of channel terminals for connecting measurement
sensors. This assembly also provides the reference junction temperature sensor circuitry
used when making thermocouple measurements.
Circuit connections between the Input Connector and A/D Converter PCAs are made via
connectors A4P1 and A4P2. Input channel and earth ground connections are made via
A4P1, while temperature sensor connections are made through A4P2.
Input connections to channels 1 through 20 are made through terminal blocks TB1 and
TB2. Channel 1 and 11 HI and LO terminals incorporate larger creepage and clearance
distances and each have a metal oxide varistor (MOV) to earth ground in order to clamp
voltage transients. MOVs A4RV1 through A4RV4 limit transient impulses to the more
reasonable level of approximately 1800V peak instead of the 2500V peak that can be
expected on 240 VAC, IEC 664 Installation Category II, ac mains. In this way, higher
voltage ratings can be applied to channels 1 and 11 than can be applied to the other rear
channels.
Strain relief for the user’s sensor wiring is provided both by the Connector PCA housing
and the two round pin headers. Each pin of the strain relief headers is electrically
isolated from all other pins and circuitry.
Temperature sensor transistor A4Q1 outputs a voltage inversely proportional to the
temperature of the input channel terminals. This voltage is 0.6V dc at 25 ºC, increasing 2
mV with each degree decrease in temperature, or decreasing 2 mV with each degree
increase in temperature. For high accuracy, A4Q1 is physically centered within and
thermally linked to the 20 input terminals. Local voltage reference A4VR1 and resistors
A4R1 through A4R3 set the calibrated operating current of the temperature sensor.
Capacitor A4C1 shunts noise and EMI to ground.
2A-63.
Display PCA
Display Assembly operation is classified into six functional circuit blocks: the Main
PCA Connector, the Front Panel Switches, the Display, the Beeper Drive Circuit, the
Watchdog Timer/Reset Circuit, and the Display Controller. These blocks are described
in the following paragraphs.
2A-64. Main PCA Connector
The 20-pin Main PCA Connector (A2J1) provides the interface between the Main PCA
and the other functional blocks on the Display PCA. Seven of the connector pins provide
the necessary connections to the four power supply voltages. (See the following table.)
Power Supply
A2J1 Pins
Nominal Voltage
VCC
8
+5.0V dc
VEE
6
-5.0V dc
VLOAD
7
-30V dc
FIL1 to FIL2
2 to 3
5.4V ac
Six pins are used to provide the interface to the Front Panel Switches (A2SWR1 through
A2SWR6). The other seven signals interface the Microprocessor (A1U1) to the Display
Controller (A2U1) and pass the reset signals between the assemblies.
2A-33
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2A-65. Front Panel Switches
The FPGA scans the 19 Front Panel Switches (A2S1 through A2S18, and A2S21) using
only six interface signals (plus the ground connection already available from the power
supply). These six signals (SWR1 through SWR6) are connected to bidirectional I/O
pins on the FPGA. Each successive column has one less switch.
This arrangement allows the unused interface signals to function as strobe signals when
their respective column is driven by the FPGA. The FPGA cycles through six steps to
scan the complete Front Panel Switch matrix. Table 2A-7 shows the interface signal state
and, if the signal state is an output, the switches that may be detected as closed.
Table 2A-7. Front Panel Switch Scanning (2635A)
Interface Signal States or Key Sensed
Step
SWR6
SWR5
SWR4
SWR3
SWR2
SWR1
1
A2S8
A2S17
A2S10
A2S12
A2S18
A2S13
2
A2S1
A2S2
A2S3
A2S4
A2S11
0
3
A2S7
A2S9
A2S5
A2S6
0
Z
4
A2S14
A2S15
A2S16
0
Z
Z
5
NA
NA
0
Z
Z
Z
6
A2S21
0
Z
Z
Z
Z
A2Sn indicates switch closure sensed.
0 indicated strobe driven to logic 0
Z indicated high impedance input; state ignored.
In step 1, six I/O pins are set to input, and the interface signal values are read. In steps 2
through 6, the pin listed as O is set to output zero, the other pins are read, and pins
indicated by a Z are ignored.
Each of the interface signals is pulled up to the +5V dc supply by a 10-kΩ resistor in
network A2Z1. Normally, the resistance between any two of the interface signals is
approximately 20 kΩ. Checking resistances between any two signals (SWR1 through
SWR6) verifies proper termination by resistor network A2Z1.
2A-66. Display
The custom vacuum-fluorescent display (A2DS1) comprises a filament, 11 grids
(numbered 0 through 10 from right to left on the display), and up to 14 anodes under
each grid. The anodes make up the digits and annunciators for their respective area of the
display. The grids are positioned between the filament and the anodes.
A 5.4V ac signal, biased at a -24V dc level, drives the filament. When a grid is driven to
+5V dc, the electrons from the filament are accelerated toward the anodes that are under
that grid. Anodes under that grid that are also driven to +5V dc are illuminated, but the
anodes that are driven to -30V dc are not. Grids are driven to +5V dc one at a time,
sequencing from GRID(10) to GRID(0) (left to right, as the display is viewed.)
2A-67. Beeper Drive Circuit
The Beeper Drive circuit drives the speaker (A2LS1) to provide an audible response to a
button press. A valid entry yields a short beep; an incorrect entry yields a longer beep.
The circuitry comprises a dual four-bit binary counter (A2U4) and a NAND gate (A2U6)
used as an inverter. One four-bit free-running counter (A2U4) divides the 1.024-MHz
clock signal (E) from the FPGA (DSCLK) by 2 to generate the 512-kHz clock (CLK1)
used by the Display Controller. This counter also divides the 1.024-MHz clock by 16,
generating the 64-kHz clock that drives the second four-bit binary counter (A2U4).
2A-34
Theory of Operation (2635A)
Detailed Circuit Description
2A
The second four-bit counter is controlled by an open-drain output on the Display
Controller (A2U1-17) and pull-down resistor A2R1. When the beeper (A2LS1) is off,
A2U1-17 is pulled to ground by A2R1. This signal is then inverted by A2U6, with
A2U6-6 driving the CLR input high to hold the four-bit counter reset. Output A2U4-8 of
the four-bit counter drives the parallel combination of the beeper (A2LS1) and A2R10 to
ground to keep the beeper silent. When commanded by the Microprocessor, the Display
Controller drives A2U1-17 high, enabling the beeper and driving the CLR input of the
four-bit counter (A2U4-12) low. A 4-kHz square wave then appears at counter output
A2U4-8 and across the parallel combination of A2LS1 and A2R10, causing the beeper to
resonate.
2A-68. Watchdog Timer and Reset Circuit
The Watchdog Timer and Reset circuit has been defeated by the insertion of the jumper
between TP1 and TP3 on the Display Assembly. In this instrument, the reset circuitry is
on the Main Assembly and the Watchdog Timer is part of the Microprocessor (A1U1).
The Display Reset signal (DRST*) drives the RESET2* signal on the Display Assembly
low when the instrument is being reset. This discharges capacitor A2C3, and NAND gate
output A2U6-11 provides an active high reset signal to the Display Processor. The
Watchdog Timer on the Display Assembly (A2U5, A2U6 and various resistive and
capacitive timing components) is held "cleared" by TP1 being held at 0V dc by a jumper,
and output A2U5-12 will always be high.
2A-69. Display Controller
The Display Controller is a four-bit, single-chip microcomputer with high-voltage
outputs that are capable of driving a vacuum-fluorescent display directly. The controller
receives commands over a three-wire communication channel from the Microprocessor
on the Main Assembly. Each command is transferred serially to the Display Controller
on the display transmit (DISTX) signal, with bits being clocked into the Display
Controller on the rising edges of the display clock signal (DSCLK). Responses from the
Display Controller are sent to the Microprocessor on the display receive signal (DISRX)
and are clocked out of the Display Controller on the falling edge of DSCLK.
Series resistor A2R11 isolates DSCLK from A2U1-40, preventing this output from
trying to drive A1U1-77 directly. Figure 2A-8 shows the waveforms during a single
command byte transfer. Note that a high DISRX signal is used to hold off further
transfers until the Display Controller has processed the previously received byte of the
command.
DSCLK
DISTX
BIT 7
DISRX
BIT 7
CLEAR TO
RECEIVE
BIT 6
BIT 6
BIT 5
BIT 5
BIT 4
BIT 4
BIT 3
BIT 3
BIT 2
BIT 2
BIT 1
BIT 1
BIT 0
BIT 0
HOLD OFF
31.5 µs
CLEAR TO
RECEIVE
31.5 µs
s18f.eps
Figure 2A-8. Command Byte Transfer Waveforms (2635A)
2A-35
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Once reset, the Display Controller performs a series of self-tests, initializing display
memory and holding the DISRX signal high. After DISRX goes low, the Display
Controller is ready for communication. On the first command byte from the
Microprocessor, the Display Controller responds with a self-test results response. If all
self-tests pass, a response of 00000001 (binary) is returned. If any self-test fails, a
response of 01010101 (binary) is returned. The Display Controller initializes its display
memory to one of four display patterns depending on the states of the DTEST* (A2U141) and LTE* (A2U1-13) inputs. The DTEST* input is pulled up by A2Z1, but may be
pulled down by jumpering A2TP4 to A2TP3 (GND). The LTE* input is pulled down by
A2R12, but may be pulled up by jumpering A2TP5 to A2TP6 (VCC). The default
conditions of DTEST* and LTE* cause the Display Controller to turn all segments on
bright at power-up.
Table 2A-8 defines the logic and the selection process for the four display initialization
modes.
Table 2A-8. Display Initialization Modes (2635A)
A2TP4
A2TP5
Power-Up Display Initialization
1
1
All Segments OFF
1
0
All Segments ON (default)
0
1
Display Test Pattern #1
0
0
Display Test Pattern #2
The two display test patterns are a mixture of on and off segments forming a
recognizable pattern that allows for simple testing of display operation. Test patterns #1
and #2 are shown in Section 5 of this manual.
The Display Controller provides 11 grid control outputs and 15 anode control outputs.
(Only 14 anode control outputs are used.) Each of these 26 high-voltage outputs provides
an active driver to the +5V dc supply and a passive 220-kΩ (nominal) pull-down to the 30V dc supply. These pull-down resistances are internal to the Display Controller.
The Display Controller provides multiplexed drive to the vacuum-fluorescent display by
strobing each grid while the segment data for that display area is present on the anode
outputs. Each grid is strobed for approximately 1.37 milliseconds every 16.56
milliseconds, resulting in each grid on the display being strobed about 60.4 times per
second. The grid strobing sequence is from GRID(10) to GRID(0), which results in leftto-right strobing of grid areas on the display. Figure 2A-9 shows grid control signal
timing.
The single grid strobing process involves turning off the previously enabled grid,
outputting the anode data for the next grid, and then enabling the next grid. This
procedure ensures that there is some time between grid strobes so that no shadowing
occurs on the display. A grid is enabled only if one or more anodes are also enabled.
Thus, if all anodes under a grid are to be off, the grid is not turned on. Figure 2A-10
describes the timing relationship between an individual grid control signal and the anode
control signals.
2A-36
Theory of Operation (2635A)
Detailed Circuit Description
2A
GRID TIMING
16.56 ms
0V
GRID(10)
1.37 ms
0V
GRID(9)
…
…
1.37 ms
0V
GRID(1)
1.37 ms
0V
GRID(0)
1.37 ms
140 µs
s19f.eps
Figure 2A-9. Grid Control Signal Timing (2635A)
GRID/ANODE TIMING
5V
0V
1.37 ms
GRID(X)
-30V
140 µs
5V
0V
ANODE(14..0)
-30V
22.5 µs
72 µs
67.5 µs
117 µs
5V
0V
GRID(X-1)
-30V
s20f.eps
Figure 2A-10. Grid-Anode Timing Relationships (2635A)
2A-70. Memory Card Interface PCA
The Memory Card Interface Assembly operation is composed of four functional circuit
blocks: the Main PCA Connector, the Microprocessor Interface, the Memory Card
Controller, and the PCMCIA Memory Card Connector. These blocks are described in the
following paragraphs.
2A-37
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Service Manual
2A-71. Main PCA Connector
The Memory Card Interface PCA interfaces to the Main PCA through a 40-pin, right
angle connector (A6P2). This connector routes eight bits of the Microprocessor data bus,
the lower four bits of the address bus, memory control, interrupt and address decode
signals from the Main PCA to the Memory Card Interface PCA. The Memory Card
Interface PCA is powered by the +5.0V dc power supply (VCC). The pinout of the high
density ribbon cable that connects the Main PCA to the Memory Card Interface PCAis
carefully selected to prevent cross-talk between signals and to provide low impedance
connections to the VCC power supply.
2A-72. Microprocessor Interface
The timing of Microprocessor read and write accesses to the Memory Card Controller
(A6U1) are controlled internally by the Memory Card Controller which determines
whether wait states are required when the Microprocessor accesses one of its internal
registers.
When a register in the Memory Card Controller (A6U1) is read, the four address bits
select one of the internal registers to read and then the XMCARD* signal (A6U1-49) is
driven to a low level by the Microprocessor. The XRDU* signal (A6U1-50) is then
driven low by A1U11-14 to enable the data outputs from the Memory Card Controller
(D8 through D15). At the end of the read access, both XMCARD* and XRDU* are
driven high again.
When a register in the Memory Card Controller (A6U1) is written, the four address bits
select one of the internal registers to write and then the XMCARD* signal (A6U1-49) is
driven to a low level by the Microprocessor. The XWRU* signal (A6U1-51) is then
driven low by A1U11-13 to initiatethe transfer of the data bus inputs on the Memory
Card Controller (D8 through D15) to the internal register. At the end of the write access,
both XMCARD* and XRDU* are driven high again and the data is latched into the
internal register.
If no wait states are required, the DTACK* signal (A6U1-58) will be driven low after the
next low to high transition of the system clock (A6U1-30) to indicate to the
Microprocessor that the data transfer has been acknowledged and the read or write
access may be completed. The DTACK* signal is a tri-state bus that is pulled up to VCC
by resistor A1R83 and pulled low by devices being accessed by the Microprocessor.
If wait states are required, the DTACK* signal (A6U1-58)will not go low until the
proper number of wait states have been inserted.The Memory Card Controller counts
cycles of the system clock (A6U1-30) and when the correct number of wait states have
been done, the DTACK* signal will go low.
Accesses to internal registers should be done with no wait states, and accesses through
the Memory Card Controller to the Memory Card automatically add two wait states.
2A-73. Memory Card Controller
The Memory Card Controller (A6U1) is a Field Programmable Gate Array (FPGA) that
automatically loads its configuration upon power-up from a serial memory device
(A6U3).While it is configuring, the FPGA holds the memory CE input (A6U3-4) low
and toggles the CLK input (A6U3-2) to serially shift the configuration data out of the
memory on the D output (A6U3-1) and into the FPGA.When configuration is complete,
the FPGA should release the CE input(A6U3-4) allowing it to be pulled high by resistor
A6R8.
2A-38
Theory of Operation (2635A)
Detailed Circuit Description
2A
The Memory Card Controller provides a register based interface for the Microprocessor
to use to access data stored on industry standard PCMCIA memory cards. A 26 bit
counter controls the address bus (CA<0> through CA<25>) to the PCMCIA Memory
Card Connector (A6P1). An eight bit data bus(CD<0> through CD<7>) and memory
card control signals (REG*, CE1*, CRD*, and CWR*) control accesses to memory on
the card.
The REG* signal (A6U1-8) is like an additional address bit. When REG* is slow
(A6U1-8), read and write accesses go to "attribute" memory on the card. Attribute
memory is typically a small EEPROM on the memory card that contains special
information that specifies the manufacturer of the card, type and size of memory on the
card, memory speed, etc. When REG* is high, read and write accesses go to the
"common" memory on the card. Common memory is the Static RAM on the memory
cards used in this instrument.
Typically, information is read and written to the memory card in a sequential manner
where the address counter automatically increments after the end of each read or write
cycle. When the Memory Card Controller reads data from the memory card data bus
(CD<0> through CD<7>), CE1* (A6U1-62) goes low followed by CRD* (A6U1-63)
going low. The data from the memory card then goes through the Memory Card
controller and is read by the Microprocessor on the D8 through D15 data bus lines.Data
is written to the memory card in a similar manner, except that the data goes from the
Microprocessor through the memory Card Controller and to the Memory Card with
CWR* (A6U2-64) going low to enable the writing of the data to the memory. The
purpose of A6U2 and resistors A6R2, A6R5, and A6R7 is to ensure that data on the
Memory Card is not accidentally modified during the time that the instrument is being
powered up or down. Each of the Memory Card data bus lines (CD<0> through CD<7>)
has a series resistor (A6Z2) that helps ensure that the instrument meets EMI/EMC
performance requirements.
The Memory Card Controller detects the insertion and removal of a Memory Card and
interrupts the microprocessor by driving the MCINT* signal(A6U1-60) low. When a
Memory Card is inserted in the PCMCIA Memory Card Connector, the CD1 (A6U1-19)
and CD2 (A6U1-21) inputs on the Memory Card Controller are driven to 0V dc and
Microprocessor (A1U1) is interrupted. The Microprocessor then powers up the Memory
Card by setting A6U1-26 low, which turns on FET A6Q1 by driving the gate low
through resistor A6R13. When FET A6Q1 is turned on the Memory Card power (CVCC
and CVPP) is approximately +5.0V dc. When the Microprocessor has completed a data
transfer with the Memory Card, FET A6Q1 is turned off again by driving A6U1-26 high.
When a Memory Card is inserted and powered up, the Memory Card outputs some status
signals to the Memory Card Controller. If the Memory Card write protect switch is
protecting data on the card, the WP signal (A6U1-22) is high. The status of the Memory
Card battery is output on the BVD1 (A6P1-18) and BVD2 (A6P1-20) pins of the
Memory Card Connector. If either of these battery status signals is low when the
Memory Card is powered up, then the Microprocessor will turn on LED A6DS2 by
driving A6U1-24 low. The Busy status LED (A6DS1) is turned on by driving A6U1-25
low when the Microprocessor has powered up the Memory Card and is transferring data
to or from the card.
2A-74. PCMCIA Memory Card Connector
The PCMCIA Memory Card Connector (A6P1) is a 68 pin connector that meets the
requirements of the Personal Computer Memory Card International Association. This
connector has pins that are three different lengths: the card detection pins (CD1 and
CD2) are the shortest, the power and ground pins are the longest, and the rest of the pins
are a length in between. This ensures that on memory card insertion, the power and
2A-39
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Service Manual
ground pins are mated first followed by the reset of the input / output signals with the
card detection signals mating last. This sequence is reversed on memory card removal.
The PCMCIA Memory Card Connector has a metal shell that is connected to chassis
ground to help ensure that the instrument meets EMI/EMC and ESD performance
requirements. A push-button mechanism is included to allow easy ejection of the
Memory Card.
2A-40
static awareness
A Message From
Fluke Corporation
Some semiconductors and custom IC's can be
damaged by electrostatic discharge during
handling. This notice explains how you can
minimize the chances of destroying such devices
by:
1. Knowing that there is a problem.
2. Leaning the guidelines for handling them.
3. Using the procedures, packaging, and
bench techniques that are recommended.
The following practices should be followed to minimize damage to S.S. (static sensitive) devices.
1. MINIMIZE HANDLING
2. KEEP PARTS IN ORIGINAL CONTAINERS
UNTIL READY FOR USE.
3. DISCHARGE PERSONAL STATIC BEFORE
HANDLING DEVICES. USE A HIGH RESISTANCE GROUNDING WRIST STRAP.
4. HANDLE S.S. DEVICES BY THE BODY.
5. USE STATIC SHIELDING CONTAINERS FOR
HANDLING AND TRANSPORT.
8. WHEN REMOVING PLUG-IN ASSEMBLIES
HANDLE ONLY BY NON-CONDUCTIVE
EDGES AND NEVER TOUCH OPEN EDGE
CONNECTOR EXCEPT AT STATIC-FREE
WORK STATION. PLACING SHORTING
STRIPS ON EDGE CONNECTOR HELPS
PROTECT INSTALLED S.S. DEVICES.
6. DO NOT SLIDE S.S. DEVICES OVER
ANY SURFACE.
9. HANDLE S.S. DEVICES ONLY AT A
STATIC-FREE WORK STATION.
10. ONLY ANTI-STATIC TYPE SOLDERSUCKERS SHOULD BE USED.
11. ONLY GROUNDED-TIP SOLDERING
IRONS SHOULD BE USED.
7. AVOID PLASTIC,VINYL AND STYROFOAM
IN WORK AREA.
PORTIONS REPRINTED
WITH PERMISSION FROM TEKTRONIX INC.
AND GERNER DYNAMICS, POMONA DIV.
 Dow Chemical
Chapter 3
General Maintenance
Title
3-1.
3-2.
3-3.
3-4.
3-5.
3-6.
3-7.
3-8.
3-9.
3-10.
3-11.
3-12.
3-13.
3-14.
3-15.
3-16.
3-17.
3-18.
3-19.
3-20.
3-21.
3-22.
3-23.
3-24.
3-25.
3-26.
3-27.
3-28.
3-29.
Introduction ..........................................................................................
Warranty Repairs and Shipping ...........................................................
General Maintenance............................................................................
Required Equipment ........................................................................
Power Requirements ........................................................................
Static Safe Handling ........................................................................
Servicing Surface-Mount Assemblies..............................................
Cleaning................................................................................................
Line Fuse Replacement ........................................................................
Disassembly Procedures.......................................................................
Remove the Instrument Case ...........................................................
Remove Handle and Mounting Brackets .........................................
Remove the Front Panel Assembly ..................................................
Remove the Display PCA ................................................................
Remove the IEEE-488 Option (2620A Only) ..................................
Remove the Memory PCA (2625A Only)........................................
Remove the Memory Card I/F PCA (2635A Only) .........................
Remove the Main PCA ....................................................................
Remove the A/D Converter PCA.....................................................
Disconnect Miscellaneous Chassis Components .............................
Assembly Procedures ...........................................................................
Install Miscellaneous Chassis Components .....................................
Install the A/D Converter PCA ........................................................
Install the Main PCA........................................................................
Install the IEEE-488 Option (2620A Only) .....................................
Install the Memory PCA (2625A Only)...........................................
Install the Memory Card I/F PCA (2635A Only) ............................
Assemble the Front Panel Assembly ...............................................
Install the Front Panel Assembly .....................................................
Page
3-3
3-3
3-3
3-3
3-3
3-3
3-4
3-4
3-5
3-5
3-6
3-6
3-6
3-6
3-11
3-11
3-11
3-12
3-12
3-13
3-13
3-13
3-13
3-14
3-14
3-14
3-15
3-15
3-15
3-1
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Service Manual
3-30.
3-31.
3-2
Install the Handle and Mounting Brackets....................................... 3-15
Install the Instrument Case............................................................... 3-15
General Maintenance
Introduction
3
3-1. Introduction
This section provides handling, cleaning, fuse replacement, disassembly, and assembly
instructions.
3-2. Warranty Repairs and Shipping
If your instrument is under warranty, see the warranty information at the front of this
manual for instructions on returning the unit. The list of authorized service facilities is
included in Section 6.
3-3. General Maintenance
3-4.
Required Equipment
Equipment required for calibration, troubleshooting, and repair of the instrument is listed
in Section 4 (Table 4-1.)
Refer to the Fluke "Surface Mount Device Soldering Kit" for a list of special tools
required to perform circuit assembly repair. (In the USA, call 1-800-526-4731 to order).
3-5.
Power Requirements
Warning
To avoid shock hazard, connect the instrument powercord to a
power receptacle with earth ground.
If you have not already done so, plug the line cord into the connector on the rear of the
instrument. The instrument operates on any line voltage between 90V ac and 264V ac
and at any frequency between 45 and 440 Hz. However, the instrument is warranted only
to meet published specifications at 50/60 Hz. The instrument also operates from dc
power (9 to 16V dc). DC input power is connected to the rear input connector J6, pin 8
(DCH), and pin 7 (DCL). If both ac and dc power sources are connected to the
instrument, the ac power source is used if the ac line voltage exceeds approximately 8.3
times the dc voltage. Automatic switchover between ac and dc occurs without
interrupting instrument operation. The instrument draws a maximum of 10 VA on ac line
power or 4W on dc power.
3-6.
Static Safe Handling
All integrated circuits, including surface mounted ICs, are susceptible to damage from
electrostatic discharge (ESD). Modern integrated circuit assemblies are more susceptible
to damage from ESD than ever before. Integrated circuits today can be built with circuit
lines less than one micron thick, allowing more than a million transistors on a 1/4-inch
square chip. These submicron structures are sensitive to static voltages under 100 volts.
This much voltage can be generated on a dry day by simply moving your arm. A person
can develop a charge of 2,000 volts by walking across a vinyl tile floor, and polyester
clothing can easily generate 5,000 to 15,000 volts during movement against the wearer.
These low voltage static problems are often undetected because a static charge must be
in the 30,000 to 40,000 volt range before a person feels a shock.
3-3
HYDRA
Service Manual
Most electronic components manufactured today can be degraded or destroyed by ESD.
While protection networks are used in CMOS devices, they merely reduce, not eliminate
component susceptibility to ESD.
ESD may not cause an immediate failure in a component; a delayed failure or wounding
effect is caused when the semiconductor’s insulation layers or junctions are punctured.
The static problem is thus complicated in that failure may occur anywhere from two
hours to six months after the initial damage.
Two failure modes are associated with ESD. First, a person who has acquired a static
charge can touch a component or assembly and cause a transient discharge to pass
through the device. The resulting current ruptures the junctions of a semiconductor. The
second failure mode does not require contact with another object. Simply exposing a
device to the electric field surrounding a charged object can destroy or degrade a
component. MOS devices can fail when exposed to static fields as low as 30 volts.
Observe the following rules for handling static-sensitive devices:
1. Handle all static-sensitive components at a static-safe work area.
Use grounded static control table mats on all repair benches, and always wear a
grounded wrist strap. Handle boards by their nonconductive edges only. Store
plastic, vinyl, and Styrofoam objects outside the work area.
2. Store and transport all static-sensitive components and assemblies in static shielding
bags or containers.
Static shielding bags and containers protect components and assemblies from direct
static discharge and external static fields. Store components in their original
packages until they are ready for use.
3-7.
Servicing Surface-Mount Assemblies
Hydra incorporates Surface-Mount Technology (SMT) for printed circuit assemblies
(pca’s). Surface-mount components are much smaller than their predecessors, with leads
soldered directly to the surface of a circuit board; no plated through-holes are used.
Unique servicing, troubleshooting, and repair techniques are required to support this
technology.
Refer to Section 5 for additional information. Also, refer to the Fluke "Surface Mount
Device Soldering Kit" for a complete discussion of these techniques (in the USA, call 1800-526-4731 to order).
3-8. Cleaning
Warning
To avoid electrical shock or damage to the instrument, never
allow water inside the case. To avoid damaging the
instrument’s housing, never apply solvents to the instrument.
If the instrument requires cleaning, wipe it down with a cloth that is lightly dampened
with water or a mild detergent. Do not use aromatic hydrocarbons, chlorinated solvents,
or methanol-based fluids when wiping the instrument. Dry the instrument thoroughly
after cleaning.
3-4
General Maintenance
Line Fuse Replacement
3
3-9. Line Fuse Replacement
The line fuse (125 mA, 250V, slow blow, Fluke Part Number 822254) is located on the
rear panel. The fuse is in series with the power supply. For replacement, unplug the line
cord and remove the fuse holder (with fuse) as shown in Figure 3-1. The instrument is
shipped with a replacement fuse loosely secured in the fuse holder.
Power-Line Cord Connector
To Remove,
Squeeze and
Slide Out
+
–
9DC16 V
PW
R
0
1
2
3
DI
GI
TR
0V
0
!
1
Co
Line Fuse
(T 125 mA, 250V,
Slow Blow)
TA
LI
/O
+3
2
mp
3
li
4
pu es wit
rsu h M
an the EE
5
t to lim TS
Su it f 08
6
bp or a 7
1
art
7
J o clas B
s
fP B
art co
15 mp
of utin
FC g
C R dev
ule ice
s
Σ
Fuse Holder
(Spare Fuse Provided)
s21f.eps
Figure 3-1. Replacing the Line Fuse
3-10. Disassembly Procedures
The following paragraphs describe disassembly of the instrument in sequence from the
fully assembled instrument to the chassis level. Start and end your disassembly at the
appropriate heading levels.
Warning
Opening the case may expose hazardous voltages.Always
disconnect the power cord and measuringinputs before
opening the case. And remember thatrepairs or servicing
should be performed only byqualified personnel.
3-5
HYDRA
Service Manual
3-11. Remove the Instrument Case
Use the following procedure to remove the instrument case.
1. Make sure the instrument is powered off and disconnected from the power source
(ac or dc).
2. Remove the screw from the bottom of the case, and remove the two screws from the
rear bezel as shown in Figure 3-2. While holding the front panel, slide the case and
rear bezel off the chassis. (At this point, the rear bezel is not secured to the case.)
3-12. Remove Handle and Mounting Brackets
Refer to Figure 3-3 during this procedure. Pull each handle pivot out slightly at the
handle mounting brackets, then rotate the handle up over the display. With the handle
pointing straight up, pull out and disengage one pivot at a time.
Use a Phillips screwdriver to remove the two handle mounting brackets. Note that these
brackets must be reinstalled in their original positions. Therefore, the inside of each
bracket is labeled (R for right, L for left) as viewed from the front of the instrument.
3-13. Remove the Front Panel Assembly
Note
Parts referenced by letter (e.g., A) are shown in Figure 3-4 (2620A or
2625A) or Figure 3-5 (2635A).
Use the following procedure to remove the Front Panel Assembly (E):
1. Remove the leads connected to the two input terminals. Using needle nose pliers,
pull and disconnect the wires at the rear of the VΩ and COM input terminals.
2. Using needle nose pliers, disconnect the display ribbon cable (G) on the Main PCA
(H) by alternately pulling up on each end of its connector. Avoid breaking the
alignment tabs on the Main PCA side of this connection.
3. Remove the Front Panel Assembly by releasing the four snap retainers (I) securing it
to the chassis. Using needle nose pliers, disconnect the display ribbon cable (G) on
the Display PCA (K) by alternately pulling up on each end of its connector. Avoid
breaking the alignment tabs on the Display PCA side of this connection. The ribbon
cable (G) may be left attached to the chassis.
4. The green power switch activator rod (J) extending from the power switch on the
Main PCA through the Front Panel Assembly can now be removed. Squeeze the end
of the rod at the power switch and lift up; the bar disengages smoothly from the
switch.
3-14. Remove the Display PCA
Two movable tabs hold the Display PCA (K) in place on the back of the Front Panel
Assembly. Release one tab at a time. Then, while prying slightly at the top of the Display
PCA, lift the pca out of its securing slots. Parts referenced by letter (e.g., A) are shown in
Figure 3-4 (2620A or 2625A) or Figure 3-5 (2635A).
3-6
General Maintenance
Disassembly Procedures
3
MOUNTING
SCREW (2)
GROUNDING
SCREW
CASE
A.
REAR BEZEL
CHASSIS
B.
s22f.eps
Figure 3-2. Removing the Case
3-7
HYDRA
Service Manual
COM
VΩ
300V
MAX
A.
B.
C.
s23f.eps
Figure 3-3. Removing the Handle and Handle Mounting Brackets
Note
The Display PCA provides a space for a center securing screw. If the two
tabs are intact, this screw is not necessary. If a tab is broken, a screw can
be used as an additional securing device.
The elastomeric Keypad Assembly (L) can now be lifted away from the Front Panel
Assembly.
Only if necessary, gently remove the display window (M) by releasing the two snaps
along its inside, bottom edge. While pushing slightly on the rear of the window, gently
lever each snap by pressing against an adjacent edge on the keypad housing.
Caution
Avoid using ammonia or methyl-alcohol cleaningagents on
either the Front Panel or the displaywindow. These types of
cleaners can damage surfacefeatures and markings. Use an
isopropyl-basedcleaning agent or water to clean the Front
Paneland the display window.
3-8
General Maintenance
Disassembly Procedures
D
C
3
B
A
X
W
V
T
E
K
L
G
M
H
Y
U
I
J
Q
Z
N
P
O
s24f.eps
Figure 3-4. 2620A and 2625A Assembly Details
3-9
HYDRA
Service Manual
D
B
C
A
X
W
V
T
E
K
L
G
M
H
Y
U
I
J
O
Q
P
s25f.eps
Figure 3-5. 2635A Assembly Details
3-10
General Maintenance
Disassembly Procedures
3
3-15. Remove the IEEE-488 Option (2620A Only)
Section 7 of this manual provides a detailed removal procedure for the IEEE-488 option.
The following removal instructions provide the essentials of this procedure. Parts
referenced by letter (e.g., A) are shown in Figure 3-4. If necessary, refer to the complete
procedure in Section 7.
1. From the bottom of the instrument, locate the IEEE-488 PCA (N). This pca is
connected to the front of Main PCA, with a ribbon cable (O) leading across both
pca’s to the Rear Panel.
2. Use needle nose pliers to disconnect the 24-line cable assembly at the IEEE-488
PCA, alternately pulling on each end of the cable connector. Leave the other end of
this cable attached to its Rear Panel connector.
3. Remove the 6-32, 1/4-inch panhead Phillips screw (P) securing the IEEE-488 PCA.
4. Disengage the IEEE-488 PCA by sliding it away from the Main PCA.
3-16. Remove the Memory PCA (2625A Only)
Use the following procedure to remove the Memory PCA from the 2625A Data Logger.
Parts referenced by letter (e.g., A) are shown in Figure 3-4.
1. From the bottom of the instrument, locate the Memory PCA (Q). This pca is
connected to front of the Main PCA.
Note
You might want to verify that this is the Memory PCA. The Memory PCA
and the IEEE-488 PCA occupy the same position and use the same
connection to the Main PCA. The Memory PCA is a standard part of the
Hydra Data Logger (Model 2625A). The IEEE-488 PCA is not available
with the 2625A but is optional with the Hydra Data Acquisition Unit
(Model 2620A).
2. Remove the panhead Phillips screw (P) securing the Memory PCA.
3. Disengage the Memory PCA by sliding it away from the Main PCA.
3-17. Remove the Memory Card I/F PCA (2635A Only)
Use the following procedure to remove the Memory Card I/F PCA from the 2635A Data
Bucket. Parts referenced by letter (e.g., A) are shown in Figure 3-5.
1. From the bottom of the instrument, locate the Memory Card I/F PCA (Q). This pca
is in the front of the instrument near the center, and is connected to the Main PCA by
a high-density ribbon cable (O).
2. Remove the three 6-32, 1/4-inch panhead Phillips screws (P) securing the Memory
Card I/F PCA.
3. Disconnect the high-density ribbon cable (O) from the connector on the Memory
Card I/F PCA (Q) and remove the assembly from the chassis.
3-11
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Service Manual
3-18. Remove the Main PCA
With the IEEE-488 option (2620A) and the Memory PCA (2625A) or Memory Card I/F
PCA (2635A) removed, the Main PCA (H) can be removed. Parts referenced by letter
(e.g., A) are shown in Figure 3-4 (2620A or 2625A) or Figure 3-5 (2635A). Use the
following procedure:
1. If it is still attached, remove the green power switch activator rod (J) extending from
the power switch on the Main PCA through the Front Panel Assembly. Squeeze the
end of the rod at the power switch and lift up; the bar disengages smoothly from the
switch.
2. Using needle nose pliers, disconnect the display ribbon cable (G) on the Main PCA
(H) by alternately pulling up on each end of its connector. Avoid breaking the
alignment tabs on the Main PCA side of this connection. (This connector has already
been detached if the Front Panel Assembly was removed.)
3. Detach the transformer connector at the Main PCA.
4. Detach the Main-to-A/D Converter cable at the A/D Converter PCA.
5. If installed, pull off the ALARM OUTPUTS and DIGITAL I/O terminal strips from
the Rear Panel.
6. Remove the RS-232 connector screws (T) at the Rear Panel. Use a 3/16-inch nut
driver to loosen the connector securing hardware.
7. If installed, remove the IEEE-488 connector. Use a 7-mm nutdriver to loosen the
two securing screws on the rear panel.
8. Now remove the two screws (U) securing the Main PCA to the chassis. Slide the
Main PCA forward. Then, while matching the pca edge indentations to the guide
tabs on each chassis side, lift the Main PCA up and away from the chassis.
3-19. Remove the A/D Converter PCA
Use the following procedure to remove the A/D Converter PCA (V). Parts referenced by
letter (e.g., A) are shown in Figure 3-4 (2620A or 2625A) or Figure 3-5 (2635A).
1. If necessary, remove the leads connecting the two front panel input terminals to the
A/D Converter PCA. Using needle nose pliers, pull and disconnect the wires at the
rear of the VΩ (red) and COM (black) input terminals. (These leads are already
disconnected if the Front Panel Assembly has been removed.)
2. At the A/D Converter PCA, detach the cable leading to the Main PCA.
3. From the Rear Panel, pull out the Input Module.
4. Remove the three Phillips head screws (W) securing the A/D Converter PCA to the
chassis.
5. Now slide the A/D Converter PCA forward to match the indentations in the pca
edges to the guides in the chassis. Then lift the pca out.
3-12
General Maintenance
Assembly Procedures
3
3-20. Disconnect Miscellaneous Chassis Components
Use the following procedure to disconnect the remaining hardware from the chassis.
Parts referenced by letter (e.g., A) are shown in Figure 3-4 (2620A or 2625A) or Figure
3-5 (2635A).
1. Use needle nose pliers to remove the internal connections at the line power plug (X).
Remove the ground screw prior to disconnecting the ground wire from the plug.
2. Remove the power plug by releasing its two snaps one at a time.
3. Disconnect the power transformer by removing the four 5/16-inch nuts (Y) that
secure it to the right side of the chassis.
4. If installed, remove the 7-mm IEEE-488 connector screws (Z) (2620A only).
3-21. Assembly Procedures
Generally, assembly procedures follow a reverse sequence of disassembly procedures.
As some differences do apply, assembly is described separately in the following
paragraphs. Begin assembly at the appropriate level, as defined by the heading.
References are made to items in Figure 3-4 (2620A or 2625A) or Figure 3-5 (2635A) for
assembly details of standard instrument parts.
Note
Parts referenced by letter (e.g., A) are shown in Figure 3-4 (2620A or
2625A) or Figure 3-5 (2635A).
3-22. Install Miscellaneous Chassis Components
Use the following procedure to replace any items that have been removed from the basic
chassis.
1. Replace the power transformer along the right side of the chassis. Use four 5/16-inch
hex nuts (Y).
2. Snap the power plug into position.
3. Use needle nose pliers to replace the interior connections at the power plug. Also,
attach the ground wire at its chassis connection.
3-23. Install the A/D Converter PCA
1. Fit the A/D Converter PCA (L) so that the chassis guides pass through notches on
both sides of the pca. Then slide the pca back until it is snug against the Input
Module enclosure.
2. Fasten the A/D Converter PCA to the chassis with three 6-32, 1/4-inch panhead
screws (W).
3. If the Front Panel Assembly is installed, attach the leads connecting the two input
terminals to the A/D Converter PCA. Using needle nose pliers, push the wire
connectors firmly onto the recessed input terminal pins (red to VΩ and black to
COM.)
4. At the A/D Converter PCA, attach the cable leading to the Main PCA.
5. From the Rear Panel, push the Input Module back into place.
3-13
HYDRA
Service Manual
3-24. Install the Main PCA
1. Fit the Main PCA (H) so that the chassis guides pass through notches on both sides
of the pca. Then slide the pca back until it is snug against the Rear Panel.
2. Replace the RS-232 connector screws (T) on the rear of the chassis. Use a 3/16-inch
nut driver to tighten the connector hardware.
3. Fasten the Main PCA to the chassis with two 6-32, 1/4-inch panhead screws (U).
4. Connect the transformer cable at connector J3 on the Main PCA. Verify that the
connector is aligned correctly (all three pins connected.)
5. Plug the Front Panel cable onto its connector (J2) on the Main PCA.
6. From the Rear Panel, push the ALARM OUTPUTS and DIGITAL I/O terminal
strips onto their appropriate connectors.
3-25. Install the IEEE-488 Option (2620A Only)
Both the instruction sheet provided with the IEEE-488 Option and Section 7 of this
manual fully describe installation. The following instructions provide installation
procedure essentials. If necessary, refer to Section 7, paying particular attention to
Figures 7-2 and 7-3.
1. Place the IEEE-488 PCA (N) into position so that the edge of the pca fits into the
chassis guide. Then line up connecting pins with the matching connector on the
Main PCA, and slide the pca into position.
2. Install the single 6-32, 1/4-inch panhead Phillips screw in the corner of the IEEE-488
PCA.
3. If necessary, attach the rear panel connector using a 7-mm nut driver.
4. At the pca, attach the ribbon cable leading from the rear panel connector.
3-26. Install the Memory PCA (2625A Only)
Note
The Memory PCA and the IEEE-488 PCA occupy the same position and
use the same connection to the Main PCA. The Memory PCA is a standard
part of the Hydra Data Logger (Model 2625A). The IEEE-488 PCA is not
available with the 2625A but is optional with the Hydra Data Acquisition
Unit (Model 2620A).
1. Place the Memory PCA into position so that the edge of the pca fits in the chassis
guide. Then line up connecting pins with the matching connector on the Main PCA,
and slide the pca into position.
2. Install the single 6-32, 1/4-inch panhead Phillips screw in the corner of the Memory
PCA.
3-14
General Maintenance
Assembly Procedures
3
3-27. Install the Memory Card I/F PCA (2635A Only)
1. Place the Memory Card I/F PCA (Q) into position so that the three mounting holes
line up with the chassis supports located at the front-center of the chassis.
2. Install the three 6-32, 1/4-inch panhead Phillips screws in the mounting holes of the
Memory Card I/F PCA.
3. Reconnect the high-density ribbon cable (O) to the connector on the Memory Card
Interface PCA (Q).
3-28. Assemble the Front Panel Assembly
As appropriate, use the following steps to assemble the Front Panel Assembly.
1. Clean the lens (M) with deionized air and, if necessary, isopropyl alcohol. Then
gently snap the lens into the front panel tabs.
2. Fit the elastomeric keypad assembly (L) through the Front Panel Assembly.
3. Slide the Display PCA into the bottom securing tabs on the back of the Front Panel
Assembly. Then gently snap the pca into place.
Note
The Display PCA provides a space for a center screw. If the peripheral
tabs are intact, this screw is not necessary. If some of the tabs are broken,
the screw can be used as an additional securing device.
4. Connect the 20-pin cable (G) to the Display PCA.
3-29. Install the Front Panel Assembly
Use the following procedure when installing the Front Panel Assembly:
1. Position the Front Panel Assembly into place and snap the four tab retainers (I) onto
the chassis.
2. Observing the alignment orientation provided by tabs on the connector, attach the
display ribbon cable connector (G) on the Main PCA.
3. Using needle nose pliers, connect the wires at the rear of the recessed input terminals
(Red to VΩ, Black to COM).
3-30. Install the Handle and Mounting Brackets
Refer to Figure 3-3 during the following procedure. Use a Phillips head screwdriver to
attach the two handle mounting brackets. Note that these brackets must be reinstalled in
their original positions. Therefore, the inside of each bracket is labeled with an R or an
L, in reference to the front view of the instrument.
Now, engage the handle. Point the handle straight up. Then pull out on each end of the
handle to engage the respective pivot in its bracket. Pull out slightly on both pivots to
rotate the handle to the desired position.
3-31. Install the Instrument Case
Reinstall the instrument case, checking that it seats properly in the front panel. Attach
the rear bezel with the two panhead Phillips screws and secure the case with the flathead
Phillips screw in the bottom. Refer to Figure 3-2.
3-15
HYDRA
Service Manual
3-16
Chapter 4
Performance Testing and Calibration
Title
4-1.
4-2.
4-3.
4-4.
4-5.
4-6.
4-7.
4-8.
4-9.
4-10.
4-11.
4-12.
4-13.
4-14.
4-15.
4-16.
4-17.
4-18.
4-19.
4-20.
4-21.
4-22.
4-23.
4-24.
4-25.
4-26.
4-28.
4-29.
Page
Introduction .......................................................................................... 4-3
Required Equipment............................................................................. 4-3
Performance Tests ................................................................................ 4-4
Accuracy Verification Test .............................................................. 4-4
Channel Integrity Test...................................................................... 4-4
Thermocouple Measurement Range Accuracy Test ........................ 4-6
4-Terminal Resistance Test.............................................................. 4-7
Thermocouple Temperature Accuracy Test..................................... 4-8
Open Thermocouple Response Test ................................................ 4-11
RTD Temperature Accuracy Test .................................................... 4-11
RTD Temperature Accuracy Test (Using Decade Resistance Source).
4-11
RTD Temperature Accuracy Test (Using DIN/IEC 751)............ 4-12
Digital Input/Output Verification Tests........................................... 4-13
Digital Output Test. ..................................................................... 4-13
Digital Input Test......................................................................... 4-14
Totalizer Test............................................................................... 4-14
Totalizer Sensitivity Test............................................................. 4-15
Dedicated Alarm Output Test .......................................................... 4-16
External Trigger Input Test.............................................................. 4-18
Calibration............................................................................................ 4-18
Using Hydra Starter Calibration Software....................................... 4-20
Setup Procedure Using Starter..................................................... 4-20
Calibration Procedure Using Starter............................................ 4-21
Using a Terminal.............................................................................. 4-22
Setup Procedure Using a Terminal.............................................. 4-22
Calibration Procedure Using a Terminal ..................................... 4-22
Reference Junction Calibration........................................................ 4-24
Concluding Calibration.................................................................... 4-25
4-1
HYDRA
Service Manual
4-30.
4-31.
4-32.
4-33.
4-34.
4-2
Updating 2635A Data Bucket Embedded Instrument Firmware..........
Using the PC Compatible Firmware Loader Software ....................
Setup Procedure for Firmware Download ...................................
Default Instrument Firmware Download Procedure....................
Using LD2635 Firmware Loader Directly ..................................
4-27
4-28
4-29
4-29
4-30
Performance Testing and Calibration
Introduction
4
4-1. Introduction
This section of the Service Manual provides performance tests that can be used at any
time to verify that Hydra (2620A, 2625A, or 2635A) operation is within published
specifications. A complete calibration procedure is also included. The performance test
and, if necessary, the calibration procedure can be performed periodically as well as after
service or repair.
4-2. Required Equipment
Equipment required for Performance Testing and Calibration is listed in Table 4-1.
Table 4-1. Recommended Test Equipment
Instrument
Type
Multifunction
Calibrator
Minimum Specifications
Recommended
Model
Fluke 5700A
DC Voltage:
Range: 90 mV to 300V dc.
Accuracy: 0.005%
AC Voltage:
Voltage
29 mV to 300V
15 mV to 300V
Frequency
1 kHz
100 kHz
Accuracy
0.05%
1.25%
Frequency:
10 kHz
Decade
Resistance
Source
1V rms
.0125%
Accuracy
0.003%
0.003%
0.003%
0.003%
0.0005%
290Ω or 190Ω
2.9 kΩ1.9 kΩ
29 kΩ19 kΩ
290 kΩ190 kΩ
2.9 MΩ1.9 MΩ
Fluke 5700A
Mercury
Thermometer
0.02 degrees Celsius resolution
Princo ASTM-56C
Thermocouple
Probe
Type K
Fluke P-20K
Room
Temperature
Oil/Water Bath
Thermos bottle and cap
Multimeter
Measures +5V dc.
Fluke 77
Signal Generator
Sinewave, 0.5 to 1V rms
10 Hz to 5 kHz
Fluke PM5136
Alternate Equipment List
(Minimum specifications are the same as in the Standard Equipment List)
Instrument Type
DMM Calibrator
Function/Signal Generator
Decade Resistance Source
Recommended Model
Fluke 5500A
Fluke PM5193 or Fluke PM5136
Gen Rad 1433H
4-3
HYDRA
Service Manual
4-3. Performance Tests
When received, the instrument is calibrated and in operating condition. The following
performance verification procedures are provided for acceptance testing upon initial
receipt or to verify correct operation at any time. All tests may be performed in sequence
to verify overall operation, or the tests may be run independently.
If the instrument fails any of these performance tests, calibration adjustment and/or
repair is needed. To perform these tests, use a Fluke 5700A Multifunction Calibrator or
equipment that meets the minimum specifications given in Table 4-1.
Each of the measurements listed in the following steps assumes the instrument is being
tested after a 1/2 hour warmup, in an environment with an ambient temperature of 18 to
28 degrees Celsius and with a relative humidity of less than 70%.
Note
All measurements listed in the performance test tables are made in the slow
reading rate unless otherwise noted.
Warning
Hydra contains high voltages that can be dangerous or fatal.
Only qualified personnel should attempt to service the
instrument.
4-4.
Accuracy Verification Test
1. Power up the instrument and wait 1/2 hour for its temperature to stabilize.
2. Connect a cable from the Output VA HI and LO connectors of the 5700A to the VΩ
and COM connectors on the Hydra front panel. Select the channel 0 function and
range on Hydra and the input level from the 5700A using the values listed in Table
4-2. Press MON to measure and display the measurement value for channel 0. The
display should read between the minimum and maximum values (inclusive) listed in
the table.
4-5.
Channel Integrity Test
Verify that the Accuracy Verification Test for channel 0 meets minimum acceptable
levels before performing this test.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the Input Module from the rear of the instrument. Open the Input Module
and connect a pair of test leads to the H (high) and L (low) terminals of channel 1.
Reinstall the Input Module into the instrument.
3. Connect the ends of the test leads together to apply a short (0 ohms).
4. Reconnect power, and turn the instrument ON.
5. For channel 1, select the 2-terminal ohms function and 300-ohms range on Hydra.
Press MON and ensure that the display reads a resistance of less than or equal to
4.0Ω. (This test assumes that lead wire resistances are less than 0.1Ω.)
6. Open the ends of the test leads and ensure that the display reads "OL" (overload).
7. Press MON to stop the measurement.
4-4
Performance Testing and Calibration
Performance Tests
4
Table 4-2. Performance Tests (Voltage, Resistance, and Frequency)
FUNCTION
RANGE
INPUT
LEVEL
short (0)
90 mV *
90 mV
90 mV *
short (0V)
300 mV
150 mV
300 mV
290 mV
300 mV
900 mV
900 mV* **
2.9V
3V
-2.9V
3V
29V
30V
150V
150V
290V
300V
* Range only used on 2635A (not used in autoranging).
** Computer I/F only (see FUNC command).
DC Volts
FREQUENCY











DISPLAY ACCURACY
(1 Year, 18-28°C)
MIN
MAX
-0.007
89.962
-0.02
149.93
289.89
899.70
2.8988
-2.9012
28.990
149.94
289.90
0.007
90.038
0.02
150.07
290.11
900.30
2.9012
-2.8988
29.010
150.06
290.10
Note
Voltages greater than 150V can only be applied to channels 0, 1, and 11.
AC Volts
300 mV
300 mV
300 mV
300 mV
3V
30V
150V
300V
20 mV
20 mV
290 mV
900 mV
2.9V
29V
150V
290V
1 kHz
100 kHz
1 kHz
100 kHz
1 kHz
1 kHz
1 kHz
1 kHz
19.71
18.50
289.26
275.00
2.8934
28.931
149.54
289.34
20.28
21.50
290.74
305.00
2.9066
29.069
150.46
290.66
Note
Voltages greater than 150V can only be applied to channels 0, 1, and 11.
The rear Input Module must be installed when measuring ac volts on
channel 0.
Resistance (4-Terminal)
Note
For 2-terminal measurements, the resistance accuracy given in this table
applies to channel 0 only and makes allowance for up to 0.05Ω of lead
wire resistance. You must add any additional lead wire resistance present
in your set up to the resistance values given in this table.
Using inputs in decades of 3:
300Ω

3 kΩ

30 kΩ
300 kΩ
3 MΩ
Using inputs in decades of 1.9:
300Ω

3 kΩ

30 kΩ
300 kΩ
3 MΩ
short
300Ω
short
3 kΩ
30 kΩ
300 kΩ
3 MΩ
0.00
299.80
0.0000
2.9981
29.980
299.81
2.9979
0.09
300.27
0.0003
3.0020
30.020
300.19
3.0021
short
190Ω
short
1.9 kΩ
19 kΩ
190 kΩ
1.9 MΩ
0.00
189.87
0.0000
1.8987
18.987
189.87
1.8986
0.09
190.20
0.0003
1.9014
19.013
190.13
1.9014
4-5
HYDRA
Service Manual
Table 4-2. Performance Tests (Voltage, Resistance, and Frequency) (cont)
FUNCTION
RANGE
INPUT
LEVEL
short
300Ω
100Ω

short
3 kΩ
1 kΩ
3 kΩ
10 kΩ
30 kΩ
100 kΩ
300 kΩ
1 MΩ
3 MΩ
10
10 MΩ
* Optional test point if standards available.
FREQUENCY
DISPLAY ACCURACY
(1 Year, 18-28°C)
MIN
MAX
0.09
0.00
100.15
99.92
0.0003
0.0000
1.0009
0.9992
10.008
9.992
100.08
99.92
1.0008
0.9992
10.014
9.986
Note
All channels (0 through 20) can accommodate 2-terminal resistance
measurements. Channel 0, with only two connections, cannot be used for 4terminal measurements. Four-terminal resistance measurements can be
defined for channels 1 through 10 only. Channels 11 through 20 are used,
as required, for 4-terminal to provide the additional two connections. For
example, a 4-terminal set up on channel 1 uses channels 1 and 11, each
channel providing two connections.
Frequency
90 kHz
10 kHz/2V p-p
9.994
10.006
8. Connect a cable from the Output VA HI and LO of the 5700A to the Input Module
test leads (observe proper polarity).
9. Select the VDC function and 300-volt range on Hydra and apply 0V dc from the
5700A. Then apply 290V dc input from the 5700A. Ensure the display reads
between the minimum and maximum values as shown in Table 4-2 for the 0 and
290V dc input levels.
Note
Channels 0, 1, and 11 can accommodate a maximum input of 300V dc or
ac. However, the maximum input for all other channels can only be 150V
dc or ac.
10. With the exception of the selected voltage range and input voltagefrom the 5700A,
repeat steps 1 through 9 for each remaining InputModule channel (2 through 20).
Channels 2 through 10 and 12 through20 should be configured for the 150V dc range
and an input voltageof 150 volts.
4-6.
Thermocouple Measurement Range Accuracy Test
Verify that the Accuracy Verification Test for channel 0 meets minimum acceptable
levels before performing this test.
Thermocouple temperature measurements are accomplished using the Hydra internal
100 mV and 1V dc ranges. (The ranges are not configurable by the operator.) This
procedure provides the means to test these ranges.
Testing the 100 mV and 1V dc ranges requires computer interfacing with a host
(terminal or computer). The host must send commands to select these ranges. These
ranges cannot be selected from the Hydra front panel.
4-6
Performance Testing and Calibration
Performance Tests
4
1. Ensure that communication parameters (i.e., transmission mode, baud rate, parity,
and echo mode) on Hydra and the host are properly configured to send and receive
serial data. Refer to Section 4 of the Hydra Users Manual.
2. Power up Hydra, and wait 1/2 hour for its temperature to stabilize.
3. Connect a cable from the Output VA HI and LO connectors of the 5700A to the VΩ
and COM connectors on the Hydra front panel.
4. Set the 5700A to output 0V dc.
5. Using either a terminal or a computer running a terminal emulation program as the
selected host, send the following commands to Hydra:
FUNC 0,VDC,I100MV <CR>
MON 1,0 <CR>
MON_VAL? <CR>
The returned value for channel 0 should be 0 mV ±0.007 mV.
Set the 5700A to output 90 mV DC. Send the following command:
MON_VAL? <CR>
The value returned should now be 90 mV ±0.038 mV (between 89.962 and 90.038
mV).
6. Change the Hydra channel 0 function to the internal 1V dc range by redefining
channel 0. Send the following commands:
MON 0 <CR>
FUNC 0,VDC,I1V <CR>
Set the 5700A to output 0.9V dc. Send the following commands:
MON 1,0 <CR>
MON_VAL? <CR>
The value returned should be 900 mV ±0.22 mV (899.78 to 900.22 mV.)
4-7.
4-Terminal Resistance Test
Verify that the channel 0 accuracy verification tests for dc volts and ohms meet
minimum acceptable levels.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the Input Module from the rear of the instrument. Open the Input Module
and connect a pair of test leads (keep as short as possible) to the H (high) and L
(low) terminals of channel 1 and a second pair of test leads to the H and L terminals
of channel 11. Reinstall the Input Module into the instrument.
3. Observing polarity, connect the channel 1 test leads to the Sense HI and LO
terminals of the 5700A and the channel 11 test leads to the Output HI and LO
terminals of the 5700A. Route wires with the method shown in Figure 4-1. Connect
the wires to the terminals shown in Figure 4-2.
Note
4-terminal connections are made using pairs of channels. 4-terminal
measurements can be made only on channels 1 through 10. The
accompanying pairs are channels 11 through 20.
4-7
HYDRA
Service Manual
4. Switch the instrument ON.
5. Select the 4-terminal OHMS function, AUTO range, for channel 1 on Hydra.
6. Set the 5700A to output the resistance values listed in Table 4-2 (Use decades of
1.9).
7. On Hydra press MON and ensure the display reads between the minimum and
maximum values (inclusive) shown in Table 4-2.
8. The 4-terminal Resistance Test is complete. However, if you desire to perform this
test on other Input Module channels (2 through 10), repeat steps 1 through 7,
substituting in the appropriate channel number.
R3
H
L
H
L
H
H
L
L
H
L
H
H
L
L
H
H
H
L
L
H
L
L
H
H
L
L
H
H
L
L
H
H
L
L
H
L
H
L
H
L
STRAIN RELIEF
11
12
13
14
15
16
17
18
19
20
H L
H L H L H L H L H L H L H L H L H L
H L
H L H L H L H L H L H L H L H L H L
1
2
3
4
5
6
7
8
9
10
s26f.eps
Figure 4-1. Input Module
4-8.
Thermocouple Temperature Accuracy Test
Verify that the Thermocouple Measurement Range Accuracy Test meets minimum
acceptable levels before performing this test.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the Input Module from the rear of the instrument. Open the Input Module,
and connect a K-type thermocouple to the H (high) and L (low) terminals of channel
1. (See Table 4-3 for lead colors). Then reinstall the Input Module into the
instrument.
4-8
Performance Testing and Calibration
Performance Tests
4
2-WIRE (2T) CONNECTION
SOURCE
11
12 13 14 15 16 17 18 19 20
HL
HL HL HL HL HL HL HL HL HL
HL
HL HL HL HL HL HL HL HL HL
(4-WIRE)
SENSE
(4-WIRE)
1
2
3
4
5
6
7
8
9
10
RESISTANCE
OR
RTD SOURCE
USE H AND L TERMINALS FOR ANY CHANNEL.
• CHANNEL 0 ON FRONT PANEL
• CHANNELS 1 THROUGH 20 ON REAR
PANEL INPUT MODULE (CHANNEL 1 SHOWN HERE).
4-WIRE (4T) CONNECTION
SOURCE
11
12 13 14 15 16 17 18 19 20
HL
HL HL HL HL HL HL HL HL HL
HL
HL HL HL HL HL HL HL HL HL
(4-WIRE)
SENSE
(4-WIRE)
1
2
3
4
5
6
7
8
9
10
RESISTANCE
OR
RTD SOURCE
USE H AND L TERMINALS FOR TWO CHANNELS ON REAR PANEL INPUT MODULE.
CONNECTIONS FOR CHANNEL 1 SHOWN HERE WITH CHANNEL 11 PROVIDING
ADDITIONAL TWO CONNECTIONS.
FOR EACH 4-WIRE CONNECTION, ONE SENSE CHANNEL (1 THROUGH 10) AND
ONE SOURCE CHANNEL (SENSE CHANNEL NUMBER +10 = 11 THROUGH 20) ARE USED.
s27f.eps
Figure 4-2. 2T and 4T Connections
4-9
HYDRA
Service Manual
Note
If other than a K type thermocouple is used, be sure that the instrument is
set up for the type of thermocouple used.
3. Reconnect power and switch the instrument ON.
4. Insert the thermocouple and a mercury thermometer (.02 degrees Celsius resolution)
in a room temperature bath. Allow 20 minutes for thermal stabilization.
5. Select the temperature function and K thermocouple type for channel 1. Then press
MON.
6. The value displayed should be the temperature of the room temperature bath (within
tolerances given in Table 4-4) as measured by the mercury thermometer.
7. The Thermocouple Temperature Accuracy Test is complete. However if you desire
to perform this test on any other Input Module channel (2 through 20) repeat steps 1
through 6 substituting in the appropriate channel number.
Table 4-3. Thermocouple Information
Type
Positive Lead
Material
Positive Lead Color
ANSI*
IEC**
Negative Lead
Material
Usable Range
(°C)
J
Iron
White
Black
Constantan
-200 to 760
C†
Tungsten
(5% Rhenium)
White
—
Tungsten
(26% Rhenium)
0 to 2316
b
Platinum
(30% Rhodium)
Gray
—
Platinum
(6% Rhodium)
0 to 1820
S
Platinum
Black
Orange
Platinum
(10% Rhodium)
-50 to 1768
R
Platinum
Black
Orange
Platinum
(13% Rhodium)
-50 to 1768
N
NICROSIL
Orange
—
NISIL
-270 to 1300
T‡
Copper
Blue
Brown
Constantan
-270 to 400
E
Chromel
Purple
Violet
Constantan
-270 to 1000
K
Chromel
Yellow
Green
Alumel
-270 to 1372
*
**
†
‡
American National Standards Institute (ANSI) device negative lead is always red.
International Electrotechnical Commission (IEC) device negative lead is always white.
Not an ANSI designation but a Hoskins Engineering Company designation.
An ANSI type T is supplied with the meter.
Table 4-4. Performance Tests for Thermocouple Temperature Function
4-10
Thermocouple Type
Themocouple Temperature Function
1 Year @ 18-28°C
J
K
N
E
T
± 0.4°C
± 0.5°C
± 0.6°C
± 0.4°C
± 0.5°C
Performance Testing and Calibration
Performance Tests
4-9.
4
Open Thermocouple Response Test
Use the following procedure to test the open thermocouple response:
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the Input Module from the rear of the instrument. Open the Input Module
and connect test leads to the H (high) and L (low) terminals of channel 1. Reinstall
the Input Module into the instrument.
3. Reconnect power and switch the instrument ON.
4. Connect the test leads from the Input Module to an 820 ohm resistor.
5. Select the temperature function and K thermocouple type for channel 1. Then press
MON.
6. The value displayed should approximate the ambient temperature.
7. Replace the 820-ohm resistor with a 4-kilohm resistor to simulate a high resistance
or open thermocouple.
8. Verify a reading of "otc".
9. The Open Thermocouple Response Test is complete. However if you desire to
perform this test on any other Input Module channel (2 through 20) repeat steps 1
through 8, substituting the appropriate channel number.
4-10. RTD Temperature Accuracy Test
The following two RTD Temperature Accuracy Tests are different in that one uses a
Decade Resistance Source and the other uses an RTD. Only one of the tests needs to be
performed to verify operation.
4-11. RTD Temperature Accuracy Test (Using Decade Resistance Source).
Verify that the channel 0 accuracy verification tests for dc volts and 300-ohm range meet
minimum acceptable levels.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the Input Module from the rear of the instrument. Open the Input Module
and connect a pair of test leads (keep as short as possible) to the H (high) and L
(low) terminals of channel 1. For 4-terminal performance testing, connect a second
pair of test leads to the H (high) and L (low) terminals of channel 11. Reinstall the
Input Module into the instrument.
3. Connect the channel 1 test leads to the Output HI and LO terminals on the Decade
Resistance Source. For 4-terminal performance testing, also connect channel 11’s
test leads to the Output HI and LO terminals of the Decade Resistance Source.
Connect as shown in Figures 4-1 and 4-2.
Note
4-terminal connections are made using pairs of channels. 4-terminal
measurements can only be made on channels 1 through 10. The
accompanying pairs are channels 11 through 20.
4. Switch the instrument ON.
5. Select the 4-terminal RTD temperature function, RTD type PT, for channel 1 on
Hydra.
6. Press MON. For each resistance, ensure that the display reads within the range
shown in Table 4-5.
4-11
HYDRA
Service Manual
7. The RTD Temperature Accuracy test is complete. However, if you desire to perform
this test on Input Module channels (2 through 10), repeat steps 1 through 5
substituting in the appropriate channel number.
Note
The only type of temperature measurement that can be made on channel 0
is 2-terminal RTD. Channels 11 through 20 support only 2-terminal RTDs.
Table 4-5. Performance Tests for RTD Temperature Function (Resistance Source)
Simulated °C Temperature
Decade Reisitance
Source
2620A/2635A*
2635A*
Temperature Accuracy Specifications
1 Year @ 18-28°C
100Ω
200Ω
300Ω
0
266.58
558.00
0
266.34
557.70
±0.24°C
±0.48°C
±0.75°C
*
RTD temperature linearizations changed between the 2620A/2625A and 2635A Hydra instrument
firmware. The 2620A & 2625A Hydra instruments are based on the International Practical Temperature
Scale of 1968 (IPTS-68). The 2635A Hydra Instrument is based on the International Temperature Scale
of 1990 (ITS-90).
These figures assume that RTD R0 is set to 100.00Ω for each channel.
Accuracy given is for 4-wire measurements only.
4-12. RTD Temperature Accuracy Test (Using DIN/IEC 751).
1. Switch OFF power to the instrument and disconnect all other high voltage inputs.
2. Remove the Input Module from the rear of the instrument. Open the Input Module
and connect a Platinum RTD, conforming to the European Standards IEC 751 (DIN
43760).
2-terminal RTD: Connect the RTD excitation leads to the H (high) and L (low)
terminals of channel 1.
4-terminal RTD: Connect the RTD excitation leads (one red and one black wire) to
the H (high) and L (low) terminals of channel 11. Connect the second pair of RTD
red and black leads to the H and L leads of channel 1. (Refer to Figures 4-1 and 4-2
for proper connection.) Reinstall the Input Module into the instrument.
Note
4-terminal connections are made using pairs of channels. 4-terminal
measurements can only be made on channels 1 through 10. Their
accompanying pairs are channels 11 through 20.
3. Switch the instrument ON.
4. Insert the RTD probe and a mercury thermometer in a room temperature bath. Allow
20 minutes for thermal stabilization.
5. Depending on the type of connection made in step 2, select either the 2-Terminal or
4-Terminal RTD temperature function, RTD type PT (DIN IEC 751), for channel 1
on Hydra. Press MON and ensure the display reads the temperature of the room
temperature bath (within tolerances shown in Table 4-6) as measured by the mercury
thermometer.
4-12
Performance Testing and Calibration
Performance Tests
4
6. The RTD Temperature Accuracy test is complete. However, if you desire to perform
this test on any other channel (0 or 2 through 20), repeat steps 1 through 5,
substituting the appropriate channel number.
Note
The only type of temperature measurement that can be made on channel 0
is 2-terminal RTD. Channels 11 through 20 support only 2-terminal RTDs.
Table 4-6. Performance Tests for RTD Temperature Function (DIN/IEC 751)
RTD Type
(DIN 43760 RTD)
Temperature Accuracy Specifications
1 Year @ 18-28°C
2-wire (channel 0)
4-wire
-0.65°C to +0.70°C
-0.65°C
(Assumes RTD R0 is set to 100.00Ω for each channel.)
4-13. Digital Input/Output Verification Tests
Digital Input/Output verification testing requires computer interfacing with a host
(terminal or computer). The host must send commands to the instrument to control the
digital lines for this test. Refer to Section 4 of the Hydra Users Manual for a description
of configuring and operating the instrument.
4-14. Digital Output Test.
1. Ensure that communication parameters (i.e., transmission mode, baud rate, parity,
and echo mode) on Hydra and the host are properly configured to send and receive
serial data.
2. Switch OFF power to the instrument and disconnect all high voltage inputs.
3. Remove the ten-terminal Digital I/O connector from the rear of the instrument and
all external connections to it. Connect short wires (to be used as test leads) to the
ground (G) and 0 through 7 terminals. Leave the other wire ends unconnected at this
time. Reinstall the connector.
4. Switch power ON to both Hydra and the host. Verify that Hydra is not scanning. If
Hydra is scanning, press SCAN to turn scanning off, then cycle power off and on
again.
5. Using a digital multimeter (DMM), verify that all digital outputs (0-7) are in the
OFF or HIGH state. This is done by connecting the low or common of the
multimeter to the ground test lead and the high of the multimeter to the digital output
and verifying a voltage greater than +3.8V dc.
6. Using either a terminal or a computer running a terminal emulation program, set up
Hydra to turn Digital Outputs ON (LOW state).
In sequence send the following commands to Hydra and measure that the correct
Digital Output line measures less than +0.8V dc (LOW state.)
DO_LEVEL 0,0 <CR>
Verify that output 0 measures a LOW state.
DO_LEVEL 1,0 <CR>
Verify that output 1 measures a LOW state.
DO_LEVEL 2,0 <CR>
Verify output 2 measures a LOW state.
Repeat the command for all eight outputs.
7. Set up Hydra to turn Digital Outputs OFF (HIGH state).
4-13
HYDRA
Service Manual
Send the following commands to Hydra in sequence, and measure that the correct
Digital Output line measures greater than +3.8V dc (HIGH state.)
DO_LEVEL 0,1 <CR>
Verify that output 0 measures a HIGH state.
DO_LEVEL 1,1 <CR>
Verify that output 1 measures a HIGH state.
Repeat the command for all eight outputs.
4-15. Digital Input Test
1. Perform the DIGITAL OUTPUT TEST steps 1 through 5.
2. Using either a terminal or a computer running a terminal emulation program, read
the Hydra Digital Input lines.
Send the following command to Hydra:
DIO_LEVELS? <CR>
Verify that the returned value is 255.
Note
The number returned is the decimal equivalent of the Digital Input binary
word (status of inputs 0 through 7). See Table 4-7 to determine if the
number returned corresponds to the inputs jumpered to ground in this
test.
3. Jumper input 0 to ground by connecting the ground test lead to the input 0 test lead.
Then send the following command to Hydra:
DIO_LEVELS? <CR>
Verify that the returned value is 254.
4. Disconnect input 0 from ground, then jumper input 1 to ground.
Send the command: DIO_LEVELS? <CR>
Verify that the returned value is 253.
5. Repeat step 4 for each input and verify the correct returned value (See Table 4-7).
Table 4-7. Digital Input Values
Terminal Grounded
State of Digital Inputs
Decimal Value
none
0
1
2
3
4
5
6
7
Inputs 0-7, all HIGH
Inputs 1-7 HIGH, input 0 LOW
Inputs 0,2-7 HIGH, input 1 LOW
Inputs 0-1 and 3-7 HIGH, input 2 LOW
Inputs 0-2 and 4-7 HIGH, input 3 LOW
Inputs 0-3 and 5-7 HIGH, input 4 LOW
Inputs 0-4 and 6-7 HIGH, input 5 LOW
Inputs 0-5 and 7 HIGH, input 6 LOW
Inputs 0-6 HIGH, input 7 LOW
255
254
253
251
247
239
223
191
127
4-16. Totalizer Test
This totalizer verification test requires toggling Digital Output line 0 and using it as the
Totalizer input. The test requires computer interfacing with a host (terminal or
4-14
Performance Testing and Calibration
Performance Tests
4
computer). The host must send commands to Hydra to control the digital line for this
test.
1. Ensure that communication parameters (i.e., transmission mode, baud rate, parity,
and echo mode) on Hydra and the host are properly configured to send and receive
serial data. Refer to Section 4 of the Hydra Users Manual.
2. Switch OFF power to the instrument and disconnect all high voltage inputs.
3. Remove the ten-terminal Digital I/O connector from the rear of the instrument and
all external connections to it. Connect short wires (to be used as test leads) to the 0
terminal and the Totalizer ( ∑ ) terminal. Leave other ends of wires unconnected at
this time. Reinstall the connector.
4. Switch ON power to both Hydra and the host.
5. Press the TOTAL button on the front panel of Hydra.
Verify that Hydra displays a 0 value.
6. Jumper output 0 to the Totalizer ( ∑ ) input by connecting the ( ∑ ) terminal test lead
to the output 0 test lead.
7. Using either a terminal or a computer running a terminal emulation program, set up
Hydra to toggle (turn ON and OFF) Digital Output 0.
Send the following commands to Hydra in sequence, and verify that Hydra measures
and displays the correct total value:
DO_LEVEL 0,0 <CR>
DO_LEVEL 0,1 <CR>
Verify that Hydra displays a totalizer count of 1.
8. Send the following commands in sequence:
DO_LEVEL 0,0 <CR>
DO_LEVEL 0,1 <CR>
A totalizer count of 2 should now be displayed.
9. Repeat step 8 for each incremental totalizing count.
10. Set the Hydra totalized count to a value near full range (65535) and test for overload.
Send the following commands to Hydra:
TOTAL 65534 <CR>
DO_LEVEL 0,0 <CR>
DO_LEVEL 0,1 <CR>
A totalizer count of 65535 should be displayed.
11. Send:
DO_LEVEL 0,0 <CR>
DO_LEVEL 0,1 <CR>
The Hydra display should now read "OL", indicating that the counter has been
overrun.
4-17. Totalizer Sensitivity Test
1. Perform a successful Totalizer Test.
2. Remove the jumper connecting the ∑ terminal test lead to the output 0 test lead.
4-15
HYDRA
Service Manual
3. Verify that Hydra is still in the total measuring mode. If not, press the TOTAL
button. Reset the totalizer count shown on the display by pressing the SHIFT and
TOTAL(ZERO) buttons.
The Hydra display should now show a value of 0.
4. Connect the output of the signal generator to the ∑ and J terminals.
5. Program the signal generator to output a 1.5V rms sine signal at 10 Hz.
The Hydra display should now show the totalizing value incrementing at a 10 count
per second rate.
4-18. Dedicated Alarm Output Test
The Dedicated Alarm Output Test verifies that Alarm Outputs 0 through 3 are
functioning properly. Because this test is dependent on voltage readings the Accuracy
Verification Test for channel 0 and the Channel Integrity Test for channels 1 through 3
should be performed if voltage readings are suspect.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the eight-terminal Alarm Output connector from the rear of Hydra and all
external connections to it. Connect short wires (to be used as test leads) to the [J]
and 0 through 3 terminals. Leave the other ends of the wires unconnected at this
time. Reinstall the connector.
3. Remove the Input Module from the rear of Hydra. Open the Input Module and
jumper the H (high) terminal of channels 1, 2, and 3 together. Connect a test lead to
the H of channel 1. Also jumper the L (low) terminals of channel 1, 2, and 3
together. Connect a second test lead to the L of channel 1. Reinstall the Input
Module into Hydra. Refer to Figure 4-3.
4. Switch power ON.
5. Using a digital multimeter (DMM), verify that alarm outputs 0 through 3 are in the
OFF or HIGH state. Perform this test by connecting the low or common of the
multimeter to the ground test lead and the high of the multimeter to the alarm output.
Verify a voltage greater than +3.8V dc.
6. Connect a cable from the Output VA HI and LO connectors of the 5700A to the VΩ
and COM connectors on the front panel of Hydra. Then jumper the Hydra VΩ
terminal to the H (high) test lead of the Input Module and the COM terminal to the L
(low) test lead.
7. On Hydra, select the VDC function, 3V range, and assign a HI alarm limit of
+1.0000 for channels 0 through 3. Set up all other channels (4-20) to the OFF
function. Select a scan interval of 5 seconds.
8. Set the 5700A to output +0.9900 volts.
9. Press SCAN. Hydra should scan channels 0 through 3 every 5 seconds.
10. Using a digital multimeter, again verify that alarm outputs 0 through 3 are in the
OFF or HIGH state.
11. Set the 5700A to output +1.1000 volts. Verify that the alarm outputs 0 through 3 are
in the ON or LOW state (measure less than +0.8V dc).
4-16
Performance Testing and Calibration
Performance Tests
ALARM OUTPUTS
ALARM
OUTPUT
CONNECTOR
++ ––
DIGITAL I/O
0 1 2 3 4 5 6 7 Σ
00 11 22 33 TR
TR
+30V
9-16 V
DC PWR
0
1 2
!
3 GND
SOURCE
INPUT
MODULE
4
11
12 13 14 15 16 17 18 19 20
HL
HL HL HL HL HL HL HL HL HL
HL
HL HL HL HL HL HL HL HL HL
(4-WIRE)
SENSE
(4-WIRE)
1
2
3
4
5
6
7
8
9
10
5700A
HYDRA
FRONT PANEL
OUTPUT
VΩA
SENSE
VΩ
WIDEBAND
HI
HI
LO
LO
REVIEW
LAST
COM
VΩ
HI
300V
MAX
FUNC
Mx+B
ALRM
AUX
GUARD GROUND
CURRENT
(USE STACKED
BANANA JACKS)
S28F.EPS
Figure 4-3. Dedicated Alarms Test
4-17
HYDRA
Service Manual
4-19. External Trigger Input Test
The External Trigger Input Test verifies that the rear panel trigger input of Hydra is
functioning properly.
1. Switch OFF power to the instrument and disconnect all high voltage inputs.
2. Remove the eight-terminal Alarm Output connector from the rear of Hydra and all
external connections to it. Connect short wires (to be used as test leads) to the Gand
TR terminals. Leave other ends of wires unconnected at this time. Reinstall the
connector. Refer to Figure 4-4.
3. Switch power ON.
4. On Hydra, select the VDC function, 30V range for channels 0 through 5. Select a
scan interval of 30 seconds.
5. Select trigger ON to enable the external trigger input. Press SHIFT, then
MON(TRIGS). (The display shows TRIG.) Then press either the up or down arrow
buttons until the display shows ON. Finally, press ENTER.
6. Press the Hydra SCAN button. Hydra should scan channels 0 through 5 once every
30 seconds.
7. During the interval when scanning is not occurring, connect (short) the test leads of
the TR and ground Alarm Output terminals.
Ensure the connection causes a single scan to occur.
8. Disconnect (open) the TR and ground connection.
Ensure the scan continues to execute at its specified interval.
ALARM OUTPUTS
++ ––
9-16 V
DC PWR
DIGITAL I/O
0 1 2 3 4 5 6 7 Σ
00 11 22 33 TR
TR
+30V
!
s29f.eps
Figure 4-4. External Trigger Test
4-20. Calibration
Hydra calibration is controlled with computer interface commands. The 2620A may be
calibrated by using the IEEE-488 or RS-232 interface, but the 2625A and 2635A may
only be calibrated via their RS-232 interface. Local (front panel) calibration is not
possible.
4-18
Performance Testing and Calibration
Calibration
4
Activate calibration mode by pressing and holding the CAL Enable button (front panel)
for approximately 4 seconds. Release the button after Hydra beeps and the CAL
annunciator lights.
Note
The CAL Enable button is located on the right side of the display and is
recessed beneath a calibration seal. Press this button with a blunt-tipped
object. Avoid using a sharper-tipped object (such as a pencil). Do not press
CAL ENABLE unless you intend to calibrate the instrument. If you have
activated Calibration and wish to exit calibration immediately, press CAL
ENABLE momentarily a second time.
The instrument must be stabilized in an environment with ambient temperature of 22 to
24ºC and relative humidity of less than 70% and have been turned on for at least 1/2
hour prior to calibration.
The instrument should normally be calibrated on a regular cycle, typically every 90 days
or 1 year. The chosen calibration cycle depends on the accuracy specification you wish
to maintain. The instrument should also be calibrated if it fails the performance test or
has undergone repair.
The instrument features closed-case calibration controlled over the Computer Interface.
Using known reference sources, closed-case calibration has many advantages. There are
no parts to disassemble, no mechanical adjustments to make, and the instrument can be
calibrated by an automated instrumentation system.
Once the instrument is in calibration mode, closed-case calibration can be made for the
four calibration groups: Volts DC, Volts AC, Resistance, and Frequency. Once begun,
each group must be completed successfully for the results of the calibration to be made
permanent. It is not necessary to perform all calibration groups. Each group is
independent of the other three groups; completion of a group sets the constants for that
group.
Analog inputs are made at the rear-panel Input Module, and computer interface
commands are used to control each step of the process. Either of the following two
closed-case calibration procedures can be used:
•
Using Hydra Starter Calibration Software
This procedure uses software supplied with this Service Manual.Instructions for each
step are presented on the PC screen.
•
Using a Terminal
This procedure relies on individual commands for each step. A summaryof these
commands is presented in Table 4-8.
With either closed-case procedure, an additional procedure (reference junction
calibration) may be used to calibrate the thermocouple temperature function. This
procedure requires physical access to the rear panel Input Module.
Note
The instrument returns a Device Dependent Error prompt (!>) if a
calibration step fails. Usually, this happens if the reference is not within an
anticipated range (5 to 15%, depending on the step). At this point, the
response to the CAL_STEP? command equals the raw, uncalibrated
reading taken on the reference input. Refer to Calibration Failures in
Section 5 for more information.
4-19
HYDRA
Service Manual
To provide accuracy at full range, calibration is not recommended below one-third of
full range (10000 counts).
Table 4-8. Calibration Mode Computer Interface Commands
Command
Cal x
Description
Start calibration of a new function.
x
Function to calibrate
1
VDC
2
VAC
3
ohms
4
Frequency
CAL_CLR
Reset all calibration constants to nominal values, clearing present calibration.
CAL_CONST? xx
Return the value of the calibration constant indicated by xx.
CAL_REF?
Return the present calibration reference.
CAL_REF < value>
Calibrate to <value>, rather than the default calibration reference value.
CAL_STEP?
Calibrate and return the calibrated value of the input.
EEREG? xx
Return the contents of the specified EEPROM register (xx).
The following additional computer interface commands can be used in calibration mode. Use of any other
command results in an execution error. Refer to Section 4 of the Hydra Users Manual for complete
information about these computer interface commands.
*CLS *ESE *ESE?*ESR?*IDN?*OPC *OPC?*RST *SRE *SRE?*STB?*TRG *WAI IEE IEE?IER?LOCS
LWLS REMS RWLS
4-21. Using Hydra Starter Calibration Software
This procedure uses the Hydra Starter Package (with Calibration Software) for closedcase calibration. This software runs on an IBM PC or equivalent using the RS-232
interface. It consists of the following three files:
•
•
•
An executable file (CAL.EXE)
A help text file (CAL.HLP)
A configuration initialization file (CAL.INI)
4-22. Setup Procedure Using Starter
Use the following procedure to set up Hydra and the PC prior to using the calibration
feature of the Hydra Starter Package:
1. Connect a pair of test leads to the channel 1 H (high) and L (low) terminals on the
Input Module. Connect a second pair of test leads to channel 11. (This second pair is
used only for 4-wire resistance calibration.) Install the Input Module into Hydra.
2. Using the RS40 Terminal Interface Cable, connect the PC COM port to the Hydra
RS-232 port. Use an RS40 and an RS41 cable in series to connect to the COM port
on an IBM PC/AT.
4-20
Performance Testing and Calibration
Calibration
4
3. From the CAL directory on the PC, type CAL. Then press any key to start the
program and access the SETUP menu.
4. On Hydra, press POWER ON. After the initialization process has concluded, use the
following procedure to set up communications:
a. Press SHIFT and then LIST(COMM).
b. With ’BAUd’ displayed, use the UP or DOWN arrow key to selectthe desired
baud rate. Then press ENTER.
c. With ’PAR’ (parity) displayed, use the UP or DOWN arrow key toselect the
parity. Then press ENTER.
d. With ’CtS’ (2635A only; Clear to Send) displayed, use the UP orDOWN arrow
key to select the Clear to Send flow control ’OFF’.Then press ENTER.
e. With ’ECHO’ displayed, use the UP or DOWN arrow key to select’OFF’. Then
press ENTER. Communications setup for Hydra is nowcomplete.
5. On the PC, use the SETUP menu to match the communication parameters defined
above for Hydra.
6. On Hydra, break the calibration seal on the front panel display. Then press and hold
the CAL Enable button (approximately 4 seconds) until ’CAL’ is displayed. Press
this button with a blunt-tipped object. Avoid using a sharper-tipped object (such as a
pencil).
7. On the PC, use the right and left arrow keys to select CAL. Then press the ENTER
key. A message asking if you want to calibrate is displayed. Press Y and ENTER.
The next displayed message specifies the voltage to be applied to channel 1.
4-23. Calibration Procedure Using Starter
Use the following procedure to calibrate Hydra with the Hydra Starter Package:
1. Connect the channel 1 test leads to the 5700A output.
2. On the 5700A, select the output voltage specified on the PC (step 7 above.)
3. On the PC, press ENTER. If the input voltage is within a predetermined acceptable
boundary, Hydra performs a calibration for this step. The program then prompts you
for the next input value.
Note
"Bad Calibration Input Value" is returned if the input is not acceptable
(the calibration step could not be executed.) Verify that the input to Hydra
channel 1 is the correct value and polarity. Also verify that the 5700A is
in OPERATE mode. If the input is correct and "Bad Calibration Input
Value" is still returned, repair of Hydra may be required.
4. Following the prompts, complete all steps for this calibration group.
5. You will then be asked if you want to perform the next calibration group. Press Y ENTER.
6. Following the prompts, complete all steps in the remaining calibration groups.
4-21
HYDRA
Service Manual
4-24. Using a Terminal
This procedure can be used with either a terminal or a computer running a terminal
emulation program.
4-25. Setup Procedure Using a Terminal.
Use the following procedure to set up Hydra and the PC:
1. Connect a pair of test leads to the high and low terminals of channel 1 on the Hydra
Input Module. Connect a second pair of test leads to channel 11.
2. Install the Input Module into Hydra.
3. Connect the COM port of the PC or terminal to the Hydra RS-232 port using an
RS40 Terminal Interface Cable. Use an RS40 and an RS41 cable in series to connect
to the COM port on an IBM PC/AT.
4. On Hydra, press POWER ON. After the initialization process has concluded, use the
following procedure to set up communications:
a. Press SHIFT and then LIST(COMM).
b. With ’BAUd’ displayed, use the UP or DOWN arrow key to selectthe desired
baud rate. Then press ENTER.
c. With ’PAR’ (parity) displayed, use the UP or DOWN arrow key toselect the
parity. Then press ENTER.
d. With ’CtS’ (2635A only; Clear to Send) displayed, use the UP orDOWN arrow
key to select the Clear to Send flow control ’OFF’.Then press ENTER.
e. With ’ECHO’ displayed, use the UP or DOWN arrow key to select’ON’. Then
press ENTER. Communications setup for Hydra is nowcomplete.
5. On the terminal, match the communication parameters used for Hydra (above).
6. On Hydra, break the calibration seal on the front panel display. Then press and hold
the CAL Enable button (approximately 4 seconds) until CAL is shown on the Hydra
display. Press this button with a blunt-tipped object. Avoid using a sharper-tipped
object (such as a pencil).
7. Connect the channel 1 test leads to the output of a 5700A.
4-26. Calibration Procedure Using a Terminal
Calibration procedures using a terminal (or a computer program that emulates a
terminal) are presented in the following tables:
•
•
•
•
DC Volts (CAL 1) Calibration:Table 4-9
AC Volts (CAL 2) Calibration:Table 4-10
Ohms (CAL 3) Calibration:Tables 4-11, 4-12
Frequency (CAL 4) Calibration: Table 4-13
In the tables, the CAL_REF? query asks Hydra for the next calibration reference value.
If some other value is to be used, the CAL_REF xxx.xxxx command tells Hydra the
calibration reference value to expect.
To provide accuracy at full range, calibration is not recommended below one-third of
full range (10000 counts).
4-22
Performance Testing and Calibration
Calibration
4
Once the calibrator output has been set to Hydra, the CAL_STEP? query performs the
calibration step and returns the calibrated value of the input. The response to
CAL_STEP? must be received before each new step can begin. With some steps, a
noticeable delay may be encountered.
Table 4-9. DC Volts Calibration
Command
Response
Action
CAL 1
=>
Puts Hydra in VDC Calibration.
CAL_REF?
+90.000E-3
You output 90 mV dc from the 5700A. Wait about 10 seconds.
CAL_STEP?
Hydra computes calibration constant 1 and returns the calibrated reading
(for example, +90.000E-3.)
Note
If the input is incorrect, the "!>" response signifies that a Device
Dependent Error was generated. The calibration step could not be
executed. Verify that the input to Hydra channel 1 is the correct value and
polarity. Also verify that the 5700A is in OPERATE mode. If the input is
correct, Hydra may require repair.
CAL_REF?
+900.00E-3
CAL_STEP?
CAL_REF?
Hydra computes calibration constant 2 and returns the calibrated reading.
+290.00E-3
CAL_STEP?
CAL_REF?
+2.9000E+0
You output 2.9V dc and wait 4 seconds.
Hydra computes calibration constant 4 and returns the calibrated reading.
+29.000E+0
CAL_STEP?
CAL_REF?
You output 290 mV dc and wait 4 seconds.
Hydra computes calibration constant 3 and returns the calibrated reading.
CAL_STEP?
CAL_REF?
You output 900 mV dc from the 5700A. Wait 4 seconds.
You output 29V dc and wait 4 seconds.
Hydra computes calibration constant 5 and returns the calibrated reading.
+290.00E+0
CAL_STEP?
You output 290V dc and wait 4 seconds.
Hydra computes calibration constant 6 returns the calibrated reading.
Now change the 5700A output to 0.0V dc
4-27. Ohms Calibration
Resistor values of 290Ω, 2.9 kΩ, 29 kΩ, 290 kΩ, and 2.9 MΩ are preferred. Use either
fixed resistors or a decade resistance source having the required accuracy (see Table 41.) Connect the channel 11 test leads and the channel 1 test leads to the source resistance.
Refer to Figure 4-5 and Table 4-11 for related setup and calibration procedures.
The 5700A can also be used as a resistance source. Connect the 5700A to Hydra for 4Wire Ohms Calibration. Connect the channel 11 test leads to the 5700A OUTPUT
terminals and the channel 1 test leads to the 5700A SENSE terminals. Verify that 5700A
EXT SNS is ON. Select the 5700A output as specified in each step. Refer to Figure 4-6
and Table 4-12 for related setup and calibration procedures.
4-23
HYDRA
Service Manual
Note
The 300 kΩ, 3 MΩ, and 10 MΩ ranges are sensitive to noise. Any
movement of the input leads can cause noisy readings. Use shielded leads
and verify these two calibration points at the conclusion of calibration.
Table 4-10. AC Volts Calibration
Command
Response
Action
CAL 2
=>
Puts Hydra in VAC Calibration.
CAL_REF?
+029.00E-3
You output 29 mV ac at 1 kHz from the 5700A. Wait about 8 seconds.
CAL_STEP?
Hydra computes calibration constant 7 and returns the calibrated reading
(for example, +029.00E-3.)
Note
If the input is incorrect, the "!>" response signifies that a Device
Dependent Error was generated. The calibration step could not be
executed. Verify that the input to Hydra channel 1 is the correct value and
polarity. Also verify that the 5700A is in OPERATE mode. If the input is
correct, Hydra may require repair.
CAL_REF?
+290.00E-3
You output 290 mV at 1 kHz from the 5700A. Wait 8 seconds.
+0.2900E+0
You output 290 mV at 1 kHz from the 5700A and wait 8 seconds.
CAL_STEP?
CAL_REF?
Hydra computes calibration constant 8 and returns the calibrated reading.
CAL_STEP?
CAL_REF?
Hydra computes calibration constant 9 and returns the calibrated reading.
+2.9000E+0
CAL_STEP?
CAL_REF?
Hydra computes calibration constants 10 and 11 and returns the
calibrated reading. (For software versions lower than 5.4, this step
computes calibration constant 10 only.)
+29.000E+0
CAL_STEP?
CAL_REF?
You output 29V at 1 kHz and wait 8 seconds.
Hydra computes calibration constants 12 and 13 and returns the
calibrated reading. (For software versions lower than 5.4, this step
computes calibration constant 11 only.)
+290.00E+0
CAL_STEP?
You output 2.9V at 1 kHz from the 5700A and wait 8 seconds.
You output 290V at 1 kHz and wait 8 seconds.
Hydra computes calibration constant 14 and returns the calibrated
reading. (For software versions lower than 5.4, this step computes
calibration constant 12.)
4-28. Reference Junction Calibration
Note
This procedure is necessary only if the Input Module has been repaired or
damaged, or if R3 on the Input Module has been inadvertently adjusted.
If thermocouple readings taken in the Thermocouple Temperature Accuracy Test section
of the performance tests are found to be out of tolerance, the Input Module Reference
Junction may require calibration. First, check the volts dc calibration. If volts dc
calibration is correct, perform the following steps:
1. Perform the Volts DC group calibration.
2. Switch OFF power to Hydra, and remove the Input Module from the rear of the
instrument.
4-24
Performance Testing and Calibration
Calibration
4
4-WIRE (4T) CONNECTION
SOURCE
11
12 13 14 15 16 17 18 19 20
HL
HL HL HL HL HL HL HL HL HL
(4-WIRE)
SENSE
HL
HL HL HL HL HL HL HL HL HL
HYDRA
INPUT
MODULE
(4-WIRE)
1
2
3
4
5
6
7
8
9
10
DECADE
RESISTANCE
SOURCE
s30f.eps
Figure 4-5. 4-Terminal Connections to Decade Resistance Source
3. Remove the module top cover by loosening the two securing screws, fully opening
the module top and gently prying either of the hinge ears away from the main body
of the module. Refer to Figure 4-1.
4. Connect a KNBS thermocouple to the H (high) and L (low) terminals of channel 15.
Refer to Table 4-3 for thermocouple lead colors. Reinstall the module (without the
top cover) into the instrument.
5. Press the Hydra POWER button ON.
6. Insert the thermocouple and a mercury thermometer in a stable, thermally-isolated,
room-temperature bath. Allow 20 minutes for thermal stabilization.
7. Select the temperature function and K thermocouple type for channel 15. Select the
slow measurement rate. Then press MON.
8. Adjust resistor R3 (see Figure 4-1) on the Input Module until Hydra displays the
same temperature reading as the mercury thermometer.
9. Calibration of the Input Module is now complete. Remove the Input Module and
disconnect the thermocouple. Then attach and secure the module cover.
4-29. Concluding Calibration
At the conclusion of this type of calibration, first make sure the source is cleared. Then
press the CAL Enable button on the instrument to exit calibration mode.
Calibration mode can also be exited at any time by sending the *RST Computer
Interface command. If this command is sent prior to completion of all calibration points
for the selected function, no changes are made to nonvolatile calibration memory for that
function.
4-25
HYDRA
Service Manual
SOURCE
11
12 13 14 15 16 17 18 19 20
HL
HL HL HL HL HL HL HL HL HL
(4-WIRE)
SENSE
HL
HL HL HL HL HL HL HL HL HL
HYDRA
INPUT
MODULE
(4-WIRE)
1
2
3
4
5
6
7
8
9
10
5700A
OUTPUT
V ΩA
SENSE
VΩ
WIDEBAND
HI
HI
LO
LO
HI
AUX
CURRENT
GUARD
GROUND
NC
NC
EX SNS
: ON
EX GRD
: OFF
2-WIRE
COMP
OFF
SENSE
SOURCE
HYDRA
5700A
SOURCE
SENSE
s31f.eps
Figure 4-6. 4-Terminal Connections to the 5700A
4-26
Performance Testing and Calibration
Updating 2635A Data Bucket Embedded Instrument Firmware
4
Table 4-11. 4-Wire Ohms Calibration (Fixed Resistor)
Command
Response
Action
CAL 3
=>
Puts Hydra in OHMS Calibration.
CAL_REF?
+290.00E+0
You source 290Ω from the decade resistance source or fixed resistor.
CAL_STEP?
Hydra computes calibration constant 15 and returns the calibrated
reading. (For software versions lower than 5.4, this step computes
calibration constant 13.)
Note
If the input is incorrect, the "!>" response signifies that a Device
Dependent Error has been generated. The calibration step could not be
executed.Verify that the input to Hydra channel 1 is the correct value. If
the input is correct, Hydra may require repair.
CAL_REF?
+2.9000E+3
CAL_STEP?
CAL_REF?
Hydra computes calibration constant 16 and returns the calibrated
reading. (For software versions lower than 5.4, this step computes
calibration constant 14.)
+29.000E+3
CAL_STEP?
CAL_REF?
CAL_STEP?
You source 29000Ω.
Hydra computes calibration constant 17 and returns the calibrated
reading. (For software versions lower than 5.4, this step computes
calibration constant 15.)
+290.00E+3
CAL_STEP?
CAL_REF?
You source 2900Ω.
You source 290000Ω.
Hydra computes calibration constant 18 and returns the calibrated
reading. (For software versions lower than 5.4, this step computes
calibration constant 16.)
+2.9000E+6
You source 2900000Ω.
Hydra computes calibration constants 19 and 20 and returns the
calibrated reading. (For software versions lower than 5.4, this step
computes calibration constants 17 and 18.)
4-30. Updating 2635A Data Bucket Embedded Instrument
Firmware
The instrument firmware in the 2635A Hydra Data Bucket can be easily updated without
even opening the instrument case or replacing any parts. The instrument firmware is
stored in electrically eraseable and programmable Flash memory.
A diskette which contains the necessary software and the latest release of 2635A Data
Bucket firmware may be obtained from either your local Fluke authorized service center
or the Fluke factory. The local service centers are listed in Section 6 of this manual.
Contact the one nearest you. To request the "2635A Embedded Firmware Memory
Loader" diskette from the factory, telephone or send a fax to:
Fluke Corporation, Data Acquisition Sales Support Telephone: (206) 356-5870 FAX:
(206) 356-5790
4-27
HYDRA
Service Manual
Table 4-12. 4-Wire Ohms Calibration (5700A)
Command
CAL 3
Action
Puts Hydra in OHMS Calibration
Note
With the following CAL_REF commands, send the actual resistance value
(e.g., xxx.xxxxx) displayed by the 5700A.
Source 190Ω from the 5700A. Then wait 4 seconds for the 5700A to settle.
CAL_REF xxx.xxxxx
CAL_STEP?
Hydra computes calibration constant 15 and returns the calibrated reading. (For
software versions lower than 5.4, this step computes calibration constant 13.)
Note
If the input is incorrect, the "!>" response signifies that a Device
Dependent Error has been generated. The calibration step could not be
executed.Verify that the input to Hydra channel 1 is the correct value. Also
verify that the 5700A is in OPERATE mode. If the input is correct, Hydra
may require repair.
Source 1.9 kΩ from the 5700A. Then wait 4 seconds for the 5700A to settle.
CAL_REF xxxx.xxxx
CAL_STEP?
Hydra computes calibration constant 16 and returns the calibrated reading. (For
software versions lower than 5.4, this step computes calibration constant 14.)
Source 19 kΩ from the 5700A. Then wait 4 seconds for the 5700A to settle.
CAL_REF xxxxx.xxx
CAL_STEP?
Hydra computes calibration constant 17 and returns the calibrated reading. (For
software versions lower than 5.4, this step computes calibration constant 15.)
Source 190 kilohms from the 5700A. Then wait 4 seconds for the 5700A to settle.
CAL_REF xxxxxx.xx
CAL_STEP?
Hydra computes calibration constant 18 and returns the calibrated reading. (For
software versions lower than 5.4, this step computes calibration constant 16.)
Source 1.9 megohms from the 5700A. Then wait 4 seconds for the 5700A to
settle.
CAL_REF xxxxxxx.x
CAL_STEP?
Hydra computes calibration constants 19 and 20 and returns the calibrated
reading. (For software versions lower than 5.4, this step computes calibration
constants 17 and 18.) Now set the 5700A output to 0.
4-31. Using the PC Compatible Firmware Loader Software
This procedure uses the 2635A Embedded Firmware Memory Loader Package for
closed-case updating of the internal firmware in the 2635A. This software runs on an
IBM PC or equivalent using the RS-232 interface. It consists of the following files:
•
•
•
•
•
4-28
An executable file (LD2635.EXE)
A text file containing usage information (README.TXT)
A 2635A instrument firmware file (DB_6_9.HEX for example)
A batch file to load the firmware via COM port #1 (LOADC1.BAT)
A batch file to load the firmware via COM port #2 (LOADC2.BAT)
Performance Testing and Calibration
Updating 2635A Data Bucket Embedded Instrument Firmware
4
Firmware downloading may be accomplished by using either of the two methods that are
described in the following paragraphs.
•
•
Default Instrument Firmware Download Procedure
Using LD2635 Firmware Loader Directly
Table 4-13. Frequency Calibration
Command
Response
Action
CAL 4
=>
Put Hydra in Frequency Cal.
CAL_REF?
+10.000E+3
Output 2.9 volts ac at 10 kHz from the 5700A. Wait about 8 seconds.
CAL_STEP?
Hydra computes calibration constant 21 and returns the calibrated reading
(for example, +10.000E+3.) (For software versions lower than 5.4, this step
computes calibration constant 19.)
Note
If the input is incorrect, the "!>" response signifies that a Device
Dependent Error has been generated. The calibration step could not be
executed.Verify that the input to Hydra channel 1 is the correct value. Also
verify that the 5700A is in OPERATE mode. If the input is correct, Hydra
may require repair.
Now set the 5700A output to 0V dc.
4-32. Setup Procedure for Firmware Download
Use the following procedure to set up the 2635A and the PC, before attempting to
download firmware to the instrument:
1. Copy the files from the diskette to your PC hard drive. All following PC operations
should be done in the directory on the PC where these files are located.
2. Using the RS40 Terminal Interface Cable, connect the PC COM port to be used to
the 2635A RS-232 port. Use an RS40 and an RS41 cable in series to connect to the
COM port on an IBM PC/AT.
3. On the 2635A, press POWER ON. After the initialization process has concluded, use
the following procedure to set up communications:
a. Press SHIFT and then LIST(COMM).
b. With ’BAUd’ displayed, use the UP or DOWN arrow key to select’19200’ baud.
Then press ENTER.
c. With ’PAR’ (parity) displayed, use the UP or DOWN arrow key toselect ’no’
parity. Then press ENTER.
d. With ’CtS’ displayed, use the UP or DOWN arrow key to selectthe Clear to Send
flow control ’On’. Then press ENTER.
e. With ’ECHO’ displayed, use the UP or DOWN arrow key to select’OFF’. Then
press ENTER. Communications setup for the 2635A isnow complete.
4-33. Default Instrument Firmware Download Procedure
Use the following procedure to download the version of 2635A instrument firmware that
is distributed on the diskette:
4-29
HYDRA
Service Manual
1. If it is important to retain the channel programming information in the instrument,
store a copy of the instrument configuration setup on a memory card. Refer to
section on "Using SETUP STORE" in section 3 of the 2635A Data Bucket Users
Manual.
2. To load the instrument firmware, run ’LOADC1.BAT’ if COM port #1 is to being
used. Otherwise, run ’LOADC2.BAT’ if COM port #2 is to being used. These batch
files execute ’LD2635’ in batch mode with the proper command line switches to
download the default instrument firmware via the proper COM port.
3. After successful loading of the instrument firmware, the instrument will be reset to
begin normal operation. It is not abnormal to see an "ERROR 6" indication
displayed by the instrument as it begins operation again. This just indicates that the
internal instrument configuration has been reset to factory defaults. If you saved the
instrument configuration during step 1, you can reload it into the instrument now.
Refer to section "Using SETUP LOAD" in section 3 of the 2635A Data Bucket
Users Manual.
4-34. Using LD2635 Firmware Loader Directly
The ’LD2635’ program may be used interactively or in batch mode by using command
line switches. The command line syntax is
LD2635 [/B /Cn /Fname]
where the command line switches are defined as follows:
/B
Execute in batch mode; program exits when firmware programming is
complete. If batch mode is not specified, user is asked whether or not another instrument
is to be updated each time an instrument is completed. (/Cn and /Fname switches must
be included if batch mode is specified.)
/Cn
Use COMM port #n (n = 1 or 2)
/Fname
Download named firmware file to the 2635A
For example, to program multiple instruments with version 6.8 of the instrument
firmware via COM port #2, execute:
ld2635 /fdb_6_9.hex /c2
or to do the same with only one instrument:
ld2635 /b /fdb_6_9.hex /c2
The ’ld2635’ program can be used interactively by running it without any command line
switches. It will then request the name of the firmware file and the COM port to be used
before going on to update the firmware in the instrument. Since this is not batch mode,
the user is asked whether or not another instrument is to be updated each time an
instrument is completed.
If any errors are detected in establishing communication with the 2635A or updating the
firmware in the instrument, descriptive error messages will be printed to the PC console
before the program exits. Make sure that the PC is connected to the 2635A as previously
described, and that the 2635A communication parameters have been set correctly.
4-30
Chapter 5
Diagnostic Testing and Troubleshooting
(2620A/2625A)
Title
5-1.
5-2.
5-3.
5-4.
5-5.
5-6.
5-7.
5-8.
5-9.
5-10.
5-11.
5-12.
5-13.
5-14.
5-15.
5-16.
5-17.
5-18.
5-19.
5-20.
5-21.
5-22.
5-23.
5-24.
5-25.
5-26.
5-27.
Introduction ..........................................................................................
Servicing Surface-Mount Assemblies ..................................................
Error Codes...........................................................................................
General Troubleshooting Procedures ...................................................
Power Supply Troubleshooting............................................................
Raw DC Supply................................................................................
Power Fail Detection........................................................................
5-Volt Switching Supply..................................................................
Inverter .............................................................................................
Analog Troubleshooting.......................................................................
DC Volts Troubleshooting...............................................................
AC Volts Troubleshooting...............................................................
Ohms Troubleshooting.....................................................................
Digital Kernel Troubleshooting ...........................................................
Digital and Alarm Output Troubleshooting .........................................
Digital Input Troubleshooting..............................................................
Totalizer Troubleshooting....................................................................
Display Assembly Troubleshooting .....................................................
Variations in the Display......................................................................
Calibration Failures ..............................................................................
Introduction......................................................................................
Calibration-Related Components.....................................................
Retrieving Calibration Constants.....................................................
Replacing the EEPROM (A1U1) .....................................................
IEEE-488 Interface PCA (A5) Troubleshooting ..................................
Memory PCA (A6) Troubleshooting ...................................................
Power-Up Problems .........................................................................
Page
5-3
5-3
5-4
5-6
5-8
5-8
5-8
5-8
5-9
5-12
5-17
5-17
5-18
5-19
5-21
5-21
5-21
5-23
5-25
5-26
5-26
5-26
5-28
5-28
5-29
5-29
5-29
5-1
HYDRA
Service Manual
5-28.
5-29.
5-2
Failure to Detect Memory PCA................................................... 5-29
Failure to Store Data.................................................................... 5-29
Diagnostic Testing and Troubleshooting (2620A/2625A)
Introduction
5
5-1. Introduction
Hydra provides error code information and semi-modular design to aid in
troubleshooting. This section explains the error codes and describes procedures needed
to isolate a problem to a specific functional area. Finally, troubleshooting hints for each
functional area are presented.
But first, if the instrument fails, check the line voltage fuse and replace as needed. If the
problem persists, verify that you are operating the instrument correctly by reviewing the
operating instructions found in the Hydra Users Manual.
Warning
Opening the case may expose hazardous voltages.Always
disconnect the power cord and measuringinputs before
opening the case. And remember thatrepairs or servicing
should be performed only byqualified personnel.
Required equipment is listed in Section 4 of this manual.
Signal names followed by a ’*’ are active (asserted) low. Signal names not so marked are
active high.
5-2. Servicing Surface-Mount Assemblies
Hydra incorporates Surface-Mount Technology (SMT) for printed circuit assemblies
(pca’s). Surface-mount components are much smaller than their predecessors, with leads
soldered directly to the surface of a circuit board; no plated through-holes are used.
Unique servicing, troubleshooting, and repair techniques are required to support this
technology. The information offered in the following paragraphs serves only as an
introduction to SMT. It is not recommended that repair be attempted based only on the
information presented here. Refer to the Fluke "Surface Mount Device Soldering Kit" for
a complete demonstration and discussion of these techniques. (In the USA, call 1-800526-4731 to order.)
Since sockets are seldom used with SMT, "shotgun" troubleshooting cannot be used; a
fault should be isolated to the component level before a part is replaced. Surface-mount
assemblies are probed from the component side. The probes should make contact only
with the pads in front of the component leads. With the close spacing involved, ordinary
test probes can easily short two adjacent pins on an SMT IC.
This Service Manual is a vital source for component locations and values. With limited
space on the circuit board, chip component locations are seldom labeled. Figures
provided in Section 6 of this manual provide this information. Also, remember that chip
components are not individually labeled; keep any new or removed component in a
labeled package.
Surface-mount components are removed and replaced by reflowing all the solder
connections at the same time. Special considerations are required.
•
The solder tool uses regulated hot air to melt the solder; there isno direct contact
between the tool and the component.
•
Surface-mount assemblies require rework with wire solder rather thanwith solder
paste. A 0.025-inch diameter wire solder composed of 63%tin and 37% lead is
recommended. A 60/40 solder is also acceptable.
5-3
HYDRA
Service Manual
•
A good connection with SMT requires only enough solder to make apositive metallic
contact. Too much solder causes bridging, while toolittle solder can cause weak or
open solder joints. With SMT, theanchoring effect of the through-holes is missing;
solder provides theonly means of mechanical fastening. Therefore, the pca must
beespecially clean to ensure a strong connection. An oxidized pca padcauses the
solder to wick up the component lead, leaving littlesolder on the pad itself.
Refer to the Fluke "Surface Mount Device Soldering Kit" for a complete discussion of
these techniques.
5-3. Error Codes
At reset, the Hydra software performs power-up self-tests and initialization of ROM,
NVRAM, Display, EEPROM, and measurement hardware. Self-test failures are reported
on the display with "Error" in the left display and an error code (1-9,A,b,C) in the right
display.
Several of these error codes might never be displayed. Certainly, errors 4 and 5, which
signify a faulty or dead display, could not be reported in the normal (displayed) manner.
Other errors might not appear on the display. Therefore, the following additional
methods exist for accessing error information:
•
The computer interfaces can be used to determine self-check statususing the *TST?
query. Refer to Section 4 of the Hydra Users Manualfor a description of the *TST?
response. Note that the extent of theerror-producing damage could also cause the
instrument to halt beforethe computer interfaces are operational.
•
The POWERUP? computer interface command can be used to determinewhich
errors were detected at power-up. POWERUP? uses the sameresponse format as
*TST?; refer to *TST? in Section 4 of the HydraUsers Manual.
•
The keyboard scan lines (A1U4, SWR1-5), which are also used as statusindicators,
can be checked as a last resort for accessing errorinformation. The software sets
SWR1 (A1U4-21) low to indicate thatthe basic operation of the processor, ROM,
and ROM decode circuitryis intact. SWR2 (A1U4-22) is set low if the ROM (A1U8)
check passes.SWR3 (A1U4-23) is set low if the external NVRAM (A1U3) check
passes,and SWR4 (A1U4-24) is set low if the internal RAM (A1U4) checkpasses.
Then, if the display self-check passes, SWR5 (A1U4-25) isset low to indicate that
the display is operational.
Table 5-1 describes the error codes.
Note
Each error code is displayed for 2 seconds.
5-4
Diagnostic Testing and Troubleshooting (2620A/2625A)
Error Codes
5
Table 5-1. Error Codes
Error
1
2
3
4
5
6
7
8
9
A
b
C
Description
ROM (A1U8) checksum error
External RAM (A1U3) test failed
Internal RAM (A1U4) test failed
Display power-up test failure
Display not responding
Instrument configuration corrupted
EEPROM instrument configuration corrupted
EEPROM calibration data corrupted
A/D not responding
A/D ROM test failure (A3U9)
A/D RAM test failure (A3U9)
A/D self test failure
Refer to Troubleshooting information later in this section.
Error 1
ROM (A1U8) checksum match failed.
All the bytes in the ROM (including a checksum byte) are summed.
Error 2
External RAM (A1U3) check failed.
Error 3
Internal RAM (A1U4) check failed.
Complementary patterns are alternately written and read from each RAM location for both
external RAM and the 256 bytes internal to the 6303Y Microprocessor (A1U4). If the pattern read
from any RAM location is not the same as the pattern written, the test fails.
Error 4
Display self-check failed
Error 5
Display dead.
The display processor automatically performs a self-check on power-up, and the Microprocessor
attempts to read the result of this test.
Error 6
Instrument configuration
The instrument configuration information stored in nonvolatile RAM (A1U3) has been corrupted.
(The Cyclic Redundancy Checksum on this memory is not correct for the information stored
there.) The instrument configuration is reset to the default configuration.
Error 7
EEPROM instrument configuration corrupted or EEPROM not initialized.
Error 8
EEPROM calibration data corrupted.
The EEPROM (A1U1) is divided into two storage areas: the instrument configuration storage and
calibration data storage. Each area uses a Cyclic Redundancy Checksum (CRC), against which
the data is checked on power-up.
•
Error 7 is reported if the instrument configuration check finds an error; the instrument
configuration is set to factory defaults.
•
If the calibration data CRC verification indicates that there is calibration data that is in error,
the front panel CAL annunciator is turned on, and Error 8 is reported.
Note
Errors 7 and 8 should always appear the first time an instrument is
powered up with a new, uninitialized EEPROM.Error 8 continues to
appear at subsequent power-ups until the instrument is fully calibrated.
Error 9
A/D Microcomputer (A3U9) failed to respond
This error is displayed if communication cannot be established with the 6301Y Microcomputer
(A3U9).
Error A
A/D ROM test failure
All bytes of internal ROM for the 6301Y Microcomputer (A3U9) (including the checksum byte) are
summed.
5-5
HYDRA
Service Manual
Table 5-1. Error Codes (cont)
Error
Description
Error b
A/D RAM test failure
Complementary patterns are alternately written to and read from each location of the 256 bytes of
RAM internal to the 6301Y Microcomputer (A3U9).
Error C
A/D self test failed
The Analog Measurement Processor (A3U8) is programmed to do self test measurements.
5-4. General Troubleshooting Procedures
Hydra allows for some fault isolation using self-diagnostic routines and descriptive error
codes. However, these features are somewhat limited and do not provide in-depth
troubleshooting tools.
Hydra incorporates a semi-modular design; determining modules not related to a
problem constitutes the first step in the troubleshooting process.
As a first step, remove the IEEE-488 Option (if installed) from the Data Acquisition Unit
(2620A) or the Memory PCA from the Data Logger (2625A). Refer to Section 3 of this
manual for removal procedures. If removal of either of these assemblies results in
improved instrument operation, refer to Section 7 for IEEE-488 Option troubleshooting
or later in this section for Memory PCA troubleshooting.
Measuring the power supplies helps to isolate a problem further. Refer to Table 5-2 and
Figure 5-1 for test point identification and readings. If power supply loading is
suspected, disconnect the Display PCA at A1J2. If this action solves the loading
problem, proceed to Display Assembly Troubleshooting elsewhere in this section.
Otherwise, refer to Power Supply Troubleshooting.
Table 5-2. Preregulated Power Supplies
PREREGULATED VOLTAGE
-9.0V
-30V
+9.25V
-8.75V
MEASUREMENT POINTS
A1CR13-2 to A1TP1
A1TP4 to A1TP1
A1CR5 cathode to A1TP30
A1CR7 anode and A1TP30
RESULTING SUPPLY
VEE
VLOAD
VDD, VDDR
VSS
If the power supplies appear good, check the E clock signal to determine whether the
Main PCA or the Display PCA is causing the problem. A correct display depends on the
E clock signal. Missing segments, intensified digits, a strobing display, or a blank
display can be caused by a faulty E clock.
Use an oscilloscope to check for the E clock at Microprocessor A1U4, pin 68. Look for a
1.2288-MHz square wave that transitions from 0 to 5V dc (VCC).
•
If this signal is present, the Display PCA is probably faulty. Referto Display
Assembly Troubleshooting elsewhere in this section.
•
If the E clock is something other than a 1.2288-MHz square wave,isolate the digital
section of the Main PCA by disconnecting theDisplay PCA at J2. Then check the E
clock again, and refer to DigitalTroubleshooting elsewhere in this section for further
problemisolation.
Refer to the Schematic Diagrams in Section 8 during the following troubleshooting
instructions. Also, these diagrams are useful in troubleshooting circuits not specifically
covered here.
5-6
Diagnostic Testing and Troubleshooting (2620A/2625A)
Power Supply Troubleshooting
A1TP16
A1TP8
A1TP4
A1TP17
A1TP15
A1TP6
A1TP11
A1TP5
Option
Interface
5
A1TP31
Display
Connector
A1TP30
A1TP32
A1TP1
A1TP3
A1TP31
A1TP10
A1TP13
A1TP12
A1TP14
A1TP18
RS-232
Connector
A1TP19
A1TP9
A1TP2
Digital
Input
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
61
NMI
STBY
RES
MP1
MP0
EXTAL
XTAL
Vss
NC
E
P70 RD*
P71 WR*
P72 R/W*
P73 LIR*
P74
P30 D0
P31 D1
A1TP20
A1TP7
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
A1U4 MICROPROCESSOR
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
P32 D2
P33 D3
P34 D4
P35 D5
P36 D6
P37 D7
NC
P10 A0
P11 A1
P12 A2
P13 A3
P14 A4
P15 A5
P16 A6
P17 A7
Vss
P40 A8
TRIG P60
P61
OPS* P62
EEDO P63
EEDI P64
DTR P65
PFAIL* P66
EECS P67
NC
Vcc
A15 A47
A14 P46
P45 A13
P44 A12
P43 A11
P42 A10
P41 A9
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
P20
P21
DSCLK P22
RX P23
TX P24
DISRX P25
DISTX P26
EESK P27
NC
IRQ1* P50
IRQ2* P51
SWR1 P52
SWR2 P53
SWR3 P54
SWR4 P55
SWR5 P56
SWR6 P57
s32f.eps
Figure 5-1. Test Point Locator, Main PCA (A1)
5-7
HYDRA
Service Manual
5-5. Power Supply Troubleshooting
Warning
To avoid electric shock, disconnect all channelinputs from the
instrument before performing anytroubleshooting operations.
5-6.
Raw DC Supply
With the instrument connected to line power (120V ac, 60 Hz) and turned ON, check for
approximately 14V dc between A1TP1 (GND) and the "+" terminal of capacitor A1C7
(or the cathode of either A1CR2 or A1CR3). (This voltage is approximately 30V dc at
240V ac line.) If no voltage or a very low voltage is present, check for approximately
24V ac across the secondary of the power transformer (or approximately 50V ac at 240V
ac line.)
The voltage at the output of A1U19 (also A1TP7), should be about +5.2V dc. At 120V
ac, 60-Hz line power input, the line current is approximately 29 mA with the IEEE-488
Option installed or 20 mA without the IEEE-488 Option installed. At 50-Hz, 120V ac
line power input, there is a 5-10% increase in these two current figures.
5-7.
Power Fail Detection
The Power Fail Detection circuit monitors the Raw Supply so that the Microprocessor
can be signaled when power is failing. Check for approximately 1.23V dc between the
inverting comparator input (A1U24-2) and GND (A1TP1). If the Raw Supply voltage is
higher than approximately +8.3V dc, comparator output (A1U24-1) should be near VCC.
If the comparator output is near 0V dc during normal operation, the Microprocessor will
sense that power is failing and will not be able to complete a scan operation.
5-8.
5-Volt Switching Supply
Use an oscilloscope to troubleshoot the 5-volt switching supply. With the oscilloscope
common connected to A1TP1, check the waveform at either A1U9, pin 4 or A1T1, pin 2
to determine the loading on the 5-volt switching supply. The output voltage of the 5-volt
switching supply at A1TP2 (VCC) is normally about 5.1V dc with respect to A1TP1
(GND). Note that a fault in the load (high or low resistance) can appear as a faulty output
voltage of the 5-volt switching supply.
• Normal Load:
The signal at A1U9-4 (with respect to A1TP1) is a square wave with a period of 9 µs to
11 µs and an ON (voltage is low) duty ratio of about 0.38 with the line voltage at 120V
ac. The amplitude is usually about 15V p-p. The positive-going edge will be "fuzzy" as
the duty ratio is varying to compensate for the ripple of the raw supply and the pulsing
load of the inverter supply. See Figure 5-2A (NORMAL LOAD).
• Very Heavy Load:
Under heavy load (example: A3 A/D Converter PCA has a short circuit) it could load
down the power supply voltage such that the current limiting feature is folding the
supply back. For example, if the supply is folded back due to excessive current draw,
unplug the ribbon cable at A3J10 on the A/D Converter PCA. When tracking down
power supply loads, use a sensitive voltmeter and look for resistive drops across filter
chokes, low value decoupling resistors, and circuit traces. Also check for devices that are
too warm. On the A3 A/D Converter PCA, all devices run cool except A3U5
microprocessor and A3U8 FPGA, which run warm, but not hot.
5-8
Diagnostic Testing and Troubleshooting (2620A/2625A)
Power Supply Troubleshooting
5
U9-7 and T2-2
20V
0V
5V/DIV
2 µS/DIV
Normal Load
s33f.eps
Figure 5-2. 5-Volt Switching Supply
If no square wave is present at A1U9-7, the oscillator can be checked by looking at the
signal at A1U9-3. The oscilloscope should be ac-coupled for this measurement. This
waveform should be a sawtooth signal with an amplitude of 0.6V p-p and a period of
approximately 14 us. Failure of the oscillator is usually caused by a defective capacitor
A1C21 or defective A1U9.
The output current of the 5-volt switching supply can be determined by measuring the
voltage across the current limit current sense resistors (A1R29, A1R30 and A1R31). The
current shunt is approximately 0.167 ohms. With line voltage at 120V ac and the
instrument not actively measuring, typical voltages across the current sense resistors are
as follows:
•
•
•
5-9.
2620A Instrument without options: 28 mV
2620A Instrument with IEEE-488 Option: 50 mV
2625A Instrument: 28 mV
Inverter
Use an oscilloscope to troubleshoot the inverter supply. The outputs of the inverter
supply are -5V dc, -30V dc, and 5.4V ac outguard, and +5.3V dc, -5.4V dc, and +5.6V dc
inguard. Refer to Figure 5-3. The signal at the drains of the two inverter switch FETs
(A1Q7 and A1Q8) should be a 10V peak square wave with a period of approximately 18
us. The gate signal is a 5.1V peak square wave with rounded leading and trailing edges.
The leading edge has a small positive rounded pulse with an amplitude of 1.8V peak and
a pulse width of about 0.3 µs. The signal at A1U22-5 and A1U22-6 is a symmetrical
square wave with an amplitude of 5.1V peak and a period of about 18 µs. The negativegoing trailing edge of both square waves is slower than the rising edge and has a small
bump at about 1.5 volts. The signal at A1U22-3 (TP14) is a symmetrical square wave
with a period of about 9 µs.
5-9
HYDRA
Service Manual
For the inverter to operate, the 110-kHz oscillator must be operating properly. If the
signal at A1U22-3 is missing, begin by checking the voltage at A1TP7. The voltage
should be about 5.1V dc. Then, using an oscilloscope, check for a square wave signal at
A1U23-9 and a square wave signal at A1U23-8. If the FETs are getting proper drive
signals, failures that heavily load the inverter supply will usually cause the inverter to
draw enough current to make the switcher supply go into current limit. Shorted rectifier
diodes and shorted electrolytic capacitors will cause heavy load conditions for the
inverter.
Note
When making voltage measurements in the invertercircuit, remember that
there are two separategrounds. The outguard ground is the ’GND’ testpoint
(A1TP1), and the inguard ground is the’COM’ test point (A1TP30).
The inguard regulator circuits for VDD and VSS have current limits. Shorts and heavy
loads between VDD and COM, VSS and COM, and VDD and VSS will cause one or
both supplies to go into current limit. The current supplied by either supply can be
checked by measuring the voltage across the current sense resistors, A1R13 and A1R15.
The typical voltage across A1R13 is 0.30 and the typical voltage across A1R15 is 0.40V.
Generally, open electrolytic capacitors in the inverter supply will cause excessive ripple
for the affected supply. Also, the rectified dc voltage for the supply with the open
capacitor will be lower than normal. Normal voltage levels at the rectifier outputs for
each inverter supply are shown in Table 5-2.
The loads for the inguard supplies can be disconnected by removing the cable to the A/D
Converter PCA at A3J10. The inguard regulator circuits and VDDR regulator will
operate with no loads, and troubleshooting can be performed by making voltage
measurements.
The normal input current to the inverter supply is about 11.25 mA, or 0.225 mV across
A1R38 (when the instrument is not measuring).
Table 5-3 provides a Power Supply troubleshooting guide.
5-10
Diagnostic Testing and Troubleshooting (2620A/2625A)
Power Supply Troubleshooting
5
TP9 AND TP10
0
2V/DIV
2µS/DIV
FET GATE SIGNAL
Q7, Q8, OR T1-1 OR -3
0
2V/DIV
2µS/DIV
FET DRAIN SIGNAL
s34f.eps
Figure 5-3. Inverter FET Drive Signals
5-11
HYDRA
Service Manual
5-10. Analog Troubleshooting
Warning
To avoid electric shock, disconnect all channelinputs from the
instrument before performing anytroubleshooting operations.
Refer to Figure 5-4 and Figure 5-5 for test point locations on the A/D Converter PCA.
First, check for analog-related errors displayed at power up. An ’Error 9’ means that the
Main Microprocessor A1U4 is not able to communicate with the A/D Microcontroller
A3U9. ’Error A’ and ’Error b’ mean that a failure has occurred in the internal memory of
the A/D Microcontroller A3U9. ’Error C’ means that the Analog Measurement Processor
A3U8 is not functioning properly.
Check the inguard power supplies on the Main PCA with and without the A/D Converter
PCA connected. The inguard supplies must be measured with respect to COM testpoint
A1TP30.
Power Supply
Test Location
Acceptable Range
VDD
VSS
VDDR
A1TP31
A1TP32
A1C6
+5.00 to 5.70V dc
-5.10 to -5.75V dc
5.30 to 5.95V dc
Check the inguard supply voltages on the A/D Converter PCA with respect to A3TP9.
The following table lists the components nearest the power supply test points.
5-12
Power Supply
Test Location
VDD
VSS
VDDR
+VAC
-VAC
A3C8
A3C9
A3C19
A3CR1
A3C26
Acceptable Range
5.00 to 5.70V dc
-5.10 to -5.75V dc
5.30 to 5.95V dc
4.7 to 5.7V dc
-4.8 to -5.7V dc
Diagnostic Testing and Troubleshooting (2620A/2625A)
Analog Troubleshooting
5
Table 5-3. Power Supply Troubleshooting Guide
Symptom
Fault
Line fuse blows.
- Shorted A1CR2 or A1CR3.
- Shorted A1CR10.
- Shorted A1C7.
- Shorted A1C26.
Supply voltage for A1U23 and A1U22 is greater than
7V (7 to 30V).
Input-to-output short of A1U19. This fault may have
caused damage to A1Q7 and A1Q8.
VCC (5.1V) supply is at the raw supply level (7.5 to
35V dc).
Shorted switch transistor in A1U9 (A1U9-5 to 7).
Open A1C26 can cause switch transistor to short.
VCC (5.1V) supply shows excessive ripple (about
1V p-p).
A1C14 open.
VCC is below approximately 4.5V. Duty cycle of 5V
switcher supply is very low (ON time near 0.1).
Drain-to-source short of A1Q7 or A1Q8.
VCC is about 1.5V. 5V switcher supply is in current
limit.
Shorted A1CR5 or A1CR6.
VCC is below approximately 1V. 5V switcher supply
is in current limit, with very low duty cycle (ON time
near 0.1).
Shorted A1C14.
VCC is below approximately 4.5V. 5V switcher
supply is in current limit, with very low duty cycle
(ON time near 0.1).
- Q or Q* output of A1U22 stuck high.
- A1U23 pin 8 output stuck high or low.
- Shorted A1CR7
- Shorted A1CR9 (either diode), pins 1-3 or 2-3.
- Shorted A1C30. A1CR13 may also be damaged.
- Shorted A1C31. A1CR13 may also be damaged.
- Shorted A1C12.
- Shorted A1C13.
- Shorted A1CR8 (either diode), pins 1-3 or 2-3.
VLOAD (-30V dc) Inverter Supply is at -36V.
Q output of A1U22 stuck low.
VLOAD (-30V dc) Inverter Supply is OFF.
Q* output of A1U22 stuck low.
VLOAD (-30V dc) Inverter Supply ripple.
- Open A1CR8 (either diode).
- Open A1CR9 (either diode).
VDD (5.3V dc) supply at approximately 9.2V.
Emitter-to-collector short of A1Q2.
VSS (-5.4V dc) supply at approximately -9.2V.
Emitter-to-collector short of A1Q5.
VDDR (5.6V dc) supply at approximately 10V.
Input-to-output short of A1U6.
VDDR supply has 4-to-5 volt spikes when the A/D
relays are switched (set or reset).
Open A1C12.
VEE (-5V dc) supply is low (near zero).
- Open A1C30.
- A1CR13 open.
A1CR13, Diode 1-3 shorted or open.
A1C30 may be shorted.
VEE supply is high (near -9V).
Input-to-Output short of A1U18.
A1U18 input has large square wave component.
Open A1C31.
5-13
HYDRA
Service Manual
Table 5-3. Power Supply Troubleshooting Guide (cont)
Symptom
Fault
A1U18 hot.
Shorted A1C32
A1U18 oscillates.
Open A1C32.
A1U19 oscillates.
Open A1C34.
A1U19 very hot.
- Shorted A1U22 (VCC to VSS).
- Shorted A1U23 (VCC to VSS).
A1U19 hot.
Shorted A1C34.
Check that the inguard Microcontroller A3U9 RESET* line is de-asserted. Check VDD
at A3TP1, referenced to A3TP9.
Check that the microcontroller crystal oscillator is running. When measured with a high
input impedance oscilloscope or timer/counter, the oscillator output at A3TP10 should
be a 3.6864-MHz sine wave (271.3 ns period), and the divided-down E clock output at
A3U9 pin 68 should be a 921.6 kHz-square wave (1.085 µs period).
Check outguard to inguard communication. Setup an input channel and enable monitor
measurements on that channel, causing the outguard to transmit to the inguard
approximately every 10 seconds.
On the Main PCA, look for outguard-to-inguard communication (5.1V (VCC) to near 0V
pulses) at A1TP15, referenced to A1TP1. On the A/D Converter PCA, check for 5.35V
(VDD) to near 0V pulses at A3TP8, referenced to A3TP9.
At the start of outguard-to-inguard communication, the A/D Microcontroller (A3U9)
should be RESET. Check for this reset pulse (5.35V (VDD) to near 0V, lasting
approximately 1-ms) on A3TP1 with respect to A3TP9.
Check for the following inguard-to-outguard communication activity:
PCA
Test Point
To
Pulses
A/D Converter
Main
A3TP7
A1TP8
A3TP9
A1TP1
5.55V (VDDR) to 0.7V
0V dc to 5.1V (VCC)
Lack of outguard-to-inguard communication activity may be due to improper operation
of circuit elements other than A3U9. Using a high input impedance oscilloscope or
timer/counter, check for proper Analog Processor (A3U8) crystal oscillator operation. A
3.84-MHz sine wave (260 ns period) should be present at A3U8 pin 37 with respect to
A3TP9.
Check the A/D Converter voltage reference:
A3TP12 to A3TP11 (across A3C12) = +1.05V (+0.10V, -0.02V)
Setup the instrument to measure ohms on the 300Ω range. Monitor ohms on a channel
with an input of approximately 270Ω. Check that the Analog Processor IC (A3U8) is
making A/D conversions. The integrator output waveform at A3TP13 (referenced to
A3TP9) should resemble the waveform shown in Figure 5-6.
Check for channel relay operation by setting up a channel and selecting and de-selecting
monitor measurement mode. One or more relays should click each time the monitor
button is pressed or channels are changed.
In general, check that the relays are getting the proper drive pulse signals for specific
functions and channels and that they are in the correct position.
5-14
Diagnostic Testing and Troubleshooting (2620A/2625A)
Analog Troubleshooting
5
A3TP2
A3TP8
A3TP7
A3TP1
RMS Converter
Network
A3TP13
A3TP3
A3TP4
A/D Microcontroller
A3TP5
A3TP6
A3TP10
A3TP11
RMS Converter
A3TP12
A3TP9
AC Buffer
Analog
Measurement
Processor
VSSAC
ACR1
ACR2
ACR3
ACR4
AGND2
AIN
ACB0
VDD
RMSI
RMSG1
VSSRMS
BIAS2
RMS0
RMSC2
ARTN
RMSF
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
61
Divider
Network
(DC/OHMS)
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
FA0
FAI
AFI
MOF
AF0
RA–
RA+
RA0
VREF–
VREF+
B3
B1
B.3
B.1
SUM
INT
VSS
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
A3U8 ANALOG
MEASUREMENT
PROCESSOR
REFJ
LO
GUARD
RRS
V4
V3
V1
GUARD
V2F
V2
GUARD
V0
GUARD
0/VS
GUARD
AGND1
DGND
FC0
FC1
FC2
FC3
FC4
FC5
FC6
FC7
OSCIN
OSC0
MRST
AS
AR
SK
CS
BRS
AC Divider
Network
Zener Reference
Intergrate Resistors, Reference Divider
s35c.eps
Figure 5-4. Test Points, A/D Converter PCA (A3, A3U9)
5-15
HYDRA
Service Manual
A3TP2
A3TP8
A3TP7
A3TP4
A3TP1
RMS Converter
Network
A3TP3
A/D Microcontroller
A3TP5
A3TP13
A3TP6
A3TP10
A3TP11
RMS Converter
A3TP12
A3TP9
AC Buffer
Analog
Measurement
Processor
Zener Reference
ZERO
K3S
K3R
K7S
K7R
K14S
K14R
VDD
RESET
VDD
VDD
Intergrate Resistors, Reference Divider
Divider
Network
(DC/OHMS)
P20
P21
P22
P23/RX
P24/TX
P25
P26
P27
NC
P50/IRQ1*
P51/IRQ2*
P52
P53
P54
P55
P56
P57
P32
P33
P34
P35
P36
P37
NC
P10
P11
P12
P13
P14
P15
P16
P17
VSS
P40
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
K13S
K13R
K6S
K6R
K5S
K5R
K12S
K12R
K1S
K1R
K2S
K2R
K11S
K11R
RELAY
DRIVERS
K10S
OTCEN
OTC
K8R
K8S
K9R
K9S
K10R
K16R
K16S
K17R
K17S
K15R
K15S
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
IRQ1*
FC7
CS
RIRQ1*
FC0
FC1
FC2
FC3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
P60
P61
P62
P63
P64
P65
P66
P67
NC
VCC
P47
P46
P45
P44
P43
P42
P41
A3U9
MICROCONTROLLER
DRX
DTX
CLK
IGRX
IGTX
AR
OTCCLK
AS
NMI*
STBY*
RES*
MP1
MP0
EXTAL
XTAL
VSS
NC
E
P70
P71
P72
P73
P74
P30
P31
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
61
AC Divider
Network
s36c.eps
Figure 5-5. Test Points, A/D Converter PCA (A3, A3U9)
5-16
Diagnostic Testing and Troubleshooting (2620A/2625A)
Analog Troubleshooting
5
A3TP13 TO A3TP9
0
1V/DIV
5 mS/DIV
s37f.eps
Figure 5-6. Integrator Output
5-11. DC Volts Troubleshooting
Setup the instrument to measure a specific channel on the 300 mV or 3V range, and
apply an input to that channel. Then trace the HI signal (referenced to the input channel
LO terminal) as described in Table 5-4.
If the input HI path traces out properly, remove the input from the channel and trace
continuity through the LO path. Check among A3L4-A3L24, A3K1-A3K14, A3R35,
A3R43, and A3U8 pin 11.
Table 5-4. DC Volts HI Troubleshooting
Checkpoint
Signal Description
Possible Fault
A3R11 HI
Input
A3K1 through A3K14, A3U4, A3U5, A3U11, A3U12,
A3L1, A3L2, A3L3
A3U8 pin 23
Input
A3R11, A3K17, A3R42, A3C32
A3U8 pin 58
Input, DC filter output
A3U8, A3Q2
5-12. AC Volts Troubleshooting
Setup the instrument to measure a channel on the 300 mV ac range, and apply a signal to
that channel. Then trace this HI signal (referenced to the input channel LO terminal) as
described in Table 5-5.
If the input HI path traces out properly, remove the input from the channel, and trace
continuity through the LO path. Check among A3L4 through A3L24, A3K1 through
A3K14, A3R43, A3R34, A3K16, and A3U8 pin 13.
5-17
HYDRA
Service Manual
Table 5-5. AC Volts HI Troubleshooting
Checkpoint
Signal Description
Possible Fault
A3R11 HI
Input
A3K1 through A3K14, A3U4, A3U5, A3U11, A3U12
A3L1, A3L2, A3L3
A3Z3 pin 1
Input
A3R11, A3C31, A3K15
A3U6 pin 13
Amplified (X 2.5) input
A3U7, A3Z3, A3Q3 through A3Q9, A3C15, A3C16,
A3R24, A3A25, A3R26, A3R27, A3R28, A3C23,
A3U6, A3Q13, A3U8
A3Z1 pin 2
DC equivalent of original input
A3Z1, A3U8, A3R20, A3C6, A3C7, A3C10, A3R16,
A3R17
A3U8 pin 61
DC equivalent of original input
A3Z1, A3U8, A3R20, A3C6, A3C7, A3C10, A3R16,
A3R17
5-13. Ohms Troubleshooting
Setup a channel with an open input for the desired ohms range and place the instrument
in monitor mode on that channel. Use a meter with high input impedance to measure the
open-circuit voltage at the channel input for the ohms range as listed in Table 5-6. If a
high input impedance meter is not available, only the 30-kΩ and lower ranges can be
checked.
Table 5-6. Ohms Open-Circuit Voltage
Range
Voltage
3V
1.3V
1.3V
3V
3V
3V
300Ω
3 kΩ
30 kΩ
300 kΩ
3 MΩ
10 MΩ
If the proper voltage is not measured, setup a channel on the 300Ω range (open input),
and have the instrument monitor that channel. Check for 3V dc with respect to A3TP9,
and work through the HI SOURCE and HI SENSE paths as described in Table 5-7.
If the HI path works correctly, trace continuity through the LO path. Check among A3L4
through A3L24, A3K1 through A3K14, A3R35, A3U8 pin 11, A3R43, A3K16, A3R34,
and A3U8 pin 13.
Table 5-7. Ohms HI Troubleshooting
Checkpoint
5-18
Signal Description
Possible Fault
A3U8 pin 14
Ohms Source
A3U8
A3R10 HI SRC
Ohms Source
A3R10, A3K16, A3RT1, A3Z4, A3Q10
Channel HI
Ohms Source
A3K1 through A3K14, A3U4, A3U5, A3U11, A3U12, A3L1,
A3L2, A3L3
A3U8 pin 23
Ohms Source
A3R11, A3K17, A3R42, A3C32
A3U8 pin 58
Ohms Source filter output
A3U8, A3Q2
Diagnostic Testing and Troubleshooting (2620A/2625A)
Digital Kernel Troubleshooting
5
5-14. Digital Kernel Troubleshooting
At power-up, if the display does not light or lights up and fails to report errors or begin
operation, use the following troubleshooting procedures.
First check the state of SWR1 (A1U4-21). If this status line is less than 0.8V, basic
processor operation is intact. Examining SWR2 through SWR5 (A1U4-22 through -25,
respectively) should indicate how far the software progressed before finding an error. If
the state of SWR1 is not less than 0.8V, the problem may be in the 6303Y
Microprocessor (A1U4), the ROM or NVRAM decode circuitry (A1U10 and A1U21),
the ROM (A1U8) or NVRAM (A1U3), or the address/data lines among these parts.
Note
The functions of SWR1 through SWR5 as power-upstatus lines persist for
only 3 to 4 seconds. Thesefunctions end when the keyboard scanner
beginsoperation (if it can). Extremely difficult casesmay require the use of
an oscilloscope triggered onthe falling edge of SWR1 to examine the states
ofSWR2 through SWR5.
To determine the relative health of the 6303Y Microprocessor (A1U4), first check for a
valid E clock at pin 68. The default for the E clock after reset is a rectangular wave with
a period of 1.221 µs and a duty cycle of about 67%.
If the processor is able to fetch instructions from the ROM, the software initializes the
processor, and the E clock becomes a square wave with a period of 0.814 us. Since this
initialization occurs almost immediately with a working instrument, the resulting square
wave on the E clock line is a good indication that the software has begun to execute.
If the E clock remains a 1.221 µs rectangular wave, the SWR2 (A1U4-22) keyboard scan
line might be shorted to ground. This condition would cause the Microprocessor to
HALT after reset. Check whether the 6303Y Microprocessor is attempting to access
ROM; LIR* (A1U4-64) should transition for a short period of time after reset. If it does,
the 6303Y Microprocessor is probably operational, and the problem is external to the
processor.
The processor can execute an instruction that stops both itself and the E clock.
Therefore, the absence of any activity on pin 68 does not necessarily mean that A1U4 or
A1Y1 is bad. If some other failure prevents proper ROM access, the processor may have
just "gone to sleep". This can be verified by checking for a rectangular wave occurring at
pin 68 for a short time after RESET* transitions high on pin 7. A1U4 and A1Y1 are
probably operational if this rectangular wave is at least momentarily present.
To check the ROM decode circuitry, verify that A1U10-6 is transitioning low and that
these transitions correspond roughly to the low-going transitions of LIR*. Pin 6 must be
low when LIR* is low. Verify that this signal also appears at the ROM Chip Enable,
A1U8-20. If the ROM Chip Enable is present, the problem is with the ROM itself or
there is a fault in the address/data lines among the 6303Y Microprocessor, ROM,
NVRAM, and Option Connector.
If SWR1 (A1U4-21) and SWR2 (A1U4-22) transition low, but SWR3 (A1U4-23)
remains high, the problem is with the NVRAM decode circuitry (A1U15, A1U21), the
external NVRAM (A1U3), or the address/data/control lines between the NVRAM and
the 6303Y Microprocessor.
To check the NVRAM decode circuitry, verify that A1U21-6 is transitioning low and
that these transitions correspond approximately to the low-going transitions of WR*
(A1U4-66). It may be necessary to continually reset (power on) the instrument to check
these lines, since the activity probably halts quickly when the instrument software goes
awry. Verify that the signal on A1U21-6 also appears at the NVRAM Chip Enable,
A1U3-20. If the NVRAM Chip Enable is present, the problem is with either the
NVRAM itself or the address, data, RD*, or WR* lines between the 6303Y
Microprocessor and the external NVRAM.
5-19
HYDRA
Service Manual
Figure 5-7 shows the timing relationships of the 6303Y Microprocessor lines LIR* and
WR* to the system clock (E) and the address lines A0..A15. The ROM and NVRAM
Chip Enables correspond to the active (low) region shown for the address lines.
If the instrument powers up without any errors, but does not recognize front-panel button
presses or computer interface commands, the problem may be in the Counter/Timer
(A1U2). Normally, this component generates a regular 50-millisecond interrupt at the
IRQ* output (A1U2-9). If this output is low (and never goes high), the Microprocessor
(A1U4) is failing to recognize the interrupt or the microprocessor interface to A1U2 is
not working correctly. Also check output A1U2-6 for a 10-Hz square wave. If this output
is not correct, check for the E clock at A1U2-17, and verify the microprocessor interface
signals (CNTR*, D0 .. D7, A0 .. A2, R/W*, and RESET*.)
t cyc
2.4V
PW EL
E
PWEH
0.8V
t AD
A 0~ A15 ,
R/W
t Er
tEf
t AH1
2.4V
0.8V
t AH2
t HRW
PW RW
t RWD
2.4V
RD,WR
0.8V
t HW2
t HW1
t DDW
2.4V
MCU Write
D0 ~ D7
0.8V
t ACC
t DSR
t HR
MCU Read
D0 ~ D7
2.0V
0.8V
t DLR
t HLR
LIR
0.8V
s38f.eps
Figure 5-7. Microprocessor Timing
5-20
Diagnostic Testing and Troubleshooting (2620A/2625A)
Digital and Alarm Output Troubleshooting
5
5-15. Digital and Alarm Output Troubleshooting
Power up Hydra while holding down the CANCL button to reset the instrument
configuration. Since the structure of the eight Digital Outputs and four Alarm Outputs is
very similar, the troubleshooting procedure presented here does not refer to specific
device and pin numbers. First verify that the input of the Output Driver (A1U17 or
A1U27) is low and that the output is near +5V dc. If the input is high, the problem may
be in the address decoding (A1U12 and A1U15) or the associated octal D-type flip-flop
(A1U16 or A1U26). If the output is not near +5V dc, use an ohmmeter to check the pullup resistor in A1Z2.
Use the proper computer interface command to change the state of the Digital Output
(DO_LEVEL x,1) or Alarm Output (ALARM_DO_LEVEL x,1), where x is the number
of the output being checked. Now verify that the input of the Output Driver is high and
that the output is near +0.8V dc. If there is no change in the input, check the address
decoding and operation of the associated octal D-type flip-flop (A1U16 or A1U26.) If
the output failed to change, the problem is most likely the inverting output driver
(A1U17 or A1U27).
5-16. Digital Input Troubleshooting
Power up Hydra while holding down the CANCL button to reset the instrument
configuration. Verify that the Input Buffer Threshold circuit generates approximately
1.4V dc at A1TP18. Drive the Digital Input (A1J5) to be checked with a signal generator
outputting a 100-Hz square wave that transitions from 0 to +5V dc. The signal generator
output common should be connected to Common (A1J5-1). Verify that the output of the
Input Buffer is a 100 Hz square wave that is the inverse of the input signal.
If the Input Buffer does not function correctly, the problem is probably A1Z1, A1Z3, or
the associated comparator (A1AR2 or A1AR3). If the Input Buffer functions correctly,
but Hydra is not able to read the state of the Digital Input correctly, the problem is most
likely the tri-state buffer A1U13. If Hydra is not able to read the states of any of the
eight Digital Inputs correctly, the problem is most likely the address decoding (A1U10
and A1U12) for the tri-state buffer.
5-17. Totalizer Troubleshooting
Power up Hydra while holding down the CANCL button to reset the instrument
configuration. Verify that the Input Buffer Threshold circuit generates approximately
1.4V dc at A1TP18. Drive the Totalizer Input (A1J5-2) with a signal generator
outputting a 100-Hz square wave that transitions from 0 to +5V dc. The signal generator
output common should be connected to Common (A1J5-1). Verify that the output of the
Input Buffer (A1AR1-7) is a 100-Hz square wave that is the inverse of the input signal.
Verify also that the input to the totalizer counter (A1TP20) is a buffered form of the
signal just verified at the output of the Input Buffer.
Use the following procedure to troubleshoot the totalizer input debouncer, Enable the
totalizer debouncer by sending the TOTAL_DBNC 1 Computer Interface command to
the instrument; verify that A1U16-16 is now high. With the signal generator still
connected and outputting a 100-Hz square wave, verify that A1U14 drives the clear input
of the counter (A1U20-11) low for 1.67 milliseconds after each edge of the input signal.
Verify that counter output A1U20-13 generates a 4.8-kHz clock while A1U20-11 is low.
Verify that the shift register output (A1U29-9) changes to the same state as the totalizer
input signal about 1.67 milliseconds after a transition occurs on the totalizer input signal
(A1U29-10).
5-21
HYDRA
Service Manual
A2TP2
A2TP3
A2TP6
A2TP1
1 2
A2TP5
A2TP4
(S21)
(S1)
(S3)
(S5)
(S7)
(S9)
(S11)
(S13)
(S15)
(S17)
(S2)
(S4)
(S6)
(S8)
(S10)
(S12)
(S14)
(S16)
(S18)
A2TP2
A2TP3
A2TP6
A2TP1
+
A2TP5
LS1
U1
A2TP4
J1
TEST POINT LOCATIONS
(DISPLAY PCA)
s39f.eps
Figure 5-8. Test Points, Display PCA (A2)
5-22
Diagnostic Testing and Troubleshooting (2620A/2625A)
Display Assembly Troubleshooting
5
5-18. Display Assembly Troubleshooting
The following discussion is helpful if it has been determined that the Display Assembly
is faulty. Refer to Figure 5-8 for Display PCA test points. This initial determination may
not be arrived at easily, since an improperly operating display may be the result of a
hardware or software problem that is not a direct functional part of the Display
Assembly. Consult the General Troubleshooting Procedures found earlier in this section
for procedures to isolate the fault to the Display Assembly. Use the following discussion
of display software operation when troubleshooting problems within a known faulty
Display Assembly. A Display Extender Cable (PN 867952) is available for use during
troubleshooting. Note that this cable must be twisted to mate correctly to the connectors
on Display and Main PCAs.
The Display Controller reads the DTEST* and LTE* inputs to determine how to
initialize the display memory. DTEST* and LTE* default to logic 1 and logic 0,
respectively, to cause all display segments to be initialized to "on". DTEST* is
connected to test points A2TP4, and LTE* is connected to A2TP5. Either test point can
be jumpered to VCC (A2TP6) or GND (A2TP3) to select other display initialization
patterns. Display Test Patterns #1 and #2 are a mixture of "on" and "off" segments with a
recognizable pattern to aid in troubleshooting problems involving individual display
segments. When either of the special display patterns is selected, the beeper is also
sounded for testing without interaction with the Microprocessor. Table 5-8 indicates the
display initialization possibilities.
Table 5-8. Display Initialization
A2TP4 DTEST*
A2TP5 LTE*
1
1
0
0
1
0
1
0
POWER-UP DISPLAY INITIALIZATION
All Segments OFF
All Segments ON (default)
Display Test Pattern #1
Display Test Pattern #2
Figure 5-9 shows the timing of communications between the Microprocessor and the
Display Controller. Figures 5-10 and 5-11 show Display Test Patterns #1 and #2,
respectively. Refer to the Display Assembly schematic diagram in Section 8 for
information on grid and anode assignments.
DSCLK
DISTX
BIT 7
DISRX
BIT 7
CLEAR TO
RECEIVE
BIT 6
BIT 6
BIT 5
BIT 5
BIT 4
BIT 4
BIT 3
BIT 3
BIT 2
BIT 2
BIT 1
BIT 1
BIT 0
BIT 0
HOLD OFF
26 µs
CLEAR TO
RECEIVE
26 µs
s40f.eps
Figure 5-9. Display Controller to Microprocessor Signals
5-23
HYDRA
Service Manual
REM SCAN
REVIEW
SET FUNC
mV
x1 k Ω
1
EXT TR
s41f.eps
Figure 5-10. Display Test Pattern #1
LAST
MAX
MIN
F
AUTO MON
Mx+B ALARM
°C °F RO
AC DC
Hz
M
LIMIT HI OFF PRN CH
2 LO CAL
s42f.eps
Figure 5-11. Display Test Pattern #2
When a Hydra display is initially powered up, all display segments should come on
automatically. If this display does not appear, proceed with the following steps:
Note
If the display is operational but has problems whenfront-panel buttons are
pressed, proceed directlyto step 9.
1. Check the three power supplies with respect to GND (A2TP3 or A2U1-42) on the
Display Assembly.
•
VCC (A2U1-21) 4.85 to 5.35V dc
•
VEE (A2U1-4)-4.75 to -5.25V dc
•
VLOAD (A2U1-5)-28.5 to -32.0V dc
2. Check the filament drive signals FIL1 and FIL2; these connect to the last two pins
on each end of A2DS1. These signals should be 5.4V ac with FIL2 biased to be
about 6.8V dc higher than the VLOAD supply (nominally a -23.2V dc level). FIL1
and FIL2 should be 180 degrees out of phase. If the dc bias of FIL2 is not at about 23.2V dc, the display segments that should be "off" will show a shadowing (or
speckling) effect.
Note
It may be necessary to disable the watchdog resetby jumpering A2TP1
(A2U5-3, A2U5-11) to GND (A2TP3) toverify the following items.
3. Check the clock signal CLK1 at A2TP2, A2U1-2, and A2U4-3. This signal should
be a 614.4-kHz square wave (1.628 ms per cycle). This signal depends on an E clock
signal of 1.2288 MHz from the Hydra Main Assembly. If the E clock is 819.2 kHz
(1.221 ms per cycle), it is possible that SWR2 (A2J1-16) is shorted to ground,
causing the Microprocessor to HALT at power-up.
4. Check the state of the RESET signal (A2U1-1). This signal should be low once the
reset time is completed (after power-up). Also verify that the RESET* signal
(A2U6-3) is high after the reset time is completed.
5-24
Diagnostic Testing and Troubleshooting (2620A/2625A)
Variations in the Display
5
5. Verify that the DISRX signal (A2U1-39) goes low after RESET (A2U1-1) goes low.
If this sequence does not occur, communication to the Microprocessor is held off
with the DISRX signal high. If DISRX stays high but is not shorted to VCC, A2U1
must be faulty.
6. Verify activity for both the DISTX and DSCLK signals. These signals are driven by
the Microprocessor and must be transitioning for the Display Controller to receive
commands from the Microprocessor.
7. If all segments of a particular digit do not turn on at power-up, the grid drive from
A2U1 may not be connected properly to A2DS1. Grids are numbered from 10 to 0
(left to right as the display is viewed). For a digit to be enabled, the respective grid
drive signals (GRID(10:0)) must be at approximately VCC (4.85 to 5.35V dc.) For a
digit to be disabled, the drive must be at VLOAD (-28.5 to -32.0V dc.)
8. If a segment under each of several (or all) grids fails to be turned on (or off)
properly, one of the anode drive signals may not be connected properly from A2U1
to A2DS1. When an anode signal is at VCC, and a grid signal is at VCC, the
corresponding segment on the display is illuminated.
9. If the Microprocessor has difficulty recognizing front-panel button presses, the
switch scanning signals (SWR1 through SWR6, A1U4-21 through -26, respectively)
should be checked. When no switch contacts are being closed, the switch scanning
lines should have about 20 kΩ of resistance between each other (through two 10-kΩ
pullup resistors to VCC). Unless one of the switches is closed, none of the switch
scanning lines should be shorted directly to GND at any time.
5-19. Variations in the Display
Note
The following procedure will not work with Hydra’s Mainframe Firmware
version 5.5.
Under normal operation, the display presents various combinations of brightly and dimly
lit annunciators and digits. However, you may encounter other, random irregularities
across different areas of the display under the following circumstances:
•
After prolonged periods of displaying the same information.
•
If the display has not been used for a prolonged period.
This phenomenon can be cleared by activating the entire display and leaving it on
overnight (or at least for several hours). Use the following procedure to keep the display
fully lit:
1. With power OFF, press and hold SHIFT, then press power ON.
2. Wait a moment for the instrument to beep, then release SHIFT. The entire display
will now stay on until you are ready to deactivate it.
3. At the end of the activation period, press any button on the front panel; the
instrument resumes the mode in effect prior to the power interruption (Active or
Inactive.)
5-25
HYDRA
Service Manual
5-20. Calibration Failures
5-21. Introduction
Calibration of Hydra through the computer interface is described in Section 4 of this
manual. Generally, a calibration failure is indicated by a Device Dependent Error and a
"!>" prompt after a CAL_STEP? command if the RS-232 interface is being used. If the
IEEE-488 interface is being used, the Device Dependent Error may be detected by
reading the Event Status Register (see the Hydra User Manual). These indications occur
if the analog input varies from what the instrument expects to see by more than ±5% or
±15%, depending on the calibration step.
Before suspecting a fault with Hydra, verify that the calibration is being conducted
properly.
• Check the connections between the source and the instrument. Are allthe
connections in place?
• Check the output of the calibration source. Does it equal the valuecalled for by this
calibration step?
• Check the calibration source. Is it in operate mode? Has it revertedto standby?
If a calibration step has failed, Hydra remains on that step so that the output from the
calibration source may be corrected or the calibration reference value (CAL_REF) being
used by Hydra may be changed if it was improperly entered. The calibration step may be
repeated by sending the CAL_STEP? command to Hydra again.
Calibration of Hydra utilizes a simple "calibration by function" approach. If you suspect
calibration errors, but the instrument does not exhibit the symptoms mentioned above,
verify that you are observing the following calibration rules:
• Independent calibration of any function results in the storage ofcalibration constants
for that function only.
• Once calibration is begun, all steps for that function must becompleted before the
calibration constants are stored. If all stepsare not completed and the procedure is
terminated, no constants forthat function are stored; only calibration constants for
previouslycompleted functions are stored.
5-22. Calibration-Related Components
If the calibration setup is correct, a faulty component within Hydra may be causing the
failure. Each measurement function depends on a combination of components in and
around the Analog Measurement Processor (A3U8).
RMS Converter
A3U6
AC Buffer
A3U7
Zener Reference
A3VR1
Divider Network (DC/Ohms)
A3Z4
Integrate Resistors, Reference Divider
A3Z2
AC Divider Network
A3Z3
RMS Converter Network
A3Z1
Basic dc measurements depend on the zener reference (A3VR1), reference divider
network (A3Z2), and integrate resistors (A3Z2). Resistance measurements and dc
measurements above three volts additionally depend on the resistors in the dc divider
network (A3Z4). AC measurements depend on the ac divider network (A3Z3), ac buffer
(A3U7), and RMS converter (A3U6), as well as the basic dc measurement components.
5-26
Diagnostic Testing and Troubleshooting (2620A/2625A)
Calibration Failures
5
Note
During calibration, the measurement rateis selected automatically as
required by thecalibration step.
Table 5-9 or Table 5-10 may be useful in isolating a calibration problem to specific
components. Table 5-9 can be used with a Hydra having a main software version number
of 5.4 or higher. Table 5-10 can be used with main software versions lower than 5.4.
Note that the software version number is not marked on the Hydra case. Use either of the
following two methods to determine your software version number:
•
From the Hydra front panel, simultaneously press [ltb] and [rtb]. Themain software
version number (e.g., "5.4") appears in the leftdisplay. (The A/D software version
number (e.g., A4.7 appears in theright display.) Press [cnc] to return to normal front
paneloperation.
•
Over the computer interface, send the *IDN? query. The main softwareversion (e.g.,
"M5.4") is returned as part of the response. Refer toSection 4 of the Hydra Users
Manual for a more detailed descriptionof *IDN?.
Table 5-9. Calibration Faults (for software versions 5.4 and above)
Input
Calibration Constant
Range
Number
Related Components
Acceptable Values
DC Volts
0.09000V
0.9000V
0.29000V
2.9000V
29.000V
290.00V
100 mV
1V
300 mV
3V
30V
300V
1
2
3
4
5
6
1.0315 to 1.1565
1.0340 to 1.1540
1.0315 to 1.1565
1.0315 to 1.1565
1.0340 to 1.1640
1.0290 to 1.1590
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2, A3Z4
A3VR1, A3Z2, A3Z4
AC Volts (1 kHz)
0.02900V
0.29000V
0.2900V
2.9000V
2.900V
29.000V
29.00V
290.00V
300 mV
300 mV
3V
3V
30V
30V
300V
300V
7
8
9
10
11
12
13
14
-0.001 to 0.001
1.0040 to 1.1840
-0.01 to 0.01
1.0040 to 1.1840
-0.1 to 0.1
1.0040 to 1.1840
-1.0 to 1.0
1.0040 to 1.1840
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
Ohms
290.00Ω
2.9000 kΩ
29.000 kΩ
290.00 kΩ
2.9000 MΩ
2.9000 MΩ
300Ω
3 kΩ
30 kΩ
300 kΩ
3 MΩ
10 MΩ
15
16
17
18
19
20
0.9965 to 1.0115
0.9975 to 1.0125
1.0015 to 1.0165
0.9965 to 1.0115
0.9990 to 1.0090
0.9990 to 1.0090
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
Frequency
10.000 kHz
2.9V rms
21
0.9995 to 1.00050005
A3Y2
5-27
HYDRA
Service Manual
5-23. Retrieving Calibration Constants
If a calibration error is suspected, the stored constant can be retrieved and verified over
the computer interface. Acceptable calibration constants for each function and range are
listed in Table 5-9 (software version 5.4 and higher) or 5-10 (software versions lower
than 5.4.) Retrieve the constant with the following command:
CAL_CONST? xx
(where xx denotes the calibration constant number)
Table 5-10. Calibration Faults (for sotware versions lower than 5.4)
Input
Calibration Constant
Range
Number
Related Components
Acceptable Values
DC Volts
0.09000V
0.9000V
0.29000V
2.9000V
29.000V
290.00V
100 mV
1V
30 mV0
3V
30V
300V
1
2
3
4
5
6
1.0315 to 1.1565
1.0340 to 1.1540
1.0315 to 1.1565
1.0315 to 1.1565
1.0340 to 1.1640
1.0290 to 1.1590
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2, A3Z4
A3VR1, A3Z2, A3Z4
AC Volts (1 kHz)
0.02900V
0.29000V
0.2900V
2.9000V
29.000V
290.00V
300 mV
300 mV
3V
3V
30V
300V
7
8
9
10
11
12
-0.001 to 0.001
1.0040 to 1.1840
-0.01 to 0.01
1.0040 to 1.1840
1.0040 to 1.1840
1.0040 to 1.1840
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
Ohms
290.00Ω
2.9000 kΩ
29.000 kΩv
290.00 kΩ
2.9000 MΩ
2.9000 MΩ
300Ω
3 kΩ
30 kΩ
300 kΩ
3 MΩ
10 MΩ
13
14
15
16
17
18
0.9965 to 1.0115
0.9975 to 1.0125
1.0015 to 1.0165
0.9965 to 1.0115
0.9990 to 1.0090
0.9990 to 1.0090
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
Frequency
10.000 kHz
2.9V rms
19
0.9995 to 1.0005
A3Y2
5-24. Replacing the EEPROM (A1U1)
The EEPROM provides nonvolatile storage for the instrument serial number, some of the
instrument configuration, and all calibration information. If the EEPROM is replaced
during repair, the new EEPROM can be programmed with the 7-digit serial number
found on the rear panel of the instrument or any 7-digit identifier of your choosing. Note
that the serial number is not programmed prior to shipment from the factory.
5-28
Diagnostic Testing and Troubleshooting (2620A/2625A)
IEEE-488 Interface PCA (A5) Troubleshooting
5
The following command may be used to program the serial number into the EEPROM:
SERIAL XXXXXXX
(xxxxxxx denotes the 7-digit number. Leading zeros
The serial number of the instrument can be accessed by using the "SERIAL?" command.
The response will be "0" (if the serial number has not yet been set) or the 7-digit serial
number.
5-25. IEEE-488 Interface PCA (A5) Troubleshooting
Refer to Section 7 for a discussion of troubleshooting the IEEE-488 Assembly.
5-26. Memory PCA (A6) Troubleshooting
5-27. Power-Up Problems
The following discussion identifies probable fault areas if the installation of a Memory
PCA causes power-up failure for the instrument. The problem is probably a short on
A6J1; the Microprocessor on the Main PCA is prevented from accessing ROM and
RAM correctly. Make the following checks:
•
First check for a GND-to-VCC short on the Memory PCA.
•
There may also be a short between an interface signal and VCC, GND,or another
interface signal. Check signals D0 .. D7, A0 .. A2, RD*,WR*, MEM*, and RESET*.
•
The short may be due to a CMOS input that has been damaged due tostatic
discharge; the short is then detectable only when the circuitis powered up. Use an
oscilloscope to check activity on each of theinterface signals. Verify that signals are
able to transitionnormally between 0 and 5.1V dc (VCC).
5-28. Failure to Detect Memory PCA
If the PRINT destination cannot be set to "StorE", Hydra was unable to determine that
the Memory PCA was installed at power-up. The PRINT destination selection procedure
is described in Section 3 of the User Manual.
If the Memory PCA is not detected by instrument software, there may be a problem with
the IRQ2* or OPS* signal. The Memory PCA connects these two signals when it is
installed. A fault with A1R2 or the Microprocessor (A1U4) could also result in failure to
detect the Memory PCA.
5-29. Failure to Store Data
Configure the instrument to fast reading rate, 3V dc range on channel 1, and scan
interval of 0:00:00. Setup storage of all scan data to the Memory PCA: press SHIFT
PRINT, select "StorE", press ENTER, select "ALL", and press ENTER. Then, if the
"PRN" annunciator is not on, enable data storage by pressing PRINT ("PRN"
annunciator comes on.)Finally, enable scanning press SCAN.
5-29
HYDRA
Service Manual
While the instrument is scanning, check that data is being stored correctly. Use an
oscilloscope to monitor activity on the 7 outputs of the Byte Counter (A6U3) and the 11
outputs of the Page Register (A6U1 and A6U4). Since the repetition rate is fairly low, it
may be necessary to use a storage oscilloscope to capture the activity. If either of these
circuit elements is not functioning, check the Address Decode circuit (A6U2, A6U5,
A6U8) for activity at the end of every scan.
If the outputs of the Page Register and the Byte Counter are showing reasonable activity,
verify that these signals are also being received by the Nonvolatile Memories (A6U6 and
A6U7). Check CS*, WR*, and OE* inputs on A6U6 and A6U7 for proper activity.
There may also be a problem in reading data back from the Memory PCA. After
allowing the Memory PCA to fill with scan data ("F" annunciator on the display lit), turn
off scanning (press SCAN). Now press the LIST button and select the "StorE" entry in
the menu. While the Hydra is formatting and sending the Memory PCA contents to the
RS-232 interface, again monitor the circuit areas described above for reasonable voltage
levels and activity.
5-30
Chapter 5A
Diagnostic Testing and Troubleshooting
(2635A)
Title
5A-1.
5A-2.
5A-3.
5A-4.
5A-5.
5A-6.
5A-7.
5A-8.
5A-9.
5A-10.
5A-11.
5A-12.
5A-13.
5A-14.
5A-15.
5A-16.
5A-17.
5A-18.
5A-19.
5A-20.
5A-21.
5A-22.
5A-23.
5A-24.
5A-25.
5A-26.
5A-27.
Introduction ..........................................................................................
Servicing Surface-Mount Assemblies ..................................................
Error Codes...........................................................................................
General Troubleshooting Procedures ...................................................
Power Supply Troubleshooting............................................................
Raw DC Supply................................................................................
Power Fail Detection........................................................................
5-Volt Switching Supply..................................................................
Inverter .............................................................................................
Analog Troubleshooting.......................................................................
DC Volts Troubleshooting...............................................................
AC Volts Troubleshooting...............................................................
Ohms Troubleshooting.....................................................................
Digital Kernel Troubleshooting ...........................................................
Digital and Alarm Output Troubleshooting .........................................
Digital Input Troubleshooting..............................................................
Totalizer Troubleshooting....................................................................
Display Assembly Troubleshooting. ....................................................
Variations in the Display......................................................................
Calibration Failures ..............................................................................
Introduction......................................................................................
Calibration-Related Components.....................................................
Retrieving Calibration Constants.....................................................
Replacing the Flash Memory (A1U14 and A1U16) ........................
Memory Card I/F PCA (A6) Troubleshooting. ....................................
Power-Up Problems .........................................................................
Failure to Detect Memory Card I/F PCA ....................................
Page
5A-3
5A-3
5A-4
5A-6
5A-8
5A-8
5A-8
5A-8
5A-9
5A-11
5A-16
5A-17
5A-17
5A-18
5A-21
5A-21
5A-23
5A-23
5A-26
5A-27
5A-27
5A-27
5A-29
5A-29
5A-30
5A-30
5A-30
5A-1
HYDRA
Service Manual
5A-28.
5A-29.
5A-30.
5A-31.
5A-32.
5A-2
Failure to Detect Insertion of Memory Card ...............................
Failure to Power Card / Illuminate the Busy Led ........................
Failure to Illuminate the Battery Led ..........................................
Failure to Write to Memory Card ................................................
Write/Read Memory Card Test (Destructive) .............................
5A-31
5A-31
5A-31
5A-32
5A-32
Diagnostic Testing and Troubleshooting (2635A)
Introduction
5A-1.
5A
Introduction
Hydra provides error code information and semi-modular design to aid in
troubleshooting. This section explains the error codes and describes procedures needed
to isolate a problem to a specific functional area. Finally, troubleshooting hints for each
functional area are presented.
But first, if the instrument fails, check the line voltage fuse and replace as needed. If the
problem persists, verify that you are operating the instrument correctly by reviewing the
operating instructions found in the Hydra Users Manual.
Warning
Opening the case may expose hazardous voltages. Always
disconnect the power cord and measuringinputs before
opening the case. And remember that repairs or servicing
should be performed only by qualified personnel.
Required equipment is listed in Section 4 of this manual.
Signal names followed by a ’*’ are active (asserted) low. Signal names not so marked are
active high.
5A-2.
Servicing Surface-Mount Assemblies
Hydra incorporates Surface-Mount Technology (SMT) for printed circuit assemblies
(pca’s). Surface-mount components are much smaller than their predecessors, with leads
soldered directly to the surface of a circuit board; no plated through-holes are used.
Unique servicing, troubleshooting, and repair techniques are required to support this
technology. The information offered in the following paragraphs serves only as an
introduction to SMT. It is not recommended that repair be attempted based only on the
information presented here. Refer to the Fluke "Surface Mount Device Soldering Kit" for
a complete demonstration and discussion of these techniques. (In the USA, call 1-800526-4731 to order.)
Since sockets are seldom used with SMT, "shotgun" troubleshooting cannot be used; a
fault should be isolated to the component level before a part is replaced. Surface-mount
assemblies are probed from the component side. The probes should make contact only
with the pads in front of the component leads. With the close spacing involved, ordinary
test probes can easily short two adjacent pins on an SMT IC.
This Service Manual is a vital source for component locations and values. With limited
space on the circuit board, chip component locations are seldom labeled. Figures
provided in Section 6 of this manual provide this information. Also, remember that chip
components are not individually labeled; keep any new or removed component in a
labeled package.
Surface-mount components are removed and replaced by reflowing all the solder
connections at the same time. Special considerations are required.
•
The solder tool uses regulated hot air to melt the solder; there isno direct contact
between the tool and the component.
5A-3
HYDRA
Service Manual
•
Surface-mount assemblies require rework with wire solder rather thanwith solder
paste. A 0.025-inch diameter wire solder composed of 63%tin and 37% lead is
recommended. A 60/40 solder is also acceptable.
•
A good connection with SMT requires only enough solder to make apositive metallic
contact. Too much solder causes bridging, while toolittle solder can cause weak or
open solder joints. With SMT, theanchoring effect of the through-holes is missing;
solder provides theonly means of mechanical fastening. Therefore, the pca must
beespecially clean to ensure a strong connection. An oxidized pca padcauses the
solder to wick up the component lead, leaving littlesolder on the pad itself.
Refer to the Fluke "Surface Mount Device Soldering Kit" for a complete discussion of
these techniques.
5A-3.
Error Codes
At reset, the Hydra Data Bucket software performs power-up self-tests and initialization
of Flash Memory, NVRAM, Display, Calibration Data, and measurement hardware.
Self-test failures are reported on the display with "Error" in the left display and an error
code (1-9,A,b,C,d) in the right display.
Several of these error codes might never be displayed. Certainly, errors 4 and 5, which
signify a faulty or dead display, could not be reported in the normal (displayed) manner.
Other errors might not appear on the display. Therefore, the following additional
methods exist for accessing error information:
•
If ’boot’ is displayed at power-up, it is likely that one ofthe memory tests failed
(Errors 1 through 3). To determinewhat the error status was, connect a terminal or
computer to theRS-232 interface (19200 baud, 8 data bits, no parity). Send a
carriagereturn or line feed character to the instrument and it should sendback a
prompt that shows a number followed by a ’>’ character. Thenumber is interpreted in
the same way as the responses for the *TST?and POWERUP? commands; refer to
*TST? in Section 4 of the HydraUsers Manual. For example, a ’4>’ prompt indicates
that the test ofthe NVRAM (A1U20 and A1U24) failed and the instrument was not
ableto safely power-up and operate.
•
The computer interfaces can be used to determine self-check statususing the *TST?
query. Refer to Section 4 of the Hydra Data BucketUsers Manual for a description of
the *TST? response. Note that theextent of the error-producing damage could also
cause the instrumentto halt before the computer interfaces are operational.
•
The POWERUP? computer interface command can be used to determinewhich
errors were detected at power-up. POWERUP? uses the sameresponse format as
*TST?; refer to *TST? in Section 4 of the HydraData Bucket Users Manual.
Table 5A-1 describes the error codes.
Note
Each error code is displayed for 2 seconds.
5A-4
Diagnostic Testing and Troubleshooting (2635A)
Error Codes
5A
Table 5A-1. Error Codes (2635A)
Error
1
2
3
4
5
6
7
8
9
A
b
C
d
Description
Boot Firmware (A1U14 and A1U16) Checksum Error
Instrument Firmware (A1U14 and A1U16) Checksum Error
NVRAM (A1U20 and A1U24) Test Failed
Display Power-up Test Failure
Display Not Responding
Instrument Configuration Corrupted
Instrument Calibration Data Corrupted
Instrument Not Calibrated
A/D Converter Not Responding
A/D Converter ROM Test Failure (A3U9)
A/D Converter RAM Test Failure (A3U9)
A/D Converter Self Test Failure
Memory Card Interface Not Installed
Refer to Troubleshooting information later in this section
Error 1
Boot Firmware (A1U14 and A1U16) Checksum Error
All the bytes in the Boot section of Firmware (including a checksum) are summed.
Error 2
Instrument Firmware (A1U14 and A1U16) Checksum Error
All the bytes in the Instrument section of Firmware (including a checksum) are summed.
Error 3
NVRAM (A1U20 and A1U24) Test Failed
A test pattern of data is written to and then read from the NVRAM locations that are not used for
Non-volatile instrument configuration and measurement data. If the pattern read from any RAM
location is not the same as the pattern written, the test fails.
Error 4
Display Power-up Test Failure
Error 5
Display Not Responding
The display processor automatically performs a self-check on power-up, and the Microprocessor
attempts to read the result of this test.
Error 6
Instrument Configuration Corrupted
The instrument configuration information stored in nonvolatile RAM (A1U20 and A1U24) has
been corrupted. (The Cyclic Redundancy Checksum on this memory is not correct for the
information stored there.) The instrument configuration is reset to the default configuration.
Error 7
Instrument Calibration Data Corrupted
The Flash Memory (A1U14 and A1U16) is divided into three storage areas: the Boot Firmware,
the Calibration Data, and the Instrument Firmware. The Calibration Data uses a Cyclic
Redundancy Checksum (CRC) for data security, against which the data is checked on power-up.
Error 8
Instrument Not Calibrated
The calibration data includes status information to indicate which of the measurement functions
(Volts DC, Volts AC, Ohms, and Frequency) have been calibrated. If any functions have not been
calibrated, this error is reported.
Note
Errors 7 and 8 should always appear the first time an instrument is
powered up with a new, uninitialized Flash Memory. Error 8 continues to
appear at subsequent power-ups until the instrument is fully calibrated.
5A-5
HYDRA
Service Manual
Table 5A-1. Error Codes (2635A) (cont)
Error
Error 9
Description
A/D Converter Not Responding
This error is displayed if communication cannot be established with the 6301Y Microcomputer
(A3U9).
Error A
A/D Converter ROM Test Failure (A3U9)
All bytes of internal ROM for the 6301Y Microcomputer (A3U9) (including the checksum byte) are
summed.
Error b
A/D Converter RAM Test Failure (A3U9)
Complementary patterns are alternately written to and read from each location of the 256 bytes of
RAM internal to the 6301Y Microcomputer (A3U9).
Error C
A/D Converter Self Test Failure
The Analog Measurement Processor (A3U8) is programmed to do self test measurements.
Error d
Memory Card Interface Not Installed
The Microprocessor checks the system at power-up to determine whether the Memory Card
Interface is installed.
5A-4.
General Troubleshooting Procedures
Hydra allows for some fault isolation using self-diagnostic routines and descriptive error
codes. However, these features are somewhat limited and do not provide in-depth
troubleshooting tools.
Hydra incorporates a semi-modular design; determining modules not related to a
problem constitutes the first step in the troubleshooting process.
As a first step, remove the Memory Card Interface (A6) from the Hydra Databucket
(2635A). Refer to Section 3 of this manual for removal procedures. If removal of this
assembly results in improved instrument operation, refer to the Memory Card Interface
troubleshooting found later in this section.
Measuring the power supplies helps to isolate a problem further. Refer to Table 5A-2
and Figure 5A-1 for test point identification and readings. If power supply loading is
suspected, disconnect the Display PCA at A1J2. If this action solves the loading
problem, proceed to Display Assembly Troubleshooting elsewhere in this section.
Otherwise, refer to Power Supply Troubleshooting.
Table 5A-2. Preregulated Power Supplies (2635A)
Preregulated Voltage
-8.9V
-30.9V
+9.2V
-8.6V
Measurement Points
A1CR13-2 to A1TP1
A1TP4 to A1TP1
A1CR5 cathode to A1TP30
A1CR7 anode and A1TP30
Resulting Supply
VEE
VLOAD
VDD, VDDR
VSS
If the power supplies appear to be good, check the Display clock signal (DCLK (A1R85)
and E clock signal (A2U4-1)). This clock signal is not symmetrical; it should be about
+5.0 volts for about 325 nanoseconds and then near 0 volts for about 651 nanoseconds. If
it is not correct at either measurement point, remove the Display Assembly and check
the Display clock again at A1R85. If it is now correct, the problem is most likely on the
Display Assembly. If it is still incorrect, the problem is probably in the Digital Kernel on
the Main Assembly.
5A-6
Diagnostic Testing and Troubleshooting (2635A)
General Troubleshooting Procedures
A1TP30
A1TP4
A1TP31
A1TP5
A1TP10
A1TP32
A1TP6
A1TP18
A1TP11
A1TP3
A1TP20
A1TP7
A1TP2
A1TP14
A1TP9
A1TP12
A15
A14
A13
A12
GND
A11
A10
A9
A8
A7
A6
A5
A4
GND
A3
A2
A1
FC0
VDD
FC1
FC2
CS0
CS1
GND
CS2
CS3
RMC
IAC
PB11
PB10
PB9
PB8
WDOG
A1TP15
A1TP1
A1TP13
VDD
A16
A17
A18
A19
GND
A20
A21
A22
A23
VDD
GND
D15
D14
D13
D12
GND
D11
D10
D9
D8
VDD
D7
D6
D5
D4
GND
D3
D2
D1
D0
CTS3
CD1
17
10
5
1
125
117
110
25
105
30
A1AU1 MICROPROCESSOR
100
35
95
40
90
45
50
55
60
65
70
75
80
83
GND
TOUT2
TIN2
TOUT1
VDD
TIN1
IACK1
IACK6
IACK7
GND
UDS
LDS
AS
R/W
GND
XTAL
EXTAL
VDD
CLK0
IPL0
IPL1
IPL2
BERR
AVEC
RESET
HALT
BR
NC1
BGACK
BG
BCLR
DTACK
GND
CTS1
RXD1
RXD2
TXD2
RCLK2
TCLK2
GND
CTS2
RTS2
CD2
SDS2
VDD
RXD3
TXD3
RCLK3
TCLK3
GND
PA12
DREQ
DACK
DONE
FRZ
DISCPU
BUSW
NC3
BRG1
CD3
RTS3
RTS1
TXD1
TCLK1
RCLK1
VDD
A1TP8
5A
s43f.eps
Figure 5A-1. Test Point Locator, Main PCA (A1) (2635A)
5A-7
HYDRA
Service Manual
Refer to the Schematic Diagrams in Section 8 during the following troubleshooting
instructions. Also, these diagrams are useful in troubleshooting circuits not specifically
covered here.
5A-5.
Power Supply Troubleshooting
Warning
To avoid electric shock, disconnect all channel inputs from the
instrument before performing any troubleshooting operations.
5A-6.
Raw DC Supply
With the instrument connected to line power (120V ac, 60 Hz) and turned ON, check for
approximately 14V dc between A1TP1 (GND) and the "+" terminal of capacitor A1C7
(or the cathode of either A1CR2 or A1CR3). (This voltage is approximately 30V dc at
240V ac line.) If no voltage or a very low voltage is present, check for approximately
24V ac across the secondary of the power transformer (or approximately 50V ac at 240V
ac line).
The voltage at the output of A1U19 (also A1TP7), should be about +5.3V dc. At 120V
ac, 60-Hz line power input, the Hydra Databucket line current is approximately 24 mA.
At 50-Hz, 120V ac line power input, there is a 5 to 10% increase in this current figure.
5A-7.
Power Fail Detection
The Power Fail Detection circuit monitors the Raw Supply so that the Microprocessor
can be signaled when power is failing. A reference voltage of nominally 1.3 volts dc
(internal to A1U10) is compared to the voltage at A1U10-4. If A1U10-4 is less than
about 1.3 volts dc, the power fail output (A1U10-5) should be low. This corresponds to a
raw supply voltage of about 8 volts dc (A1C7). If the raw supply voltage is greater than
8 volts dc, the power fail output (A1U10-5) should be high. If the power fail output is
near 0V dc during normal operation, the Microprocessor will sense that power is failing
and will not be able to complete a scan operation.
5A-8.
5-Volt Switching Supply
Use an oscilloscope to troubleshoot the 5-volt switching supply. With the oscilloscope
common connected to A1TP1, check the waveform at either A1U9, pin 4 or A1T1, pin 2
to determine the loading on the 5-volt switching supply. The output voltage of the 5-volt
switching supply at A1TP2 (VCC) is normally about 5.0V dc with respect to A1TP1
(GND).
•
Normal Load:
The signal at A1U9-4 (with respect to A1TP1) is a square wave with a period of 9 µs to
11 µs and an ON (voltage is low) duty ratio of about 0.38 with the line voltage at 120V
ac. The amplitude is usually about 15V p-p. The positive-going edge will be "fuzzy" as
the duty ratio is varying to compensate for the ripple of the raw supply and the pulsing
load of the inverter supply. See Figure 5A-2 (NORMAL LOAD).
•
Very Heavy Load or 5V Supply Shorted:
Under heavy load (example: A3 A/D Converter PCA has a short circuit) it could load
down the power supply voltage such that the current limiting feature is folding the
supply back. For example, if the supply is folded back due to excessive current draw,
unplug the ribbon cable at A3J10 on the A/D Converter PCA. When tracking down
power supply loads, use a sensitive voltmeter and look for resistive drops across filter
chokes, low value decoupling resistors, and circuit traces. Also check for devices that are
too warm. On the A3 A/D Converter PCA, all devices run cool except A3U5
microprocessor and A3U8 FPGA, which run warm, but not hot.
5A-8
Diagnostic Testing and Troubleshooting (2635A)
Power Supply Troubleshooting
5A-9.
5A
Inverter
Use an oscilloscope to troubleshoot the inverter supply. The outputs of the inverter
supply are -5V dc (VEE), -30V dc (VLOAD), and 5.4V ac (FIL1 and FIL2) outguard,
and +5.3V dc (VDD), -5.4V dc (VSS), and +5.6V dc (VDDR) inguard. Refer to Figure
5A-3. The signal at the drains of the two inverter switch FETs (A1Q7 and A1Q8) should
be a 10V peak square wave with a period of approximately 18 us. The gate signal is a
5.1V peak square wave with rounded leading and trailing edges. The leading edge has a
small positive rounded pulse with an amplitude of 1.8V peak and a pulse width of about
0.3 us. The signal at A1U22-5 and A1U22-6 is a symmetrical square wave with an
amplitude of 5.1V peak and a period of about 18 us. The negative-going trailing edge of
both square waves is slower than the rising edge and has a small bump at about 1.5 volts.
The signal at A1U22-3 (TP14) is a symmetrical square wave with a period of about 9 us.
For the inverter to operate, the 110-kHz oscillator must be operating properly. If the
signal at A1U22-3 is missing, begin by checking the voltage at A1TP7. The voltage
should be about +5.3V dc. Then, using an oscilloscope, check for a square wave signal at
A1U23-9 and a square wave signal at A1U23-8. If the FETs are getting proper drive
signals, failures that heavily load the inverter supply will usually cause the inverter to
draw enough current to make the switcher supply go into current limit. Shorted rectifier
diodes and shorted electrolytic capacitors will cause heavy load conditions for the
inverter.
U9-7 and T2-2
20V
0V
5V/DIV
2 µS/DIV
Normal Load
s33f.eps
Figure 5A-2. 5-Volt Switching Supply (2635A)
5A-9
HYDRA
Service Manual
TP9 AND TP10
0
2V/DIV
2µS/DIV
FET GATE SIGNAL
Q7, Q8, OR T1-1 OR -3
0
2V/DIV
2µS/DIV
FET DRAIN SIGNAL
s45f.eps
Figure 5A-3. Inverter FET Drive Signals (2635A)
5A-10
Diagnostic Testing and Troubleshooting (2635A)
Analog Troubleshooting
5A
Note
When making voltage measurements in the invertercircuit, remember that
there are two separategrounds. The outguard ground is the ’GND’ testpoint
(A1TP1), and the inguard ground is the’COM’ test point (A1TP30).
The inguard regulator circuits for VDD and VSS have current limits. Shorts and heavy
loads between VDD and COM, VSS and COM, and VDD and VSS will cause one or
both supplies to go into current limit. The current supplied by either supply can be
checked by measuring the voltage across the current sense resistors, A1R13 and A1R15.
The typical voltage across A1R13 is 0.30, and the typical voltage across A1R15 is
0.40V.
Generally, open electrolytic capacitors in the inverter supply will cause excessive ripple
for the affected supply. Also, the rectified dc voltage for the supply with the open
capacitor will be lower than normal. Normal voltage levels at the rectifier outputs for
each inverter supply are shown in Table 5A-2.
The loads for the inguard supplies can be disconnected by removing the cable to the A/D
Converter PCA at A3J10. The inguard regulator circuits and VDDR regulator will
operate with no loads, and troubleshooting can be performed by making voltage
measurements.
The normal input current to the inverter supply is about 11.25 mA, or 0.225 mV across
A1R38 (when the instrument is not measuring).
Table 5A-3 provides a Power Supply troubleshooting guide.
5A-10. Analog Troubleshooting
Warning
To avoid electric shock, disconnect all channelinputs from the
instrument before performing anytroubleshooting operations.
Refer to Figure 5A-4 and Figure 5A-5 for test point locations on the A/D Converter
PCA.
First, check for analog-related errors displayed at power up. An ’Error 9’ means that the
Main Microprocessor A1U1 is not able to communicate with the A/D Microcontroller
A3U9. ’Error A’ and ’Error b’ mean that a failure has occurred in the internal memory of
the A/D Microcontroller A3U9. ’Error C’ means that the Analog Measurement Processor
A3U8 is not functioning properly.
Check the inguard power supplies on the Main PCA with and without the A/D Converter
PCA connected. The inguard supplies must be measured with respect to COM testpoint
A1TP30.
Power Supply
Test Location
Acceptable Range
VDD
VSS
VDDR
A1TP31
A1TP32
A1C6+
5.00 to 5.70V dc
-5.10 to -5.75V dc
5.30 to 5.95V dc
5A-11
HYDRA
Service Manual
Table 5A-3. Power Supply Troubleshooting Guide (2635A)
Symptom
5A-12
Fault
Line fuse blows.
- Shorted A1CR2 or A1CR3.
- Shorted A1CR10.
- Shorted A1C7.
- Shorted A1C26.
Supply voltage for A1U23 and A1U22 is greater than
7V (7 to 30V).
Input-to-output short of A1U19. This fault may have
caused damage to A1Q7 and A1Q8.
VCC (5.1V) supply is at the raw supply level (7.5 to
35V dc).
Shorted switch transistor in A1U9 (A1U9-5 to 7).
Open A1C26 can cause switch transistor to short.
VCC (5.1V) supply shows excessive ripple (about
1V p-p).
A1C14 open.
VCC is below approximately 4.5V. Duty cycle of 5V
switcher supply is very low (ON time near 0.1).
Drain-to-source short of A1Q7 or A1Q8.
VCC is about 1.5V. 5V switcher supply is in current
limit.
Shorted A1CR5 or A1CR6.
VCC is below approximately 1V. 5V switcher supply
is in current limit, with very low duty cycle (ON time
near 0.1).
Shorted A1C14.
VCC is below approximately 4.5V. 5V switcher
supply is in current limit, with very low duty cycle
(ON time near 0.1).
- Q or Q* output of A1U22 stuck high.
- A1U23 pin 8 output stuck high or low.
- Shorted A1CR7
- Shorted A1CR9 (either diode), pins 1-3 or 2-3.
- Shorted A1C30. A1CR13 may also be damaged.
- Shorted A1C31. A1CR13 may also be damaged.
- Shorted A1C12.
- Shorted A1C13.
- Shorted A1CR8 (either diode), pins 1-3 or 2-3.
VLOAD (-30V dc) Inverter Supply is at -36V.
Q output of A1U22 stuck low.
VLOAD (-30V dc) Inverter Supply is OFF.
Q* output of A1U22 stuck low.
VLOAD (-30V dc) Inverter Supply ripple.
- Open A1CR8 (either diode).
- Open A1CR9 (either diode).
VDD (5.3V dc) supply at approximately 9.2V.
Emitter-to-collector short of A1Q2.
VSS (-5.4V dc) supply at approximately -9.2V.
Emitter-to-collector short of A1Q5.
VDDR (5.6V dc) supply at approximately 10V.
Input-to-output short of A1U6.
VDDR supply has 4-to-5 volt spikes when the A/D
relays are switched (set or reset).
Open A1C12.
VEE (-5V dc) supply is low (near zero).
- Open A1C30.
- A1CR13 open.
A1CR13, Diode 1-3 shorted or open.
A1C30 may be shorted.
VEE supply is high (near -9V).
Input-to-Output short of A1U18.
A1U18 input has large square wave component.
Open A1C31.
Diagnostic Testing and Troubleshooting (2635A)
Analog Troubleshooting
5A
Table 5A-3. Power Supply Troubleshooting Guide (2635A) (cont)
Symptom
Fault
A1U18 hot.
Shorted A1C32
A1U18 oscillates.
Open A1C32.
A1U19 oscillates.
Open A1C34.
A1U19 very hot.
- Shorted A1U22 (VCC to VSS).
- Shorted A1U23 (VCC to VSS).
A1U19 hot.
Shorted A1C34.
Check the inguard supply voltages on the A/D Converter PCA with respect to A3TP9.
The following table lists the components nearest the power supply test points.
Power Supply
Nearest Component
Acceptable Range
5.00 to 5.70V dc
-5.10 to -5.75V dc
5.30 to 5.95V dc
4.7 to 5.7V dc
-4.8 to -5.7V dc
A3C8
A3C9
A3C19
A3CR1
A3C26
VDD
VSS
VDDR
+VAC
-VAC
Check that the inguard Microcontroller A3U9 RESET* line is de-asserted. Check VDD
at A3TP1, referenced to A3TP9.
Check that the microcontroller crystal oscillator is running. When measured with a high
input impedance oscilloscope or timer/counter, the oscillator output at A3TP10 should
be a 3.6864-MHz sine wave (271.3 ns period), and the divided-down E clock output at
A3U9 pin 68 should be a 921.6 kHz-square wave (1.085 µs period).
Check outguard to inguard communication. Setup an input channel and enable monitor
measurements on that channel, causing the outguard to transmit to the inguard
approximately every 10 seconds.
On the Main PCA, look for outguard-to-inguard communication (5.0V (VCC) to near 0V
pulses) at A1TP15, referenced to A1TP1. On the A/D Converter PCA, check for 5.35V
(VDD) to near 0V pulses at A3TP8, referenced to A3TP9.
At the start of outguard-to-inguard communication, the A/D Microcontroller (A3U9)
should be RESET. Check for this reset pulse (5.35V (VDD) to near 0V, lasting
approximately 1 millisecond) on A3TP1 with respect to A3TP9.
Check for the following inguard-to-outguard communication activity:
PCA
Test Point
To
Pulses
A/D Converter
Main
A3TP7
A1TP8
A3TP9
A1TP1
5.55V (VDDR) to 0.7V
5.0V dc (VCC) to 0.0V
5A-13
HYDRA
Service Manual
A3TP2
A3TP8
A3TP7
A3TP4
A3TP1
RMS Converter
Network
A3TP3
A/D Microcontroller
A3TP5
A3TP13
A3TP6
A3TP10
A3TP11
RMS Converter
A3TP12
A3TP9
AC Buffer
Analog
Measurement
Processor
Zener Reference
ZERO
K3S
K3R
K7S
K7R
K14S
K14R
VDD
RESET
VDD
VDD
Intergrate Resistors, Reference Divider
Divider
Network
(DC/OHMS)
P20
P21
P22
P23/RX
P24/TX
P25
P26
P27
NC
P50/IRQ1*
P51/IRQ2*
P52
P53
P54
P55
P56
P57
P32
P33
P34
P35
P36
P37
NC
P10
P11
P12
P13
P14
P15
P16
P17
VSS
P40
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
K13S
K13R
K6S
K6R
K5S
K5R
K12S
K12R
K1S
K1R
K2S
K2R
K11S
K11R
RELAY
DRIVERS
K10S
OTCEN
OTC
K8R
K8S
K9R
K9S
K10R
K16R
K16S
K17R
K17S
K15R
K15S
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
IRQ1*
FC7
CS
RIRQ1*
FC0
FC1
FC2
FC3
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
P60
P61
P62
P63
P64
P65
P66
P67
NC
VCC
P47
P46
P45
P44
P43
P42
P41
A3U9
MICROCONTROLLER
DRX
DTX
CLK
IGRX
IGTX
AR
OTCCLK
AS
NMI*
STBY*
RES*
MP1
MP0
EXTAL
XTAL
VSS
NC
E
P70
P71
P72
P73
P74
P30
P31
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
61
AC Divider
Network
s46c.eps
Figure 5A-4. Test Points, A/D Converter PCA (A3, A3U8) (2635A)
5A-14
Diagnostic Testing and Troubleshooting (2635A)
Analog Troubleshooting
5A
A3TP2
A3TP8
A3TP7
A3TP1
RMS Converter
Network
A3TP13
A3TP3
A3TP4
A/D Microcontroller
A3TP5
A3TP6
A3TP10
A3TP11
RMS Converter
A3TP12
A3TP9
AC Buffer
Analog
Measurement
Processor
VSSAC
ACR1
ACR2
ACR3
ACR4
AGND2
AIN
ACB0
VDD
RMSI
RMSG1
VSSRMS
BIAS2
RMS0
RMSC2
ARTN
RMSF
9
8
7
6
5
4
3
2
1
68
67
66
65
64
63
62
61
Divider
Network
(DC/OHMS)
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
FA0
FAI
AFI
MOF
AF0
RA–
RA+
RA0
VREF–
VREF+
B3
B1
B.3
B.1
SUM
INT
VSS
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
A3U8 ANALOG
MEASUREMENT
PROCESSOR
REFJ
LO
GUARD
RRS
V4
V3
V1
GUARD
V2F
V2
GUARD
V0
GUARD
0/VS
GUARD
AGND1
DGND
FC0
FC1
FC2
FC3
FC4
FC5
FC6
FC7
OSCIN
OSC0
MRST
AS
AR
SK
CS
BRS
AC Divider
Network
Zener Reference
Intergrate Resistors, Reference Divider
s47c.eps
Figure 5A-5. Test Points, A/D Converter PCA (A3U9) (2635A)
5A-15
HYDRA
Service Manual
Lack of outguard-to-inguard communication activity may be due to improper operation
of circuit elements other than A3U9. Using a high input impedance oscilloscope or
timer/counter, check for proper Analog Processor (A3U8) crystal oscillator operation. A
3.84-MHz sine wave (260 ns period) should be present at A3U8 pin 37 with respect to
A3TP9.
Check the A/D Converter voltage reference:
A3TP12 to A3TP11 (across A3C12) = +1.05V (+0.10V, -0.02V)
Setup the instrument to measure ohms on the 300Ω range. Monitor ohms on a channel
with an input of approximately 270Ω. Check that the Analog Processor IC (A3U8) is
making A/D conversions. The integrator output waveform at A3TP13 (referenced to
A3TP9) should resemble the waveform shown in Figure 5A-6.
A3TP13 TO A3TP9
0
1V/DIV
5 mS/DIV
s48f.eps
Figure 5A-6. Integrator Output (2635A)
Check for channel relay operation by setting up a channel and selecting and de-selecting
monitor measurement mode. One or more relays should click each time the monitor
button is pressed or channels are changed.
In general, check that the relays are getting the proper drive pulse signals for specific
functions and channels and that they are in the correct position.
5A-11.
DC Volts Troubleshooting
Setup the instrument to measure a specific channel on the 300 mV or 3V range, and
apply an input to that channel. Then trace the HI signal (referenced to the input channel
LO terminal) as described in Table 5A-4.
If the input HI path traces out properly, remove the input from the channel and trace
continuity through the LO path. Check among A3L4-A3L24, A3K1-A3K14, A3R35,
A3R43, and A3U8 pin 11.
5A-16
Diagnostic Testing and Troubleshooting (2635A)
Analog Troubleshooting
5A
Table 5A-4. DC Volts HI Troubleshooting (2635A)
Checkpoint
Signal Description
Possible Fault
A3R11 HI
Input
A3K1 through A3K14, A3U4, A3U5, A3U11, A3U12,
A3L1, A3L2, A3L3
A3U8 pin 23
Input
A3R11, A3K17, A3R42, A3C32
A3U8 pin 58
Input, DC filter output
A3U8, A3Q2
5A-12.
AC Volts Troubleshooting
Setup the instrument to measure a channel on the 300 mV ac range, and apply a signal to
that channel. Then trace this HI signal (referenced to the input channel LO terminal) as
described in Table 5A-5.
If the input HI path traces out properly, remove the input from the channel, and trace
continuity through the LO path. Check among A3L4 through A3L24, A3K1 through
A3K14, A3R43, A3R34, A3K16, and A3U8 pin 13.
Table 5A-5. AC Volts HI Troubleshooting (2635A)
Checkpoint
Signal Description
Possible Fault
A3R11 HI
Input
A3K1 through A3K14, A3U4, A3U5, A3U11, A3U12
A3L1, A3L2, A3L3
A3Z3 pin 1
Input
A3R11, A3C31, A3K15
A3U6 pin 13
Amplified (X 2.5) input
A3U7, A3Z3, A3Q3 through A3Q9, A3C15, A3C16,
A3R24, A3A25, A3R26, A3R27, A3R28, A3C23,
A3U6, A3Q13, A3U8
A3Z1 pin 2
DC equivalent of original input
A3Z1, A3U8, A3R20, A3C6, A3C7, A3C10, A3R16,
A3R17
A3U8 pin 61
DC equivalent of original input
A3Z1, A3U8, A3R20, A3C6, A3C7, A3C10, A3R16,
A3R17
5A-13.
Ohms Troubleshooting
Setup a channel with an open input for the desired ohms range and place the instrument
in monitor mode on that channel. Use a meter with high input impedance to measure the
open-circuit voltage at the channel input for the ohms range as listed in Table 5A-6. If a
high input impedance meter is not available, only the 30-kΩ and lower ranges can be
checked.
If the proper voltage is not measured, setup a channel on the 300Ω range (open input),
and have the instrument monitor that channel. Check for 3V dc with respect to A3TP9,
and work through the HI SOURCE and HI SENSE paths as described in Table 5A-7.
If the HI path works correctly, trace continuity through the LO path. Check among A3L4
through A3L24, A3K1 through A3K14, A3R35, A3U8 pin 11, A3R43, A3K16, A3R34,
and A3U8 pin 13.
5A-17
HYDRA
Service Manual
Table 5A-6. Ohms Open-Circuit Voltage (2635A)
Range
Voltage
3V
1.3V
1.3V
3V
3V
3V
300Ω
3 kΩ
30 kΩ
300 kΩ
3 MΩ
10 MΩ
Table 5A-7. Ohms HI Troubleshooting (2635A)
Checkpoint
Signal Description
Possible Fault
A3U8 pin 14
Ohms Source
A3U8
A3R10 HI SRC
Ohms Source
A3R10, A3K16, A3RT1, A3Z4, A3Q10
Channel HI
Ohms Source
A3K1 through A3K14, A3U4, A3U5, A3U11, A3U12, A3L1,
A3L2, A3L3
A3U8 pin 23
Ohms Source
A3R11, A3K17, A3R42, A3C32
A3U8 pin 58
Ohms Source filter output
A3U8, A3Q2
5A-14. Digital Kernel Troubleshooting
At power-up, if the display does not light or lights up and fails to report errors or begin
operation, use the following troubleshooting procedures.
To determine the relative health of the MC68302 Microprocessor (A1U1), first check for
a valid system clock (SCLK) at TP11. Use an oscilloscope to check for the SCLK clock
at A1TP11. Look for a 12.288-MHz square wave that transitions from 0 to 5V dc (VCC).
•
If this signal is present, check for a similar waveform at pinA1U25-30 of the FPGA.
If a 12.288-MHz square wave is not presentthere, resistor A1R107 is probably bad.
•
If the SCLK signal (A1TP11) is something other than a 12.288-MHzsquare wave, it
is most likely that the problem is related to thecrystal oscillator circuit (A1U1,
A1Y1, A1C3, A1C8, or A1R2).
If the SCLK signal is good, check the Display Clock (DCLK) output from A1U25-19.
DCLK should have a frequency of 1.024-MHz (period of 976 nanoseconds). The DCLK
signal is not symmetrical; use an oscilloscope to verify that it is high for about 325
nanoseconds and then low for about 651 nanoseconds. The operation of the Display
assembly depends on the DCLK signal. Missing segments, intensified digits, a strobing
display, or a blank display can be caused by a faulty DCLK clock.
5A-18
•
If the DCLK signal (A1U25-19) is not present but the SCLK signal iscorrect at
A1U25-30, the problem may be that A1U25 was notconfigured correctly at powerup or A1U25 is defective.
•
If the OCLK signal (A1U25-22) is a 3.072-MHz square wave but the DCLKsignal is
wrong, A1U25 must be defective.
Diagnostic Testing and Troubleshooting (2635A)
Digital Kernel Troubleshooting
5A
During instrument power-up, the RESET* and HALT* signals are held low for 140 to
280 milliseconds after the VCC power supply is greater than 4.65 volts dc. Before the
Microprocessor can begin execution of the firmware stored in the Flash Memory, the
reset circuit must release the RESET* and HALT* signals (A1U2-11 and A1U2-8
respectively) and allow them to go high. Verification of the operation of the RESET*
and HALT* signals is best done by using a storage oscilloscope.
After the Microprocessor has begun execution of the instructions stored in Flash
Memory (A1U14 and A1U16), the Microprocessor may drive the HALT* signal (A1U191) low if the instructions executed are not correct. Another sign of incorrect instruction
execution is the Bus Error signal (BERR*;A1U1-94) going low to indicate that an access
to an unused area of memory space was done. To troubleshoot these problems, use an
oscilloscope to check the activity of the address, data, and control signals to the Flash
Memory devices (A1U14 and A1U16). It may also be useful to check signal continuity
by using a DMM with the instrument power off.
To check the Flash Memory control signals, verify that A1U1-128 is going low and is
also appearing on pins A1U14-22 and A1U16-22 of the Flash Memory devices. It may
be necessary to continually reset (power on) the instrument to check these lines, since
the activity probably halts quickly when the instrument software goes awry. Verify that
RDU* (A1U11-14 and A1U14-24) goes low when A1U1-128 is low. Verify that RDL*
(A1U11-19 and A1U16-24) goes low when A1U1-128 is low. If all this is true, the
problem is with the Flash Memory or there is a fault in the address/data lines from the
MC68302 Microprocessor.
Verify that the XINIT* output (A1U25-65) goes high after RESET* goes high. Verify
that the mode pins and extra chip select input on the FPGA (A1U25) are properly
connected to VCC and GND. Pins 6, 29, 54, and 56 must be about 5 volts dc. Pins 52 and
93 must be near 0 volts dc. If the Microprocessor is able to correctly fetch instructions
from the Flash Memory, the Microprocessor tries to program the FPGA.
Address decoding for I/O devices like the FPGA is done by A1U11. Verify that the
PGA* output (A1U11-12) goes low when the Microprocessor attempts to access the
FPGA. Verify the address and I/O* inputs to A1-U11 (pins 2 through 8) according to the
decoding shown in the following table.
Output
A<12>
A<11>
A<10>
A<9>
A<8>
A<7>
I/O*
PGA* (A1U11-12)
RTC* (A1U11-16)
OPTE* (A1U11-12)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
0
Programming of the FPGA is initiated by the Microprocessor by driving the XD/P*
(A1U25-80) and RESET* (A1U25-78) signals low simultaneously. RESET* is pulsed
low by the Microprocessor for approximately 10 microseconds. The Microprocessor then
waits for XINIT* (A1U25-65) to go high; if this doesn’t happen, the Watchdog Timer in
the Microprocessor will reset the instrument after several seconds by driving POR*
(A1U1-117) low. Verify that the Microprocessor waits until XRDY (A1U25-99) is high
before writing each byte to the FPGA. (A1U25-88 and A1U25-5 both go low during the
write cycle.) Check the XD/P* signal (A1U25-80) at the end of the FPGA programming;
if it doesn’t go high, the Microprocessor will repeat the FPGA programming sequence
until it works correctly or the Watchdog Timer in the Microprocessor resets the
instrument by driving POR* (A1U1-117) low. If FPGA programming is failing, check
the D<8> through D<15>, PGA*, WRU*, XINIT*, XRDY, XD/P*, and RESET* signals
for activity with an oscilloscope. It may also be necessary to check the continuity of
these signals with a DMM when the instrument power is off.
5A-19
HYDRA
Service Manual
If the instrument powers up and displays ’boot,’ it is likely that one of the memory test
errors (Errors 1 through 3) was detected. To determine what the error status was, connect
a terminal or computer to the RS-232 interface (19200 baud, 8 data bits, no parity).
Assuming that the RS-232 interface is functional, send a carriage return or line feed
character to the instrument, and it should send back a prompt that shows a number
followed by a ’>’ character. The number is interpreted in the same way as the responses
for the *TST?and POWERUP? commands; refer to *TST? in Section 4 of the Hydra
Data Bucket Users Manual. For example, a ’4>’ prompt indicates that the test of the
NVRAM (A1U20 and A1U24) failed and the instrument was not able to safely power-up
and operate.
Now send a ’t’ character followed by a carriage return to the instrument to request a retest
of the firmware stored in Flash Memory. If both the boot firmware and the instrument
firmware checksums are correct, the response will be as follows:
Boot image OK
Hydra image OK
0>
If the boot firmware checksum is not correct, the message "Bad boot image -- use at own
risk!" might be seen. The code that must be executed to generate this message is part of
the boot firmware that is bad, so there is no guarantee that this message will be seen.
If the instrument firmware checksum is not correct, one of the following error messages
may be seen:
Bad rom pointer
"Invalid pointer to checksum structure"
Bad checksum pointer
"Invalid pointer to instrument checksum"
Bad checksum
"Incorrect instrument checksum"
Invalid instrument firmware may be corrected by using a personal computer to load new
instrument firmware into the Hydra Databucket. To do this see the section entitled
"Updating the 2635A Instrument Firmware" in Section 4 of this manual.
If the NVRAM (A1U20 and A1U24) do not operate correctly, the problem must be
corrected before new instrument firmware may be loaded or the instrument can power up
completely. Use an oscilloscope to check the activity of the address, data, and control
signals to the NVRAM devices (A1U14 and A1U16). It may be necessary to continually
reset (power on) the instrument to check these lines, since the activity probably halts
quickly when the instrument software goes awry. To check the NVRAM control signals,
verify that A1U1-127 is going low, propogating through A1U26, and also appearing on
pins A1U20-22 and A1U24-22 of the NVRAM devices. Verify that RDU* (A1U11-14
and A1U24-24) goes low when A1U1-127 is low. Verify that RDL* (A1U11-19 and
A1U20-24) goes low when A1U1-127 is low. If all this is true, the problem is with the
NVRAM itself or there is a fault in the address/data lines from the MC68302
Microprocessor. It may also be useful to check signal continuity by using a DMM with
the instrument power off. Verify also that pin 30 on A1U24 and A1U20 is pulled up to
approximately 5.0 volts dc by resistor A1R45.
5A-20
Diagnostic Testing and Troubleshooting (2635A)
Digital and Alarm Output Troubleshooting
5A
Figure 5A-7 shows the timing relationships of the MC68302 Microprocessor address,
data, and memory control signals used for memory read and write cycles. The chip
selects from the Microprocessor (FLASH*, SRAM*, XMCARD*, and I/O*) are decoded
internally from the address bus and the address strobe (AS*) signal. Therefore the AS*
waveform is the same as the chip select signal for the device that the Microprocessor is
accessing.
If the instrument powers up without any errors, but does not recognize front-panel button
presses, the problem may be in the Keyboard Interrupt (KINT*) signal from the FPGA.
If the KINT* output (A1U25-62) is low (and never goes high), the Microprocessor
(A1U1) is failing to recognize the interrupt, or the microprocessor interface to A1U25 is
not working correctly. Verify that the KINT* signal gets to the input pin (A1U1-121) on
the Microprocessor.
If the interval time does not count down properly when scanning is enabled, the problem
may be in the Real-Time Clock Interrupt (CINT*) signal from the Real-Time Clock
(A1U12). If the CINT* output (A1U12-3) is low (and never goes high), the
Microprocessor (A1U1) is failing to recognize the interrupt or the microprocessor
interface to A1U12 is not working correctly. Verify that the CINT* signal gets to the
input pin (A1U1-96) on the Microprocessor. Also verify that the Real-Time Clock is
actively keeping time by checking for a 1-Hz square wave output on A1U12-4. Pin
A1U12-2 must also be properly connected to GND for the Real-Time Clock to operate.
The interface to the Microprocessor operates very much like the interface to NVRAM
device A1U20.
5A-15. Digital and Alarm Output Troubleshooting
Power up Hydra while holding down the CANCL button to reset the instrument
configuration. Since the structure of the eight Digital Outputs and four Alarm Outputs is
very similar, the troubleshooting procedure presented here does not refer to specific
device and pin numbers. First verify that the input of the Output Driver (A1U17 or
A1U27) is low and that the output is near +5V dc. If the input is high, the problem may
be in the FPGA (A1U25). If the output is not near +5V dc, use an ohmmeter to check the
pull-up resistor in A1Z2.
Use the proper computer interface command to change the state of the Digital Output
(DO_LEVEL x,1) or Alarm Output (ALARM_DO_LEVEL x,1), where x is the number
of the output being checked. Now verify that the input of the Output Driver is high and
that the output is near +0.8V dc. If there is no change in the input, check the address
signals to the FPGA (A1U25-85, A1U25-90, A1U25-96, A1U25-97) and the behavior of
the output pin on the FPGA that goes to the input of the Output Driver (A1U17 or
A1U27). If the output of the Output Driver fails to change when the input does, the
problem is most likely the inverting output driver (A1U17 or A1U27).
5A-16. Digital Input Troubleshooting
Power up Hydra while holding down the CANCL button to reset the instrument
configuration. Verify that the Input Buffer Threshold circuit generates approximately
1.4V dc at A1TP18. Drive the Digital Input (A1J5) to be checked with a signal generator
outputting a 100-Hz square wave that transitions from 0 to +5V dc. The signal generator
output common should be connected to Common (A1J5-1). Verify that the output of the
Input Buffer is a 100-Hz square wave that is the inverse of the input signal.
5A-21
HYDRA
Service Manual
S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 W W W W S5 S6 S7
CLK
A1 – A23
AS
UDS
LDS
R/W
DTACK
D8 – D15
D0 – D7
READ
WRITE
SLOW READ
READ AND WRITE CYCLE TIMING DIAGRAM
S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 S5 S6 S7
CLK
A1 – A23
A0*
AS
UDS
LDS
R/W
DTACK
D8 – D15
D0 – D7
WORD READ
ODD BYTE READ
EVEN BYTE READ
*INTERNAL SIGNAL ONLY
WORD AND BYTE READ CYCLE TIMING DIAGRAM
S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 S5 S6 S7 S0 S1 S2 S3 S4 S5 S6 S7
CLK
A1 – A23
A0*
AS
UDS
LDS
R/W
DTACK
D8 – D15
D0 – D7
WORD WRITE
ODD BYTE WRITE
EVEN BYTE WRITE
*INTERNAL SIGNAL ONLY
WORD AND BYTE WRITE CYCLE TIMING DIAGRAM
s49f.eps
Figure 5A-7. Microprocessor Timing (2635A)
5A-22
Diagnostic Testing and Troubleshooting (2635A)
Totalizer Troubleshooting
5A
If the Input Buffer does not function correctly, the problem is probably A1Z1, A1Z3, or
the associated comparator (A1U3 or A1U4). If the Input Buffer functions correctly, but
Hydra is not able to read the state of the Digital Input correctly, the problem is most
likely the FPGA (A1U25). If Hydra is not able to read the states of any of the eight
Digital Inputs correctly, the problem is most likely in the address signals going to the
FPGA (A1U25-85, A1U25-90, A1U25-96, A1U25-97).
5A-17. Totalizer Troubleshooting
Power up Hydra while holding down the CANCL button to reset the instrument
configuration. Verify that the Input Buffer Threshold circuit generates approximately
1.4V dc at A1TP18. Drive the Totalizer Input (A1J5-2) with a signal generator
outputting a 100-Hz square wave that transitions from 0 to +5V dc. The signal generator
output common should be connected to Common (A1J5-1). Verify that the output of the
Input Buffer (A1U8-1) is a 100-Hz square wave that is the inverse of the input signal.
Verify also that the input to the totalizer counter (A1TP20) is a buffered form of the
signal just verified at the output of the Input Buffer.
Use the following procedure to troubleshoot the totalizer input debouncer, Enable the
totalizer debouncer by sending the TOTAL_DBNC 1 Computer Interface command to
the instrument. With the signal generator still connected and outputting a 100-Hz square
wave, verify that the waveform at the input to the totalizer counter (A1TP20) is delayed
by 1.75 milliseconds from the waveform at A1U8-1.
5A-18. Display Assembly Troubleshooting.
The following discussion is helpful if it has been determined that the Display Assembly
is faulty. Refer to Figure 5A-8 for Display PCA test points. This initial determination
may not be arrived at easily, since an improperly operating display may be the result of a
hardware or software problem that is not a direct functional part of the Display
Assembly. Consult the General Troubleshooting Procedures found earlier in this section
for procedures to isolate the fault to the Display Assembly. Use the following discussion
of display software operation when troubleshooting problems within a known faulty
Display Assembly. A Display Extender Cable (PN 867952) is available for use during
troubleshooting. Note that this cable must be twisted to mate correctly to the connectors
on Display and Main PCAs.
The Display Controller reads the DTEST* and LTE* inputs to determine how to
initialize the display memory. DTEST* (A2TP4) and LTE* (A2TP5) default to logic 1
and logic 0, respectively, to cause all display segments to be initialized to "on."Either
test point can be jumpered to VCC (A2TP6) or GND (A2TP3) to select other display
initialization patterns. Display Test Patterns #1 and #2 are a mixture of "on" and "off"
segments with a recognizable pattern to aid in troubleshooting problems involving
individual display segments. When either of the special display patterns is selected, the
beeper is also sounded for testing without interaction with the Microprocessor. Table
5A-8 indicates the display initialization possibilities.
Figure 5A-9 shows the timing of communications between the Microprocessor and the
Display Controller. Figures 5A-10 and 5A-11 show Display Test Patterns #1 and #2,
respectively. Refer to the Display Assembly schematic diagram in Section 8 for
information on grid and anode assignments.
When a Hydra display is initially powered up, all display segments should come on
automatically. If this display does not appear, proceed with the following steps:
5A-23
HYDRA
Service Manual
A2TP2
A2TP3
A2TP6
A2TP1
1 2
A2TP5
A2TP4
(S21)
(S1)
(S3)
(S5)
(S7)
(S9)
(S11)
(S13)
(S15)
(S17)
(S2)
(S4)
(S6)
(S8)
(S10)
(S12)
(S14)
(S16)
(S18)
A2TP2
A2TP3
A2TP6
A2TP1
+
A2TP5
LS1
U1
A2TP4
J1
TEST POINT LOCATIONS
(DISPLAY PCA)
s50f.eps
Figure 5A-8. Test Points, Display PCA (A2) (2635A)
5A-24
Diagnostic Testing and Troubleshooting (2635A)
Display Assembly Troubleshooting.
5A
Table 5A-8. Display Initialization (2635A)
A2TP4 DTEST*
A2TP5 LTE*
1
1
0
0
1
0
1
0
POWER-UP DISPLAY INITIALIZATION
All Segments OFF
All Segments ON (default)
Display Test Pattern #1
Display Test Pattern #2
DSCLK
DISTX
BIT 7
DISRX
BIT 7
BIT 6
BIT 6
BIT 5
BIT 5
BIT 4
BIT 4
BIT 3
BIT 3
BIT 2
BIT 2
BIT 1
BIT 1
CLEAR TO
RECEIVE
BIT 0
BIT 0
CLEAR TO
RECEIVE
HOLD OFF
31.5 µs
31.5 µs
s54f.eps
Figure 5A-9. Display Controller to Microprocessor Signals (2635A)
REM SCAN
REVIEW
SET FUNC
mV
x1 k Ω
1
EXT TR
s51f.eps
Figure 5A-10. Display Test Pattern #1 (2635A)
LAST
MAX
MIN
F
AUTO MON
Mx+B ALARM
°C °F RO
AC DC
Hz
M
LIMIT HI OFF PRN CH
2 LO CAL
s52f.eps
Figure 5A-11. Display Test Pattern #2 (2635A)
Note
If the display is operational but has problems whenfront-panel buttons are
pressed, proceed directlyto step 9.
1. Check the three power supplies with respect to GND (A2TP3 or A2U1-42) on the
Display Assembly.
VCC (A2U1-21)
VEE (A2U1-4)
VLOAD A2U1-5)
4.75 to 5.25V dc
-4.75 to -5.25V dc
-28.5 to -32.0V dc
5A-25
HYDRA
Service Manual
2. Check the filament drive signals FIL1 and FIL2; these connect to the last two pins
on each end of A2DS1. These signals should be 5.4V ac with FIL2 biased to be
about 6.8V dc higher than the VLOAD supply (nominally a -23.2V dc level). FIL1
and FIL2 should be 180 degrees out of phase. If the dc bias of FIL2 is not at about 23.2V dc, the display segments that should be "off" will show a shadowing (or
speckling) effect.
3. Check the clock signal CLK1 at A2TP2, A2U1-2, and A2U4-3. This signal should
be a 512-kHz square wave (1.953 microseconds per cycle). This signal depends on
an E clock signal (also known as DCLK) of 1.024 MHz from the Main Assembly. If
the E clock is not correct, the problem may be in A1U25 or in the ribbon cable
system connecting the two assemblies.
4. Check the state of the RESET signal (A2U1-1). This signal should be low once the
reset time is completed (after power-up). Also verify that the RESET* signal
(A2U6-3) is high after the reset time is completed.
5. Verify that the DISRX signal (A2U1-39) goes low after RESET (A2U1-1) goes low.
If this sequence does not occur, communication to the Microprocessor is held off
with the DISRX signal high. If DISRX stays high but is not shorted to VCC, A2U1
must be faulty.
6. Verify activity for both the DISTX and DSCLK signals. These signals are driven by
the Microprocessor and must be transitioning for the Display Controller to receive
commands from the Microprocessor.
7. If all segments of a particular digit do not turn on at power-up, the grid drive from
A2U1 may not be connected properly to A2DS1. Grids are numbered from 10 to 0
(left to right as the display is viewed). For a digit to be enabled, the respective grid
drive signals (GRID(10:0)) must be at approximately VCC (4.75 to 5.25V dc.) For a
digit to be disabled, the drive must be at VLOAD (-28.5 to -32.0V dc.)
8. If a segment under each of several (or all) grids fails to be turned on (or off)
properly, one of the anode drive signals may not be connected properly from A2U1
to A2DS1. When an anode signal is at VCC, and a grid signal is at VCC, the
corresponding segment on the display is illuminated.
9. If the Microprocessor has difficulty recognizing front-panel button presses, the
switch scanning signals SWR1 through SWR6 should be checked (A1U25-67,
A1U25-68, A1U25-71, A1U25-73, A1U25-70, and A1U25-69 respectively). When
no switch contacts are being closed, the switch scanning lines should have about 20kΩ of resistance between each other (through two 10-kΩ pullup resistors to VCC).
Unless one of the switches is closed, none of the switch scanning lines should be
shorted directly to GND at any time.
5A-19. Variations in the Display
Under normal operation, the display presents various combinations of brightly and dimly
lit annunciators and digits. However, you may encounter other, random irregularities
across different areas of the display under the following circumstances:
•
After prolonged periods of displaying the same information.
•
If the display has not been used for a prolonged period.
This phenomenon can be cleared by activating the entire display and leaving it on
overnight (or at least for several hours). Use the following procedure to keep the display
fully lit:
1. With power OFF, press and hold SHIFT, then press power ON.
5A-26
Diagnostic Testing and Troubleshooting (2635A)
Calibration Failures
5A
2. Wait a moment for the instrument to beep, then release SHIFT. The entire display
will now stay on until you are ready to deactivate it.
3. At the end of the activation period, press any button on the front panel; the
instrument resumes the mode in effect prior to the power interruption (Active or
Inactive.)
5A-20. Calibration Failures
5A-21.
Introduction
Calibration of Hydra through the computer interface is described in Section 4 of this
manual. Generally, a calibration failure is indicated by a Device Dependent Error and a
"!>" prompt after a CAL_STEP? command if the RS-232 interface is being used. This
occurs if the analog input varies from what the instrument expects to see by more than
±5% or ±15%, depending on the calibration step.
Before suspecting a fault with Hydra, verify that the calibration is being conducted
properly.
•
Check the connections between the source and the instrument. Are allthe
connections in place?
•
Check the output of the calibration source. Does it equal the valuecalled for by this
calibration step?
•
Check the calibration source. Is it in operate mode? Has it revertedto standby?
If a calibration step has failed, Hydra remains on that step so that the output from the
calibration source may be corrected or the calibration reference value (CAL_REF) being
used by Hydra may be changed if it was improperly entered. The calibration step may be
repeated by sending the CAL_STEP? command to Hydra again.
Calibration of Hydra utilizes a simple "calibration by function" approach. If you suspect
calibration errors, but the instrument does not exhibit the symptoms mentioned above,
verify that you are observing the following calibration rules:
•
Independent calibration of any function results in the storage ofcalibration constants
for that function only.
•
Once calibration is begun, all steps for that function must becompleted before the
calibration constants are stored. If all stepsare not completed and the procedure is
terminated, no constants forthat function are stored; only calibration constants for
previouslycompleted functions are stored.
5A-22.
Calibration-Related Components
If the calibration setup is correct, a faulty component within Hydra may be causing the
failure. Each measurement function depends on a combination of components in and
around the Analog Measurement Processor (A3U8).
RMS Converter
A3U6
AC Buffer
A3U7
Zener Reference
A3VR1
Divider Network (DC/Ohms)
A3Z4
Integrate Resistors, Reference Divider
A3Z2
AC Divider Network
A3Z3
RMS Converter Network
A3Z1
5A-27
HYDRA
Service Manual
Basic dc measurements depend on the zener reference (A3VR1), reference divider
network (A3Z2), and integrate resistors (A3Z2). Resistance measurements and dc
measurements above three volts additionally depend on the resistors in the dc divider
network (A3Z4). AC measurements depend on the ac divider network (A3Z3), ac buffer
(A3U7), and RMS converter (A3U6), as well as the basic dc measurement components.
Note
During calibration, the measurement rateis selected automatically as
required by thecalibration step.
Table 5A-9 may be useful in isolating a calibration problem to specific components.
Table 5A-9. Calibration Faults (for software versions 5.4 and above) (2635A)
Input
Calibration Constant
Range
Number
Related Components
Acceptable Values
DC Volts
0.09000V
0.9000V
0.29000V
2.9000V
29.000V
290.00V
100 mV
1V
300 mV
3V
30V
300V
1
2
3
4
5
6
1.0315 to 1.1565
1.0340 to 1.1540
1.0315 to 1.1565
1.0315 to 1.1565
1.0340 to 1.1640
1.0290 to 1.1590
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2
A3VR1, A3Z2, A3Z4
A3VR1, A3Z2, A3Z4
AC Volts (1 kHz)
0.02900V
0.29000V
0.2900V
2.9000V
2.900V
29.000V
29.00V
290.00V
300 mV
300 mV
3V
3V
30V
30V
300V
300V
7
8
9
10
11
12
13
14
-0.001 to 0.001
1.0040 to 1.1840
-0.01 to 0.01
1.0040 to 1.1840
-0.1 to 0.1
1.0040 to 1.1840
-1.0 to 1.0
1.0040 to 1.1840
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
A3U6, A3VR1, A3Z1, A3Z2, A3Z3
Ohms
290.00Ω
2.9000 kΩ
29.000 kΩ
290.00 kΩ
2.9000 MΩ
2.9000 MΩ
300Ω
3 kΩ
30 kΩ
300 kΩ
3 MΩ
10 MΩ
15
16
17
18
19
20
0.9965 to 1.0115
0.9975 to 1.0125
1.0015 to 1.0165
0.9965 to 1.0115
0.9990 to 1.0090
0.9990 to 1.0090
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
A3Z2, A3Z4
Frequency
10.000 kHz
2.9V rms
5A-28
21
0.9995 to 1.00050005
A3Y2
Diagnostic Testing and Troubleshooting (2635A)
Calibration Failures
5A-23.
5A
Retrieving Calibration Constants
If a calibration error is suspected, the stored constant can be retrieved and verified over
the computer interface. Acceptable calibration constants for each function and range are
listed in Table 5A-9. Retrieve the constant with the following command:
CAL_CONST? xx
(where xx denotes the calibration constant number)
The entire calibration of the Hydra Databucket can be retrieved from the instrument in
tabular form by using the following command:
EEM_LIST?
The instrument response from this command shows the currently used FLASH memory
block and page numbers, and each calibration constant in hexadecimal and floating point
with a description of what function and range each calibration constant is used on. The
following is a sample of a typical EEM_LIST? response:
Page 10 of Parameter Block 1 is currently in use.
Register Hex Value F.P. Value
Description
--------------------------------------------------------------0-1
0x3F8A847A1.
0821679100
Millivolt DC Gain
2-3
0x3F8A5D751.
08097711
Volt DC Gain
4-5
0x3F8A63571.
0811566300
Millivolt DC Gain
6-7
0x3F8A5BC01.
08092503
Volt DC Gain
8-9
0x3F8B4F571.
088358830
Volt DC Gain
10-11 0x3F8A7C8A1.
0819256150/300
Volt DC Gain
12-13 0xB8F20A00
-0.0001154300
Millivolt AC Offset
14-15 0x3F8A51191.
0805999300
Millivolt AC Gain
16-17 0xBA974800
-0.00115423
Volt AC Offset
18-19 0x3F8A7F291.
08200563
Volt AC Gain
20-21 0xBC3A6C00
-0.011378330
Volt AC Offset
22-23 0x3F8A863A1.
082221330
Volt AC Gain
24-25 0xBDE81400
-0.1133194150/300 Volt AC Offset
26-27 0x3F8AC8861.
0842445150/300
Volt AC Gain
28-29 0x3F808EAB1.
0043539
300 Ohm Gain
30-31 0x3F8097591.
0046188
3 Kilo Ohm Gain
32-33 0x3F80FD781.
0077353
30 Kilo Ohm Gain
34-35 0x3F7FF46C0.
9998233
300 Kilo Ohm Gain
36-37 0x3F7FFDD00.
9999666
3 Mega Ohm Gain
38-39 0x3F7FFDD00.
9999666
10/30 Mega Ohm Gain
40-41 0x3F80073D1.
0002209
Frequency Gain
42
0x000F
Calibration Status
43-44 0xAAAAAAAA
Product Serial Number
45
0xFFFF
Unused EEM Register #1
46
0xFFFF
Unused EEM Register #2
47
0xFFFF
Unused EEM Register #3
48
0x62F4
CRC of EEM Data (0x62F4)
5A-24.
Replacing the Flash Memory (A1U14 and A1U16)
The FLASH Memory provides nonvolatile storage for the instrument serial number, the
instrument firmware, and all calibration information. If the "boot" firmware in FLASH
memory has been determined to be faulty, A1U14 and A1U16 must both be replaced.
Many other problems may be corrected by loading new instrument firmware in the
instrument (see the section entitled "Updating the 2635A Instrument Firmware" in
Section 4 of this manual), or recalibrating the instrument.
If the FLASH Memories must be replaced during repair, the instrument must be
recalibrated. The new FLASH Memory can be programmed with the 7-digit serial
number found on the rear panel of the instrument or any 7-digit identifier of your
choosing. Note that the serial number is not programmed prior to shipment from the
factory.
5A-29
HYDRA
Service Manual
The following command may be used to program the serial number into the FLASH
Memory:
SERIAL XXXXXXX
(xxxxxxx denotes the 7-digit number. Leading zeros must be
entered. Note: once entered, the number cannot be changed.)
The serial number of the instrument can be accessed by using the “SERIAL?” command.
The response will be “0” )if the serial number has not yet been set) or the 7-digit serial
number.
5A-25. Memory Card I/F PCA (A6) Troubleshooting.
5A-26.
Power-Up Problems
The following discussion identifies probable fault areas if the installation of a Memory
Card I/F PCA causes power-up failure for the instrument. The problem is probably a
short on A6P2; the Microprocessor on the Main Assembly is prevented from accessing
Flash Memory and NVRAM correctly. Make the following checks:
5A-27.
•
First check for a GND-to-VCC short on the Memory Card I/F PCA.
•
There may also be a short between an interface signal and VCC, GND, or another
interface signal. Check signals D8 .. D15, A1 .. A4, XRDU*, XWRU*, MCARD*,
XSCLK, DTACK*, MCINT*, and RESET*.
•
The short may be due to a CMOS input that has been damaged due to static
discharge; the short is then detectable only when the circuit is powered up. Use an
oscilloscope to check activity on each of the interface signals. Verify that signals are
able to transition normally between 0 and 5.0V dc (VCC).
Failure to Detect Memory Card I/F PCA
Proper detection of the Memory Card Interface depends on the FPGA (A6U1) being
properly configured at power-up. Proper FPGA configuration is indicated by a low to
high transition on A6U1-80 shortly after power-up. Normally A6U1-80 should be high
before RESET* (A6U1-78) goes high. If the Memory Card Interface is not installed
properly, an "ERROR d" is displayed by the Microprocessor during power-up. The
Microprocessor checks for the presence of the Memory Card Interface by attempting to
read one of the registers in the Memory Card Controller (A6U1). If A6U1-58 fails to
drive the DTACK* signal low during the read access, the Microprocessor will abort the
memory cycle and report the Memory Card Interface as being not installed.
Verify the RESET*, XMCARD*, XRDU*, XSCLK, and DTACK* signals on the
Memory Card Interface. RESET* (A6U1-78) must be high. Using a storage oscilloscope,
verify that DTACK* (A6U1-58) goes low while XMCARD* (A6U1-49) is low for the
first read memory cycle to the Memory Card Controller (A6U1) during instrument
power-up. It may be necessary to cycle the power on the instrument several times to
verify this operation.
5A-30
Diagnostic Testing and Troubleshooting (2635A)
Memory Card I/F PCA (A6) Troubleshooting.
5A-28.
5A
Failure to Detect Insertion of Memory Card
When a Memory Card is inserted into the Memory Card Interface, the card detect signals
(CD1 and CD2; A6U1-19 and A6U1-21) are driven low. Verify that the Memory Card
Controller detects this and interrupts the Microprocessor (A1U1) by driving the
MCINT* signal (A6U1-60) low. Failure to generate the interrupt may be due to
problems with the data bus (D8..D15), the address bus (A1..A4), or one of the control
signals (XSCLK, XMCARD*, XWRU*, XRDU*, and RESET*). Consult the schematics
found in Section 8 of this manual and verify these interconnections. Consider the ribbon
cable that connects the Main Assembly (A1) to the Memory Card Interface Assembly
(A6) as a possible source of the problem as well. It may be necessary to repeatedly insert
and remove the card to observe the behavior of these signals.
5A-29.
Failure to Power Card / Illuminate the Busy Led
When a Memory Card is properly inserted and then detected by the Microprocessor
(A1U1), the Memory Card should be powered up and the BUSY LED should be
illuminated for a short period of time. If the BUSY LED is not visibly illuminated when
the card is inserted, verify the following things using a storage oscilloscope. Verify that
the gate of transistor A6Q1 is driven low by A6U1-26 (check both ends of resistor
A6R13). When the gate of A6Q1 is near 0 volts dc, the drain of transistor (A6Q1-5
through A6Q1-8) should be near 5 volts dc.
Approximately 50 milliseconds after the transistor drain pins (A6Q1-5 through A6Q1-8)
go to about 5 volts dc, the BUSY LED should be turned on by A6U1-25 going low to
sink current through the LED (A6DS1) and current limiting resistor (A6R10). When the
Microprocessor (A1U1) is done accessing data on the memory card, A6U1-25 and
A6U1-26 will both go high again to turn off the BUSY LED and the card power supply.
If the 50 millisecond delay between the memory card power being turned on and the
BUSY LED being turned on may be extended up to a total of 250 milliseconds if the
RDY/BSY signal (A6U1-23) is being held low by the memory card.
5A-30.
Failure to Illuminate the Battery Led
The yellow BATTERY LED is controlled by a Memory Card Controller output (A6U124). The Microprocessor checks the BVD1 and BVD2 outputs (A6U1-18 and A6U1-20
respectively) from the memory card about 50 milliseconds after it is powered up. The
BATTERY LED is turned on by A6U1-24 going low to sink current through the LED
(A6DS2) and current limiting resistor (A6R11).
Verify that the BATTERY LED state matches the state of the BVD1 and BVD2 signals
as shown in the following table (H = 5 volts dc, L = 0 volts dc).
Battery LED
BVD1
BVD2
Off
On
On
On
H
H
L
L
H
L
H
L
5A-31
HYDRA
Service Manual
5A-31.
Failure to Write to Memory Card
The installed memory card controls the state of the write protect (WP) signal that is an
input to the Memory Card Controller (A6U1-22). This signal must be near 0 volts dc
when the memory card is powered up and any operation requiring write access to the
memory card is done. Verify that the state of the WP signal (A6U1-22) correctly follows
the state of the write protect switch on the memory card as indicated in the following
table (H = 5 volts dc, L = 0 volts dc).
Write Protect
WP (A6U1-22)
Enabled
Disabled
L
H
If the problem with the interface has not been isolated yet, the problem is probably in the
card address (CA<0> .. CA<25>, REG*), card data (CD<0> .. CD<7>), and control
signals (CE1*, CRD*, CWR*). The card data (CD<0> .. CD<7>) signals each go
through a series termination resistor (Z2) so verify these series resistances. The control
signals (CE1*, CRD*, CWR*) each go from the Memory Card Controller (A6U1)
through an analog switch (A6U2) as they go to the Memory Card Connector (A6P1), so
verify that each control signal functions properly. The card read (CRD*) and card write
(CWR*) signals must go low for read and write cycles respectively. The following table
describes the memory card access modes to "attribute" memory (only read accesses are
done by the instrument).
Memory Card Access Modes
Transfer Mode
No Operation
Attribute Byte Read
Common Byte Read
Common Byte Write
5A-32.
REG*
CE1*
CRD*
CWR*
Data Direction
x
L
H
H
H
L
L
L
H
L
L
H
H
H
H
L
CD->D
CD->D
D->CD
Write/Read Memory Card Test (Destructive)
The instrument has a special computer interface command that may be used gain
diagnostic information about what is failing to function correctly in the Memory Card
Interface.
Warning
Use of the following command will destroy any data stored on
the memory card that is installed in the instrument. After
completion of the troubleshooting and repair of the memory
card interface, the memory card used must be formatted again
before it may be used again for data storage.
To make use of this command, connect a terminal or computer to the RS-232 interface
and set the instrument communication parameters as follows:
5A-32
•
Press SHIFT and then LIST(COMM).
•
With ’BAUd’ displayed, use the UP or DOWN arrow key to select the desired baud
rate. Then press ENTER.
•
With ’PAR’ (parity) displayed, use the UP or DOWN arrow key to select the parity.
Then press ENTER.
Diagnostic Testing and Troubleshooting (2635A)
Memory Card I/F PCA (A6) Troubleshooting.
•
With ’CtS’ (Clear to Send) displayed, use the UP or DOWN arrow key to select
’OFF’. Then press ENTER.
•
With ’ECHO’ displayed, use the UP or DOWN arrow key to select ’ON’. Then press
ENTER. Communications setup for Hydra is now complete.
5A
Assuming that the RS-232 interface is functional, send a carriage return or line feed
character to the instrument and it should send back a prompt. With a Static RAM
memory card installed in the instrument, send the following command followed by a
carriage return or line feed:
MCARD_DESTRUCTIVE_TEST? <size> where the <size> parameter is the number
of kbytes (1024 bytes) of the card to test.
Use <size> = 256 for a 256 kbyte card and
<size> = 1024 for a 1 Mbyte card.<end>
This command writes data to the memory card and then reads and compares the data to
the pattern that was written. A maximum of twenty lines of output will be generated, but
all locations on the card are sequentially written and then read. The messages output by
this command are summarized below:
MEMORY CARD IS NOT INSERTED!
The Memory Card Controller doesn’t recognize that the memory card is inserted
in connector A6P1. Verify that A6U1-19 and A6U1-21 are both near 0 volts dc.
MEMORY CARD IS WRITE PROTECTED!
The Memory Card Controller is indicating that the memory card is write
protected. Verify that the switch on the rear edge of the memory card is in the
proper position and that A6U1-22 is near 0 volts dc when the memory card is
powered up.
MEMORY CARD TEST PASSED.
The memory card test passed without detecting any errors.
ADDRESS 0x000000: DATA WAS 0x14, EXPECTED 0xC9
ADDRESS 0x000001: DATA WAS 0x3D, EXPECTED 0x2D
ADDRESS 0x000002: DATA WAS 0xAB, EXPECTED 0xBD
These are typical errors indicating in hexadecimal the address, the data that was
read from the card and the data that was expected. It may be possible to get some
indication of which address or data signals to probe with an oscilloscope to
determine where the fault is.
When probing signals to detect activity, it may be useful to change the <size> parameter
to be 16384 so that it will attempt to test the card as if it is a 16 Mbyte memory card.
This guarantees that error messages will be output, but it will take longer to complete the
test thus allowing more time to probe signals before having to send the memory card test
command again.
5A-33
HYDRA
Service Manual
5A-34
Chapter 6
List of Replaceable Parts
Title
6-1.
6-2.
6-3.
6-4.
6-5.
6-6.
Page
Introduction .......................................................................................... 6-3
How to Obtain Parts ............................................................................. 6-3
Manual Status Information................................................................... 6-3
Newer Instruments................................................................................ 6-4
Service Centers..................................................................................... 6-4
..............................................................................................................6-4
6-1
HYDRA
Service Manual
6-2
List of Replaceable Parts
Introduction
6
6-1. Introduction
This section contains an illustrated list of replaceable parts for the 2620A, 2625A, and
2635A. Parts are listed by assembly; alphabetized by reference designator. Each
assembly is accompanied by an illustration showing the location of each part and its
reference designator. The parts lists give the following information:
•
•
•
•
•
•
Reference designator
An indication if the part is subject to damage by static discharge
Description
Fluke stock number
Total quantity
Any special notes (i.e., factory-selected part)
Caution
A * symbol indicates a device that may be damaged by static
discharge.
6-2. How to Obtain Parts
Electrical components may be ordered directly from the manufacturer by using the
manufacturers part number, or from the Fluke Corporation and its authorized
representatives by using the part number under the heading FLUKE STOCK NO. In the
U.S., order directly from the Fluke Parts Dept. by calling 1-800-526-4731. Parts price
information is available from the Fluke Corporation or its representatives. Prices are also
available in a Fluke Replacement Parts Catalog which is available on request.
In the event that the part ordered has been replaced by a new or improved part, the
replacement will be accompanied by an explanatory note and installation instructions, if
necessary.
To ensure prompt delivery of the correct part, include the following information when
you place an order:
•
•
•
•
•
•
Part number and revision level of the pca containing the part.
Reference designator
Fluke stock number
Description (as given under the DESCRIPTION heading)
Quantity
Instrument Model, Serial Number, and Firmware Numbers
Note
Instrument Firmware Numbers can be retrieved over the computer
interface using the *IDN? query. Refer to Section 4 of the Hydra Users
Manual for more information.
6-3. Manual Status Information
The Manual Status Information table that precedes the parts list defines the assembly
revision levels that are documented in the manual. Revision levels are printed on the
component side of each pca.
6-3
HYDRA
Service Manual
6-4. Newer Instruments
Changes and improvements made to the instrument are identified by incrementing the
revision letter marked on the affected pca. These changes are documented on a manual
supplement which, when applicable, is included with the manual.
6-5. Service Centers
To locate an authorized service center, call Fluke using any of the phone numbers listed
below, or visit us on the World Wide Web: www.fluke.com
1-800-443-5853 in U.S.A and Canada
31 40 267 8200 in Europe
206-356-5500 from other countries
6-6.
Note
This instrument may contain a Nickel-Cadmium battery. Do not mix with
the solid waste stream. Spent batteries should be disposed of by a qualified
recycler or hazardous materials handler. Contact your authorized Fluke
service center for recycling information.
Warning
This instrument contains two fusible resistors (pn 650085). To
ensure safety, use exact replacement only.
Manual Status Information
Ref. or
Option No.
6-4
Assembly Name
Fluke Part No.
Revision
A1
2620A/2625A Main PCA
814186
F
A1
2635A Main PCA
925669
C
A2
Display PCA
814194
-
A3
A/D Converter PCA
814202
K
A4
Analog Input PCA
814210
C
A5
IEEE-488 Interface PCA
872593
A
A6
2625A Memory PCA
886135
A
A6
2635A Memory Card I/F PCA
931977
B
List of Replaceable Parts
Service Centers
6
Table 6-1. 2620A/2625A Final Assembly
Reference
Designator
Description
Fluke Stock
No
Tot Qty
814186
1
A1
MAIN PCA
A2
DISPLAY PCA
814914
1
A3
A/D CONVERTER PCA
814202
1
A4
ANALOG INPUT PCA
814210
1
A5
IEEE-488 INTERFACE PCA
872593
1
A6
F1,2
MEMORY PCA
W FUSE,5X20MM,0.125A,250V,SLOW
886135
1
822254
2
114116
2
H50
SCREW,FH,P,LOCK,STL,8-32,.375
H51
SCREW,PH,P,LOCK,SS,6-32,.375
334458
2
H52
SCREW,PH,P,LOCK,STL,6-32,.250
152140
7
H53
SCREW,FHU,P,LOCK,SS,6-32,.250
320093
4
H54
SCREW,TH,P,SS,4-40,.187
721118
2
H65
SCREW,KNURL,SL,CAPT,STL,6-32,.500
876479
2
H70
NUT,HEX,STL,6-32
110551
4
MP1
BEZEL,REAR, GRAY #8.
874081
1
MP2
ISOTHERMAL CASE,BOTTOM
874107
1
MP3
ISOTHERMAL CASE,TOP
874110
1
MP4
SEAL,CALIBRATION
735274
1
MP5
DECAL,REAR PANEL
874128
1
MP6
ROD,POWER SWITCH
784827
1
MP7
LABEL, CE MARK, SILVER
600715
1
MP10
CHASSIS ASSY
871561
1
MP11
FRONT PANEL
795062
1
MP12
ELASTOMERIC KEYPAD
795070
1
MP13
CASE FOOT,BLACK
824433
2
MP14
HANDLE, PAINTED GRAY #8
949511
1
MP15
LENS, FRONT PANEL
784777
1
MP16
MOUNTING PLATE,HANDLE (LEFT)
884267
1
MP17
MOUNTING PLATE,HANDLE (RIGHT)
884270
1
MP18
CASE,OUTER
884262
1
MP20
COVER,IEEE
885983
1
MP22
PWR PLUG,PANEL,6.3A,250V,3 WIRE
780817
1
MP25
DECAL,ISOTHERMAL CASE
874131
1
MP26
NAMEPLATE
877845
1
MP35
DECAL, CSA
864470
1
MP43
TEST LEAD ASSY, TL70A
855820
1
MP47
PWR PLUG PART,FUSE HOLDER
780825
1
MP48
CONN ACC,D-SUB,FEMALE SCREWLOCK,.250
844704
2
MP59
DECAL, NAMEPLATE
784736
1
MP66
TERM STRIP,SOCKET,.197CTR,8 POS
875877
1
MP67
TERM STRIP,SOCKET,.197CTR,10 POS
875880
1
Notes
1
6
2
3
6-5
HYDRA
Service Manual
Table 6-1. 2620A/2625A Final Assembly (cont)
Reference
Designator
MP80
Description
HYDRA STARTER SOFTWARE
Fluke Stock
No
Tot Qty
890645
1
MP99
T/C CABLE,ASSY
871512
1
MP101
LABEL,VINYL,1.500,.312
844712
4
T1
TRANSFORMER,POWER,100-240V
931105
1
TM1
HYDRA MANUAL SET (ENGLISH)
886015
1
TM2
HYDRA (STARTERS PKG) APPLICATION SOFTWA
890632
1
TM3
HYDRA & DATA BUCKETSERVICE MANUAL
202231
0
5
TM4
HYDRA DATA LOGGER MANUAL
891457
0
5
TM5
HYDRA USERS MANUAL (GERMAN)
919220
0
5
TM6
HYDRA USERS MANUAL (FRENCH)
885991
0
5
W1
WIRE ASSY,GROUND
874099
1
W2
CABLE ASSY,FLAT,20 COND,MMOD,FERRITE
876185
1
W4
CORD,LINE,5-15/IEC,3-18AWG,SVT,7.5 FT
284174
1
1.
2.
3.
4.
5.
THIS IS AN OPTION ONLY. NOT AVAILABLE FOR THE 2625A
USED ON THE 2620A ONLY.
USED ON THE 2625A ONLY.
INCLUDES: HYDRA USERS MANUAL (885988), AND HYDRA QUICK SETUP CARD (895883).
AVAILABLE THROUGH PARTS DEPARTMENT.
W TO ENSURE SAFETY, USE EXACT REPLACEMENT ONLY.
6-6
Notes
4
MP14
MP11
A6
(2620A Only)
A5
(Option for 2625A)
MP4
MP12
A2
H50
MP16
MP6
W2
H70
MP10
H52
A5 (Option -05) see Table 6-6 for replacement parts.
MP59
MP15
1
W4
MP 56
MP22
MP20
MP7
MP48
H52
A1
MP5
MP17
A3
F1, F2
MP47
MP18
H53
MP35
MP1
H54
H51
MP13
MP23
List of Replaceable Parts
Service Centers
6
2620A/2625A T&B
(1 of 3)
Figure 6-1. 2620A/2625A Final Assembly
s55f.eps
6-7
HYDRA
Service Manual
W2 (Ref)
H52 (Ref)
A1 (Ref)
Bottom View
2620A/2625A T&B
(2 of 3)
s56f.eps
Figure 6-1. 2620A/2625A Final Assembly (cont)
6-8
List of Replaceable Parts
Service Centers
6
A3
T1 (Ref)
H52 (Ref)
Top View
W1
2620A/2625A T&B
(3 of 3)
s57f.eps
Figure 6-1. 2620A/2625A Final Assembly (cont)
6-9
HYDRA
Service Manual
A4
MP2
MP66
MP3
A4
H65
MP67
2620A-100
s58f.eps
Figure 6-1. 2620A/2625A Final Assembly (cont)
6-10
List of Replaceable Parts
Service Centers
6
Table 6-2. 2635A Final Assembly
Reference
Designator
Description
Fluke Stock
No
Tot Qty
925669
1
A1
MAIN PCA
A2
DISPLAY PCA
814194
1
A3
A/C CONVERTER PCA
814202
1
A4
ANALOG INPUT PCA
814210
1
A6
MEMORY CARD I/F PCA
931977
1
F1,2
W FUSE,5X20MM,0.125A,250V,SLOW
822254
2
H50
SCREW,FH,P,LOCK,STL,8-32,.375
114116
2
H51
SCREW,PH,P,LOCK,SS,6-32,.375
334458
2
H52
SCREW,PH,P,LOCK,STL,6-32,.250
152140
8
H53
SCREW,FHU,P,LOCK,SS,6-32,.250
320093
4
H54
SCREW,TH,P,SS,4-40,.187
721118
2
H65
SCREW,KNURL,SL,CAPT,STL,6-32,.500
876479
2
H70
NUT,HEX,STL,6-32
110551
4
MP1
BEZEL,REAR, GRAY #8.
874081
1
MP2
ISOTHERMAL CASE,BOTTOM
874107
1
MP3
ISOTHERMAL CASE,TOP
874110
1
MP4
SEAL,CALIBRATION
735274
1
MP5
DECAL,REAR PANEL
874128
1
MP6
ROD,POWER SWITCH
784827
1
MP10
CHASSIS ASSY
871561
1
MP7
LABEL, CE MARK, SILVER
600715
1
MP11
PANEL,FRONT
932058
1
MP12
KEYPAD,ELASTOMERIC
932066
1
MP13
CASE FOOT,BLACK
824433
2
MP14
HANDLE, PAINTED GRAY #8
949511
1
MP15
LENS, FRONT PANEL
784777
1
MP16
MOUNTING PLATE,HANDLE (LEFT)
884267
1
MP17
MOUNTING PLATE,HANDLE (RIGHT)
884270
1
MP18
CASE,OUTER
884262
1
MP22
PWR PLUG,PANEL,6.3A,250V,3 WIRE
780817
1
MP25
DECAL,ISOTHERMAL CASE
874131
1
MP35
DECAL, CSA
864470
1
MP43
TEST LEAD ASSY, TL70A
855820
1
MP47
PWR PLUG PART,FUSE HOLDER
780825
1
MP48
CONN ACC,D-SUB,FEMALE SCREWLOCK,.250
844704
2
MP59
NAMEPLATE
931873
1
MP66
TERM STRIP,SOCKET,.197CTR,8 POS
875877
1
MP67
TERM STRIP,SOCKET,.197CTR,10 POS
875880
1
MP80
HYDRA STARTER SOFTWARE
890645
1
MP99
T/C CABLE,ASSY
871512
1
MP101
LABEL,VINYL,1.500,.312
844712
4
Notes
4
6-11
HYDRA
Service Manual
Table 6-2. 2635A Final Assembly (cont)
Reference
Designator
Description
MP111
MP112
LABEL,PAPER,ITS-90
*
Fluke Stock
No
Tot Qty
928101
1
CARD,MEMORY,SRAM,256KB,BATTERY
927512
1
MP998
COVER,IEEE
885983
1
T1
TRANSFORMER,POWER,100-240V
931105
1
TM1
HYDRA DATA BUCKET MANUAL SET (ENGLISH)
932160
1
TM2
HYDRA (STARTERS PKG) APPLICATION SOFTWA
890632
1
TM3
HYDRA & DATA BUCKET SERVICE MANUAL
889589
1
3
TM4
HYDRA DATA BUCKET USERS MANUAL (FRENCH)
931902
1
3
TM5
HYDRA DATA BUCKET USERS MANUAL (GERMAN)
931907
1
3
W1
WIRE ASSY,GROUND
874099
1
W2
CABLE ASSY,FLAT,20 COND,MMOD,FERRITE
876185
1
W3
CABLE, MEMORY
931113
1
W4
CORD,LINE,5-15/IEC,3-18AWG,SVT,7.5 FT
284174
1
1. FOR 256KB MEMORY CARD ORDER FLUKE PN 927512.
FOR 1 MB MEMORY CARD ORDER FLUKE PN 927517
FOR 2 MB MEMORY CARD ORDER FLUKE PN 944313.
2. INCLUDES: HYDRA USERS MANUAL (885988), AND HYDRA QUICK SETUP CARD (895883).
3. AVAILABLE THROUGH PARTS DEPARTMENT.
W TO ENSURE SAFETY, USE EXACT REPLACEMENT ONLY.
6-12
Notes
1
2
MP15
MP59
MP14
MP12
?
?
MP11
A2
H50
MP16
MP6
W2 H70
MP10
H52
A6
T1
A3
W3
MP101
A1
MP5
MP17
MP48
H52
H52
MP7
MP22
MP998
F1, F2
MP47
MP18
H53
MP101
MP35
MP1
H54
H51
MP13
MP23
List of Replaceable Parts
Service Centers
6
2635A T&B
(1 of 3)
Figure 6-2. 2635A Final Assembly
s59f.eps
6-13
HYDRA
Service Manual
Part of W2
MP102
H52
(Ref)
A6
W3
(Cable Assembly)
A1
Bottom View
2635A T&B
(2 of 3)
s60f.eps
Figure 6-2. 2635A Final Assembly (cont)
6-14
List of Replaceable Parts
Service Centers
T1 (Ref)
6
A3
H52
W1
Top View
2635A T&B
(3 of 3)
s61f.eps
Figure 6-2. 2635A Final Assembly (cont)
6-15
HYDRA
Service Manual
A4
MP2
MP66
MP3
A4
H65
MP67
2620A-100
s62f.eps
Figure 6-2. 2635A Final Assembly (cont)
6-16
List of Replaceable Parts
Service Centers
6
Table 6-3. 2620A/2625A A1 Main PCA
Fluke Stock
No
Tot Qty
IC,OP AMP,DUAL,LOW POWER,SOIC
867932
1
IC,OP AMP,QUAD,LOW POWER,SOIC
742569
2
CAP,CER,0.1UF,+-10%,25V,X7R,1206
747287
747287
747287
747287
747287
20
Reference
Designator
Description
AR1
*
AR2,AR3
*
C1,C3,C8,
C11,C19,C21C25,C27-29,
C33,C36-38,
C40-42
C2
CAP,CER,0.033UF,+-10%,200V,X7R,1206
602547
1
C4,C5,C32,
C34
CAP,AL,1UF,+-20%,50V
782805
782805
4
C6
CAP,AL,10UF,+-20%,63V,SOLV PROOF
816843
1
C7
CAP,AL,10000UF,+-20%,35V,SOLV PROOF
875203
1
C9,C10,C43C52,C54-59
CAP,CER,180PF,+-10%,50V,C0G,1206
769778
769778
18
C12,C13
CAP,AL,470UF,+-20%,16V,SOLV PROOF
772855
2
C14
CAP,AL,2200UF,+-20%,10V,SOLV PROOF
875208
1
C15,C16
CAP,CER,33PF,+-10%,50V,C0G,1206
769240
2
C17
CAP,AL,2.2UF,+-20%,50V
769687
1
C18,C20
CAP,AL,220UF,+-20%,35V,SOLV PROOF
929708
2
C26
CAP,AL,47UF,+-20%,100V,SOLV PROOF
837492
1
C30,C31
CAP,AL,47UF,+-20%,50V,SOLV PROOF
822403
2
C35,C53
CAP,CER,1000PF,+-5%,50V,C0G,1206
867408
2
C39
CAP,CER,0.047UF,+-10%,100V,X7R
844733
1
CR1,CR10
DIODE,SI,60 PIV,3 AMP,SCHOTTKY
943097
2
DIODE,SI,600 PIV,1.5 AMP
112383
2
DIODE,SI,BV=75V,IO=250MA,SOT-23
830489
830489
3
CR2,CR3
CR4,CR11,
CR12
*
CR5,CR6
*
DIODE,SI,40 PIV,1 AMP,SCHOTTKY
837732
2
CR7,CR14CR16,CR18,
CR19
*
*
*
DIODE,SI,BV=70V,IO=50MA,DUAL,S0T-23
742544
742544
742544
6
CR8,CR9,
CR13,CR17
*
DIODE,SI,BV=100,IO=100MA,DUAL,SOT-23
821116
821116
4
J1
SOCKET,2 ROW,PWB,0.100C,RT ANG,26 POS
543512
1
J2
HEADER,1 ROW,.050CTR,20 PIN
831529
1
J3
HEADER,1 ROW,.100CTR,3 PIN
845334
1
J4
CONN,D-SUB,PWB,RT ANG,9 PIN
855221
1
J5
HEADER,1 ROW,.197CTR,RT ANG,10 PIN
875695
1
J6
HEADER,1 ROW,.197CTR,RT ANG,8 PIN
875690
1
L1
FERRITE CHIP,95 OHMS @100 MHZ,3612
867734
1
L2
CHOKE,6TURN
320911
1
P10
CABLE ASSY,FLAT,10 CONDUCT,6.0”
714022
1
Q1-3
*
TRANSISTOR,SI,PNP,40V,300MW,SOT-23
742684
3
Q4-6
*
TRANSISTOR,SI,NPN,60V,350MW,SOT-23
742676
3
Q7,Q8
*
TRANSISTOR,SI,N-MOS,50W,D-PAK
927806
2
Notes
6-17
HYDRA
Service Manual
Table 6-3. 2620A/2625A A1 Main PCA (Cont)
Reference
Designator
6-18
Description
Fluke Stock
No
Tot Qty
Q9
*
TRANSISTOR,SI,NPN,30V,200MW,SOT-23
820902
1
R1,R2,R11,
R12,R22
*
*
RES,CERM,47K,+-5%,.125W,200PPM
746685
746685
5
R3,R4,R14,
R20,R21,R25,
R42,R47,R64
*
*
*
RES,CERM,10K,+-5%,.125W,200PPM
746610
746610
746610
9
R5
*
RES,CERM,1K,+-1%,.125W,100PPM,1206
783241
1
R6
*
RES,CERM,3.32K,+-1%,.125W,100PPM
810788
1
R7,R16
*
RES,CERM,100K,+-5%,.125W,200PPM
740548
2
R8,R63
*
RES,CERM,270,+-5%,.125W,200PPM
746354
2
R9,R10,R35
*
RES,CERM,4.7K,+-5%,.125W,200PPM
740522
3
R13
*
RES,CERM,20,+-5%,.125W,200PPM,1206
746222
1
R15
*
RES,CERM,33,+-5%,.125W,200PPM,1206
746248
1
R19,R28,
R34,R49,R58
*
*
RES,CERM,470,+-5%,.125W,200PPM
740506
740506
5
R26
*
RES,CERM,100,+-5%,.125W,200PPM
746297
1
R30
*
RES,CERM,45.3K,+-1%,0.1W,100PPM
930201
1
R31
*
RES,CERM,11K,+-1%,0.1W,100PPM,0805
928796
1
R36,R37
*
RES,CERM,15K,+-5%,.125W,200PPM
746628
2
R38
*
RES JUMPER,0.02,0.25W
682575
1
R39
*
RES,CERM,63.4K,+-1%,.125W,100PPM
836627
1
R40
*
RES,CERM,5.1K,+-5%,.125W,200PPM
746560
1
R41
*
RES,CERM,11K,+-1%,.125W,100PPM
867291
1
R43
*
RES,CERM,39K,+-5%,.125W,200PPM
746677
1
R44
*
RES,CERM,1.30K,+-1%,.125W,100PPM
780999
1
R45
*
RES,CERM,1M,+-1%,.125W,100PPM,1206
836387
1
R46
*
RES,CERM,4.02K,+-1%,.125W,100PPM
783266
1
R48
RES,CF,10K,+-5%,0.25W
697102
1
R50-57,R59R62
RES,CF,47,+-5%,0.25W
822189
822189
12
RT1
THERMISTOR,DISC,0.46,25 C
875240
1
RV1
VARISTOR,39V,+-20%,1.0MA
831735
1
S1
SWITCH,PUSHBUTTON,DPDT,PUSH-PUSH
836361
1
T1
TRANSFORMER,INVERTER
873968
1
T2
INDUCTOR,FXD,DUAL,EE24-25,0.4M
817379
1
TP1,TP30
JUMPER,WIRE,NONINSUL,0.200CTR
816090
2
U1
IC,CMOS,64 X 16 BIT EEPROM,SERIAL,SO8
876789
1
U2
*
IC,NMOS,TRPL PROGRAMMABLE TIME
866991
1
U3
*
MODULE,8KX8 SRAM,ZERO PWR,TIME
867945
1
U4
*
IC,CMOS,8-BIT MPU,1.5MHZ,256BY
876896
1
U5,U7
*
ISOLATOR,OPTO,LED TO TRANSISTOR
851790
2
U6
*
IC,VOLT REG,ADJ,1.2 TO 37 V,1.5 AMPS
460410
1
U8
*
2620A-PROGRAMMED EPROM
894555
1
U9
*
IC,V REG,SWITCHING,100KHZ,5A,T0-220
929591
1
Notes
List of Replaceable Parts
Service Centers
6
Table 6-3. 2620A/2625A A1 Main PCA (Cont)
Reference
Designator
Description
Fluke Stock
No
Tot Qty
U10
*
IC,CMOS,TRIPLE 3 INPUT NOR GATE,SOIC
867981
1
U11
*
IC,CMOS,3-8 LINE DCDR W ENABLE,SOIC
783019
1
U12,U28
*
IC,CMOS,QUAD INPUT NAND GATE,SOIC
830703
2
U13
*
IC,CMOS,OCTL LINE DRVR,SOIC
801043
1
U14
*
IC,CMOS,QUAD 2 INPUT XOR GATE,SOIC
867973
1
U15
*
IC,CMOS,QUAD INPUT NOR GATE,SOIC
830711
1
U16,U26
*
IC,CMOS,OCTAL D F/F,+EDG TRG,SOIC
838029
2
U17,U27
*
IC,ARRAY,7 NPN DARLINGTON PAIR
821009
2
U18
*
IC,VOLT REG,FIXED,-5.0 VOLTS,0.1 AMPS
454793
1
U19
*
IC,VOLT REG,ADJ,1.2 TO 32 V,0.1 A
810242
1
U20
*
IC,CMOS,12 STAGE BIN RIPPLE CNTR,SOIC
831636
1
U21
*
IC,CMOS,TRIPLE 3 INPUT NAND GATE,SOIC
867978
1
U22
*
IC,CMOS,DUAL D F/F,+EDG TRG,SOIC
782995
1
U23
*
IC,CMOS,HEX INVERTER,UNBUFFERED,SOIC
806893
1
U24
*
IC,COMPARATOR,DUAL,LOW PWR,SOIC
837211
1
U25
*
IC,CMOS,RS232 DRIVER/RECEIVER,SOIC
821538
1
U29
*
IC,CMOS,8 BIT P/S-IN,S-OUT SHFT,SOIC
782904
1
U31
*
IC,OP AMP,DUAL,LOW POWER,SOIC
867932
1
VR1
*
ZENER,UNCOMP,5.6V,5%,20MA,0.2W
875604
1
VR2
*
ZENER,UNCOMP,6.0V,5%,20MA,0.2W
837161
1
VR3
*
ZENER,UNCOMP,6.8V,5%,20MA,0.2W
837195
1
VR4
*
IC, 1.23V,150 PPM T.C.,BANDGAP V, REF
634451
1
Y1
CRYSTAL,4.9152 MHZ,+/- 0.005%,HC-18/U
800367
1
Z1
RES,CERM,NET,CUSTOM
821157
1
Z2
RES,CERM,SOIC,16 PIN,15 RES,22K,+-2%
867841
1
Z3
RES,CERM,SOIC,20 PIN,10 RES,47K,+-2%
867846
1
Notes
6-19
HYDRA
Service Manual
2620A-1601
s63f.eps
Figure 6-3. 2620A/2625A A1 Main PCA
6-20
List of Replaceable Parts
Service Centers
6
Table 6-4. 2635A A1 Main PCA
Reference
Designator
Description
Fluke Stock
No
Tot Qty
BT1
BATTERY,LITHIUM,3.0V,0.560AH
821439
1
C1,C18
CAP,AL,220UF,+-20%,35V,SOLV PROOF
929708
2
C2
CAP,CER,0.033UF,+-10%,200V,X7R,1206
602547
1
C3,C8
CAP,CER,27PF,+-10%,50V,C0G,1206
800508
2
C4,C5,C32,
C34
CAP,AL,1UF,+-20%,50V
782805
782805
4
C6
CAP,AL,10UF,+-20%,63V,SOLV PROOOF
816843
1
C7
CAP,AL,10000UF,+-20%,35V,SOLV PROOF
875203
1
C9,C10,C43C52,C54-59
CAP,CER,180PF,+-10%,50V,C0G,1206
769778
769778
18
C11,C15,C16,
C19,C21-25,
C28,C29,C33,
C36,C38 C40C42,C60-65,
C68,C70-73,
C75,C76
CAP,CER,0.1UF,+-10%,25V,X7R,1206
747287
747287
747287
747287
747287
747287
747287
30
C12,C13
CAP,AL,470UF,+-20%,16V,SOLV PROOF
772855
2
C14
CAP,AL,2200UF,+-20%,10V,SOLV PROOF
875208
1
C17
CAP,AL,2.2UF,+-20%,50V
769687
1
C26
CAP,AL,47UF,+-20%,100V,SOLV PROOF
837492
1
C30,C31,C66,
C67
CAP,AL,47UF,+-20%,50V,SOLV PROOF
822403
822403
4
C35,C53,C74
CAP,CER,1000PF,+-5%,50V,C0G,1206
867408
3
C39
CAP,CER,0.047UF,+-10%,100V,X7R
844733
1
C69
CAP,CER,4700PF,+-10%,50V,X7R,1206
832279
1
CR1,CR10
DIODE,SI,60 PIV,3 AMP,SCHOTTKY
943097
2
CR2,CR3
DIODE,SI,600 PIV,1.5 AMP
112383
2
CR4,CR11,
CR12,CR20
*
*
DIODE,SI,BV=75V,IO=250MA,SOT-23
830489
830489
4
CR5,CR6,
CR21
*
*
DIODE,SI,40 PIV,1 AMP,SCHOTTKY
837732
837732
3
CR7,CR14CR16,CR18,
CR19
*
*
*
DIODE,SI,BV=70V,IO=50MA,DUAL,SOT-23
742544
742544
742544
6
CR8,CR9,
CR13,CR017
*
*
DIODE,SI,BV=100,IO=100MA,DUAL,SOT-23
821116
821116
4
J1
SOCKET,2 ROW,PWB,0.100C,RT ANG,26 POS
543512
1
J2
HEADER,1 ROW,.050CTR,20 PIN
831529
1
J3
HEADER,1 ROW,.100CTR,3 PIN
845334
1
J4
CONN,D-SUB,PWB,RT ANG,9 PIN
855221
1
J5
HEADER,1 ROW,.197CTR,RT ANG,10 PIN
875695
1
J6
HEADER,1 ROW,.197CTR,RT ANG,8 PIN
875690
1
L1
FERRITE CHIP,95 OHMS @100 MHZ,3612
867734
1
L2
CHOKE,6TURN
320911
1
Notes
6-21
HYDRA
Service Manual
Table 6-4. 2635A A1 Main PCA (cont)
Fluke Stock
No
Tot Qty
PCB ASSY, MAIN SM
932017
1
P4
HEADER,2 ROW,.050CTR,40 PIN
838573
1
P10
CABLE ASSY,FLAT,10 CONDUCT,6.0”
714022
1
Reference
Designator
Description
MP101
6-22
Q1-3,Q10
*
TRANSISTOR,SI,PNP,40V,300MW,SOT-23
742684
4
Q4-6
*
TRANSISTOR,SI,NPN,60V,350MW,SOT-23
742676
3
Q7,Q8
*
TRANSISTOR,SI,N-MOS,50W,D-PAK
927806
2
Q9
*
TRANSISTOR,SI,NPN,30V,200MW,SOT-23
820902
1
R1,R11,R12,
R22,R25,R45
*
*
RES,CERM,47K,+-5%,.125W,200PPM
746685
746685
6
R2
*
RES,CERM,698K,+-1%,.125W,100PPM
867296
1
R3,R4,R14,
R42,R47,R64,
R65,R68,R70,
R72-75,R78,
R79,R81
*
*
*
*
*
RES,CERM,10K,+-5%,.125W,200PPM
746610
746610
746610
746610
746610
16
R5,R98
*
RES,CERM,1K,+-1%,.125W,100PPM,1206
783241
2
R6
*
RES,CERM,3.32K,+-1%,.125W,100PPM
810788
1
R7,R16,R35
*
RES,CERM,100K,+-5%,.125W,200PPM
740548
3
R8,R21
*
RES,CERM,270,+-5%,.125W,200PPM
746354
2
R9,R10,R39,
R41,R71,R77,
R83
*
*
*
RES,CERM,4.7K,+-5%,.125W,200PPM
740522
740522
740522
7
R13
*
RES,CERM,20,+-5%,.125W,200PPM,1206
746222
1
R15,R86,R107 *
RES,CERM,33,+-5%,.125W,200PPM,1206
746248
3
R19,R31
*
RES,CERM,11K,+-1%,0.1W,100PPM,1206
928796
2
R20
*
RES,CERM,59K,+-1%,.125W,100PPM
851803
1
R26
*
RES,CERM,100,+-5%,.125W,200PPM
746297
1
R28,R34,R49,
R58
*
*
RES,CERM,470,+-5%,.125W,200PPM
740506
740506
4
R30
*
RES,CERM,45.3K,+-1%,0.1W,100PPM
930201
1
R36
*
RES,CERM,3.6K,+-5%,.125W,200PPM
746537
1
R37
*
RES,CERM,9.1K,+-5%,.125W,200PPM
746602
1
R38
*
RES JUMPER,0.02,0.25W
682575
1
R40
*
RES,CERM,5.1K,+-5%,.125W,200PPM
746560
1
R43,R63,R84,
R92
*
*
RES,CERM,1.5K,+-5%,.125W,200PPM
746438
746438
4
R44
*
RES,CERM,1.30K,+-1%,.125W,100PPM
780999
1
R46
*
RES,CERM,4.02K,+-1%,.125W,100PPM
783266
1
R48
*
RES,CF,10K,+-5%,0.25W
697102
1
R50-57,R59R62
*
*
RES,CF,47,+-5%,0.25W
822189
822189
12
Notes
List of Replaceable Parts
Service Centers
6
Table 6-4. 2635A A1 Main PCA (cont)
Reference
Designator
Description
Fluke Stock
No
Tot Qty
RES,CERM,47,+-5%,.0625W,200PPM
927707
927707
927707
927707
927707
35
RT1
THERMISTOR,DISC,0.46,25 C
875240
1
RV1
VARISTOR,41.5V,+-9%,1.0MA,1206
914114
1
R66,R67,R69,
R80,R82,R85,
R87-91,R93R97 R99-106,
R108-118
*
*
*
*
*
S1
SWITCH,PUSHBUTTON,DPDT,PUSH-PUSH
836361
1
T1
TRANSFORMER,INVERTER
873968
1
T2
INDUCTOR,FXD,DUAL,EE24-25,0.4MH,1.2A
817379
1
T3
INDUCTOR,20UH,+-20%,1.15ADC
914007
1
TP1,TP30
TERM,UNINSUL,WIRE FORM,TEST POINT
781237
2
U1
*
IC,INTEGR MLTIPROTOCOL MPU,16 MHZ,QFP
910831
1
U2
*
IC,CMOS,QUAD BUS BUFFER W/3-ST,SOIC
866801
1
U3,U4
*
IC,OP AMP,QUAD,LOW POWER,SOIC
742569
2
U5,U7
*
ISOLATOR,OPTO,LED TO TRANSISTOR
851790
2
U6
*
IC,VOLT REG,ADJ,1.2 TO 37 V,1.
460410
1
U8,U28
*
IC,OP AMP,DUAL,LOW POWER,SOIC
867932
2
U9
*
IC,V REG,SWITCHING,100KHZ,5A,TO-220
929591
1
U10
**
IC,CMOS,MICROPROCESSOR SUPERVISOR,DIP
913975
1
U11
*
GAL,PROGRAMMED,I/O DECODER
931910
1
U12
*
IC,CMOS,PARALLEL I/O CAL/CLCK
914036
1
U13
*
IC,CMOS,RS232 DRIVER/RECEIVER,SOIC
821538
1
U14,U16
*
IC,FLASH,128K X 8,12 V,BOT BOOT,PLCC
914106
2
U15
*
IC,CMOS,REGULATOR,STEP-UP,PWM,SO16
914080
1
U17,U27
*
IC,ARRAY,7 NPN DARLINGTON PAIR
821009
2
U18
*
IC,VOLT REG,FIXED,-5.0 VOLTS,0.1 AMPS
454793
1
U19
*
IC,VOLT REG,ADJ,1.2 TO 32 V,0.1 A
810242
1
U20,U24
*
IC,CMOS,SRAM,128K X 8,100 NS,SO32
914101
2
U22
*
IC,CMOS,DUAL D F/F,+EDG TRG,SOIC
782995
1
U23
*
IC,CMOS,HEX INVERTER,UNBUFFERED,SOIC
806893
1
U25
*
IC,PROG GATE ARRAY,3000 G,70 MHZ,PQFP
887138
1
U26
*
IC,CMOS,QUAD INPUT NAND GATE,SOIC
830703
1
VR1
*
ZENER,UNCOMP,5.6V,5%,20MA,0.2W
875604
1
VR2
*
ZENER,UNCOMP,6.0V,5%,20MA,0.2W
837161
1
VR3
*
ZENER,UNCOMP,6.8V,5%,20MA,0.2W
837195
1
HEADER,1 ROW,.100CTR,2 PIN
643916
1
W3
Y1
CRYSTAL,12.288MHZ,50PPM,SURFACE MT
913942
1
Z1
RES,CERM,NET,CUSTOM
821157
1
Z2
RES,CERM,SOIC,16 PIN,15 RES,22
867841
1
Z3
RES,CERM,SOIC,20 PIN,10 RES,47
867846
1
Notes
6-23
HYDRA
Service Manual
2635A-1601
s64f.eps
Figure 6-4. 2635A A1 Main PCA
6-24
List of Replaceable Parts
Service Centers
6
Table 6-5. A2 Display PCA
Fluke Stock
No
Tot Qty
CAP,CER,0.1UF,+-10%,25V,X7R,1206
747287
5
CAP,TA,4.7UF,+-20%,16V,3528
745976
1
DIODE,SI,BV=75V,IO=250MA,SOT-23
830489
1
DS1
TUBE,DISPLAY,VAC FLUOR,7 SEG,10 CHAR
783522
1
J1
HEADER,1 ROW,.050CTR,20 PIN
831529
1
LS1
AF TRANSD,PIEZO,22 MM
602490
1
MP102
DISPLAY, PWB ASSY, SM
873901
1
MP321
WIRE,JUMPER,TEF,22AWG,WHT,.300
528257
1
Reference
Designator
Description
C1,C3-6
C2
CR3
*
R1,R10,R12
*
RES,CERM,10K,+-5%,.125W,200PPM
746610
3
R2
*
RES,CERM,2.2M,+-5%,.125W,200PPM
811778
1
R3
*
RES,CERM,1.2M,+-5%,.125W,200PPM
806240
1
R11
*
RES,CERM,1K,+-5%,.125W,200PPM,1206
745992
1
U1
*
IC,CMOS,4-BIT MPU,FLUKE 45-90002
820993
1
U4
*
IC,CMOS,DUAL DIV BY 16 BIN CNTR,SOIC
837054
1
U5
*
IC,CMOS,DUAL MONOSTB MULTIVBRTR,SOIC
806620
1
U6
*
IC,CMOS,QUAD 2 IN NAND W/SCHMT,SOIC
837245
1
W1
WIRE,JUMPER,TEF,22AWG,WHT,.300
528257
1
Z1
RES,CERM,SOIC,16 PIN,15 RES,10K,+-2%
836296
1
Notes
1
1. W1 IS NOT INSTALLED ON 2620A AND 2625A INSTRUMENTS.
6-25
HYDRA
Service Manual
CKT 1
CKT 2
2620A-4002
s65f.eps
Figure 6-5. A2 Display PCA
6-26
List of Replaceable Parts
Service Centers
6
Table 6-6. A3 A/D Converter PCA
Reference
Designator
Description
Fluke Stock
No
Tot Qty
C1-3,C18,C21,
C22,C25,C29,
C33
CAP,CER,0.1UF,+-10%,25V,X7R,1206
747287
747287
747287
9
C4,C5
CAP,CER,15PF,+-10%,50V,C0G,1206
837393
2
C6,C7,C10
CAP,POLYPR,0.1UF,+-10%,160V
446781
3
C8,C9,C19
CAP,TA,10UF,+-20%,10V
714766
3
C11
CAP,POLYPR,2200PF,+-5%,100V
854505
1
C12
CAP,TA,2.2UF,+-10%,35V
697433
1
C13
CAP,POLYPR,0.033UF,+-10%,63V
721050
1
C14,C34
CAP,POLYPR,1000PF,+-1%,100V
844816
2
C15,C16
CAP,TA,33UF,+-10%,6V
866897
2
C17
CAP,POLYES,1UF,+-10%,50V
733089
1
C20,C24
CAP,CER,4.3PF,+-10%,50V,C0G,1206
844738
2
C23
CAP,CER,4.3PF,+-0.5PF,50V,C0G,0805
514216
1
C26,C28
CAP,AL,470UF,+-20%,10V,SOLV PROOF
822387
2
C27
CAP,POLYPR,100PF,+-1%,100V
844803
1
C30
CAP,CER,0.01UF,+-10%,50V,X7R,1206
747261
1
C31
CAP,POLYES,0.1UF,+-10%,1000V
837518
1
C32
CAP,CER,2500PF,+-20%,250V,X7R
485680
1
C35-38
CAP,CER,180PF,+-10%,50V,C0G,1206
769778
4
CR1,CR2,CR4 *
DIODE,SI,BV=70V,IO=50MA,DUAL,SOT-23
742320
3
J1
CONN,DIN41612,TYPE C,RT ANG,48 PIN
867333
1
J2
CONN,MICRO-RIBBON,PLUG,RT ANG,20 POS
876107
1
J10
HEADER,2 ROW,.100CTR,10 PIN
756858
1
K1,K2,K15-17
RELAY,ARMATURE,2 FORM C,5VDC,LATCH
603001
5
K3,K5-14
RELAY,ARMATURE,4 FORM C,5 V,LATCH
642444
11
L1-24
FERRITE CHIP,95 OHMS @100 MHZ,3612
867734
24
MP125,MP126
RIVET,S-TUB,OVAL,AL,.087,.343
838458
2
Q1
*
TRANSISTOR,SI,PNP,40V,300MW,SOT-23
742684
1
Q2,Q12,Q13
*
TRANSISTOR,SI,N-JFET,SEL,SOT-23
876263
3
Q3-9
*
Q10,Q11,Q14, *
Q15
*
TRANSISTOR,SI,N-JFET,SEL,SOT-23
820860
7
TRANSISTOR,SI,NPN,25V,0.3W,SEL,SOT-23
821637
821637
4
R1
*
RES,CERM,10K,+-1%,.125W,100PPM
769794
1
R2,R36,R40,
R41
*
*
RES,CERM,30.1K,+-1%,.125W,100PPM
801258
801258
4
R3,R4
*
RES,CERM,470K,+-5%,.125W,200PPM
746792
2
R5
*
RES,CERM,100K,+-1%,.125W,100PPM
769802
1
R6,R08,R9,
R19,R23,R34
*
*
RES,CERM,10K,+-5%,.125W,200PPM
746610
746610
6
R7
*
RES,CERM,360,+-5%,.125W,200PPM
783290
1
R10,R11
W RES,MF,1K,+-1%,100PPM,FLMPRF,FUSIBLE
650085
2
R12,R33,R39,
R44
*
*
745992
745992
4
RES,CERM,1K,+-5%,.125W,200PPM,1206
Notes
2
1
6-27
HYDRA
Service Manual
Table 6-6. A3 A/D Converter PCA (cont)
Fluke Stock
No
Tot Qty
RES,CF,270,+-5%,0.25W
810424
2
Reference
Designator
Description
R13,R43
R14,R24-28
*
RES,CERM,47K,+-5%,.125W,200PPM
746685
6
R15
*
RES,CERM,61.9K,+-1%,.125W,100PPM
821330
1
R16,R17,R20
*
RES,CERM,200K,+-5%,.125W,200PPM
746743
3
R18
*
RES,CERM,16.9K,+-1%,.125W,100PPM
836635
1
R21
*
RES,CERM,845,+-1%,.125W,100PPM
821322
1
R22
*
RES,CERM,91K,+-5%,.125W,200PPM
811828
1
R29,R30
*
RES,CERM,22,+-5%,.125W,200PPM,1206
746230
2
R31,R32,R38
*
RES,CERM,100K,+-5%,.125W,200PPM
740548
3
R35,R42
*
RES,CERM,100K,+-5%,3W
820811
2
R37
*
RES,CERM,24.9K,+-1%,.125W,100PPM
867689
1
R45,R46
RES,MF,10K,+-1%,0.100W,100PPM
601432
2
RT1
THERMISTOR,DISC,POS,1K,+-40%,25 C
820878
1
RV1,RV2
VARISTOR,910,+-10%,1.0MA
876193
2
JUMPER,WIRE,NONINSUL,0.200CTR
816090
1
IC,COMPARATOR,QUAD,14 PIN,SOIC
741561
1
TP9
U1
*
U3
*
IC,CMOS,DUAL D F/F,+EDG TRG,SOIC
782995
1
U4,U5,U10-12
*
IC,ARRAY,7 NPN DARLINGTON PAIRS,SOIC
821009
5
U6
*
IC,BPLR,TRUE RMS TO DC CONVERTER
707653
1
U7
*
IC,OP AMP,JFET INPUT,DECOMP,SOIC
837237
1
U8
*
MEAS PROCESSOR & A/D CONV, CMOS IC.
776195
1
U9
*
IC,CMOS,MCU,8 BIT,1 MHZ,ROMMEDPLCC68
601317
1
U13
*
IC,OP AMP,DUAL,HIGH BW,SNGL SUP,SO8
929075
1
U14
*
IC,COMPARATOR,DUAL,LOW PWR,SOIC
837211
1
VR1
*
STABILITY TESTED ZENER
387217
1
VR2,VR3
*
ZENER,UNCOMP,6.0V,5%,20MA,0.2W,SOT-23
837161
2
W1
WIRE ASSY,(H)
834929
1
W2
WIRE ASSY,INPUT (L)
874086
1
Y1
CRYSTAL,3.6864MHZ,+-0.005%,HC-18V
570606
1
Y2
CRYSTAL,3.84MHZ,+-0.05%,HC-18/U
650390
1
Z1
RNET,CERM,SIP,2620 LO V DIVIDER
849984
1
Z2
RNET,MF,POLY,SIP,2620 A TO D CONV
884544
1
Z3
RNET,CERM,SIP,2620 HI V AMP GAIN
847363
1
Z4
RNET,MF,POLY,SIP,2620 HI V DIVIDER
851100
1
1. W FUSIBLE RESISTOR. TO ENSURE SAFETY, USE EXACT REPLACEMENT ONLY.
2. SEE DETAIL IN FIGURE 6-6 FOR RELAY INSTALLATION POLARITY.
6-28
Notes
List of Replaceable Parts
Service Centers
6
K3, K5-K14 Relay Polarity
Install with marked end as shown.
Aromat or Nais
Omron
2620A-1603
s66f.eps
Figure 6-6. A3 A/D Converter PCA
6-29
HYDRA
Service Manual
Table 6-7. A4 Analog Input PCA
Reference
Designator
Description
C1
CAP,CER,1000PF,+-5%,50V,C0G,1206
Fluke Stock
No
Tot Qty
867408
1
H55
RIVET,S-TUB,OVAL,AL,.087,.375
106473
2
L1
CORE,BALUN,FERRITE,.136,.079,.093
106184
1
M1,M2
HEADER,1 ROW,.156CTR,15 PIN
414458
2
MP4
ANALOG INPUT CONNECTOR,PWB
873815
1
P1
CONN,DIN41612,TYPE R,RT ANG,48 SCKT
867338
1
P2
CONN,MICRO-RIBBON,REC,RT ANG,20 POS
876102
1
TRANSISTOR,SI,NPN,TMP SENSR,SEL,TO-92
741538
1
R1
RES,MF,5.49K,+-1%,0.125W,100PPM
334565
1
R2
RES,MF,10K,+-1%,0.125W,25PPM
328120
1
R3
RES,VAR,CERM,50K,+-10%,0.5W
876573
1
RV1-4
VARISTOR,910,+-10%,1.0MA
876193
4
TB1,TB2
TERM STRIP,PWB,45 ANG,.197CTR,20 POS
875195
2
VR1
IC, 2.5V,100 PPM T.C.,BANDGAP REF
723478
1
Q1
*
REFER TO TABLE 6-1 FOR ORDERING INFORMATION ON CASE TOP, BOTTOM AND DECAL.
6-30
Notes
List of Replaceable Parts
Service Centers
6
2620A-1604
s67f.eps
Figure 6-7. A4 Analog Input PCA
6-31
HYDRA
Service Manual
Table 6-8. A5 (Option -05) IEEE-488 Interface PCA
Reference
Designator
Description
Tot Qty
747287
3
C1-3
CAP,CER,0.1UF,+-10%,25V,X7R,1206
J1
HEADER,2 ROW,.100CTR,RT ANG,26 PIN
512590
1
J2
HEADER,2 ROW,.100CTR,24 PIN
831834
1
R1
*
TP1
RES,CERM,5.1K,+-5%,.125W,200PPM
746560
1
TERM,UNINSUL,WIRE FORM,TEST POINT
781237
1
U1
*
IC,NMOS,GPIB CONTROLLER,PLCC
887190
1
U2
*
IC,LSTTL,OCTAL GPIB XCVR,SOIC
831651
1
U3
*
IC,LSTTL,OCTAL GPIB XCVR,SOIC
831669
1
U4
*
IC,CMOS,QUAD INPUT NAND GATE,SOIC
830703
1
ATTACHING HARDWARE AND CABLE ARE LISTED BELOW:
H52
SCREW,PH,PSTL,LOCK,6-32,250
MP56
CONN ACC,MICRO-RIBBON,SCREW LOCK KIT
W4
IEEE,CABLE ASSY
6-32
Fluke Stock
No
152140
836585
874094
Notes
List of Replaceable Parts
Service Centers
6
2620A-1605
s68f.eps
Figure 6-8. A5 IEEE-488 Interface PCA (Option -05)
6-33
HYDRA
Service Manual
Table 6-9. 2625A A6 Memory PCA
Reference
Designator
Description
C1-8
6-34
CAP,CER,0.1UF,+-10%,25V,X7R,1206
Fluke Stock
No
Tot Qty
747287
8
J1
HEADER,2 ROW,.100CTR,RT ANG,26 PIN
512590
1
TP1,TP2
TERM,UNINSUL,WIRE FORM,TEST POINT
781237
2
U1
*
IC,CMOS,OCTAL D TRANSPARNT LATCH,SOIC
876235
1
U2
*
IC,CMOS,QUAD 2 INPUT AND GATE,SOIC
853317
1
U3
*
IC,CMOS,DUAL DIV BY 16 BIN CNTR,SOIC
837054
1
U4
*
IC,CMOS,4BIT BISTBL LTCH W/ENABL,SOIC
876243
1
U5
*
IC,CMOS,QUAD INPUT NAND GATE,SOIC
830703
1
U6,U7
*
IC,CMOS,128K X 8 SRAM,120 NSEC,NVM
876250
2
U8
*
IC,CMOS,3-8 LINE DCDR W/ENABLE,SOIC
867726
1
Notes
List of Replaceable Parts
Service Centers
6
2625A-1606
s69f.eps
Figure 6-9. 2625A A6 Memory PCA
6-35
HYDRA
Service Manual
Table 6-10. 2635A A6 Memory Card I/F PCA
Reference
Designator
Description
Tot Qty
C1-4,C6-8
CAP,CER,0.1UF,+-10%,25V,X7R,1206
747287
7
C5
CAP,TA,47UF,+-20%,10V,7343
867580
1
C9
CAP,TA,1UF,+-20%,35V,3528
866970
1
DS1
LED,RED,RIGHT ANGLE,3.0 MCD
927389
1
DS2
LED,YELLOW,RIGHT ANGLE,3 MCD
914242
1
P1
CONN,MEMORY CARD,HEADER,RT ANG,68 PIN
914184
1
P2
HEADER,2 ROW,.050CTR,RT ANG,40 PIN
838540
1
Q1
*
TRANSISTOR,SI,P-MOS,2W,SOIC
914031
1
R1,R3,R4,R8
*
RES,CERM,10K,+-5%,.125W,200PPM
746610
4
R2,R5,R7,
R9,R12,R14,
R16,R17
*
*
*
RES,CERM,47K,+-5%,.125W,200PPM
746685
746685
746685
8
R6,R10,R11
*
RES,CERM,360,+-5%,.125W,200PPM
783290
3
R13
*
RES,CERM,1.5K,+-5%,.125W,200PPM
746438
1
R15
*
TP1
RES,CERM,33,+-5%,.125W,200PPM,1206
746248
1
TERM,UNINSUL,WIRE FORM,TEST POINT
781237
1
U1
*
IC,PROG GATE ARRAY,3000 G,70 MHZ, PQFP
601275
1
U2
*
IC,CMOS,QUAD BILATERAL SWITCH,SOIC
914098
1
U3
*
IC,EPROM,36KBIT,SERIAL,PROGRAMMED, SO8
601267
1
RES,CERM,SOIC,16 PIN,8 RES,100
838086
1
Z2
6-36
Fluke Stock
No
Notes
List of Replaceable Parts
Service Centers
6
2635A-1606
s70f.eps
Figure 6-10. 2635A A6 Memory Card I/F PCA
6-37
HYDRA
Service Manual
6-38
Chapter 7
IEEE-488 Option -05
Title
7-1.
7-2.
7-3.
7-4.
7-5.
7-6.
7-7.
7-8.
7-9.
7-10.
7-11.
7-12.
7-13.
7-14.
7-15.
7-16.
7-17.
7-18.
7-19.
7-20.
7-21.
7-22.
7-23.
Introduction ..........................................................................................
Theory of Operation .............................................................................
Functional Block Description ..........................................................
IEEE-488 PCA Detailed Circuit Description (2620A Only) ...............
Main PCA Connector.......................................................................
IEEE-488 Controller ........................................................................
IEEE-488 Transceivers/Connector ..................................................
General Maintenance............................................................................
Removing the IEEE-488 Option ......................................................
Installing the IEEE-488 Option........................................................
Performance Testing.............................................................................
Troubleshooting ...................................................................................
Power-Up Problems .........................................................................
Communication Problems................................................................
Failure to Select IEEE-488 Option ..............................................
Failure to Handshake on IEEE-488 Bus ......................................
Failure to Enter Remote...............................................................
Failure to Receive Multiple Character Commands .....................
Failure to Transmit Query Responses .........................................
Failure to Generate an End or Identify (EOI)..............................
Failure to Generate a Service Request (SRQ) .............................
List of Replaceable Parts......................................................................
Schematic Diagram ..............................................................................
Page
7-3
7-3
7-3
7-3
7-4
7-4
7-5
7-5
7-5
7-7
7-7
7-8
7-8
7-8
7-8
7-8
7-8
7-9
7-9
7-9
7-9
7-9
7-9
7-1
HYDRA
Service Manual
7-2
IEEE-488 Option -05
Introduction
7
7-1. Introduction
The IEEE-488 Interface turns the Data Acquisition Unit 2620A into a fully
programmable instrument for use with the IEEE Standard 488.1 (1987) interface bus
(IEEE-488 bus). With the IEEE-488 Interface, the instrument can become part of an
automated instrumentation system.
The IEEE-488 Interface cannot be used with the Hydra Data Logger (2625A).
7-2. Theory of Operation
7-3.
Functional Block Description
The IEEE-488 Assembly (A5) requires power supply voltages, address, data and control
signals from the instrument Main Assembly (A1) to operate. The A5 assembly
implements the circuitry necessary to satisfy the IEEE-488.1 standard for programmable
instrumentation.
7-4. IEEE-488 PCA Detailed Circuit Description (2620A Only)
The IEEE-488 PCA comprises the following functional blocks: the Main PCA
Connector, the IEEE-488 Controller, and the IEEE-488 Transceivers and Connector.
These three blocks are described in the following paragraphs. Refer to Section 8 for a
schematic diagram of the IEEE-488 PCA.
Pin numbering for the IEEE Controller (A5U1) differs somewhat on early production
units. All A5U1 pin references in this section relate to newer production units.
Differences for early production units can be identified by referencing the manufacturer’s
number on the A5U1 chip with the information provided in Table 7-1.
Table 7-1. A5U1 Pin Differences
WD9914 (Early Production A5U1)
REFERENCE
A5U1-1
A5U1-2
A5U1-3
A5U1-4
A5U1-5
A5U1-6
A5U1-17
A5U1-19
A5U1-20
A5U1-21
A5U1-22
A5U1-23
A5U1-24
A5U1-25
A5U1-26
A5U1-27
A5U1-28
TMS9914A (Newer Production A5U1)
NAME
ACCRQ*
ACCGR*
CE*
WE*
DBIN
(nc)
(nc)
D1
D0
CLK
RESET*
VSS
TE
REN
IFC
NDAC
NRFD
NAME
(nc)
ACCRQ*
ACCGR*
CD*
WE*
DBIN
D1
D0
CLK
RESET*
VSS
TE
REM
IFC
NDAC
NRFD
(nc)
REFERENCE
A5U1-1
A5U1-2
A5U1-3
A5U1-4
A5U1-5
A5U1-6
A5U1-17
A5U1-19
A5U1-20
A5U1-21
A5U1-22
A5U1-23
A5U1-24
A5U1-25
A5U1-26
A5U1-27
A5U1-28
7-3
HYDRA
Service Manual
7-5.
Main PCA Connector
The IEEE-488 PCA interfaces to the Main PCA through a 26-pin, right-angle connector
(A5J1). This connector routes the 8-bit data bus, the lower three bits of the address bus,
memory control, system clock, and address decode signals from the Main PCA to the
IEEE-488 PCA. The IRQ2* interrupt request signal is routed from the IEEE-488 PCA to
the Main PCA. The IEEE-488 PCA is powered by the +5.1V dc power supply (VCC).
The IEEE-488 PCA is sensed by the Microprocessor on the Main PCA through the
connection of logic common to the option sense signal OPS* (A5J1-22).
7-6.
IEEE-488 Controller
The IEEE-488 Controller (A5U1) is an integrated circuit that performs the transfer of
information between the IEEE-488 standard bus and the Main PCA Microprocessor
(A1U4). Once it has been programmed by the Microprocessor via the eight-register
microprocessor interface, A5U1 performs IEEE-488 bus transactions independently until
it must interrupt the Microprocessor for additional information or data.
The IEEE-488 Controller is clocked by a 1.2288-MHz square-wave clock. This clock
(A5U1-20) is generated by the Microprocessor. The IEEE-488 Controller uses this clock
to run the internal state machines that handle IEEE-488 bus transactions. The IEEE-488
Controller is reset when the system RESET* signal (A5U1-21) is low.
For each character that it receives or transmits, the IEEE-488 Controller generates an
interrupt to the Microprocessor. These interrupts are generated by driving the open-drain
interrupt output A5U1-10 low. This signal drives the IRQ2* input to the Microprocessor
low. When the Microprocessor responds to the interrupt and takes the necessary actions
by reading and writing registers in the IEEE-488 Controller, A5U1-10 goes high again.
Resistor A5R1 provides a pull-up termination on open-drain interrupt output A5U1-10.
When the Microprocessor performs a memory cycle to the IEEE-488 Controller, the
lower three bits of the address bus select the register being accessed in A5U1. When a
memory read cycle is performed, chip-enable A5U1-4 goes low, and A5U1-6 (DBIN)
goes high. These actions enable A5U1, driving the contents of the selected register onto
the data bus to the Microprocessor. When a memory write cycle is performed, chipenable A5U1-4 goes low, and A5U1-5 (WE*) goes first low and then high to latch the
data being driven from the Microprocessor into the IEEE-488 Controller.
The IEEE-488 Controller interfaces to the IEEE-488 Transceivers using an eight-bit data
bus, eight interface signals, and two transceiver control signals (A5U1-33 and A5U123).
The controller-in-charge signal (A5U1-33), which should always be high, controls the
direction of the SRQ, ATN, IFC, and REN IEEE-488 transceivers in A5U3.
The talk enable output (A5U1-2) is either low when the IEEE-488 Controller is not
addressed to talk or high when the controller is addressed to talk. This signal determines
the direction of all IEEE-488 Transceivers except SRQ, ATN, IFC, and REN.
7-4
IEEE-488 Option -05
General Maintenance
7-7.
7
IEEE-488 Transceivers/Connector
The IEEE-488 Transceivers (A5U2 and A5U3) are octal transceivers that are specifically
designed to exhibit the proper electrical drive characteristics to meet the IEEE-488
standard. These transceivers are configured to match the control signals available on the
IEEE-488 Controller. Assuming that A5U1-33 is always high, Table 7-2 describes the
transceiver direction control. The IEEE-488 Transceivers connect to a 24-position
connector (A5J2), which mates with the ribbon cable leading to the IEEE-488 connector
mounted at the rear of the instrument chassis.
Table 7-2. IEEE-488 Transceiver Control
TRANSCEIVER
TE = 0 (LISTENER)
DI01..DI08
SRQ
ATN
EOI
DAV
NRFD
NDAC
IFC
REN
Receiver
Transmitter
Receiver
Receiver
Receiver
Receiver
Transmitter
Transmitter
Receiver
Receiver
TE = 1 (TALKER)
Transmitter
Transmitter
Receiver
Receiver (ATN = 0)
Transmitter (ATN = 1)
Transmitter
Receiver
Receiver
Receiver
Receiver
7-8. General Maintenance
7-9.
Removing the IEEE-488 Option
Remove the instrument cover as shown in Figure 7-1. Then remove the IEEE-488 Option
with the following procedure:
Note
Parts referenced by letter (e.g., A) are shown in Section 3 (Figure 3-4.)
1. From the bottom of the instrument, locate the IEEE-488 PCA (N). This pca is
connected to the front of Main PCA, with a ribbon cable (O) leading across both
pca’s to the Rear Panel. Refer to Figure 7-1.
2. Use needle nose pliers to disconnect the 24-line cable assembly at the IEEE-488
PCA, alternately pulling on each end of the cable connector. Leave the other end of
this cable attached to its Rear Panel connector.
3. Remove the 6-32, 1/4-inch panhead Phillips screw (P) securing the IEEE-488 PCA.
See Figure 7-1.
4. Disengage the IEEE-488 PCA by sliding it away from the Main PCA.
7-5
HYDRA
Service Manual
MOUNTING
SCREW (2)
GROUNDING
SCREW
CASE
REAR BEZEL
REMOVE
PLASTIC PLUG
FROM CASE
CHASSIS
IEEE-488 PCA
RETAINING
SCREWS
6-32,1/4 INCH
PANHEAD SCREW
24-LINE RIBBON
CABLE ASSEMBLY
s53f.eps
Figure 7-1. Installation
7-6
IEEE-488 Option -05
Performance Testing
7
7-10. Installing the IEEE-488 Option
1. Place the IEEE-488 PCA into position so that the edge of the pca fits in the chassis
guide. Then line up connecting pins with the matching connector on the Main PCA,
and slide the pca into position.
2. Install the single 6-32, 1/4-inch panhead Phillips head screw in the corner of the
IEEE-488 PCA.
3. If necessary, attach the rear panel connector using 7 mm nut driver.
4. At the pca, attach the ribbon cable leading from the rear panel connector.
7-11. Performance Testing
Use the following performance test program to verify operation of the IEEE-488
Interface. This program is written for use with the Fluke 1722A Instrument Controller
and its interpreted BASIC language. The program may be adapted to the language of any
IEEE-488 controller.
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
500
510
520
530
540
550
560
999
IA% = 0%!
S% = -1%!
TERM!
INIT PORT 0
CLEAR @@IA%
PRINT @@IA%,"*cls"
ON SRQ GOTO 530
PRINT @@IA%,"*cls;*sre 16;*idn?"
WAIT 500% FOR SRQ
IF S% >>= 0% THEN 260
PRINT "Instrument failed to generate
STOP
PRINT "Serial Poll =";S%;"(should be
PRINT "Identification Query Response
STOP
!
! Service Request interrupt
!
S% = SPL(IA%)
IF S% AND 16% THEN 550 ELSE 560
INPUT LINE @IA%,R$
RESUME 230
END
instrument IEEE address
initialize spl response
terminate input only on EOI
! initialize IEEE-488 bus
! selective device clear
! clear instrument status
! enable SRQ interrupt
! SRQ on Message Available
! allow time to execute commands
a Service Request"
80)."
= ";R$
! get instrument serial poll status
! if MAV set get the response
! end of SRQ interrupt
This performance test communicates to an instrument that has been configured for IEEE488 operation at address 0. Lines 170 and 180 initialize the IEEE-488 bus and send a
selective device clear to the instrument. A multiple byte command is sent to the
instrument (by line 190) to clear the instrument status. Another command sequence
(including a query) is sent to the instrument by line 210; the instrument asserts Service
Request (SRQ) to signal that a response is available. Lines 530 through 560 first poll the
instrument for status, then input the response from the instrument. Lines 230 through
270 test for proper operation and print the results.
7-7
HYDRA
Service Manual
7-12. Troubleshooting
7-13. Power-Up Problems
The following discussion identifies probable fault areas if the installation of an IEEE488 Option causes power-up failure for the instrument. The problem is probably a short
on A5J1; the Microprocessor on the Main Assembly is prevented from accessing ROM
and RAM correctly.
•
First check if VCC is shorted to GND on the IEEE Assembly.
•
The short may also be caused by an interface signal to either VCC, GND, or another
interface signal. The logical signals to check are D7 .. D0, A2 .. A0, RD*, IEEE*,
WR*, E, RESET*, and IRQ2*.
•
The short may be due to a CMOS input that has been damaged due to static
discharge; the short is then detectable only when the circuit is powered up. Use an
oscilloscope to check activity on each of the interface signals. Verify that signals are
able to transition normally between 0 and 5V dc.
7-14. Communication Problems
7-15. Failure to Select IEEE-488 Option
IEEE-488 Interface selection procedures are described in Section 3 of the Hydra User
Manual.
If the IEEE-488 option is not detected by instrument software, there may be a problem
with the OPS* signal. The IEEE option grounds the OPS* signal (A5J1-22), which is
normally pulled up to VCC on the instrument Main PCA. The Microprocessor
determines that the IEEE-488 option is not installed if OPS* (A1U4-29) is high during
the power-up option detection.
7-16. Failure to Handshake on IEEE-488 Bus
After power-up or when the active computer interface is changed from RS-232 to IEEE488, the Microprocessor sends six write cycles to initialize A5U1. The IRQ2* interrupt
is then enabled, and the serial poll status byte is initialized. At this point, the IEEE-488
option is ready to respond to transactions on the IEEE-488 bus.
7-17. Failure to Enter Remote
If the IEEE-488 option does not enter remote, check that the remote/local control circuit
is operating properly. When the IEEE-488 option is the active instrument interface, the
remote/local control state is polled by the Microprocessor approximately every 400 ms.
Normally, A5U1-4 goes low for approximately 800 ns during the read cycle that checks
the state of A5U1. If D(0) (A5U1-11) is low during the read cycle, A5U1 is in the local
state. If A5U1-11 is high during the read cycle, A5U1 is in the remote state. When A5U1
indicates that it is in remote, the REM indicator on the display is turned on.
7-8
IEEE-488 Option -05
List of Replaceable Parts
7
7-18. Failure to Receive Multiple Character Commands
Monitor the IRQ2* interrupt signal from A5U1-10 during attempts to communicate with
the instrument. Each byte received with the ATN signal (A5U1-31) high should cause
the interrupt signal to go low. Verify that the signal arrives at A5J1 properly. An
interrupt not detected by A1U4 will remain low indefinitely. A5U1-10 will go high only
when both the interrupt is detected and the received byte is removed from A5U1 by
A1U4.
7-19. Failure to Transmit Query Responses
Check that TE (A5U1-23) goes high when the interface is addressed to talk. This signal
must go high to allow the bus interface transceivers to change the direction of DIO1
through DIO8, EOI, DAV, NRFD, and NDAC. Verify that each of these signals passes
through A5U2 and A5U3 properly.
7-20. Failure to Generate an End or Identify (EOI)
When the IEEE-488 option sends the Line Feed termination character at the end of a
response, the EOI signal should also be set true. When EOI is true, A5U1-30 should go
low. Follow this signal from A5J2 through A5U3 to A5U1.
7-21. Failure to Generate a Service Request (SRQ)
When a Service Request is being generated, A5U1-32 should be low. Follow this signal
through A5U3 to connector A5J2. When a Serial Poll (SPL) is performed by the IEEE488 bus controller, A5U1-32 will go high again.
Note
If the instrument is in the remote state without front panel lockout (i.e.,
REMS), a service request can be sent from the front panel by pressing the
up arrow button.
7-22. List of Replaceable Parts
Refer to Section 6 for an illustrated parts list of the IEEE-488 Option.
7-23. Schematic Diagram
The schematic diagram for the IEEE-488 Option is included in Section 8 of this manual.
7-9
HYDRA
Service Manual
7-10
Chapter 8
Schematic Diagrams
Figure
8-1.
8-2.
8-3.
8-4.
8-5.
8-6.
8-7.
8-8.
Title
Page
A1 Main PCA (2620A/2625A)..............................................................................8-3
A1 Main PCA (2635A)..........................................................................................8-8
A2 Display PCA ....................................................................................................8-14
A3 A/D Converter PCA.........................................................................................8-16
A4 Analog Input PCA............................................................................................8-20
A5 (Option -05) IEEE-488 Interface PCA.............................................................8-22
A6 Memory PCA (2625A).....................................................................................8-24
A6 Memory Card I/F PCA (2635A) ......................................................................8-26
8-1
HYDRA
Service Manual
8-2
Schematic Diagrams
8
2620A-1601
s88f.eps
Figure 8-1. A1 Main PCA (2620A/2625A)
8-3
Schematic Diagrams
NOTES:
1.
8
UNLESS OTHERWISE SPECIFIED
ALL RESISTORS ARE 1/4W 5%.
ALL CAPACITOR VALUES ARE IN MICROFARADS.
REF
DES
POWER SUPPLY PIN NUMBERS
VCC
GND
VEE
VDDR
COM
DO_GND
A01AR1
8
4
-
-
-
-
A01AR2
4
11
-
-
-
-
A01AR3
4
11
-
-
-
-
A01U1
8
5
-
-
-
-
A01U2
14,16
1,2,5,7,26
-
-
-
-
A01U3
26,28
14
-
-
-
-
A01U4
5,36
2,6,45
-
-
-
-
A01U5
5
-
-
1
-
-
A01U7
-
-
-
-
4
-
A01U8
28
14,22
-
-
-
-
A01U9
3
-
-
-
-
-
INTERCONNECT DIAGRAM
REFERENCE DESIGNATIONS
LAST USED
NOT USED
SHEET 2
A01U10
14
7
-
-
-
-
A01U11
16
5,8
-
-
-
-
AR
C
CR
J
L
P
Q
R
RT
A01U12
14
7
-
-
-
-
RV
A01U13
20
10
-
-
-
-
A01U14
4,9,10,14
7
-
-
-
-
A01U15
14
7
-
-
-
-
A01U16
20
10
-
-
-
-
A01U17
-
-
-
-
-
8
A01U20
16
8
-
-
-
-
A01U21
13,14
7
-
-
-
-
A01U22
-
7,11,12
-
-
-
-
S
T
TP
U
VR
W
Y
Z
A01U23
-
7,11,13
-
-
-
-
A01U24
-
4,5,6
-
-
-
-
A01U25
1,16
2,6,9,14
8
-
-
-
A01U26
20
10
-
-
-
-
A01U27
-
-
-
-
-
8
A01U28
14
7
-
-
-
-
A01U29
16
8,15
-
-
-
-
A01U31
5
2,3,4
-
-
-
-
A01Z2
16
-
-
-
-
-
AR3
C59
CR19
J6
L2
P10
Q9
R64
RT1
RV1
S1
T2
TP32
U31
VR4
W1
Y1
Z3
P1-P9
DCH
DCH
DCL
DCL
VCC
VCC
GND
GND
VEE
VLOAD
R17-18,23-24,27,29,32-33
SHEET 4
SHEET 3
FIL1
FIL2
-PFAIL
TRIG
TOTALIZE
A<15..0>
D<7..0>
-RD
TP21-29
U30
VDDR
-WR
VDD
-DIO
COM
-RESET
VSS
E
SHLD
2620A-1001
(1 of 4)
s71f.eps
Figure 8-1. A1 Main PCA (2620A/2625A) (cont)
8-4
Schematic Diagrams
8
RT1
CR1
RAW SUPPLY
DCH
MBRD360
DCH
SH4
RXE065
DCL
SH4
C59
180PF
PFAIL*
SH3
DCL
1/8A SB
J3
T401
3
L
R48
10K
S1 O1
1N5397
250V
INGUARD SUPPLIES
POWER FAIL DETECTION
CR3
P1
U6
C39
.047
C1
2
R43
39K
O2
P2
R45
C2
CR2
R42
10K
1.0M
1%
1
EG
1N5397
TP7
U19
C7
10000
35V
IN
TL317
OUT
R39
3
63.4K
1%
2
U24
LM393DT
4
+5.2V
Q2
MMBT3906
C9
Q1
VR4
LM385
1.23V
ADJ
R5
1.00K
1%
20
R41
11.0K
1%
IBIAS
R6
3.32K
1%
R13
PFAIL*
1
T1
U23
U23
U23
COM
U23
C12
470
16V
CR6
1
HCU04
2
3
HCU04
4 5
6
HCU04
9
HCU04
8
R4
11
R47
10K
8
R40
5.1K
C35
1000PF
1
3
4
C13
470
16V
CR7
BAW56
U31
LM358DT
COM
SH3
10K
MBR140
UNUSED
R12
R10
47K
4.7K
C5
1.0
50V
Q3
MMBT3906
C10
Q6
MMBT3904
9
7
180PF
4
U22
2
SWITCHER
3
C26
VC
3
1
G
470
S
CR12
2
TP5
TP6
HC74
5
GND
SHLD
SH3
Q8
R34
5
D PR Q
BAS16
4
8
3
6
CL Q
4
R26
100
Q7
G
470
CR10
MBRD360
5VAC
8
D
R28
5
6
TP10
BAS16
1
LM358DT
6
U31
FIL1
SH3
7
CR11
47
100V
2
7
S
OUTGUARD SUPPLIES
5
TP4
CR9
MMBD7000
+5.1V
-30V
4
C21
.1
25V
U22
HCU04
U23
HCU04
4
12
U24
LM393DT
D PR Q
U18
CL Q
VEE
-5.0V
79L05
IN
OUT
11
13
TP1
9
HC74
7
13
C17
2.2
50V
TP3
12
8
6
C14
2200
10V
10
10
5
R30
45.3K
1%
VLOAD
SH3
C30
47
50V
U23
11
VR3
1N5235B
6.8V
CR8
MMBD7000
TP2
UNUSED
C18
220
35V
FIL2
SH3
R38
0.02
VCC
R31
11.0K
1%
C20
220
35V
VSS
SH3
-5.6V
Q5
MMBT3904
33
D
2
VSW
TP32
CR4
BAS16
R15
1
TP9
4
LT1170
U 9 FB
VR1
1N5232
5.6V
10
T2
VIN
TP30
R14
10K
MBR140
12
TP14
C4
1.0
50V
4.7K Q 4
MMBT3904
CR5
VDD
SH3
TP31
VR2
1N5233
6.0V
R9
47K
INVERTER
R46
4.02K
1%
180PF
MMBT3906
R11
C34
1.0
VDDR
SH3
C6
10
63V
8
R44
1.30K
1%
2
+5.6V
LM317
OUT
ADJ
C2
.033
N
IN
VCC
8
GND
CR13
MMBD7000
C31
47
50V
C32
1.0
50V
R22
47K
2620A-1001
(2 of 4)
s72f.eps
Figure 8-1. A1 Main PCA (2620A/2625A) (cont)
8-5
Schematic Diagrams
8
2620A-1001
(3 of 4)
s73f.eps
Figure 8-1. A1 Main PCA (2620A/2625A) (cont)
8-6
Schematic Diagrams
8
VCC
Z3
1
R58
20
47K
470
Z 2 16
1
CR15
BAW56
VCC
AR1
LM358DT
8
22K
C54
180PF
6
7
1
10
5
Z1
Z3
2
4
350K
R49
19
47K
19
470
Z 2 16
2
55K
TP19
3
4
U14
2
9
8
TP20
10
U28
10
HC00
4
11
U28
HC4040
10
HC244
BINARY
D7
D6
D5
D4
D3
D2
D1
D0
1
10
2
15
0
3
3Y
3
A
17
1
5
2
Y
2
A
15
2
7
1Y
1A
13
3
U29
Q7
7
Q7
9
9
0
Y
0
A
C50
2
11
6
19
10
AR2
LM324D
Z1
350K
5
11
5
HC86
CR18
BAW56
U27
7
HC86
3Y
3
A
8
5
14
2
Y
2
A
6
6
16
1Y
1A
4
8
7
18
0
A
2
10
Y
0
Z1
350K
10
AR3
LM324D
14
U27
ULN2004
14
1
RD*
SH3
9
10
11
0
U12
U10
8
2
3
HC00
HC27
7
6
5
4
3
2
1
0
18
17
14
13
8
7
4
3
4
1
U12
5
6
HC273
D7
Q7
D6
Q6
D5
Q5
D4
Q4
D3
Q3
D2
Q2
D1
Q1
D0
Q0
10
19
16
15
12
9
6
5
2
U15
14
10
9
U12
10
2
12
AR2
LM324D
Z1
350K
HC00
8
HC273
D7
Q7
D6
Q6
D5
Q5
D4
Q4
D3
Q3
D2
Q2
D1
Q1
D0
Q0
19
16
15
12
9
6
5
2
U27
13
R59
47
Z 2 16
22K
C56
180PF
180PF
16
10
Z1
350K
9
C46
Z3
CR16
BAW56
U27
15
55K
R60
47
10
6
AR3
LM324D
350K
5
9
D<7..0>
VCC
SH3
3
U17
11
6
HC86
U17
7
R35
4.7K
ULN2004
9
10
15
ULN2004
180PF
L2
6T
R62
47
C52
180PF
C53
Z 2 16
10
C58
180PF
L1
1T
1000PF
9
C44
16
ULN2004
180PF
VCC
1
15K
9
1
9
C45
22K
TP18
9
2
11 Z 2 16
22K
AR1
R37
UNUSED
U17
Z 2 16
R50
47
Z 3 11
U17
47
DCH
22K
47K
17
C57
180PF
OUT3
OUT2
OUT1
OUT0
DCL
R61
1
2
3
4
5
6
7
8
180PF
R51
11
55K
14
ULN2004
ULN2004
VCC
9
3
10
11
Z1
Z 2 16
22K
12 Z 2 16
22K
47
9
7
4
12
47K
3
AR3
LM324D
CL
R52
47
11
9
2
10
10
9
13
U17
1
18
8
4
ULN2004
Z 3 13
47K
ULN2004
RESET*
SH3
U14
U17
Z 2 16
22K
C47
7
VCC
C55
180PF
ULN2004
7
9
6
1
A<2..0>
SH3
12
Z 2 16
22K
47
8
13
55K
U16
18
17
14
13
8
7
4
3
14
J6
8
13
HC02
7
6
5
4
3
2
1
0
5
12
14
CL
13
CR19
BAW56
U27
11
9
U17
180PF
R53
47K
12
AR3
LM324D
14
ULN2004
11
12
350K
Z3
5
1
DIO*
SH3
WR*
SH3
Z1
55K
11
HC00
C48
VCC
Z 2 16
22K
13
7
13
12
180PF
R54
47
9
4
1
U26
22K
C49
6
9
55K
OE
C36
.1
25V
Z 2 16
5
9
6 Z 3 15
47K
8
13
VCC
47
ULN2004
12
10
9
8
7
6
5
4
3
2
1
R55
16
3
4
9
U14
Z3
47K
55K
12
U14
180PF
5
HC244
6
15
7
OE
4
J5
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
Z 2 16
22K
ULN2004
74HCT165DT
VCC
11
47
4
U27
U13
R
180PF
R56
9
5
6
PL
DS
CP
CE
10
AR2
LM324D
55K
CTR
1
15
14
12
13
4
2
3
5
6
7
9
Z1
350K
22K
16
ULN2004
9
4
Z 2 16
3
4 Z 3 17
47K
8
U13
47
9
1
13
5
180PF
R57
C51
U28
HC00
HC00
C41
25V
.1
CR14
BAW56
3
U27
U20
10
350K
11
12
2
6
E
Z1
U28
HC00
Q11
Q10
Q9
Q8
Q7
Q6
Q5
Q4
Q3
Q2
Q1
Q0
2
3
AR2
LM324D
55K
1
3
3 Z 3 18
47K
1
2
HC86
TOTAL
TOT
VCC
1
TRIG
XT*
22K
C43
2
R36
15K
C29
.1
25V
Q9
MMBT5089
CR17
LM358DT
16
Z2
22K
15
MMBD7000
RV1
39V
DO_GND
ULN2004
SH2
DCL
2620A-1001
(4 of 4)
DCH
SH2
s74f.eps
Figure 8-1. A1 Main PCA (2620A/2625A) (cont)
8-7
Schematic Diagrams
8
POWER SUPPLY PIN NUMBERS
REF
DES
GND
VCC
(5.0V dc)
VBB
(+5V dc)
COM
VDDR
(5.6V dc)
A1U1
------A1U2
-A1U3
A1U4
A1U5
A1U7
A1U8
A1U9
A1U10
A1U11
A1U12
-A1U13
A1U14
A1U15
A1U16
A1U20
A1U22
A1U23
A1U24
A1U25
----A1U26
A1Z2
3, 13, 23,
29, 34,
44, 50,
57, 67,
73, 84,
102, 107,
116, 126
2, 5, 7,
9, 12
11
11
4
-4
-3
10
1, 2, 12,
21
9
16
7, 8, 9
16
16
7, 11, 12
7, 11, 13
16
4, 16, 28,
52, 53,
66, 77,
93
-7
--
18, 28,
39, 62,
72, 74,
83, 99,
112, 131
--14
-4
4
--8
4
2
20
--1, 16
32
16
32
----3, 6, 27,
29, 41,
54, 55,
56, 79,
91
-16
---------------1
-24
-----32
--32
-----9, 12, 14
--
------------4
----------------------
-----------1
-----------------------
Reference Designations
Lasted Used
BT
C
CR
J
L
P
Q
R
RT
RV
S
T
TP
U
VR
W
Y
Z
BT1
C76
CR21
J6
L2
P10
Q10
R118
RT1
RV1
S1
T3
TP32
U27
VR3
W4
Y1
Z3
Not Used
-C27, 37
---P1-3, 5-9
-R76
----TP16-17, 19, 21-29
U21
-W2
---
2635A-1601
s89f.eps
Figure 8-2. A1 Main PCA (2635A)
8-8
Schematic Diagrams
RT1
CR1
2620A-6501
1/8A SB
J3
MBRD360
RXE065
CR3
C59
1
L
180PF
1N5397
SHEET 5
DCH
DCL
SHEET 4
VPF
S1
C2
2
.033
100V
N
R20
CR2
R13
20
R19
1N5397
OFF
Q2
IN
R48
R11
OUT
MBR140
R44
C39
C1
C7
220
35V
10000
35V
T1
NOTE: U22 AND U23 ARE BIASED BY IBIAS
C4
1.0
50V
LM317T
IN
OUT
VDDR
P10
ADJ
R6
R5
3.32K
1%
1.00K
1%
TP30
470
16V
IBIAS
9
6
7
4
5
1
10
8
C6
10
63V
RCOM
SHLD
C34
11
1.0
50V
U23
8
HCU04
U23
9
6
HCU04
U23
5
4
U23
3
HCU04
2
C13
HCU04
R14
470
16V
1
C35
R40
10
R47
1000PF
10K
2
5.1K
R12
10K
4.7K
IRL024
Q 5 C10
Q8
7
R34
T2
2
FLUKE45-6401
5
1
BAS16
U22
R28
LM358DT
7
VC
1
8
R31
100
CL Q
TP6
8
J2
5
470
4
FIL1
FIL2
TP4
TP10
VLOAD
VEE
1
BAS16
VCC
1
2
3
4
7
6
8
CR9
MMBD7000
CR11
1
MBRD360
11.0K
1%
TP5
6
6
CR10
6
U28
R26
5
7
5VAC
3
Q7
47
50V
MMBT3904
IRL024
4
2
TP32
VSS
R38
VR3
TP2
4
0.02
1/4W
C21
0.1
25V
CR8
1N5235B
MMBD7000
C30
10
12
D PR Q
C17
47
50V
RI
9
R22
U18
U23
HC74
11
C18
R30
C14
220
35V
45.3K
1%
2200
10V
11
HCU04
CL Q
U23
13
TP1
13
HCU04
2.2
50V
VEE
47K
GND
CR13
8
TP3
LM79L05A
IN
OUT
10
U22
VCC
DISPLAY SUPPLIES
HC74
3
C26
3
D PR Q
33
BAS16
TP9
CR12
5
GND
2
CR4
180PF
R15
470
4
4
2
LT1170
U 9 FB
VR1
1N5232
1
TP14
VSW
MMBT3906
MMBT3904
LM358DT
9
VIN
1.0
50V
Q6
U28
4
C5
R10
47K
1
3
Q3
CR7
BAW56
8
A
10K
R4
A/D SUPPLIES
4.02K
1%
U6
C12
R46
MMBT3904
4.7K
MBR140
12
.047
100V
R9
47K
CR5
1.30K
1%
1N5233
Q4
MMBT3906
ADJ
10K
1/4W
180PF
VR2
CR6
LM317L
MH1
C9
Q1
11.0K
1%
TP7
U19
TP31
MMBT3906
VDD
59.0K
1%
3
EG
8
MMBD7000
12
C31
C32
47
50V
RI
1.0
50V
2635A-1001
(1 of 5)
s75f.eps
Figure 8-2. A1 Main PCA (2635A) (cont)
8-9
Schematic Diagrams
8
2635A-1001
(2 of 5)
s76f.eps
Figure 8-2. A1 Main PCA (2635A) (cont)
8-10
Schematic Diagrams
8
2635A-1001
(3 of 5)
s77f.eps
Figure 8-2. A1 Main PCA (2635A) (cont)
8-11
Schematic Diagrams
8
KEYBOARD I/F
J2
15
16
20
19
17
18
SWR1
SWR2
SWR6
SWR5
SWR3
SWR4
6
4
5
3
A<23..1>
XTI
RDU*
3
0
VCC
R87
OCLK
PAD5
PAD6
PAD15
PAD16
PAD25
PAD26
PAD27
PAD31
PAD35
PAD36
PAD37
PAD42
PAD43
PAD44
PAD45
PAD46
PAD47
PAD48
PAD49
PAD50
PAD52
PAD53
22
21
11
10
97
96
95
90
86
85
84
75
74
73
72
71
70
69
68
67
64
63
47
PGA*
88
93
100
98
94
92
89
87
83
81
8
9
10
11
12
13
14
15
SCLK
R107
33
VCC
D0-DIN-IO
D1-IO
D2-IO
D3-IO
D4-IO
D5-IO
D6-IO
D7-IO
XC3030-70PQ100C
30
82
76
TCLKIN-IO
XTL1-BCLKIN-IO
XTL2-IO
2
54
52
56
99
78
29
CCLK
M0-RTRIG
M1-RDATA
M2-IO
RDY/BUSY-RCLK-IO
RESET
PWRDWN
U25
R70
R64
10K
10K
VCC
A0-WS-IO
A1-CS2-IO
A2-IO
A3-IO
A4-IO
A5-IO
A6-IO
A7-IO
A8-IO
A9-IO
A10-IO
A11-IO
A12-IO
A13-IO
A14-IO
A15-IO
5
6
8
9
13
15
18
20
24
26
25
23
19
17
14
12
INIT-IO
HDC-IO
LDC-IO
DOUT-IO
DONE-PG
65
57
59
1
80
WRU*
TOTO
XTINT*
R85
DCLK
47
TOTI*
XINIT*
XD/P*
PAD54
PAD55
PAD56
PAD58
PAD61
PAD62
PAD63
PAD64
PAD65
PAD66
PAD67
PAD68
PAD69
PAD70
PAD71
PAD72
PAD73
PAD74
PAD75
PAD76
PAD77
PAD78
PAD79
XRDY
RESET*
CS0-IO
CS1-IO
R42
10K
0
1
2
3
4
5
6
7
62
61
60
58
51
50
49
48
47
46
45
44
43
42
40
39
38
37
36
35
34
33
32
D<15..0>
DI<7..0>
1
0
2
3
4
5
7
6
KINT*
2
1
DO<7..0>
AO<3..0>
CONTROL
U25
U25
U25
U25
VCC
C60
C19
C76
C75
.1
25V
.1
25V
.1
25V
.1
25V
2635A-1001
(4 of 5)
s78f.eps
Figure 8-2. A1 Main PCA (2635A) (cont)
8-12
Schematic Diagrams
8
XTI
TOTI*
EXTERNAL TRIGGER
AND TOTALIZER
INPUTS
VCC
VCC
10
350K
CR14
5
9
18
8
1
18
10
17
15
1
14
10
350K
55K
2
6
17
12
10
Z1
350K
1
8
6
10
350K
4
10
13
11
10
8
10
5
55K
7
C52
C53
180PF
1000PF
DO_GND
16
R60
22K
14
U17
Z2
U27
1T
47
1/4W
C56
RV1
41V
180PF
47
1/4W
16
22K
9
3
R50
Z3 8
7
47
1/4W
C57
11
11
47K
L1
6T
R61
Z2
9
ULN2004
ULN2004
13
U17
2
180PF
9
L2
16
22K
15
C45
22K
47
1/4W
180PF
47
1/4W
16
6
Z1
350K
6
U27
6
2
OUT0
OUT1
OUT2
OUT3
8
7
6
5
4
3
2
1
R62
C58
10
R51
Z2
47K
J6
16
Z2
9
ULN2004
Z3 9
BAW56
7
7
U17
10
9
8
7
6
5
4
3
2
1
SHEET 2
DCH
DCL
180PF
12
CR16
U4
LM324D
J5
22K
16
C46
ULN2004
3
6
9
47
1/4W
16
5
55K
6
1
9
U27
3
UNUSED
U17
Z2
9
ULN2004
1
Z1
350K
9
VCC
180PF
12
3.6K
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
R52
Z2
5
22K
2
R36
7
11
0
Z 3 10
5
C29
.1
25V
ULN2004
13
47K
1
2
.1
25V
9
ULN2004
12
U4
LM324D
6
C33
.1
25V
U17
55K
5
C38
.1
25V
180PF
4
Z1
350K
10
C61
C47
22K
U27
14
U17
47
1/4W
16
BAW56
U4
LM324D
5
9
U8
R53
Z2
4
CR19
55K
4
U3
180PF
Z 3 20
7
U4
VCC
14
47K
10
Z1
5
C48
ULN2004
9
7
ULN2004
9
3
R37
9.1K
6
47
1/4W
16
22K
U4
LM324D
4
3
U8
LM358D
16
TP18
R54
Z2
U27
VCC
22K
180PF
9
Z3 4
11
55K
3
47
1/4W
15
47K
5
180PF
MMBT5089
Z2
C49
ULN2004
7
3
C43
470
R55
16
2
U3
LM324D
16
22K
CR17
22K
U27
13
Q9
MMBD7000
Z2
BAW56
TOT
Z2
15
1
CR18
R49
Z 3 16
180PF
Z3 6
13
3
16
47K
3
Z1
180PF
C50
ULN2004
2
C54
47
1/4W
16
9
U27
16
22K
47K
55K
Z2
2
1
U3
LM324D
2
5
Z1 10 3 5 0 K 15
R56
Z3 3
22K
55K
1
2
16
12
47K
10
Z1
350K
180PF
ULN2004
14
470
BAW56
U8
LM358D
1
U3
LM324D
XT*
Z2
CR15
C51
9
U17
47
1/4W
16
22K
BAW56
19
55K
0
8
R58
Z 3 14
47K
Z2
47K
12
Z1
7
R57
Z3 2
DIGITAL I/O
1
7
19
14
0
DO<7..0>
13
ALARM OUTPUTS
U3
LM324D
DI<7..0>
C44
180PF
9
3
4
Z2
9
12
13
ULN2004
16
22K
C55
R59
47
1/4W
180PF
10
ULN2004
2635A-1001
(5 of 5)
AO<3..0>
s79f.eps
Figure 8-2. A1 Main PCA (2635A) (cont)
8-13
Schematic Diagrams
8
CKT 1
CKT 2
2620A-4002
s90f.eps
Figure 8-3. A2 Display PCA
8-14
Schematic Diagrams
8
POWER SUPPLY PIN NUMBERS
REF DES
A2U1
A2U4
A2U5
A2U6
A2Z1
VCC
(5.1V dc)
21
16
10, 16
14
16
GND
VEE
(5.0V dc)
42
2, 8
8
7, 9, 10
--
4
-----
VLOAD
(-28.5 to -30.0V dc)
5
-----
2620A-1002
s80c.eps
Figure 8-3. A2 Display PCA (cont)
8-15
Schematic Diagrams
8
K3, K5-K14 Relay Polarity
Install with marked end as shown.
Aromat or Nais
Omron
2620A-1603
s91c.eps
Figure 8-4. A3 A/D Converter PCA
8-16
Schematic Diagrams
8
POWER SUPPLY PIN NUMBERS
REF
DES
VCC
(5.3V dc)
VSS
(5.4V dc)
ANALOG_GND
VDDR
(5.6V dc)
A3U1
A3U2
A3U3
-A3U4
A3U5
A3U6
A3U7
A3U8
A3U9
A3U10
A3U11
A3U12
A3U13
A3U14
A3Z1
A3Z2
A3Z3
3
1, 16
1, 10, 11,
12, 13, 14
----1
5, 6, 9, 36
---8
8
-1
--
-8
------44
-----4
----
10, 11, 12
6, 9
2, 7
---1, 3, 4
3
4, 25, 27, 38
2, 45
---4
-4
-8
----9
9
----9
9
9
------
RCOM
----8
8
----8
8
8
------
2620A-1003
(1 of 3)
s81c.eps
Figure 8-4. A3 A/D Converter PCA (cont)
8-17
Schematic Diagrams
8
2620A-1003
(2 of 3)
s82c.eps
Figure 8-4. A3 A/D Converter PCA (cont)
8-18
Schematic Diagrams
8
2620A-1003
(3 of 3)
s83c.eps
Figure 8-4. A3 A/D Converter PCA (cont)
8-19
Schematic Diagrams
8
2620A-1604
s92f.eps
Figure 8-5. A4 Analog Input PCA
8-20
Schematic Diagrams
TB2
NOTES:
UNLESS OTHERWISE SPECIFIED.
ALL CAPACITOR VALUES ARE IN MICROFARADS.
M1
1
2
3
6
8
4
11
10
14
13
12
15
5
9
7
CH1_HI
CH1_LO
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
CH2_HI
CH2_LO
CH3_HI
CH3_LO
CH4_HI
CH4_LO
CH5_HI
CH5_LO
CH6_HI
CH6_LO
CH7_HI
CH7_LO
CH8_HI
CH8_LO
CH9_HI
CH9_LO
CH10_HI
C H 1 0_LO
M2
RV4
910V
910V
P1
CH1_HI
CH1_LO
CH2_HI
CH2_LO
CH3_HI
CH3_LO
CH4_HI
CH4_LO
CH5_HI
CH5_LO
CH6_HI
CH6_LO
CH7_HI
CH7_LO
CH8_HI
CH8_LO
CH9_HI
CH9_LO
CH10_HI
CH10_LO
CH11_HI
CH11_LO
CH12_HI
CH12_LO
CH13_HI
CH13_LO
CH14_HI
CH14_LO
CH15_HI
CH15_LO
CH16_HI
CH16_LO
CH17_HI
CH17_LO
CH18_HI
CH18_LO
CH19_HI
CH19_LO
CH20_HI
CH20_LO
RV1
3
5
7
9
11
13
15
1
6
8
4
2
14
12
10
RV2
910V
910V
TB1
1
2
CH11_HI
CH11_LO
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
CH12_HI
C H 1 2_LO
CH13_HI
C H 1 3 _LO
CH14_HI
C H 1 4_LO
CH15_HI
C H 1 5 _LO
CH16_HI
C H 1 6_LO
CH17_HI
C H 1 7 _LO
CH18_HI
C H 1 8_LO
CH19_HI
C H 1 9 _LO
CH20_HI
CH20_LO
A6
C6
A10
C10
A12
A14
B15
A16
C18
A18
B21
A22
B23
C24
B25
B27
C28
C30
C32
B31
A4
C4
A8
C8
C12
B13
C14
C16
B17
B19
A20
C20
C22
A24
C26
A26
B29
A28
A30
A32
B11
B9
B7
B5
B3
B1
A2
C2
P2
R1
5.49K
R3
50K
25PPM/C
R2
10K
25PPM/C
CW
1.
1
2
RV3
8
RGRD
CB2
CB1
VR1
LM385-2.5
VDD
AGND2
AGND1
Q1
STS1018
C1
1000PF
SHLD
A10
B10
A9
B9
A8
B8
A7
B7
A6
B6
A5
B5
A4
B4
A3
B3
A2
B2
A1
B1
2620A-1004
s84f.eps
Figure 8-5. A4 Analog Input PCA (cont)
8-21
Schematic Diagrams
8
2620A-1605
s93f.eps
Figure 8-6. A5 IEEE-488 Interface PCA (2620A Only)
8-22
Schematic Diagrams
REF DES
POWER SUPPLY PIN NUMBERS
VCC
(5.1V dc)
A5U1
A5U2
A5U3
A5U4
8
3, 44
20
20
14
GND
22
10,11
10
1,2,4,5,7,9,10
2620A-1005
s85c.eps
Figure 8-6. A5 IEEE-488 Interface PCA (2620A Only) (cont)
8-23
Schematic Diagrams
8
2625A-1606
s94f.eps
Figure 8-7. A6 Memory PCA (2625A)
8-24
Schematic Diagrams
REF DES
POWER SUPPLY PIN NUMBERS
VCC
(5.1V dc)
A6U1
A6U2
A6U3
A6U4
A6U5
A6U6
A6U7
A6U8
8
20
14
14
5
14
32
32
16
GND
1, 10
7, 12, 13
7
3, 12
7
16
16
5, 8
2625A-1006
s86c.eps
Figure 8-7. A6 Memory PCA (2625A) (cont)
8-25
Schematic Diagrams
REF
DES
A6U1
--A6U2
A6U3
POWER SUPPLY PIN NUMBERS
VCC
(5.0V dc)
1, 11, 12, 13, 14, 15, 17,18
19, 20, 21, 31, 41, 51, 61,
71, 81, 91, 101, 105, 111,
7
2, 4, 6, 7, 8, 10
GND
16, 27, 46, 60, 76, 106, 107,
113, 116, 120
-14
20
8
Reference Designations
Lasted Used
C
DS
P
Q
R
TP
U
Z
C9
DS2
P2
Q1
R15
TP1
U3
Z3
Not Used
----R14
--Z1
2635A-1606
s95f.eps
Figure 8-8. A6 Memory Card I/F PCA (2635A)
8-26
Schematic Diagrams
Q1
VCC
P2
R11
DS2
DS1
VPP1
VPP2
VCC
VCC
R17
R9
47K
47K
C9
C6
1.0
35V
.1
25V
CD<0>
58
66
32
65
33
63
62
31
64
30
RESET
D10
D2
D9
WP
BVD1
BVD2
D1
D8
D0
CA<0>
CA<1>
CA<2>
CA<3>
REG*
CA<4>
CA<5>
CA<6>
CA<25>
44
45
57
60
43
29
28
27
26
61
25
24
23
56
RFU1
RFU2
RFU3
RFU4
RFSH
A0
A1
A2
A3
REG
A4
A5
A6
A25
CVCC
CRESET
Z2
1.5K
R10
47
10V
8
7
6
5
R13
10
7
CD<2>
WP
BVD1
BVD2
CD<1>
100
360
HLMP-1302-101
Z2
9
8
Z2
11
6
R16
61
96
22
18
20
97
95
29
26
VCC
25
24
20
21
24
27
30
33
36
40
18
52
17
51
CVPP
10K
360
HLMP-1402-101
C5
G
4
R1
P1
SI9405DY
S
D
2
3
2
7
12
17
39
33
35
36
39
43
45
48
47
D0
D1
D2
D3
D4
D5
D6
D7
26
22
25
23
A1
A2
A3
A4
34
38
44
40
A1
A2
A3
A4
9
6
4
14
11
XMCARD*
XRDU*
XWRU*
DTACK*
MCINT*
49
50
51
58
60
CS
RD
WR
DTACK
IRQ
19
XSCLK
30
SCLK
CRESET
CD2
CWP
ALM1
ALM2
CD1
CD0
D8
D9
D10
D11
D12
D13
D14
D15
PWRDWN
28
32
34
38
29
31
35
37
VCC_SEL0
BUSYLED
BATTLED
47K
R15
2635A
PCMCIA
INTERFACE
U1
XC3030A-7PQ100C
33
100
DIN
XC1736-DS08C
CA15
CA22
CA16
CA21
84
87
89
74
CA<15>
CA<22>
CA<16>
CA<21>
20
53
19
50
A15
A22
A16
A21
CA20
83
CA<20>
49
A20
CA19
CA14
CRDY
CA18
CA13
CA17
CA8
71
82
23
69
75
68
72
CA<19>
CA<14>
RDY/BSY
CA<18>
CA<13>
CA<17>
CA<8>
48
14
16
47
13
46
12
1
34
35
68
69
70
A19
A14
RDY/BSY
A18
A13
A17
A8
GND
GND
GND
GND
EARTH
EARTH
11
10
8
41
40
6
39
5
38
4
37
3
2
36
67
59
A9
A11
A10
D15
D14
D7
D13
D6
D12
D5
D11
D4
D3
CD1
CD2
WAIT
15
9
42
7
WE
OE
CE2
CE1
CD3
CD4
CD5
CD6
CD7
CA10
CA11
CA9
A7
A24
A12
A23
93
90
88
85
86
67
70
73
22
55
21
54
CP1
CP0
CA<7>
CA<24>
CA<12>
CA<23>
21
19
U3
10
98
94
92
CEL
CRD
CWR
CWAIT
D/P
RESET
CCLK
CA7
CA24
CA12
CA23
62
63
64
17
80
78
2
47K
14
15
6
13
8
12
11
9
5
M0
M1
M2
CEO
CE
D
R/OE
CLK
4
3
2
R12
CA0
CA1
CA2
CA3
REG
CA4
CA5
CA6
CA25
54
52
56
6
1
VCC
P3
1
2
3
4
5
6
16
1
3
5
8
10
13
15
18
R8
10K
CCLK
D/P*
DIN
8
R14
R2
R7
R5
47K
47K
47K
47K
CA<9>
CA<11>
CA<10>
R6
360
Z2
15
Z2
Z2
Z2
Z2
100
2
CD<7>
16
1
CD<6>
14
3
CD<5>
13
12
4
5
CD<4>
CD<3>
CD1
CD2
CWAIT*
RESET*
CWR*
CRD*
R4
R3
10K
10K
TP1
HC4066
U2
VCC
MH1
MH2
MH3
RESET*
CE1*
11
12
8
6
4
5
1
13
X0
E0
X1
E1
X2
E2
X3
E3
Y0
10
Y1
9
Y2
3
Y3
2
NOTES;
UNLESS OTHERWISE SPECIFIED
1. ALL CAPACITOR VALUES ARE IN MICROFARADS.
2. ALL RESISTOR VALUES ARE IN OHMS.
3. ALL RESISTOR ARE 1/8W,5%.
4. THIS DRAWING IS ARCHIVED ON
TAPE: 2635A-C97006:MT.
SEE SCD: 2635A-C90006.
VCC
C1
C2
C3
C4
C7
C8
.1
25V
.1
25V
.1
25V
.1
25V
.1
25V
.1
25V
U1
U1
U1
U1
U2
U3
PCMCIA68
2635A-1006
s87f.eps
Figure 8-8. A6 Memory Card I/F PCA (2635A) (cont)
8-27
Schematic Diagrams
8
8-28
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