Hewlett-Packard 3478A Digital Multimeter Service Manual

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HP 3478A Digital Multimeter

Service Manual

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HEWLETT

~~PACKARD

SERVICE MANUAL

MODEL 3478A

DIGITAL MUL TIMETER

Serial Numbers: This manual applies directly to instruments with Serial Number 2619A37795 and above.

IMPORTANT NOTICE

If the Serial Number of your instrument is lower than the one on this Title Page, the manual contains revisions that do not apply to your instrument. Backdating information given in Section VI adapts the manual to earlier instruments.

WARNING

I

To help minimize the possibility of electrical fire or shock hazards, do not expose this instrument to rain or excess moisture.

The information in this manual is for the use of Service Trained Personnel. To avoid shock, do not perform any procedures in the manual or do any servicing to the 347BA unless you are qualified to do so.

Manual Part No. 03478-90008

Microfiche Part No. 03478-99008

©Copyright Hewlett-Packard Company 1981, 1987,

P.O. Box 301, Loveland, Colorado, 80539 U.S.A

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Section I, II, Ill

General Information

Installation and Operation

Section IV

Performance Test and Calibration

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Section V

Replaceable Parts

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Section VI

Backdating

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Section VII

Service

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Appendix

Printed: September 1987

Edition 2: E0987

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CERTIFICATION

Hewlett-Packard Company certifies that this product met its published specifications at the time vl shipment from the factory. Hewlett-Packard further certifies that its calibration measurements are traceable to the National Institute of Standards and Technologies, to the extent allowed by the Institllle's calibration facility, and to the calibration facilities of other International Standards Organization members.

WARRANTY

This Hewlett-Packard instrument product is warranted against defects in materials and workmanship for a period of one year from date of shipment [,except that in the case of certain components listed in Section I of this manual, the warranty shall be for the specified period]. During the warranty period, Hewlett-Packard Company will, at its option, either repair or replace products which prove to be defective.

For warranty service or repair, this product must be returned to a service facility designated by -hp-. Buyer shall prepay shipping charges to -hp- and -hp- shall pay shipping charges to return the product to Buyer. However,

Buyer shall pay all shipping charges, duties, and taxes for products returned to -hp- from another country.

Duration and conditions of warranty for this instrument may be superceded when the instrument is integrated into (becomes a part of) other -hp- instrument products.

Hewlett-Packard warrants that its software and firmware designated by -hp- for use with an instrument will execute its programming instructions when properly installed on that instrument. Hewlett-Packard does not warrant that the operation of the instrument, or software, or firmware will be uninterrupted or error free.

LIMITATION OF WARRANTY

The foregoing warranty shall not apply to defects resulting from improper or inadequate maintenance by Buyer,

Buyer-supplied software or interfacing, unauthorized modification or misuse, operation outside of the environmental specifications for the product, or improper site preparation or maintenance.

NO OTHER WARRANTY IS EXPRESSED OR IMPLIED. HEWLETT-PACKARD SPECIFICALLY

DISCLAIMS THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PAR-

TICULAR PURPOSE.

EXCLUSIVE REMEDIES

THE REMEDIES PROVIDED HEREIN ARE BUYER'S SOLE AND EXCLUSIVE REMEDIES. HEWLETT-

PACKARD SHALL NOT BE LIABLE FOR ANY DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CON-

SEQUENTIAL DAMAGES, WHETHER BASED ON CONTRACT, TORT, OR ANY OTHER LEGAL

THEORY.

ASSISTANCE

Product maintenance agreements and other customer assistance agreements are available for Hewlett-Packard products.

For any assistance, contact your nearest Hewlett-Packard Sales and Service Office. Addresses are provided at the back of this manual.

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3/11/83

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Herstellerbescheinigung

Hiermit wird bescheinigt,

da{3

das Geri:lt/System __ in Ubereinstimmung mit den Bestimmungen von PostverfOgung 1046/84 funkentstort ist.

Der Deutschen Bundespost wurde das lnverkehrbringen dieses Gerates/Systems angezeigt und die Berechtigung zur UberprUfung der Serie auf Einhaltung der Bestimmungen eingeraumt.

Zusatzinformation fur

Mef3·

und Testgeriite

Werden Me{3- und Testgedhe mit ungeschirmten Kabeln und/oder in offenen Me{3aufbauten verwendet, so ist vom Betreiber sicherzustellen,

da{3

die Funk-Entstarbestimmungen unter

Betriebsbedingungen an seiner GrundstUcksgrenze eingehalten werden.

Manufacturer's declaration

• is in accordance with the Radio Interference Requirements of Directive FTZ 1 046/84. The German Bundespost was notified that this equipment was put into circulation, the right to check the series for compliance with the requirements was granted .

Additional Information for Test· and Measurement Equipment

If Test- and Measurement Equipment is operated with unscreened cables and/or used for measurements on open set-ups, the user has to assure that under operating conditions the Radio

Interference Limits are still met at the border of his premises .

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SAFETY SUMMARY

The following general safety precautions must be observed during all phases of operation, service, and repair of this instrument. Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safety standards of design, manufacture, and intended use of the instrument. Hewlett-Packard Company assumes no liability for the customer's failure to comply with these requirements. This is a Safety Clau 1 instrument.

GROUND THE INSTRUMENT

To minimize shock hazard, the instrument chassis and cabinet must be connected to an electrical ground. The instrument is equipped with a three-conductor ac power cable. The power cable must either be plugged into an approved three-contact electrical outlet or used with a three-contact to two-contact adapter with the grounding wire (green) firmly connected to an electrical ground (safety ground) at the power outlet. The power jack and mating plug of the power cable meet International Electrotechnical Commission (IEC) safety standards.

DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE

Do not operate the instrument in the presence of flammable gases or fumes. Operation of any electrical instrument in such an environment constitutes a definite safety hazard.

KEEP AWAY FROM LIVE CIRCUITS

Operating personnel must not remove instrument covers. Component replacement and internal adjustments must be made by qualified maintenance personnel. Do not replace components with power cable connected. Under certain conditions, dangerous voltages may exist even with the power cable removed. To avoid injuries, always disconnect power and discharge circuits before touching them.

DO NOT SERVICE OR ADJUST ALONE

Do not attempt internal service or adjustment unless another person, capable of rendering first aid and resuscitation, is present.

DO NOT SUBSTITUTE PARTS OR MODIFY INSTRUMENT

Because of the danger of introducing additional hazards, do not install substitute parts or perform any unauthorized modification to the instrument. Return the instrument to a Hewlett-·

Packard Sales and Service Office for service and repair to ensure that safety features are maintained.

DANGEROUS PROCEDURE WARNINGS

Warnings, such as the example below, precede potentially dangerous procedures throughout this manual. Instructions contained in the warnings must be followed.

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WARNING

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Dangerous voltages, capable of causing death, are present in this instrument. Use ex· treme caution when handliRg, testing, and adjusting.

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HEWLETT

SAFETY SYMBOLS

General Definitions of Safety Symbols Used On Equipment or In Manuals.

Instruction manual symbol: the product will be marked with this symbol when it is necessary for the user to refer to the instruction manual in order to protect against damage to the instrument.

Indicates dangerous voltage (terminals fed from the interior by voltage exceeding 1000 volts must be so marked).

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OR

-

Protective conductor terminal. For protection against electrical

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Low-noise or noiseless, clean ground (earth) terminal. Used for a signal common, as well as providing protection against electrical shock in case of a fault. A terminal marked with this symbol must be connected to ground in the manner described in the installation

(operating) manual, and before operating the equipment.

m

OR.L

Frame or chassis terminal. A connection to the frame (chassis) of the equipment which normally includes all exposed metal structures.

Alternating current (power line).

Direct current (power line).

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Alternating or direct current (power line).

WARNING

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The WARNING sign denotes a hazard. It calls attention to a procedure, practice, condition or the like, which, if not correctly per-

The CAUTION sign denotes a hazard. It calls attention to an operating procedure, practice, condition or the like, which,if not correctly performed or adhered to, could result in damage to or destruction of part or all of the product.

NOTE:

The NOTE sign denotes important information. It calls attention to procedure, practice, condition or the like, which is essential to highlight.

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TABLE OF CONTENTS

Section

I.

Page

GENERAL INFORMATION .............. 1-1

1-1. Introduction ....................... 1-1

1-3.

Section I, General Information ...... 1-1

1-5. Section II, Installation Procedures ... 1-1

1-7. Section III, Operation ............. 1-1

1-9. Section IV, Performance Test and

Calibration ...................... 1-1

1-11. Section V, Replaceable Parts ....... 1-1

1-13. Section VI, Backdating ............. 1-1

1-15. Section VII, Service ............... 1-1

1-17. Appendix A ...................... 1-1

1-19. Description ........................ 1-1

1-22. Specifications ...................... 1-1

1-24. Instrument and Manual

Identification .................... 1-1

1-27. Options ........................... 1-5

1-29. Accessories Available ............... 1-5

Section

III. OPERATION (Cont'd)

Page

3-51. General .......................... 3-6

3-54. Number of Digits Displayed ........ 3-6

3-57. Auto zero ......................... 3-7

3-60. Self-Test/Reset Operation .......... 3-7

3-63. Calibration ....................... 3-7

3-66. Miscellaneous Operations ............ 3-8

3-67. Voltmeter Complete ............... 3-8

3-69. Remote Operation .................. 3-8

3-70. General .......................... 3-8

3-74. 3478A Response to Bus Messages ... 3-8

3-92. 3478A Addressing ................ 3-10

3-96. Talk-Only Mode (No Controller) ... 3-10

3-98. 3478A HP-IB Programming ....... 3-11

3-117. Advanced Programming ........... 3-14

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Section Page

II. INSTALLATION ........................ 2-1

2-1. Introduction ....................... 2-1

2-3. Initial Inspection ................... 2-1

2-5. Power Requirements ................ 2-1

2-7. Line Frequency and Line

Voltage Selection ................. 2-1

2-9. Power Cords and Receptacles ........ 2-2

2-11. Grounding Requirements ............ 2-2

2-13. Bench Use and Rack Mounting ...... 2-2

2-14. Bench Use ........................ 2-2

2-16. Rack Mounting ................... 2-3

2-18. HP-IB Interface Connections ........ 2-3

2-21. Address Selection ................... 2-3

2-24. Environmental Requirements ......... 2-3

2-25. Operating and Storage

Temperature ..................... 2-3

2-27. Repackaging for Shipment ........... 2-4

Section Page

Ill. OPERATION ............................ 3-1

3-1. Introduction ....................... 3-1

3-4. General Information ................ 3-1

3-5. AC Power Operation .............. 3-1

3-7. Turn-On ......................... 3-1

3-10. Display .......................... 3-1

3-12. Input Terminals ................... 3-3

3-15. Input Terminals Cleaning .......... 3-3

3-17. Front Panel Operation .............. 3-3

3-18. DC Volts Measurements ............ 3-3

3-22. AC Volts Measurements ............ 3-4

3-26. Resistance Measurements ........... 3-4

3-30. DC Current Measurements ......... 3-5

3-34. AC Current Measurements ......... 3-5

3-38. Ranging .......................... 3-5

3-43. Triggering ........................ 3-5

3-50. Shifted Operation .................. 3-6

Section Page

IV. PERFORMANCE TEST AND

CALIBRATION ....................... 4-1

4-1. Introduction ....................... 4-1

4-3. Test Equipment. ................... 4-1

4-5. Test Cards ........................ .4-1

4-7. Performance Test Failures ........... 4-2

4-9. Test Considerations ................. 4-2

4-10. Front and Rear Terminals .......... 4-2

4-12. Specification ...................... 4-2

4-16. Reference Temperature ............. 4-2

4-18. Accuracy of Standards ............. 4-2

4-21. Performance Tests ................. .4-3

4-23. DC Volts Test. .................. .4-3

4-28. DC Current Test. ................. 4-6

4-33. AC Volts Test. ................... 4-6

4-38. AC Current Test. ................ .4-8

4-43. Ohms Test. ...................... .4-9

4-48. Calibration Procedure ............. .4-11

4-49. General ......................... 4-11

4-55. Calibration Messages ............. 4-12

4-57. DC Volts Calibration ............. 4-12

4-61. DC Current Calibration .......... .4-13

4-66. AC Volts Calibration ............. 4-13

4-72. AC Current Calibration .......... .4-14

4-78. Ohms Calibration ................ 4-14

4-84. Remote Calibration ............... .4-15

4-85. General ......................... 4-15

4-89. Remote Calibration Example ...... 4-15

Section Page

V. REPLACEABLE PARTS ................. 5-1

5-l. Introduction ....................... 5-1

5-4. Ordering Information ............... 5-1

5-6. Non-Listed Parts ................... 5-1

5-8. Parts Changes ..................... 5-1

5-10. Propriety Parts ..................... 5-1

5-12. 3478A Disassembly Procedure ....... 5-1

TABLE OF CONTENTS (Cont'dl

Section Page

VI. BACKDATING .......................... 6-1

6-1. Introduction ....................... 6-1

6-4. 2136A03480 & below .............. 6-1

6-7. 2301A08635 & below .............. 6-1

6-8. 2301A18860 & below .............. 6-1

6-9. 2520A19795 & below .............. 6-1

6-10. 2520A20970 & below .............. 6-1

6-11. 2520A22585 & below .............. 6-2

6-15. 2545A24740 & below .............. 6-3

6-16. 2545A26015 & below .............. 6-3

6:20. 2619A26305

& below .............. 6-5

6-22. 2619A32988

& below .............. 6-5

Section Page

VII. SERVICE ............................... 7-1

7-1. Introduction ....................... 7-1

7-3. Safety Considerations ............... 7-1

7-8. Recommended Test Equipment. ...... 7-1

7-10. Miscellaneous Information ........... 7-1

7-11. Instrument Disassembly

(PC Board Replacement) .......... 7-1

Section

VII. SERVICE (Cont'd)

Page

7-13. Fuse Replacement. ................ 7-1

7-15. Troubleshooting .................... 7-2

7-16. Introduction ...................... 7-2

7-18. 3478A Self-Test. .................. 7-2

7-27. Service Group Selection ............ 7-2

Service Groups Page

A DC Volts and DC Current

Troubleshooting ............... 7-A-1

B AC Volts and AC Current

C

D

Troubleshooting ................ 7-B-1

Ohms Troubleshooting ............ 7-C-1

AID

Converter and Logic

Troubleshooting ............... 7-D-1

E Power Supplies and Reference

Troubleshooting ................ 7-E-1

F Theory of Operation .............. 7-F-1

G Schematics ...................... 7-G-1

APPENDIX A ............................... A-1

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LIST OF TABLES

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3-5.

3-6.

3-7.

4-1.

4-2.

4-3.

4-4.

4-5.

4-6.

4-7.

5-l.

5-2.

5-3.

5-4.

Tables

1-1.

3-1.

3-2.

3-3.

3-4.

Page

Specifications .......................... 1-2

Shifted Operations ..................... 3-6

3478A Error Messages .................. 3-7

3478A Bus Capabilities ................. 3-8

Status Byte Definitions ................ 3-10

3478A Address Codes ................. 3-11

3478A Program Codes ................. 3-12

Binary Status Byte Definition ........... 3-14

Abbreviated Specifications Table ........ .4-1

Recommended Test Equipment. ........ .4-1

DC Volts Test Limits ................... 4-3

DC Current Test Limits ................ 4-6

AC Volts Test Limits .................. .4-7

AC Current Test Limits ................ 4-8

Ohms Test Limits .................... .4-10

Standard Abbreviations ................. 5-1

Code List of Manufacturers ............. 5-2

Replaceable Parts List. ................. 5-3

3478A Mechanical and Miscellaneous

Parts ............................... 5-8

Table

6-1.

6-2.

6-3.

6-4.

6-5.

6-6.

6-7.

6-8.

6-9.

6-10.

6-11.

6-12.

6-13.

7-1.

7-F-1.

7-F-2.

A-1.

A-2.

Page

Changes to Table 5-3 ................... 6-1

Changes to Table 6-9 ................... 6-1

Changes to Table 6-9 ................... 6-1

Changes to Table 5-3 ................... 6-1

Changes to Table 1-1. .................. 6-2

Changes to Table 4-1. .................. 6-2

Changes to Table 4-3 ................... 6-3

Changes to Table 4-5 ................... 6-3

3478A Mechanical and Miscellaneous

Parts ............................... 6-4

Changes to Table 5-3 ................... 6-5

Changes to Table 5-3 ................... 6-5

Changes to Table 5-4 ................... 6-5

Changes to Table 5-4 ................... 6-5

3478A Service Groups .................. 7-2

Ohms Current and Ranges ............ 7-F-7

AC Amplifier Gains .................. 7-F-9

3478A Device Capability ............... A-3

HP-IB Worksheet. ............ .

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4-7 .

4-8.

4-9.

5-1.

5-2.

5-3.

5-4.

5-5.

5-6.

5-7.

4-6.

3-4.

3-5.

3-6.

4-1.

4-2.

4-3.

4-4.

5-8.

6-1.

6-2.

6-3.

6-4.

6-5.

6-6.

6-7.

6-8.

LIST OF ILLUSTRATIONS

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Figure

2-1.

2-2.

2-3.

2-4.

2-5.

2-6.

3-1.

3-2.

3-3.

4-5.

Page

Line Frequency Switch ................. 2-1

Line Select Jumper ..................... 2-2

Power Cords .......................... 2-2

Typical HP-IB System Interconnection ... 2-3

HP-IB Connector ...................... 2-4

3478A Address Switch .................. 2-4

3478A Front and Rear Panel Features .... 3-3

Typical Input Measurement Connection ... 3-3

Typical Current· Measurement

Connection .......................... 3-3

Ohms Connections ..................... 3-4

Autoranging Points .................... 3-6

Status Byte ............................ 3-9

Ambiguous Regions ................... .4-3

DC Voltage Test and Calibration

Connections ......................... 4-4

DC Common Mode Rejection Test ....... 4-5

DC Current Test and Calibration

Connections ......................... 4-7

AC Voltage Test and Calibration

Connections ......................... 4-8

AC Current Test and Calibration

Connections ......................... 4-9

2-Wire Ohms Test and Calibration

Connections ........................ 4-11

4-Wire Ohms Test and Calibration

Connections ........................ 4-11

4-Wire Ohms Short. ................. .4-12

3478A Front Panel View ................ 5-9

3478A Left Side View .................. 5-9

3478A Rear Panel View ................. 5-9

3478A Right Side View ................. 5-9

Top View With Cover Removed ......... 5-9

Regulator Detail View .................. 5-9

Motherboard and Front Panel

Assembly ........................... 5-9

Front Panel Assembly, Rear View ....... 5-9

Component Locator Rev B .............. 6-7

Schematic 4 Revision B Boards .......... 6-7

Component Locator Revision C ......... 6-8

Schematic 1 Input Circuitry ............. 6-9

Schematic 3 AID Converter & Control

Logic .............................. 6-11

34 78A Front Panel View ............... 6-13

3478A Rear Panel View ................ 6-13

3478A Bottom View ................... 6-13

Figure

6-9.

6-10.

6-11.

6-12.

6-13.

7-A-1.

7-B-1.

7-C-1.

7-D-1.

7-D-2.

7-D-3.

7-D-4.

7-D-5.

7-D-6.

7-D-7.

7-F-1.

7-F-2.

Page

34 78A Left Side View ................. 6-13

Bottom View With Cover Removed ..... 6-13

Top View With Cover Removed ........ 6-13

Front Panel Bracket View .............. 6-13

Front Panel Assembly ................. 6-13

JM403 SA Connection ............... 7-A-4

JM403 SA Connection ................ 7-B-2

JM403 SA Connection ............... 7-C-4

U501 ALE Signal. ................... 7-D-2

Flowchart A ........................ 7-D-3

Flowchart B ......................... 7-D-5

Flowchart C ........................ 7-D-6

U 462 ALE Signal .................... 7-D-8

Flowchart D ........................ 7-D-9

JM403 SA Connection .............. 7-D-10

3478A Simplified Block Diagram ....... 7-F-2

Simplified Schematic of the Input

Switching Circuitry ................. 7-F-4

7-F-3. Simplified Schematic of the DCIOhms

Input Amplifier .................... 7-F-6

7-F-4.

7-F-5.

7-F-6.

Ohms Circuitry Configuration ......... 7-F-6

AC Gain Configurations .............. 7-F-8

Dual Slope Conversion ............... 7-F-9

7-F-7.

7-F-8.

7-F-9.

7-F-10.

Simplified AID Converter ............ 7-F-10

Integrator (U401) Output Slopes ...... 7-F-10

Runup Slopes (4 112 Digit Model) .... 7-F-11

Runup Slopes For Zero Inputs

(4 1/2 Model) .................... 7-F-12

7-F-11. Slope S+4 Generation ............... 7-F-12

7-F-12. Slope S-4 Generation ............... 7-F-12

7-F-13. Slope S+O and S-0 Generation ...... 7-F-13

7-F-14. Rundown Slopes .................... 7-F-13

7-F-15. Determining the DAC Setting ......... 7-F-15

7-F-16. AID Hybrid (U403) ................. 7-F-15

7-F-17. 3478A Simplified Reference Circuitry .. 7-F-16

7-F-18. Power-On Circuitry ................. 7-F-17

7-F-19. Reset Circuitry ...................... 7-F-18

7-G-1. General Schematic Notes ............. 7-G-1

7-G-2. 3478A Block Diagram ................ 7-G-3

7-G-3. Input Circuitry and Ohms Current

Source ............................ 7-G-5

7-G-4.

7-G-5.

7-G-6.

ACto DC Converter ................. 7-G-7

AID

Converter and Control Logic ..... 7-G-9

Power Supplies ..................... 7-G-11

A-1. Interface Connection and Bus

Structure ........................... A-2

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SECTION I

GENERAL INFORMATION

WARNING

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The information in this manual is for the use of Service Trained Personnel. To avoid electrical shock, do not perform any procedures in the manual or do any servicing to the

3478A unless you are qualified to do so.

1·1. INTRODUCTION

1-2. The information in this manual is for the Installation, Operation, Performance, Calibration, and Service of the 3478A Digital Multimeter. The manual is designed for the use of Service Trained Personnel. Other users should refer to the Operators Manual. This manual is separated into the following sections.

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1-3. Section I, General Information

1-4. A short description of the manual and introduction to the 3478A is in Section I. The section also lists instrument options, specifications, and accessories.

1-5. Section II, Installation Procedures

1-6. This section explains how the 3478A is prepared for use and includes power requirements, line voltage selection, etc. The section also explains how to connect the multimeter for remote operation.

1· 7. Section Ill, Operation

1-8. The condensed operating instructions of the

3478A, for the use of Service Trained Personnel, is in this section. For more complete instructions, refer to the

Operators Manual.

1-9. Section

IV,

Performance Test and Calibration

1-10. The 3478A's Performance Test and Calibration

Procedures are in Section IV. The Required Equipment

Table and an abbreviated specification table are also included.

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1·11. Section V, Replaceable Parts

1-12. Section V lists the replaceable parts of the 3478A.

It also includes pictures and illustrations of chassis and mechanical parts.

1·13. Section

VI,

Backdating

1-14. This section has information which adapts this manual to 3478A's with serial numbers below the ones shown on the title page.

1-15. Section

VII,

Service

1-16. The 3478A's Troubleshooting Procedures,

Theory Of Operation, and Schematics are in Section

VII. The troubleshooting information is in the form of

Service Groups which are symptoms oriented (i.e., what is the failure). The complete theory of operation is in

Service Group F and the Schematics are in Service

Group G (last group).

1-17. Appendix A

1-18. The appendix has a condensed description of the

HP-IB (Hewlett-Packard Interface Bus) .

1·19. DESCRIPTION

1-20. The -hp- Model 3478A is a versatile multimeter with de and ac volts, de and ac currents, and resistance measurement capabilities. The multimeter is excellent for bench use, and since it is remotely programmable, it can be used in measurement systems. A feature of the instrument is that the reading can be displayed in either

5 112, 4 112, or 3 112 digits. Other features are

Autozero (for good stability), and an Alphanumeric

Liquid Crystal Display.

1-21. Another excellent feature is Electronic Calibration. No mechanical adjustments are necessary to calibrate the 3478A.

1·22. SPECIFICATIONS

1-23. Specifications of the 3478A are the performance characteristics of the multimeter which are certified.

The specifications are listed in Table 1-1 and Table 4-1

(in Section IV). They are the performance standards or limits against which the multimeter can be tested.

1-24. 'INSTRUMENT AND MANUAL IDENTIFICATION

1-25. Instrument Identification is by a serial number located on the multimeter's rear panel. Hewlett-

Packard uses a two-part serial number, with the first part (prefix) identifying a series of instruments and the

1-1

General Information

3478A

Input Characteristics:

Range

Maximum

Reading

(5Y, Digit)

DC VOLTAGE

5% Digit

Resolution

4Y, Digit

Table 1-1. Specifications

JY, Digit

Noise Rejection:

In dB, with ·1 k!1 imbalance in Lo lead. AC rejection for 50,

60Hz ± 0.1 %. Auto-zero ON.

Display

AC

NMR

AC

ECMR

DC

CMR

5% digits 80

4% digits

3% digits

59

0

150

130

70

140

140

140

30mV ±30.3099mV

100nV

300mV

3

30

300 v

±303.099mV

±3.03099 v

1J.!V v

±30.3099 v

100J.!V v

±303.099 v

10J.!V

1mV

1J.IV

10J.IV

100J.IV

1mV

10mV

10J.!V

100J.!V

1mV

10mV

100mV

Input Resistance:

30mV, 300mV,3V ranges:

>

1 0

10

!1

30V, 300V ranges: 1 OM!1 ± 1%

Maximum Input Voltage: (non-destructive)

Hi to Lo: 303V rms or 450V peak

Hi or Lo to Earth Ground: ± 500V peak

Measurement Accuracy:

± (% of reading

Auto-zero ON

+ number of counts)

5 Y, Digit Mode:

Range

Cal. Temp.

±1 c

24

Hours

90

Day

Cal. Temp.

±5 c

1 Year

30 mV 0.025

300 mV 0.004

3

+

40 0.0275

+

40 0.035

+

40

+

4 0.005

+

5 0.007

+

5 v

0.003

+

2 0.004

+

2 0.006

+

2

30

300 v

0.004

+

3 0.005

+

4 0.007

+

4 v

0.004

+

2

0.005

+

2 0.007

+

2

4Yz and JY, Digit Mode:

Accuracy is the same as 5% digit mode for% of reading; use

1 count for number of counts on all ranges except 30mV range use 4 counts.

The Cal. Temp. (Calibration Temperature) is the temperature of the environment where the 34 78A was calibrated. Cali· bration should be performed with the temperature of the environment between 20°C and 30°C.

Auto·Zero Off:

(5% digit) for a stable environment ( ± 1 ° C), for

<

24 hrs., add

11 0 counts to accuracy specification for 30mV range, 11 counts for 300mV and 30V ranges, 3 counts for 3V and 300V range.

Temperature Coefficient:

0°C to 55°C

5% digit display, auto-zero ON

± (% of reading

+ number of counts)/°C

Range Temperature Coefficient

30mV

300mV

3 v

30

300 v v

0.0028

0.0005

0.0004

0.0006

0.0004

+

5.0

+

0.5

+

0.05

+

0.5

+

0.05

1-2

Maximum Reading Rates: (readings/sec)

First reading is correct when triggered coincident with step input.

The reading rates are dependent on the speed of the controller being used.

Line

Frequence

Auto Resolution

Zero JY, Digits 4Y, Digits 5Y, Digits

60Hz

50Hz

Off

On

Off

On

AC VOLTAGE(true rms responding)

Input Characteristics:

Range

Maximum

Reading

(5Y, Digit)

90

60

85

50

35

20

30

17

4.4

2.3

3.7

1.9

5Yz Digit

Resolution

4Y, Digit JY, Digit

300mV

3

30

300 v

303.099mV

3.03099 v

IJ.!V v

30.3099 v

100J.!V v

303.099 v

10J.!V

1mV

Input Impedance:

1 M!1 ± 1% shunted by

<

60pF

Maximum Input Voltage: (non-destructive)

Hi to Lo: 303Vrms or 450V peak

Hi or Lo to Earth Ground: ± 500V peak

10J.!V

100J.!V

1mV

10mV

100J.!V

1mV

10mV

100mV

Measurement Accuracy:

± (% of reading

+ number of counts)

Auto-zero ON. 5% digit display. Accuracy is specified for sinewave inputs only,

>

10% of full scale.

1 Year, Cal. Temp. ± 5°C

Input

Frequency

30DmV

Ranges

3V, 3DV 3DDV

20Hz-50Hz

50Hz-100Hz

1OOHz- 20kHz

20kHz- 50kHz

50kHz- 1OOkHz

1OOkHz- 300kHz

1 . 14

0.46

0.20

0.38

1.20

+

1 63 1 . 14

+

1 02 1 . 18

+

1 02

+

163 0.46

+

103 0.50

+

102

+

120 0.20

+

70 0.24

+

70

+

205 0.26

+

140 0.42

+

140

+

840 0.87

+

780 0.98

+

780

10.1

+

3720

(30V Range

Only)

•

•

•

3478A

General Information

Table 1-1. Specifications (Cont'd)

•

Auto Zero Off:

(5% digits) for a stable environment ( ± 1 °C), for < 24 hrs., add

10 counts to accuracy specifications for all ranges.

Temperature Coefficient:

2-Wire Ohms Accuracy:

Same as 4-wire ohms, except add a maximum of 200mQ offset. On the 3M ohm Range, add .0016% of reading and on the 30M ohm Range, add .0083%.

Auto·Zero Off:

0°C to 55°C

5% digit display, auto-zero ON.

For frequencies <20kHz, ± (0.016% of reading

For frequencies >20kHz, ± (0.04% of reading

+

10 counts)/°C

+

10 counts)/°C

(5% digit) for a stable environment ( ± 1 °C), for < 24 hrs., add

11 0 counts to accuracy specification for 30Q range, 11 counts for 300Q, 3 counts for 3KQ through 300KQ ranges, 8 counts for 3MQ range, and 33 counts for 30MQ range.

Crest Factor:

Temperature Coefficient:

>4: 1 at full scale.

0°C to 55°C

5% digit display, auto-zero ON

± (% of reading

+ number of counts)/°C

Common Mode Rejection:

With 1 kQ imbalance in Lo lead, > 70d8, at 60Hz.

Range Temperature Coefficient

Maximum Reading Rates:

(readings/sec)

First reading is correct within 70 counts of final value, when on correct range, triggered coincident with step input. Add 0.6 seconds for each range change.

Reading rates are the same as de volts using fast trigger (T5).

Using Normal Trigger (T1, T2, T3):

For 50 or 60Hz operation, auto-zero ON or OFF.

3% or 4% digits: 1.4

5% digits: 1 .0

30Q

300Q

3k- 300kQ

3MQ

30MQ

0.003

0.0009

0.0009

0.0021

0.021

+

5

+

.5

+

.05

+

.05

+

.05

Current

Current Through Unknown:

Range

RESISTANCE

(2-wire Q, 4-wire

Q)

•

Input Characteristics:

Range

Maximum

Reading

(SY,

Digit)

30

300 n

30.3099 n n

303.099 n

3 kQ 3.03099 kQ

30 kQ

300 kQ

30.3099 kQ

303.099 kQ

3MQ

3.03099MQ

30MQ 30.3099MQ

SY,

Digit

Resolution

4Y•

Digit

100

~<n

1mQ

10mQ

100mQ

1 n

10

100 n n

3Y,

Digit

1mQ

10mQ

10mQ 100mQ

100mQ

1

1 n n

10 n

10

100 n

100 n n

1 kQ

1 kQ

10 kQ

Input Protection: (non-destructive)

Hi source to Lo source: ± 350V peak

Hi sense to Lo sense: ± 350V peak

Hi or Lo to Earth Ground: ± 500V peak

Maximum Open Circuit Voltage:

6.5V

Maximum Reading Rates:

Same as de volts, except for 3MQ and 30MQ ranges. For 3MQ range, add 30ms; for 30MQ range, add 300ms per reading.

Input Characteristics:

30 ohm

300 ohm

3K ohm

30K ohm

300K ohm

3M ohm

30M ohm

DC CURRENT

1mA

1mA

1mA

1001'A

101'A

11'A

100nA

Maximum

Reading

(SY,

Digit)

Measurement Accuracy:

± (% of reading

+ number of counts)

Auto-zero ON. 4-wire ohms.

Maximum INPUT LO impedance is 3.3% of full scale.

Range

SY,

Digit'

Resolution

4Y,

Digit

3Y,

Digit

300m A

3 A

±303.099mA

± 3.03099 A

11'A

101'A

101'A

1001'A

1001'A

1mA

SY,

Digit Mode:

•

Range

30Q

300Q

3k- 300kQ

3 MQ

30MQ

Cal. Temp ± 1

oc

24 Hours

Note

Cal. Temp. ±S°C

90 Day 1 Year

0.023

0.0045

0.0035

0.0052

0.036

+

35

0.027 + 41 0.034

+

+ 4 0.012

+

5 0.017

+

+

2 0.011 + 2 0.016 +

+ 2 0.011

+

2 0.016

+

+ 2

0.066

+

2

0.078

+

41

5

2

2

2

>

30 M ohm Range accuracy is approximately

0.002%/M ohm.

Maximum Input:

(non-destructive)

3A from < 250V source; fuse protected

Measurement Accuracy:

± (% of reading

+ number of counts)

Auto-zero ON. 5% digit display.

Range

Cal. Temp. ±S°C

90 Days 1 Year

300m A

3A, < 1 A input

3A, > 1 A input

0.11

0.14

1.0

+

40

+

6

+

30

0.15

0.17

1.0

+

40

+

6

+

30

1-3

1-4

General Information

Table 1-1. Specifications (Cont'd)

Auto·Zero Off:

(5% digit) for a stable environment ( ± 1 °C), for < 24 hrs., add

11 0 counts to accuracy specification for 300m A range, 11 counts for 3A range.

Temperature Coefficient:

0°C to 55°C.

5% digits, auto-zero ON.

±

(0.021% of reading + 10 counts)/°C

Temperature Coefficient:

0°C to (Cal. Temp. - 5°C),(Cal. Temp. +5° C) to 55°C

5% digit display, auto-zero ON

± (% of reading + number of counts)/°C

Range Temperature Coefficient

Maximum Burden at Full Scale:

1V

Crest Factor:

>

4: 1 at full scale

300m A

3 A

0.012+5

0.012 + 0.5

Maximum Reading Rates:

Same as ac volts

Maximum Burden at Full Scale:

1V

GENERAL INFORMATION

Maximum Reading Rates:

Same as de volts

Operating Temperature:

0 to 55°C

AC CURRENT (true rms responding)

Humidity Range:

95% R.H., 0 to 40°C

Input Characteristics:

Storage Temperature:

- 40°C to 75°C

Range

300m A

3 A

Maximum

Reading

(5Y, Digit)

303.099mA

3.03099 A

5Y, Digit

11-'A

101-'A

Maximum Input: (non-destructive)

3A from < 250V source; fuse protected

Resolution

4Yz Digit

101-'A

1001-'A

3Yz Digit

1001-'A

1mA

Warm·up Time:

1 hr. to meet all specifications.

Integration Time:

Number of Digits

Line Frequency

50Hz 60Hz

Measurement Accuracy:

± (% of reading + number of counts)

Auto-zero

ON,

5% digit display, accuracy specified for sinewave inputs only

>

10% of full scale.

1 YEAR, CAL. TEMP.

±

5°C

Frequency 300mA

Ranges

3A

20Hz- 50Hz

50Hz-1kHz

1.54 + 163 2.24 + 163

0.81 + 163 1. 5

+ 163

1kHz-10kHz 0.72 + 163 1.42 + 163

1OkHz- 20kHz

0.86 + 163 1.56 + 163

Auto·zero Off:

( 5% digits) for a stable environment (

±

1 ° C), for < 24 hrs., add 10 counts to accuracy specification.

5%

4%

3

y,

200ms

20ms

2ms

166.7ms

16.67ms

1.667ms

Power:

AC Line 48- 440Hz; 86- 250V, (see configuration)

Maximum Power:

<25 watts

Size:

102mm H x 215mm W x 356mm D

(4 in H x 8 in W x 14 in D)

Weight:

3Kg (6.5 lbs.)

3478A

•

•

•

3478A General Information

• second part (suffix) identifying a particular instrument within a series. An -hp- assigned alpha character between the prefix and suffix identifies the country in which the 3478A was manufactured.

1-26. This manual applies to instruments with the serial number identified on the title page. Updating of the manual is accomplished either by a change sheet or revised manual.

1-27. OPTIONS

1-28. The following options are available for the 3478A.

Your instrument may have either metric or

English hardware. DO NOT intermix the different hardware or damage to the instrument'sframe and cabinet may result. For instruments with serial prefix 2520 and above, use metric handle/rack mounting hardware (listed above). For instruments with serial prefix 2301 and below, use

English handle/rack mounting hardware

(listed above). Contact your local Hewlett-

Packard Sales and Support Office if additional information is needed.

•

Option 315: set for 1 OOV, 50Hz Power Source

Option 316: set for 100V, 60Hz Power Source

Option 325: set for 120V, 50Hz Power Source

Option 326: set for 120V, 60Hz Power Source

Option 335: set for 220V, 50Hz Power Source

Option 336: set for 220V, 60Hz Power Source

Option 345: set for 240V, 50Hz Power Source

Option 346: set for 240V, 60Hz Power Source

Option 907: Front Handle Kit

(For serial prefix 2301 and below, use English hardware -hp- Part No. 5061-0088. For serial prefix 2520 and above, use Metric hardware -hp- Part No.

5061-9688,)

Option 908: Rack Mounting Kit -includes one rack flange and one extension adapter (For serial prefix

2301 and below, use English hardware -hp- Part No.

5061-0072). For serial prefix 2520 and above, use

Metric hardware -hp- Part No. 5061-9672.

Option 910: additional set of Operators and Service

Manuals

Option W30: Three Year Extended Warranty .

1-29. ACCESSORIES AVAILABLE

1-30. The following is a list of available accessories for the 3478A.

Accessory No.

Description

10023A

10833A

10833B

10833C

10833D

11096B

34111A

34118A

34119A

03478-10085

Temperature Probe

HP-IB Cable 1 meter (39.37 in)

HP-IB Cable 2 meter (78.74 in)

HP-IB Cable 4 meter (157.48 in)

HP-IB Cable 0.5 meter (19.69 in)

RF Probe

High Voltage Probe, DC 40 kV

Test Lead Kit

High Voltage probe, AC or DC 5 kV

Test and Calibration Software (for HP

85B)

•

1-5/1-6

•

SECTION II

INSTALLATION

2-1. INTRODUCTION

2-2. This section of the manual has the necessary information and instructions to install and interface the -hp-

Model3478A Digital Multimeter. Included are initial inspection procedures, power requirements, environmental information, and instructions for repacking the instrument for shipment. The information in this section is for Service Trained Personnel.

I

WARNING

I

The information in this manual is for the use of Service Trained Personnel. To avoid electrical shock, do not perform any procedures in this manual or do any servicing to the

3478A unless you are qualified to do so.

•

2·3. INITIAL INSPECTION

2-4. The 3478A was carefully inspected both mechanically and electrically before shipment. It should be free of mars or scratches and in perfect electrical order upon receipt. The multimeter should be inspected for any damage that may have occurred in transit. If the shipping container or cushioning material is damaged, it should be kept until the contents of the shipment have been checked for completeness and the instrument has been mechanically and electrically checked. Procedures for checking the electrical performance of the 3478A are in Section IV.

If there is mechanical damage, the contents are incomplete, or the multimeter does not pass the

Performance Test, notify the nearest Hewlett-Packard office (a list of the -hp-Sales/Service offices is located in the back of the manual). If the shipping container is damaged or the cushioning material shows signs of stress, notify the carrier as well as the Hewlett-Packard office. Save the shipping material for the carrier's inspection.

2-5. POWER REQUIREMENTS

2-6. The 3478A requires a power source of 100V, 120V,

220V, or 240V ac ( -10%,

+

5%), 48Hz to 440Hz single phase. The maximum power consumption is 25V A. For the 3478A to meet its noise and normal mode rejection

• specifications, the multimeter must be operated using a

line

frequency of either 50Hz or 60Hz (dependent on instrument option). A listing of the 3478A's power options, the corresponding power line voltages and frequencies, and fuses are as follows:

Option

Option 315

Option 316

Option 325

Option 326

Option 335

Option 336

Option 345

Option 346

Voltage and Frequency

1 OOV ac

@

50Hz

1 OOV ac

@

60Hz

120V ac

@

50Hz

120V ac

@

60Hz

220V ac

@

50Hz

220V ac

@

60Hz

240V ac

@

50Hz

240V ac

@

60Hz

Fuse

250mAT

250mAT

250mAT

250mAT

125mAT

125mAT

125mAT

125mAT

Before connecting power to the 3478A, make sure the power source matches the power requirements of the multimeter, as marked on the rear panel (below the power receptacle). If the instrument is incompatible with the available power source, go to paragraph 2-7 to reconfigure the multimeter.

2-7.

Line Frequency and Line Voltage Selection

WARNING

I

To avoid electrical shock and personal injury, make sure the multimeter is disconnected from its external power voltage source before removing any covers.

2.8 The Power Line Frequency configuration of the

3478A is set by the leftmost switch in the 8 secion "DIP" switch on the multimeter's rear panel. Locate the switch and set the rocker to the desired line power frequency

(either 50 Hz or 60Hz). The switch is shown in Figure

2-1 (shown set for 60 Hz operation). To set the 3478's input line voltage, perform the following procedure.

[

• • e-PWR ON SRQ

•1

•.0

•16•4• 1

'-ADRS-'

1-:-50Hz, 0-60Hz

Figura 2-1. Line Frequency Switch

2-1

2-2

Installation a. Remove the 3478A rear bezel and top cover as described in Section V of this manual. b. Locate the Line Select wire (gray) and the line terminals. The Line and the terminals are located between the 3478A's power transformer and rear panel. c. Refer to Figure 2-2 and connect the gray wire to the line terminal corresponding to the desired input line voltage.

CONI'-iECT THE WIRE

TO THE APPROPRIATE

TEST POINT (SHOWN IN

THE 120V CONFIGURATION)

POWER

TRANSFORMER

~ 0,'~:~

8

_j w

(f)

0

220V

_j

0

240V

3478. F. 2. 2

Figure 2·2. Line Select Jumper

3478A d. After changing the Line Voltage, make sure the correct fuse is installed. For 100 V or 120 V operation, use a .25AT 250 V fuse (-hp- Part No. 2110-0201). For 220 V or 240 V operation, use a .125AT 250 V fuse (-hp- Part

No. 2110-0318). e. Reinstall the 3480A top cover and rear bezel.

2·9. POWER CORDS AND RECEPTACLES

2-10. Figure 2-3 illustrates the different power plug configurations that are available to provide power to the

3478A. The -hp- part number shown directly below the individual power plug drawing is the part number for the power cord set equipped with the appropriate mating plug for that receptacle. If the appropriate power cord is not included with the instrument, notify the nearest -hp- Sales and Support Office and a replacement will be provided.

2·11. GROUNDING REQUIREMENTS

2-12. To protect operating personnel, the National

Electrical Manufacturing Association (NEMA) recommendation is to ground the instrument panel and cabinet. The 3478A is equipped with a three conductor power cable which, when plugged into an appropriate receptacle, grounds the instrument.

2-13. BENCH USE AND RACK MOUNTING

2·14. Bench Use

•

•

@

AUSTRALIA

POWER CORDS

€3

L

~

EUROPE

D

N

•

GREAT BRITAIN

0

~* ~*

SWITZERLAND UNITED STATES UNITED STATES

120V 240V

Country

Australia

Denmark

Europe

Great Britain

Switzerland

*United States

*United States

Part Number Opt.

8120-1369

8120-2956

8120-1689

8120-1351

8120-2104

8120-1378

8120-0698

Voltage

901

250V 6A

912 250V 6A

902 250V 6A

900

250V 6A

906

250V 6A

903 120V 10A

904 240V 10A

Power cords supplied by HP have polarities matched to the power input socket on the instrument:

• L

• N

• E

=

Line or Active Conductor (also called "live" or "hot").

=

Neutral or Identified Conductor

=

Earth or Safety Ground

NOTE: Plugs are viewed from connector end. Shape of molded plug may vary within country.

• GSA certification includes only these Power Plugs

Figure

2-3.

Power Cords

•

3478A

•

2-15. The 3478A is equipped with feet and tilt stands installed and is ready for use as a bench instrument. The feet are shaped to permit stacking with other halfmodule Hewlett-Packard instruments.

2-16. Rack Mounting

2-17. The 3478A may be rack mounted by adding rack mounting kit Option 908. The basic hardware and instructions for rack mounting is contained in the kit. The kit is designed to permit the 3478A to be mounted in a standard 19 inch rack, provided that sufficient rear support is available.

2·18.

HP-IB INTERFACE CONNECTIONS

2-19. The 3478A is compatible with the Hewlett-

Packard Interface Bus (HP-IB).

NOTE

HP-IB is Hewlett-Packard's implementation of IEEE Std. 488-1978, "Standard Digital

Interface For Programmable Instrumentation" and ANSI MC. 1.1.

2-20. The interface connection is made by an HP-IB Interface Cable to the 24 pin HP-IB connector located at the rear panel. A typical interconnection of an HP-IB system is shown in Figure 2-4, in which ends of the

• cables have both a male and female connector to enable connections to other instruments and cables. As many as

15

instruments can be connected to the same interface bus. However, the maximum length of cable that can effectively be used to connect a group of instruments should not exceed 2 meters (6.56 ft.) times the number of instruments connected, or 20 meters (65.6 ft.), whichever is less. For a pictorial view of the HP-IB connector and its pin designation, refer to Figure 2-5.

2-21. ADDRESS SELECTION

2-22. 3478A Address. The HP-IB "talk" and "listen"

Installation address of the 3478A is set by the multimeter's address switch (located at the rear panel). The talk and listen address is a 5-bit code which is selected to provide a unique address for each HP-IB instrument. The 3478A normally leaves the factory with the address switch set to Decimal

Code "23". The corresponding ASCII Code is a listen address code of "7" and a talk code of "W". Refer to

Figure 2-6 for the factory address setting of the switch.

Refer to the Remote Operation Chapter in Section III of this manual, for more information on addressing and address codes.

2-23. 3478A Talk-Only Mode. The 3478A has a Talk-

Only Mode which is selected by the Address Switch. The mode is selected by setting all the address switches

(switch 4 to 8) up (on). Refer to the Remote Operation

Chapter in Section III of this manual for more information.

2·24. ENVIRONMENTAL REQUIREMENTS

WARNING

I

To prevent electrical fire or shock hazards, do not expose the instrument to rain or excessive moisture.

2-25. Operating and Storage Temperature

2-26. To meet and maintain the specifications listed in

Table 1-1, the 3478A should be operated within ±5°C

( ± 9°F) of the Reference Temperature. The Reference

Temperature is the temperature in which the 3478A was last calibrated. For example, if the last Reference

Temperature was 23°C (73°F), the 3478A should maintain its specifications if operated within ± 5°C ( ± 9°F) of that temperature. The factory temperature is from l8°C to 28°C (64°F to 82°F). The 3478A may be operated within an ambient temperature range of 0°C to

55°C (32°F to 131 °F) with less accuracy .

•

Figure 2·4. Typical HP-18 System Interconnection

2-3

3478A

Installation

20

21

22

23

24

6

7

8

15

16

5

17

9

10

1 1

12

18

19

PIN

1

2

3

4

13

14

LINE

DI01

DI02

DI03

DI04

DI05

DI06

Dl07

DI08

EOI

REN

The 34

7

BA contains metric threaded HP-18 cable mounting studs as opposed to English threads. Metric

DAV

threaded -hp- 10833A, 8, or C HP-18 cable lockscrews must be used to secure the cable to the instru-

NRFD

NDAC

IFC

SAO

ATN

ment. Identification of the two types of mounting studs and lockscrews is made by their color. English threaded fasteners are colored silver and metric threaded fasteners are colored black. DO NOT mate silver and black fasteners to each other or the threads of either or both will be destroyed. Metric threaded HP-18 cable hardware illustrations and part numbers follow.

---. y:--T

SHIELD-CHASSIS GROUND

P/0 TWISTED PAIR WITH PIN 6

P/0 TWISTED PAIR WITH PIN 7

--

==

-

-

-

=

__T"'

P/0 TWISTED PAIR WITH PIN 8

P/0 TWISTED PAIR WITH PIN 9

P/0 TWISTED PAIR WITH PIN 10

THESE PINS

ARE

INTERNALLY

GROUNDED

LOCKSCREW

1390-0360

i

LONG MOUNTING STUD

••SMM

___i

P/0 TWISTED PAIR WITH PIN 11

SHORT MOUNTING STUD

0380-0644

0380-0643

ISOLATED DIGITAL GROUND

Figure 2-5. HP·IB Connector

2-27. REPACKAGING FOR SHIPMENT

NOTE

If the instrument is to be shipped to Hewlett-

Packard for service or repair, attach a tag to the instrument identifying the owner and indicating the required service or repair. Include the model number and full serial number of the instrument. In any correspondence, identify the instrument by model number and full serial number. If you have any questions, contact your nearest

-hp- Sales/Service office.

2-28. Place the instrument in its original container with appropriate packaging material and secure with strong tape or metal bands. If the original container is not available, a replacement can be obtained from your nearest -hp- Sales/Service office. Hewlett-Packard suggests that you always insure shipments.

2-29. If the original container is not to be used, do the following: a. Wrap the instrument in heavy plastic, before placing in an inner container. b. Place packing material around all sides of the instrument and protect the front panel with cardboard strips. c. Place the instrument in the inner container in a heavy carton. Seal the carton with strong tape or metal bands. d. Mark shipping container "DELICATE INSTRU-

MENT", "FRAGILE", etc.

•

•

2-4

INSTRUMENT

~

Shown at Factory

Default Address

(23). This number is called the

Primary Address.

16 4

Figure 2-6. 3478A Address Switch

•

•

3·1. INTRODUCTION

3-2. This section has the information and instructions for the operation of the 3478A Multimeter, showing front panel and remote operation. The information is an abbreviated description of the operation and is written for a Service Trained Person, rather than an

Operator. For more complete operating instructions, refer to the 3478A's Operators Manual. To familiarize yourself with the front and rear panel features or for a review of instrument operations, refer to Figure 3-1.

SECTION Ill

OPERATION

•

•

3-3. The Operation Section is separated into the following major areas: General Information, Front Panel

Operation, Shifted Operation, Miscellaneous Operation, and Remote Operation (HP-IB). It is suggested that you read the Remote Operation Chapters last, since you need to know the other operations to understand the remote operations. The major areas are as follows: a. General Information - paragraph 3-4.

Title

AC Power Operation

Turn-On

Display

Input Terminals

Input Terminals Cleaning

Paragraph

3-5

3-7

3-10

3-12

3-15 b. Front Panel Operation - paragraph 3-17.

Title Paragraph

DC Volts Measurements

AC Volts Measurements

Resistance Measurements

DC Current Measurements

AC Current Measurements

Ranging

Triggering

3-18

3-22

3-26

3-30

3-34

3-38

3-43 c. Shifted Operation - paragraph 3-50.

Title

General

Number Of Digits Displayed

Autozero

Self-Test/Reset Operation

Calibration

Paragraph

3-51

3-54

3-57

3-60

3-63 d. Miscellaneous Operation - paragraph 3-66.

Title Paragraph

Voltmeter Complete 3-67 e. Remote Operation - paragraph 3-69.

Title

General

3478A Response to Bus

Messages

3478A Addressing

Talk-Only Mode (No

Controller)

3478A HP-IB Programming

Advanced programming

Paragraph

3-70

3-74

3-92

3-96

3-98

3-117

3·4. GENERAL INFORMATION

3-5. AC Power Operation

3-6. Before connecting ac power to the 3478A, make sure the power source matches the power requirement of the multimeter (as marked on the rear panel). If the instrument is incompatible with the power source, refer to

Section II of this manual for power requirement modification.

3-7. Turn-On

3-8. When the 3478A is first turned on, the multimeter goes through an Internal Test routine. During the test, the instrument displays "SELF TEST" and, when the test is completed and it passes, the instrument displays "SELF

TEST OK". If the Self-Test fails, refer to Section VII of this manual for troubleshooting information. For more information on the Self-Test, refer to paragraph 3-60.

NOTE

For 3478As with serial numbers 230JA03760 and below or any instruments that have the

Revision B ROM (U502) installed, the instrument displays its remote (HP-/B) address for about one second instead of "SELF TEST

OK". The address is displayed as "HP/B

ADRS,dd", where "dd" is the address code of the instrument.

3-9. Once the Self-Test is completed, the 3478A goes to its turn-on state which is:

FUNCTION .................... DCV

RANGE ...................... AUTO

TRIGGER ............... INTERNAL

AUTO ZERO ..................... ON

NUMBER OF DIGITS DISPLAYED .. 5

3·1 0. Display

3-11. The Display is a 12 character alphanumeric Liquid Crystal Display (LCD) with 12 annunciators. The display is normally used to show readings, however, the

3-1

Operation

.,;:'\1 347BA OlGJTAL HULTJHETER

-oN

.a OFF

LINE a

D D

['

~REI

[4

~REI EJG 0

RANGE/~

D1GIT0

AUTO

ZERO

TEST/

3 RESET AORS CAL

[ill [QJ

~

EJ

B

CAL

ENABLE !D

0

11, SENSE INPUT

~"'FiJ

100V;::::;

~~~

~-

3A

,,~, ~~

3A/250V

FUSE

3478A

•

[Q]

[Q]

@

INPUT

WARNING:

FOR fiSENSE

(4 WIRE) (2 WIRE)

~I~

300V;;c

PROTECTION FROM

ELECTRICAL SHOCK

POWER CORD GROUND

MUST NOT BE DEFEATED.

MAX

~L0\1)

ALL

TERM

±seevpK

MAX

_L

HE'o\.ETT PAa<.ARO 00.

MADE IN USA

111111111111

*

!I

2619A34899

HPIB~

[Q]

EXT TRIG

5V MAX

@)

··~QIISRQ

! ........

I! t··~~~

1-51Hz.~

@)

B

(§)

111JI1JV 1211JV 2211JV 24~

0 • 0 0

2511JmAT - - 125mAT

[Q]

•

3478A-3-1

Q)

Use the measurement keys along the top row to select the type of measurement you want to make.

(!)These keys are used to select special operating features of the

34 7SA. The blue shift key allows for selecting the "SHIFTED" functions of the bottom row of keys.

0

The 1 2 character alphanumeric display includes 1 2 dedicated annunciators. The display is read directly in engineering units, i.e., MV for milli-volts, MOHM for Meg-ohm resistance, etc.

The Internal Trigger is selected by this key. In this mode, the

347SA triggers itself.

G)

If the blue key is pressed before another key, the function shown above that key is executed.

Autozero is a function that allows you. to enable or disable the internal zero correction circuitry.

(D

These terminals are used for the voltmeter sense leads when making 4-wire ohms measurements.

Pressing the Single Trigger key causes the 34 7 SA to take one reading and wait for the next trigger impulse. This impulse can come from either the Single Trigger key or the External Trigger input (rear panel BNC).

(D

These terminals are the voltmeter and 2-wire ohms input,

4-wire ohms source current terminals.

C!)

This is the Amps input terminal and is used with the INPUT

LOW terminal. (3 Amp fuse protected)

Q)

When this switch is out, the front panel input terminals are selected. If the switch is in, the rear panel terminals are used.

The Test/Reset key performs an internal self test, then resets the

34 7 SA to its turn-on state. Any errors in the self test are noted in the display.

The front panel SRQ (Service Request) key is an HP-IB operation that enables you to manually interrupt the controller. This key is enabled by setting the SRQ mask.

Figure 3·1. 347BA Front and Rear Panel Features

3-2

•

3478A

Operation

•

The 34 78A HP-IB Address is displayed when the Address key is pressed.

@The Rear Input Terminals are only used in the DC Volts, AC

Volts, and Ohms Functions. They are selected with the

Front/Rear Switch in the "in" position.

The Local key returns the 34 78A to front panel control from the

REMOTE mode.

@The External Trigger connector is used to externally trigger the

3478A, when in the Single Trigger mode.

The 34 78A features total electronic calibration. The Cal key is used as part of that procedure. See Section IV.

@HP-IB Connector.

@The Voltmeter Complete Connector outputs a pulse after each measurement cycle.

(!)The range keys are used to select the proper range for the measurement. Press any of the keys to select the manual range mode. Note theM RNG annunciator in the display. The

Auto/Man key will return the meter to autorange.

@The Fuse is 2 50mA for the 1 OOV and 1 20V operation, or

1 25mA for the 220V and 240V operation.

@The Option Label shows the instrument's power option.

@The "SHIFTED" functions of the range keys are used to select alternate numbers of display digits.

@These switches select the 34 78A's HP-IB Address, the Power-

On SRO feature, and correct power line frequency (50Hz-60Hz).

Figure 3-1. 3478A Front and Rear Panel Features (cont'd)

display can also show alphanumeric messages (sent remotely). The four characters to the right show the function (and to a certain extent, the range) and the 8 characters to the left show the reading (e.g.

+

12.3657

MVDC). An "OVLD" is displayed if the input is out of range for the selected range and function.

3-12. Input Terminals

•

3-13. The 3478A has one set of Input Terminals on the front panel and one set on the rear panel. The front panel terminals consist of an "INPUT HI", "INPUT

LO", "0 SENSE HI", 0 SENSE LO", and "A"

(Amps) terminal. Except for the "A" terminal, the rear panel has the same set of terminals. The two sets of terminals are selected by the Front/Rear Switch (located on the front panel). The front terminals are selected with the switch "out" and the rear with the switch

"in".

0

SENSE

1\LLTERII

•500V~< l NPUT

•

3-14. The INPUT HI and LO Terminals are used for measuring de volts, ac volts, and resistance in the

2-Wire Ohms configuration. Refer to Figure 3-2 for a typical connection. The n

SENSE HI and n

SENSE LO

Terminals (in conjunction with the INPUT Terminals) are used in the 4-Wire Ohms configuration. Refer to

Figure 3-4 for a typical ohms connection. The A (Amps)

Terminal with the INPUT LO Terminal is used to

0

SENSE

@l

INPUT

@dl a~

l

3A/250V

FUSE

DC OR AC

VOLTAGE

SOURCE

3478 3-2

Figure 3-2. Typical Input Measurement Connection

=.

111

3478 3-3

Figure 3-3. Typical Current Measurement Connection

measure ac or de current. Refer to Figure 3-3 for a typical current connection.

3-15. Input Terminals Cleaning

3-16. The high input impedance of the 3478A requires that the area surrounding the multimeter's Input Terminals (front or rear) must be free of leakage causing paths (e.g. dirt, fingerprints, etc.). The paths can be removed by using a soft cotton swab dipped in isopropyl alcohol.

3·17. FRONT PANEL OPERATION

3·18. DC Volts Measurements

3-19. The 3478A is able to make de volts measurements from .1uV to 300V in five ranges: 30mV, 300mV, 3V,

30V, and 300V. All ranges are protected from input voltages up to 450V peak. Select the DCV Function for de volts measurements by pressing the

=

v

button .

3-20. In the DC Volts Function, ranging is done in the

Input Circuitry of the 3478A. The result is that the input to the AID Converter (which changes the voltage to digital information) has the same value in all ranges for

3-3

Operation

3478A all full scale inputs (e.g. lOY input to the AID for

30mV, 300mV, 3V, etc. inputs to the 3478A).

3-21. When the DC Volts Function is selected, the right side of the display shows "MVDC" or "VDC", dependent on the range selected. The reading can be displayed either as a 5 112, 4 1/2, or 3 1/2 digit reading, dependent on the selected Number Of Digits Displayed (see paragraph 3-54). Refer to Table 1-1 or Table 4-1 for the

DC Volts Function's accuracy specifications.

3·22. AC Volts Measurements

3-23. The 3478A uses a True RMS ACto DC Converter to measure ac voltages from 1uV to 300V in four ranges:

300mV, 3V, 30V, and 300V. The response of the converter is from 20Hz to 100KHz on all ranges (to 300KHz on the 30V Range only). All ranges are protected from input voltages up to 450V peak. Select the AC Volts

Function for ac volts measurements by pressing the ""'v button.

3-24. The AC to DC Converter changes the ac input voltage to de volts, which is then measured by the

3478A's AID Converter. All ranging is done in the AC to DC Converter, applying the same voltage value to the

AID Converter for all full scale inputs.

3-25. When the AC Volts Function is selected, the right side of the display shows "MY AC" or "V AC", dependent on the range selected. The reading can be displayed either as a 5\12, 4\12, or 3\12 digit reading, dependent on the selected Number of Digits Displayed (see paragraph

3-54.) A .6 second delay is also applied in the ACV

Function before a reading is taken (also, during a range change). Refer to Table 1-1 or Table 4-1 for the AC

Volts Function's accuracy specifications.

3-26. Resistance Measurements

3-27. The 3478A is able to make resistance measurements from .0001 ohms to 30M ohms in seven ranges. The ranges extend from the 30 ohm to the 30M ohm range. All ranges are protected from input voltages up to 350V peak. Resistance measurements can be made using either the 2-Wire or 4-Wire ohms configuration, which are selected by the 2 WIRE 0 and 4 WIRE 0 buttons, respectively. Refer to Figure 3-4 for the correct ohms connections.

3-28. Resistance measurements are made by applying a known current (generated by the 3478A) to the unknown resistance. The resultant voltage drop is then measured by the 3478A's de circuitry (Input Circuitry and AID Converter). In the 2-Wire Ohms Function, the voltage drop is measured across the HI and LO INPUT

Terminals. In the 4-Wire Ohms Function, the voltage is measured across the HI and LO 0 SENSE Terminals.

The Ohms Current Source generates the known current which is applied to the unknown resistance (in both

3-4

UNKNOWN

RESISTANCE

Rx

2-WIRE OHMS MEASUREMENT

UNKNOWN

RESISTANCE

Rx

4-WIRE OHMS MEASUREMENT

•

•

Figure 3·4. Ohms Connections

ohms functions) from the HI INPUT Terminal. The current values are as follows:

Range

30 ohm

300 ohm

3K ohm

30K ohm

300K ohm

3M ohm

30M ohm

Current

1mA

1mA

1mA

100uA lOu A

1uA

.1uA

3-29. When an Ohms Function is selected, the right side of the display shows either "OHM", "KOHM", or

"MOHM", dependent on the range selected. In addition, the "2 0" annunciator is on for the 2-Wire Ohms

Function and the "4 0" annunciator is on for the

4-Wire Ohms Function. The ohms reading c~n be displayed either as a 5 1/2, 4 1/2, or 3 1/2 digit reading,

•

Operation

3478A

• dependent on the selected Number Of Digits Displayed

(see paragraph 3-54). A .03 second or a .3 second delay is also applied before each reading in the 3M ohm and

30M ohm Ranges, respectively. Refer to Table 1-1 or

Table 4-1 for the Ohms Function's accuracy specifications.

NOTE

To insure 4- Wire Ohms accuracy when using long leads, it is suggested to keep the lead resistance as follows:

I. Ohms Sense Lead: ranges

<

IOK ohms on all

2. Ohms LO Source Lead:

<

I /30 ohms of full scale on all ranges.

3. Ohms HI Source Lead:

<

1/30 ohms of full scale on the 3K through 30M ohm ranges and

<

3K ohms on the 30 and 300 ohms ranges.

3·30. DC Current Measurements

3-31. The 3478A can make de current measurements from 1 uA to 3A in two ranges: 300mA and 3A. The ranges are protected from excessive currents and voltages by a 3A 250V fuse. Select the DC Current

Function to measure de currents by pressing the . :-::

A

• button.

3-32. In the DC Current Function, the current is applied between the INPUT LO and A Terminals. Since a known value resistor (.1 ohm) is connected between the terminals, a voltage proportional to the unknown current and the resistor is generated. This voltage is measured by the 3478A's de circuitry (Input Circuitry and

AID

Converter).

3-33. When the DC Current Function is selected, the right side of the display shows "MADC" or "ADC", dependent on the range selected. The readings can be displayed either as a

5 Y2,

4

Y2,

or 3

Y2

digit reading, depending on the selected Number of Digits Displayed

(see paragraph 3-54). Refer to Table 1-1 or Table 4-1 for the DC Current Function's accuracy specifications.

NOTE

Current inputs of greater than about I amp may cause the current shunt's (.I ohm

Resistor) value to change slightly due to selfheating. This may cause inaccuracies in the measurement. Sufficient time should be allowed for the circuitry to settle after the measurement is complete and before other critical

•

current measurements are made.

3-34. AC

Current Measurements

3-35. The 3478A can make ac current measurements from 1 uA to 3A in two ranges: 300mA and 3A. The frequency response is from 20Hz to 20KHz. The ranges are protected from excessive currents and voltage by a 3A fuse. Select the AC Current Function to measure ac currents by pressing the "-

A button.

3-36. The AC Current Function is similar to the DC

Current Function (see paragraph 3-30); a voltage drop across a resistor is measured. The difference is that the resultant ac voltage is changed from ac to de using the

ACto DC Converter. Similar to the AC Volts Function, all ranging is done in the converter.

3-37. When the AC Current Function is selected, the right side of the display shows "MAAC" or "AAC", dependent on the range selected. The readings can be displayed either as a

5

1/2, 4 1/2, or 3 1/2 digit reading, dependent on the selected Number Of Digits Displayed

(see paragraph 3-54). Refer to Table 1-1 or Table 4-1 for the AC Current Function's accuracy specifications.

3-38. Ranging

3-39. The 3478A has two range modes: Manual and

Autorange. Manual ranging is selected by pressing the

AUTO/MAN button (if the 3478A is in Autorange) or by pressing either the

0 or

0 buttons. The "M

RNG" annunciator on the display then turns on. The following explains the different range modes.

3-40. Uprange. The 3478A upranges to the next higher range each time the

0 button is pressed. The highest selectable range depends on the function selected (e.g.

300V for the AC Volts and DC Volts Functions).

If a function is selected with its highest range lower than the previous range, the multimeter defaults to the new highest range.

3-41. Downrange. The 3478A downranges to the next lower range each time the

0 button is pressed. The lowest selectable range depends on the function selected

(e.g. 30mV for the DC Volts Function). If a function is selected with its lowest range higher than the previous function, the multimeter defaults to the new lowest range.

3-42. Autorange. The 3478A selects the optimum range when this mode is selected. The mode is selected when the 3478A is first turned on or by pressing the

AUTO/MAN button (if in Manual Range). If

Autorange is enabled, the 3478A upranges when the reading is at or above ± 303099 and downranges at or below ± 027000 (delete one or two zeroes from the numbers for the 4 1/2 and 3 1/2 Digit modes, respectively). The numeric range points are irrespective of decimal placement. Refer to Figure 3-5 for the autorange points (the example is for the DCV Function; other functions are similar).

3-43.

Triggering

3-44. The 3478A has three local trigger modes: Internal, Single, and External. In addition to these, a Hold

3-5

Operation

RANGE

300V

i

Figure 3-5. Autoranging Points

3476 3-5 and a Fast trigger mode can be selected, but only over the HP-IB (remote operation). When the multimeter is triggered, the right most digit on the display blinks

(showing that the display is updated). The following paragraphs explain the trigger modes.

3-45. Internal Trigger. In this mode, the measurement cycle is internally initiated and the 3478A makes the measurements at the maximum reading rate. The Internal Trigger is selected at instrument turn on or by pressing the INT /TRIG button.

3-46. Single Trigger. In this mode, a measurement cycle is initiated each time the SOL/TRIG button is pressed.

When the button is initially depressed, the 3478A initiates a measurement cycle and then places the multimeter in the Single Trigger Mode. If the button is pressed during a measurement cycle (while in the Single

Trigger mode), the 3478A starts a new measurement cycle. When the cycle is completed, a new cycle can then be initiated by pressing the Single Trigger button.

3-47. External Trigger. This mode is selected by pressing the SOL/TRIG button and operates the same as the

Single Trigger mode. The difference is that the 3478A can be triggered from the External Trigger input on the rear panel. The input is TTL logic compatible and the trigger pulse should be at least lOOnS wide. The 3478A is triggered on the negative edge of the TTL pulse.

3-48. Trigger Hold. In this mode, no triggering is done by the 3478A (no measurement cycle is initiated). This mode can only be selected using the 3478A's remote operation.

3-49. Fast Trigger. This trigger is the same as the Single

Trigger except the delays in the ACV and ACI Functions, and high Ohms Ranges are omitted. This trigger can only be selected using the remote operation.

NOTE

When the 3478A is in the Single Trigger mode and an attempt is made to change

3-6

3478A

range or function, the left portion of the display goes blank (except for the decimal point) until another reading is taken (instrument triggered).

3-50. SHIFTED OPERATION

3-51. General

3-52. The Shifted Operation of the 3478A is used to expand the capabilities of the multimeter using the same number of front panel pushbuttons. This is done by using the bottom row of front panel buttons for two different operations, shifted and unshifted. An unshifted operation (AUTO/MAN, INT/TRIG, etc.) is normally selected by pressing a single button. A shifted operation is done by first pressing the blue "SHIFT" button (on the right end of the upper row of buttons) and then pressing one button (on the lower row). To select a new shifted operation, press the blue Shift button again and the button for the new operation. Table 3-1 lists the shifted operations and corresponding buttons. The shifted operations are also shown in blue lettering above the buttons.

3-53. When the blue Shift button is pressed, the

"SHIFT" annunciator on the display is on. The annunciator remains on until a different button is pressed.

Shifted

Operation

Table 3-1. Shifted Operations

Select

Button

Description Of

Operation

3 Digit (Disp)

4 Digit (Disp)

5 Digit (Disp)

Az

Test/Reset

Adrs

Cal

AUTO/MAN

.0

0

INT/TRIG

SGL/TRIG

SRQ

LOCAL

Selects 3 Digits Displayed

(see paragraph 3-54).

Selects 4 Digits Displayed

(see paragraph 3-54).

Selects 5 Digits Displayed

(see paragraph 3-54).

Turns Autozero on or off

(see paragraph 3-57).

Places the 3478A into its

Internal Test Mode (see paragraph 3-61).

Displays the 3478A's current HP-IB Address Code

(see paragraph 3-92).

Places the 34 78A into the calibration mode (see Section IV of this manual).

•

•

3-54. Number Of Digits Displayed

3-55. The 3478A can display readings in either 5 1/2, 4

1/2, or 3 1/2 digits. The

5

1/2, 4 1/2, and 3 1/2 digits can be selected by first pressing the blue Shift button and then either the AUTO/MAN,

0, orO button, respectively.

3-56. The Number Of Digits Displayed affects the reading rate of the multimeter. This is because the number of digits determines the integration time of the

AID Converter. In the 4 1/2 digit mode, the integration

•

Operation

3478A

• time is 1/60 second (or 1/50 second for the 50Hz option), which is called 1 PLC (Power Line Cycle). In the 3

1/2 digit mode, the time is 1/600 second (or 1/500 second for the 50Hz option) which is .1 PLC. In the 5 1/2 digit mode, the 3478A takes 10 readings using the 4 1/2 digit mode and averages them together for an extra digit of resolution. This takes a time of 1/6 second (or 1/5 second in the 50 Hz option) which is 10 PLC. For more information on run-up time and the A/D Converter, refer to this manual's Section VII (Service Group F,

AID

Converter theory of operation).

3·57. Autozero

3-58. The Autozero Function of the 3478A is used to compensate for offsets that may be present in the multimeter's internal circuitry (DC/Ohms Input

Amplifier,

AID

Converter, etc). The method used is to temporarily connect the input of the amplifier to ground

(the INPUT LO Terminal) and make a measurement

(the INPUT HI Terminal is open at this time). The offset reading is then stored into the 3478A's internal memory. After that, the short is removed and a regular input measurement is made. The offset reading is then subtracted from the input reading and the compensated reading is displayed.

3-59. The Autozero Function is enabled when the

•

3478A is turned on and after doing a Self-Test (see paragraph 3-60). The feature can be disabled by pressing the blue Shift button and then the INT /TRIG button. The "AZ OFF" annunciator on the display will light, showing that the function is off. After the function is turned off, the multimeter immediately takes an offset reading and stores it into memory. This last reading is then subtracted from the input measurements that follow. Since no more offset readings are taken, the reading rate of the 3478A is faster (up to twice as fast).

If a range, function, or digit change is made, or an attempt is made to calibrate the 3478A, a new offset reading is taken. With Autozero off, the 3478A's input circuitry remains in a static state. This is useful when making measurements in extremely high impedance circuits where the internal switching transients of the

3478A may affect the reading accuracy.

NOTE

The 3478A 's long term stability may be affected if the Autozero feature is disabled.

3·60. Self-Test/Reset Operation

3-61. The 3478A uses an Internal Self-Test to check its display and internal circuitry. The multimeter goes through the test at turn-on and also when the Self-Test

• is selected. The test can be selected by pressing the blue

Shift

button and then the SOL/TRIG button. When the test is selected from the front panel, all the segments of the display are on except are on as long as the test button is pressed. After that, "SELF TEST" will be displayed during the time of the test. When the test is completed, "SELF TEST OK" will be displayed (if the test passes). The 3478A then resets to its turn-on state

(see paragraph 3-9), not the previous state before the test was selected. For 3478As with serial numbers 2301A03760 and below or any instruments that have the Revision B

ROM (U502) installed, the instrument turns on all the segments in the display for about five seconds. The display then may show a certain message for about 1/4 second. When the Self-Test is completed, the multimeter's displays its remote (HP-IB) address for about one second.

The address is displayed as "HPIB ADRS,dd", where

"dd" is the address code of the instrument.

3-62. If the Self-Test fails, an error message will be displayed indicating the type of failure. If there are multiple failures, only one failure will be displayed. The

3478A then attempts to operate normally (even if a test fails). If another failure is noted while trying to operate normally, the new failure will be displayed. This continues until the test(s) passes or the instrument is taken out of the Self-Test mode.

Table 3·2. 3478A Error Messages

Error Message Definition

U.C. RAM FAIL The 34 78A has failed its internal RAM self test

U.C. ROM FAIL The 3478A has failed its internal ROM self test indicating an error in the ROM

CAL RAM FAIL

UNCALIBRATED The Calibration CMOS RAM has an incorrect checksum showing that calibration is needed

A:D LINK FAIL

An attempt to write to the Calibration

CMOS RAM was unsuccessful

The internal CPU (A/D Controller) is unable to communicate with the A/D Converter

A:D SLOPE ERR The A/D Converter is unable to do a proper conversion

A:D TEST FAIL The A/D Converter has failed its self-test.

3·63. Calibration

3-64. The 3478A does not have any adjustments to calibrate the instrument; calibration is done electronically. A known good calibration source is applied to the multimeter and the value of the known source is entered into the instrument. A reading is then taken and compared with the value entered. A Calibration Constant is calculated (from the entered value) to correct the reading to the known value, and then stored into memory. The correct readings are calculated using the constants and then displayed .

3-65. There are two steps in calibrating the 3478A.

First, the front panel Calibration Switch has to be set to

3-7

Operation

CAL/ENABLE. Second, the blue Shift button and the

LOCAL (CAL) button have to be pressed for each calibration step (e.g. press the buttons for the DC Volts

Function's zero calibration and press the buttons again for the function's full scale calibration). Refer to Section IV of this manual for the calibration procedures.

NOTE

The CAL ENABLE Switch on the front panel should not be in theCAL/ENABLE position under normal use. It should only be in that position to calibrate the instrument.

3·66. MISCELLANEOUS OPERATIONS

3·67. Voltmeter Complete

3-68. The Voltmeter Complete connector is a BNC connector which outputs a signal at the end of the

AID

cycle. The signal is a negative going TTL compatible pulse with a time period of approximately 1/LS. The Voltmeter

Complete connector is located on the rear panel.

3·69. REMOTE OPERATION

3·70. General

3-71. The following paragraphs gives device dependent information necessary to remotely operate the 3478A over the Hewlett-Packard Interface Bus (HP-IB).

Directions for mechanical interface connections to the

HP-IB are given in Section II of this manual.

Familiarize yourself with the front panel operation

(local) before attempting to use the multimeter in remote (HP-IB).

NOTE

HP-IB

is

Hewlett-Packard's implementation of IEEE Std.

488-1978,

"Standard Digital

Interface for Programmable Instrumentation, and ANSI MC

1.1.

3-72. A general description of the HP-IB is in this manual's Appendix A. Refer to the appendix for any non-3478A related HP-IB information.

It is assumed, in the following paragraphs, that you are knowledgeable about the HP-IB.

3-73. The following lists the different 3478A remote operations. a. 3478A Response to Bus Messages (paragraph

3-74).

Title

Paragraph

Data

Trigger (GET)

Clear (DCL or SDC)

Remote

Local

Local Lockout

3-76

3-77

3-78

3-79

3-80

3-81

3-8

3478A

Clear Lockout and Set Local 3-82

Require Service (SRQ)

3-83

Status Byte

3-85

Status Bit

Pass Control

Abort

3-89

3-90

3-91 b. 3478A Addressing (paragraph 3-92) and Talk-

Only Mode (paragraph 3-96). c. 3478A HP-IB Programming (paragraph 3-98).

Title Paragraph

General

Program Codes

Programming the SRQ

3-99

3-101

Mask

Clearing Status

3-103

Register (Status Byte)

3-105

Power-On SRQ

3-106

Sending Data to the Display

3-107

Home Commands

Reading Data from the

3-110

3478A 3-111

Front/Rear Switch Position

3-113

Data Ready Feature

Front Panel SRQ

Fast Trigger

3-114

3-115

3-116 d. Advanced Programming (paragraph 3-117).

Title Paragraph

General

Extended Ohms Operation

Reading the Binary Status

Byte

Reading the Error Register

3-118

3-119

3-120

3-121

3·74. 3478A Response to Bus Messages

3-75. The following paragraphs explain the 3478A's response to Bus Messages. The multimeter's Bus capabilities are in Table 3-3.

Table 3·3. 3478A's Bus Capabilities

Mnemonic

Interface Function Nama

SH1

AH1

T5

L4

Source Handshake Capability

Acceptor Handshake Capability

Talker (Basic Talker, Serial poll, Talk Only

Mode, Unaddressed to Talk if Addressed to listen) listener (Basic listener, Unaddressed to Listen if Addressed to Talk)

LEO

TEO

No Extended Listener

No Extended Talker

Service Request Capability

SR1

RL1

PPO

DC1

Remote/Local Capability with Local Lockout

No Parallel Poll Capability

Device Clear Capability

DT1

Device Trigger Capability co

No Controller Capability

•

•

•

3-78. Clear (DCL or SDC: Device Clear or Selective

•

Device Clear). A Clear places the 3478A into its turn-on routine (see paragraph 3-7). In addition, the multimeter's address switch (see paragraph 3-92) is read and the SRQ Mask is set to zero or octal 200 (if the

Power-On SRQ switch is on, see paragraph 3-106). If during the turn-on routine an error is detected, the hardware error bit in the serial poll register is set.

3-79. Remote. The Remote Message allows the 3478A to be controlled over the HP-IB. In remote, the front panel buttons, except the LOCAL and Front Panel SRQ buttons, are disabled. The Local and Front Panel SRQ buttons are only disabled when the 3478A is in remote and local lockout (see paragraph 3-81). The instrument state in remote is determined by the local state before being placed in remote. The RMT annunciator on the display will also be on with the 3478A in remote.

3-80. Local. This message clears the remote operation of the 3478A and enables its front panel operation.

Pressing the front panel LOCAL button also places the multimeter in the local state (if the button has not been

Operation 3478A

•

3-76. Data. The Data Message is used to transfer information between the 3478A and the controller. a. The message is used to send data to the multimeter and consists primarily of set-up information (e.g. DC

Volts, 30V Range, etc.). The 3478A is the Listener and the controller is the Talker. b. The message is also used by the controller to receive data from the 3478A. This includes the multimeter's output (readings) and status information.

In this case, the 3478A is the Talker and the contrqller is the Listener.

3-77. Trigger (GET, Group Execute Trigger). The

Trigger message causes the 3478A to initiate a measurement cycle. It is an HP-IB Trigger and triggers the multimeter in any trigger mode, since it has priority over the other trigger modes. If the 3478A is triggered during a measurement cycle, the cycle is aborted and a new cycle is initiated. There may be a delay (up to .5 sec) if a cycle is in progress when the trigger is received. The multimeter has to be programmed to "listen" to execute the trigger. disabled by the Local Lockout Message, see next paragraph).

3-81. Local Lockout. All the front panel buttons are disabled with this message, if the 3478A is in remote.

The message is in effect until cleared over the HP-IB or power is cycled.

3-82. Clear Lockout and Set Local. This message placed the 3478A into local and the Local Lockout Message is cleared.

3-83. Require Service (SRQ). The Require Service

Message (SRQ Message) is independent of all other HP-

IB activity and is sent on a single line called the SRQ

Line. Its state is either true or false (low= true and high= false). The 3478A must be programmed to send the SRQ Message. This is done by programming the

SRQ Mask (see paragraph 3-103). The front panel SRQ annunciator is on when the 3478A requires service.

3-84. Since more than one device (on the same Bus) can output the SRQ Message, the devices can be polled by the controller (by a Serial Poll) to determine if the

3478A (or another device) requires service. The 3478A then outputs a Status Byte (see paragraph 3-85) which shows for what reason the multimeter requires service.

3-85. Status Byte. The Status Byte is output by the

3478A in response to a Serial Poll. The message has the same information as the 3478A's Status Register (see next paragraph), and sets the corresponding bit true for any true SRQ condition shown in Table 3-4 (whether the

SRQ Mask is set or not). The bit is represented in Figure

3-6.

3-86. The 3478A can require service if any condition in

Table 3-4 is true. Since the SRQ Mask must be set to output the Require Service Message (except for bit 7, which is set by the Power-On SRQ switch), the 3478A's

Status Register is used to monitor the conditions. This way, only the condition that is set by the mask outputs the SRQ Message. Other true conditions that can cause an SRQ Message, but which are not set by the SRQ

Mask, remain in the Status Register as a true condition.

They will not cause the SRQ Message to be output. For example, suppose the Front Panel SRQ condition is the only one set in the SRQ Mask. If the Data Ready condition is true, but not Front Panel SRQ, no SRQ Message

Invalid Calibration

I b71 b61 b51 b41 b31 b21 b1

I bO

I

-----J'

I

I I I I

I

I

Data Ready

· '-· - - - - - - Bit Always 0

Syntax Error

Front Panel SRQ Internal Error

•

Figure 3·6. Status Byte

3-9

Operation

Octal

Code

001

Table 3-4. Status Byte Definitions

Decimal

Code

Bit Definitions

0 Data Ready - Indicates to the controller that measurement data is ready to be output. The Require Service Message and bit is cleared when the controller begins to accept the data or when the reading is no longer available. See paragraph 3-1 1 4.

002

004

010

020

040

100

200

2

4

8

16

32

64

128

1 This bit is always at 0 (0 =high).

2 Syntax Error- This shows that an invalid Program Code(s) has been sent to the 3478A (e.g. F9).

3 Internal Error · Shows that a failure in the 34 7 SA is detected. This may be a failure in the Self-Test Routine

(see paragraph 3-60). the A/D Converter, or a checksum error in the

Calibration RAM (checked every time a reading is taken). More information can be obtained by reading the 3478A's error register. See paragraph 3-1 20.

4 Front Panel SRQ - This bit is set when the 34 78A's Front Panel SRQ button is pressed. See paragraph

3-1 1 5.

5

Invalid Calibration · When this bit is set, an attempt to calibrate the

34 78A has failed.

6 This is the SRQ bit. This bit is true only if a Require Service Message is output.

7 Power-On SRQ - Shows that a power-on reset has occurred. See paragraph 3- 1 06.

Note: More than one bit in the Status Byte can be true (see paragraph 3-87). is output (the Status Register's Data Ready bit is true).

The only way the SRQ Message is output is if the Front

Panel SRQ condition is true.

3-87. More than one bit in the Status Byte Message can be true. For example, bit 0, 2, and 4 are true (remember, bit 6 is true for any SRQ condition, if the SRQ Mask is set for the condition) making the resultant Status Byte look like the following: b7 bO lol1joj1lol1lo111

NOTE

3-10

A "1 ,, in this example shows a true condition.

3478A

3-88. The byte is output as shown in the previous example with the corresponding octal number of the example at 125 shown as follows:

•

3-89. Status Bit. The 3478A does not respond to a

Parallel Poll. The Status Bit is used only for Parallel

Poll and should not be confused with the bits in the

Status Byte Message.

3-90. Pass Control. The 3478A does not have controller capabilities.

3-91. Abort (Interface Clear). All HP-IB communication is terminated (including the 3478A's Bus communication). Control is returned to the controller. The

Abort Message does not remove the 3478A from remote control.

3-92. 3478A Addressing

3-93. HP-IB requires that each device on the Bus needs to be identified as a Listener or a Talker, in order to execute the Bus Messages and commands. Because of this, each device has its own unique "listen" and "talk" address. The address of the 3478A is set by the Address

Switch on its rear panel. Setting the 3478A's Listen Address also sets its Talk Address.

3-94. The address switch is an eight section "DIP" switch with five sections used for addressing. The switch is shown in Table 3-5. The allowable address settings are also listed in Table 3-5. The factory address setting of the 3478A is decimal 23 (refer to Section II of this manual for the switch setting).

•

3-95. Instrument address commands (sent by the controller) are usually in this form: universal unlisten, device talk, device listen. The universal unlisten command removes all listeners from the Bus to allow only the addressed listener(s) to receive data. The data is sent by a talker which is designated by the device talk command.

3-96. Talk-Only Mode (No Controller)

3-97. The 3478A's Talk-Only Mode allows the multimeter to send measurement data to an external device (like a printer) without a Bus controller. The multimeter is placed into the Talk-Only Mode by setting the five address switches (on the rear panel "DIP" switch) to 1 (set only the five address switches to the up position). Measurement data is then output after each trigger. Function and range settings are selected from the front panel.

•

Operation

3478A

•

•

Table 3-5. 3478A Address Codes

INSTRUMENT

~

Shown at Factory

Default Address

123). This number is called the

Primary Address.

16 4

2

3

4

I

a

1

5

6

7

8

9

ASCII Code

Character

Listen Talk

SP

#

$

%

&

@

A

B c

D

E

F

G

H

I

+

<

>

K

L

M

~ p

X y

[ z

0

R s

T u v w

\

I

Address Switches

A5 A4 A3 A2 A 1

0 0 0 0 0

0 0 0 0 1

0 0 0 1 0

0 0 0 1 1

0 0 1 0 0

0 0 1 0 1

0 0 1 1 0

0 0 1 1 1

0 1 0 0 0

0 1 0 0 1

0 1 0 1 0

0 1 0 1 1

0 1 1 0 0

0

0

0

1

1

1

1 0 1

1 1 0

1 1 1

1 0 0 0 0

1 0 0 0 1

1 0 0 1 0

1 0 0 1 1

1 0 1 0 0

1

1

1

1

1

1

1 0

1 0

1 0

1 0

1 1

1

0

1 1 1

1 1 0 0 0

1 0 0

1 0 1

1

0

1 0 1 1

1 1 0 0

1 1 0 1

1 1 1 0

5-bit

Decimal Code

17

18

25

26

27

28

29

30

19

20

21

22

23

24

00

01

02

03

04

05

06

07

08

09

10

11

12

13

14

15

16

CMD MODE

"";, ..

-=~::'~:~;

?

J

I u

7 controller "talk" address

34 78A "listen" address

DATA MODE

F1 RA T3

I

L s;oglo To;gg••

Autorange

L - - - - - - DCV Function

3-102. The Program Codes are a series of 7-bit

ASCII characters (the parity bit is ignored). All lower case characters, spaces, commas, and semicolons are ignored (they may be used with the codes as separators). All null characters, carriage return, line feed, form feed, vertical tab, and horizontal tab characters are also ignored. Other characters which are not included in Table 3-6, cause a Syntax Error (bit 2 in the Status Register set). In addition, a Syntax Error is caused if the characters are sent in a different order than shown in the table (e.g. "IF" causes a Syntax Error).

3-98. 3478A HP-IB Programming

3-99. General. The following paragraphs explain how to program the 3478A over the HP-IB. The information is given using the HP-IB format, rather than controller dependent language. If the information is desired using controller dependent language, refer to the 3478A's

Operator's Manual.

3-100. Programming the 3478A is done by DATA messages. Set-up information (Range, Function, etc.) is

DATA sent by the controller and is done using program codes. The DATA received by the controller (from the

3478A) is measurement data, and other data like the

Status Byte and the five bytes from the Output Binary

Status Byte.

•

3-101. Program Codes. All the program codes for the

3478A

are

listed in

Table 3-6. The 3478A must be in

"remote" and "listen" to receive the codes (the RMT and LSTN annunciators are on when the 3478A is in remote and listening). An example is as follows:

Do not send program codes "W" and/or

"X" to the 3478A. These codes can, under certain conditions, uncalibrate the instrument.

The letters "W" and "X" can, however, be sent behind program codes "D2" or "D3"

(which are used to send text to the display; see paragraph 3-107).

3-103. Programming the SRQ Mask. The SRQ Mask must be set for the 3478A to output a Require Service

Message. Setting the SRQ Mask will not set the bits in the Status Byte; these bits are automatically set (except bit 6) when any corresponding require service condition is true. For example, you wish to know if the multimeter has received an incorrect program code (Syntax Error) or has an internal failure (Internal Error). If the conditions are true, bits 2 and 3 of the Status Byte are set; but no Require Service Message is output. The message will not be output until the SRQ Mask is set to the corresponding bits of the Status Byte (which are are bits 2 and 3). Since the mask is to be set in octal, the resultant code for the bits is "14". The mask is set by sending

"Mdd", where dd is the octal code for the bits. This is shown in the following example.

"";'"""' ""';""" oommood controller "talk" address

34 78A "listen" address

? U 7 M14

J

II

L set mask

(where 1 4 is the octal code for bits

2 and 31

3-104. Only bits 0 to 5 can be set by programming the

SRQ Mask. Bit 6 of the Status Byte is set whenever the

Require Service Message is output and bit 7 is set by the

Power-On SRQ switch on the rear panel (see paragraph

3-106). Because of this, only a two digit octal code (00

3-11

Operation

3-12

R3

R4

R5

R6

R7

RA

ZO

Z1

01

02

03

N3

N4

N5

T1

T2

T3

T4

T5

Type

Table 3·6. 3478A Program Codes

FUNCTION

Program

Code

F1

F2

F3

F4

F5

F6

F7

Description

DC Volts

AC Volts

2-Wire Ohms

4-Wire Ohms

DC Current

AC Current

Extended Ohms (see paragraph

3-118).

RANGE

DIGITS

DISPLA YEO

TRIGGER

AUTOZERO

DISPLAY

R-3

R-2

R-1

RO

R1

R2 most sensitive range on any function

30mV DC, or most sensitive range on any other function

300mV DC, 300mV AC, 300mA

DC, 300mA AC, or most sensitive range on any other function

3V DC, 3V AC, 3A DC, 3A AC, or most sensitive range on any other function

30V DC, 30V AC, 30 Ohm, or most sensitive range on any other function

300V DC, 300V AC, 300 Ohm, or least sensitive range on any other function

3K Ohm or least sensitive range on any other function

30K Ohm or least sensitive range on any other function

300K Ohm or least sensitive range on any other function

3M Ohm or least :;ensitive range on any other function

30M Ohm or least sensitive range on any other function.

Autorange

3 1/2 Digits Displayed

4 1/2 Digits Displayed

5 1/2 Digits Displayed

Internal Trigger

External Trigger

Single Trigger

Hold Trigger

Fast Trigger (see paragraph 3-116)

Autozero Disabled

Autozero Enabled

Normal Display Operation

Display Text and update Annunciators

Display Text and turn off Annunciators

HOME

COMMAND

MISC.

COMMANDS

B c

E

HO

H1

H2

H3

H4

H5

H6

H7

K

M s

Equivalent to "F1T4R-2RAZ1 N4"

Equivalent to "F1 R-2RAZ1 N4T3"

Equivalent to "F2R-2RAZ 1 N4 T3"

Equivalent to "F3R-2RAZ1 N4T3"

Equivalent to "F4R-2RAZ1 N4T3"

Equivalent to "F5R-2RAZ1 N4T3"

Equivalent to "F6R-2RAZ1 N4T3"

Equivalent to "F7R-2RAZ1 N4T3"

Read Status of the 34 7 SA in Binary.

See paragraph 3-11 9.

Calibrate (see Section IV of this manual)

Read the Error Register. See paragraph 3-1 20.

Clears Status Register

Set SRO Mask IMdd, where dd is the oc~al code of the bits)

Front/Rear Switch Position

(0

=Rear, 1 =Front)

3478A

77) can be sent to program the mask. The mask can be cleared by sending: "MOO". Remember, the mask is only set to output a Require Service Message (not the

Status Byte) for a certain SRQ condition.

3-105. Clearing Status Register (Status Byte). Bits 2 through

5

and 7 of the register can be cleared by sending program code "K", and by a device CLEAR message.

Bit 0 (Data Ready) is not cleared since it represents the

3478A's current status (the bit is cleared when the

3478A outputs its reading). Bit 6 is the SRQ bit which can be cleared by a Serial Poll or if the SRQ Mask is set to 00.

3-106. Power-On SRQ. This feature is enabled by setting the Power-On SRQ switch to On (switch

#

3 on the rear panel in the up position). When the feature is enabled, the 3478A Requires Service (generates an SRQ) each time power is cycled or a reset condition is generated by the instrument (e.g. due to an instrument failure or selecting the Self-Test).

3-107. Sending Data to the Display. Up to 12 ASCII characters can be displayed at a .time by the 3478A's display. The legal characters are decimal 32 through 95 of the 128 ASCII characters. Only upper case letters and numbers can be displayed. Lower case letters generate characters which do not resemble the letters. Commas, periods, and semicolons can go between characters. The

ASCII characters can be sent in two different modes.

The following paragraphs explain the two modes.

3-108. In one display mode, the display is continuously updated. This is enabled by program code "D2" (e.g.

"D23478A DMM" where "3478A DMM" is the message displayed). In this mode, the annunciators continue to be updated. If more than 12 characters are sent to the display, the extra characters are ignored until a control character is received. If the control character is different than HT (Horizontal Tab), VT (Vertical Tab),

LF (Line Field), CR (Carriage Return), or FF (Form

Feed), a Syntax Error is generated. A "D2" code locks the display until a "D1" (Selects Normal Display) is sent, a CLEAR message is sent, an error condition occurs, or a front panel button is pressed.

3-109. The other display mode is selected by sending code "D3". This mode is the same as the previous mode, except the display is not updated and all annunciators are turned off. The text on the display remains on for about 10 minutes and then the display goes blank. The display can be restored by sending any of the display codes (D 1, D2, or D3) or by pressing the

LOCAL button (if not disabled by the LOCAL

LOCKOUT Message).

3-110. Home Commands. The Home Commands

(when sent to the 3478A over the HP-IB) are used to set the 3478A into a predefined operating state. The program code is "Hn", where n is the number which

•

•

•

3478A

• defines the state. The following lists the home commands and the corresponding operating states.

a. HO Command. The instrument state for this command is as follows:

Function...................... DCV (Fl)

Range ......................... 30mV, Auto (R-2RA)

Trigger....................... Hold (T4)

Number of Digits Displayed.... 4 1/2 (N4)

Autozero. .. ... .. ..... ..... .... On (Zl)

In addition, the 3478A's External Trigger is disabled and the instrument is set into the lowest range (R-2) before Autorange is selected. Also, any data (reading) output to the Bus or the front panel is erased when the home command is sent. The corresponding program codes of the instrument state are: "Fl T4R-2RAZ1N4".

b. Hl Command (DCV). This command is the same as the "HO"command, except a trigger occurs and the resultant output can be read. The corresponding program codes are: "F1R-2RAZ1N4T3".

c. H2 Command (ACV). The same as the "Hl" command, except the selected function is AC Volts. The corresponding program codes are:

•

"F2R-2RAZ1N4T3".

d. H3 Command (2-Wire Ohms). Same as the "Hl" command, except the selected function is 2-Wire Ohms.

The corresponding program codes are:

"F3R-2RAZ1N4T3".

e. H4 Command (4-Wire Ohms). Same as the "Hl" command, except the selected function is 4-Wire Ohms.

The corresponding program codes are:

"F4R-2RAZ1N4T3".

f.

H5 Command (DC!). Same as the "HI" command, except the selected function is DC Current. The corresponding

"F5R-2RAZ1N4T3". program codes are:

g.

H6 Command (ACI). Same as the "HI" command, except the selected function is AC Current. The corresponding program codes are:

"F6R-2RAZ1N4T3".

h. H7 Command

(Ext. Ohms). Same as the "HI "command, except the selected function is Extended Ohms (see paragraph 3-119). The corresponding program codes are:

"F7R-2RAZ1N4T3".

3-111.

Reading Data from the

3478A.

Data in the form

• of readings can be output by the 3478A over the HP-IB

(other data that can be output is discussed in later paragraphs). To output a reading (if available), the

3478A has to be addressed to "talk". The readings are output using 13 ASCII characters and are in the following form:.

Operation

,;t_D.DDDDDE ± D CR LF!EOI!

Polarity of reading (a"+"

_j~ is sent for ac readings)

Reading expressed in scientific notation (0 is a decimal digit)

Carriage Return

Line Feed (with End o r - - - - - - - - - - - - '

Identify Line set)

3-112. Each character in the output statement (except

EOI) is one byte, which adds up to 13. The exponent will be in engineering notation (E-3, E

+

0, E

+

3, or

E

+

6) and the mantissa will always have 1, 2, or 3 digits before the decimal point (D.DDDDD, DD.DDDD, or

DDD.DDD). If the 3478A is in the 4 1/2 or 3 1/2 Digit mode, the 5th and/or 6th digits will be output as zeroes.

An overload condition (whether plus or minus) will be output as:

+

9.99999E

+

9. If a different output is requested (Binary, Front/Rear Switch position, etc.), the other output supercedes the reading. If a data transfer is interrupted while being output, the 3478A continues the output wherever it left off, when addressed again. This partial output (or any output) can be disabled by a

Group Execute Trigger (GET), Clear Message (DCL or

SOC), sending any valid program code, or pressing the

LOCAL, Shift, and TEST /RESET buttons on the front panel.

3-113. Front/Rear Switch Position. The 3478A's

Front/Rear Switch position can be remotely determined by sending program code "S" to the multimeter and then reading its output. If "0" (CR LF) is output the switch is set to Rear, and if "1" (CR LF) is output the switch is set to Front.

3-114.

Data Ready Feature. The Data Ready feature of the 3478A, when enabled, outputs a Require Service

Message (SRQ) after each completed measurement cycle. Before the message can be output, bit 0 of the SRQ

Mask must be set. This is done by sending program code

"MOl" (bit 0 of the Status Byte and Status Register).

When the Require Service Message is sent, the front panel "SRQ" annunciator turns on and bit 0 of the

Status Byte is set. The SRQ condition remains until the data is read by the controller, or a Serial Poll is done.

3-115. Front Panel SRQ. The Front Panel SRQ feature of the 3478A outputs a Require Service Message (SRQ) each time the Front Panel SRQ button is pressed.

Before the message can be output, bit 4 of the SRQ

Mask must be set. This is done by sending program code

"M20" (bit 4 of the Status Byte and Status Register).

Once this is done, the Require Service Message will be output and the front panel SRQ annunciator turns on, whenever the SRQ button is pressed. The SRQ condition remains until a Serial Poll is done by the controller.

3-13

Operation

3-116.

Fast Trigger. This trigger mode can only be selected over the HP-IB. It is the same as the Single

Trigger, except the delays in the AC Volts Function, AC

Current Function, and the high Ohms Ranges are omitted. The mode can be selected by sending program codes

"T5".

3·117. Advanced Programming

3-118. General. The following paragraphs have advanced programming information for the 3478A. It includes Extended Ohms Operation, Reading the Binary

Status Byte, and Reading the Error Register.

3-119.

Extended Ohms Operation. This operation (or function) is only available over the HP-IB and is used to measure resistance above 30M ohm. The function is selected by sending program code "F7" or "H7"

(Home Command, see paragraph 3-110). The 3478A is set to the 2-Wire Ohms Function and the 30M ohm

Range. A 10M ohm resistor is connected in parallel with the input. Measure the resistance first and then measure the unknown resistance. The unknown resistance can then be calculated by this formula:

Rx

Ri

*

Rt

= - - -

Ri- Rt where

Rx is the unknown resistance, Ri is the measured

IOM ohm resistor, and Rt is the measured value of the parallel combination.

3-120. Reading the Binary Status Byte. The current status (or state) of the 3478A can be determined by reading its Binary Status Byte. The total number of bytes is five, with each byte 8 bits wide. The bytes can be read by sending program code "B" to the 3478A and then reading its output. A small program to read the output using the -hp- Model 85 Personal Computer is as follows: lO OUTPUT 723 ;"B"

20 ENTER 723 USING "5(1B)" ;Bl,B2,B3,B4,B5

The bytes are in variables Bl, B2, B3, B4, and B5. The bytes and corresponding meanings of the bits (when true) are in Table 3-7. Program Code "B" clears the Error Register (byte 4; see Table 3-7).

3-121. Reading the Error Register. Besides using Binary

Status Byte 4 (see previous paragraph), the status of the

Error Register can also be determined by sending program code "E" to the 3478A and then reading its output. The output is a two digit octal number followed by a carriage return and line feed. The number shows which bit(s) of the register is true (a two digit number can be used since only 6 bits are used by the register).

For example, bits 0 and 5 are true which results in octal

"41" (the maximum value is "77"}: Refer to Table 3-7

(byte 4) for the definitions of the bits. The Error

Register is also cleared by sending program code "E".

3-14

3478A

Table 3·7. Binary Status Byte Definition

Byte# Definition

Bits

True

XXXXXX01

XXXXXX10

XXXXXX11

XXX001XX

XXX010XX

XXX011XX

XXX100XX

XXX101XX

XXX110XX

XXX111XX

001XXXXX

010XXXXX

011XXXXX

100XXXXX

101XXXXX

110XXXXX

111XXXXX

Function, Range, and Number Of Digits

Displayed

5 1/2 Digits Displayed

4 1/2 Digits Displayed

3 1

I

2 Digits Displayed

30mV DC, 300mV AC, 30 Ohm,

300mA AC or DC, or Extended Ohms

Ranges

300mV DC, 3V AC, 300 Ohm, 3A AC or DC Ranges

3V DC, 30V AC, 3K Ohm Ranges

30V DC, 300V AC, 30K Ohm Ranges

300V DC, 300K Ohm Ranges

3M Ohm Range

30M Ohm Range

DC Volts Function

AC Volts Function

2-Wire Ohms Function

4-Wire Ohms Function

DC Current Function

AC Current Function

Extended Ohms Function

2

3

4

5

1

2

3

4

5

6

7

1

2

3

4

5

6

7

Bits

0-7

Bit#= 1

0

1

2

3

4

5

6

7

Bit#= 1

0

Bit#= 1

0

Instrument Status Bits

Internal Trigger Enabled

Autorange Enahled

Autozero Enabled

3478A set for 50Hz Operation

Front/Rear Switch in Front Position

Calibration RAM Enabled

External Trigger Enabled

Always Zero (not true)

SRQ Mask

Data Ready - SRQ for every available reading to the HP-IB

Not used

Syntax Error - SRQ if Syntax Error occurs

Internal Error - SRQ if Hardware Error occurs

Front Panel SRQ - SRQ if SRQ button is pressed

Calibration Error - SRQ if CAL procedure failed

Always Zero (not true)

Power-On SRQ - PON SRQ switch on last time power was turned on or DCL message was received

Internal Error Information

Set if any of the Calibration RAM locations have incorrect checksums or if a range with an incorrect checksum is selected

The Main CPU RAM Self-Test has failed

The Control ROM Self-Test has failed

An A/D Slope Error was detected

The A/D has failed its Internal Self- Test

A failure in the A/D link (between U403 aild U462)

Always Zero

Always Zero

A/D DAC Value

A decimal value between 0 to 63 represents the setting of the internal

Digital to Analog Converter (DAC).

(Refer to this manual's Section VII for information.!

•

•

•

•

4-1. INTRODUCTION

4-2. This section of the manual contains Performance

Tests and Calibration Procedures. The Performance Tests and Calibration Procedures use the specifications listed in Table 1-1 and summarized in Table 4-1. All Performance Tests and Calibration Procedures can be accomplished without removing the 3478A cover.

Table 4-1. Abbreviated Specifications Table

DC Volts Function (accuracy

=

±(% of raading

+ number of counts))

Range 24 Hour

30mV 0.025 +

40

300mV 0.004 + 4

3V

0.003 +

2

30V

0.004

+ 3

300V 0.004 +

2

90 Day

0.0275

+

40

0.005 + 5

0.004 + 2

0.005 + 4

0.005 + 2

1 Year

0.035 + 40

0.007 + 5

0.006 + 2

0.007 + 4

0.007 + 2

DC Current Function (accuracy

=

±(% of reading

+ number of counts))

Range 90 Day

300m A

3A<1A

3A>1A

0.11 + 40

0.14 +

6

1.0

+ 30

•

Ohms Function (accuracy

=

±(% of reading + number of counts))

Range

30 ohm

300 ohm

3K ohm

30K ohm

300K ohm

3M ohm

30M ohm

24 Hour

0.023 + 35

0.0045 +

4

0.0035 + 2

0.0035 + 2

0.0035 + 2

0.0052 + 2

0.036 + 2

1 Year

0.15

+

40

0.17 + 6

1.0 + 30

90 Day

0.027

+

41

0.012 + 5

0.011 +

2

0.011

+

2

0.011

+

2

0.011 +

2

0.066 +

2

1 Year

0.034

+

41

0.017 + 5

0.016 + 2

0.016

+

2

0.016

+

2

0.016 + 2

0.078

+

2

AC Volts Function 1 Year Limits (accuracy counts))

=

±(% of reading + number of

Frequency

20Hz-50Hz

50Hz-100Hz

1OOHz-20KHz

20KHz-50KHz

50KHz-1OOKHz

1OOKHz-300KHz

300mV Range 3V,30V Range

1.14

+

163 1.14 + 102

0.46 + 163 0.46 + 103

0.20

+

120 0.20 + 70

0.38 + 205 0.26 + 140

1.20 + 840 0.87 + 780

10.1 + 3720

(30V Range

Only)

300V Range

1.18 + 102

0.50

+

102

0.24 +

70

0.42

+

140

0.98

+

780

AC Currant Function 1 Year Limits (accuracy of counts))

=

±(% of reading + number

Frequency

20Hz-50Hz

50Hz-1KHz

1KHz-10KHz

1OKHz-20KHz

300mA Range

1.54 + 163

0.81 + 163

0.72 + 163

0.86 + 163

3A Range

2.24

+

163

1.50 + 163

1.42 + 163

1.56 + 163

•

4-3. TEST EQUIPMENT

SECTION IV

PERFORMANCE TEST AND CALIBRATION

4-4. Table 4-2 lists the recommended test equipment for the Performance Tests, Calibration Procedures, and

Troubleshooting. The recommended equipment is listed along with the critical specifications so that substitute equipment may be used. The HP Model3456A Voltmeter is only recommended if the Standards to be used do not have the required acuracy. In these cases, the Standard and the HP 3456A are connected in parallel and the displayed reading on the 3456A is used as the Standard.

A summary of the test equipment required to perform each Performance Test or Calibration Procedure is listed at the beginning of each procedure.

Instrument

Table 4-2. Recommended Test Equipment

Critical Specifications

Recommended Use

Model

Digital Voltmeter

Bus System

Analyzer

Range: 30mV to 300V

Accuracy:

± .0020% @ 300V

± .0015% @ IV, 3V, 30V

± .0025% @ 300mV

±. 015%@ 30mV

HP-IB Control Capability

HP 3456A

HP Model

59401A

PCT

DC Volts Standard Range: 30mV to 300V Datron 4000A or 4707

PC

Accuracy ± .005%

AC Volts Standard

Frequency: 20Hz to 300KHz Datron 4200 or

4707 PC

Range: 30mV to 300V

Accuracy: ±1%

Datron 4000A or 4707 PC

Resistance

Standard

AC Current

Standard

Range: 1011 to 10MI1

Accuracy: ±.03%

Frequency: 1KHz to 5KHz

Range: 1 OOmA to 1 A

Accuracy: ±.1%

Desktop Computer

HP-18 Capability

Datron 4200 or

4707 PC

HP Model

85B CT

HP Model 9000

Series 200/300

T

Oscilloscope Bandwidth: DC to 100MHz HP Model

1740A T

Signature Analyzer

HP Model

5004A

T

P

=

Performance Test C

=

Calibration T

=

Troubleshooting

4-5. TEST CARDS

4-6. Performance Test Cards are provided at the end of this section. The Performance Test Cards are used to record the 3478A's test results. It is recommended that the cards be used as an outline of the Performance Tests and that they be filled out as the test progresses. Each

Performance Test Card shows the tests required, the upper test limits, and the lower test limits. There is a separate Performance Test Card for the 24 hour limits,

90 day limits, and 1 year limits. The Performance Test

Cards can be used as an abbreviated test procedure once

4-1

Performance you become familiar with the detailed test procedure given in the text. The Performance Test Cards can be used as a permanent record of the 3478A. The cards may be reproduced without written permission from Hewlett-

Packard.

NOTE

The Performance Test Cards at the end of this section only apply to 3478A 's with serial prefix 2545 and above. Refer to Section VI of this manual if you are Performance Testing or Calibrating a 3478A with a serial prefix below 2545.

4-7. PERFORMANCE TEST FAILURES

4-8. If the 3478A fails any of the Performance Tests, first attempt the Calibration Procedure for the range and function that is failing.

If the failure cannot be corrected by calibration, refer to Section VII of this manual for troubleshooting procedures.

4-9. TEST CONSIDERATIONS

4-10. Front and Rear Terminals

4-11. In the Performance Tests and Calibration

Procedures the 3478A set-up is specified for the front panel input terminals. For all tests and procedures except the AC and DC Current Tests and Procedures, the rear panel terminals may be used. The signals for the AC and

DC Current Tests and Procedures may only be applied to the front panel terminals. For either set of terminals make sure the FRONT /REAR Switch is in the correct position before applying the signals.

4-12. Specifications

4-13. The 3478A's specifications are grouped according to instrument function in Table 1-1 and Table 4-1 (DC

Volts, AC Volts, etc.). Within each functional group are one, two, or three sets of specifications: 24 hour limits,

90 day limits, and 1 year limits. When Performance Tests or Calibration Procedures are used, be sure to select the appropriate set of specifications. The Performance Test

Cards, located at the end of this section, are also divided into 24 hour limits, 90 day limits, and 1 year limits where appropriate.

4-14. Each set of specifications includes an accuracy specification for each voltage, ohms, and current range.

The accuracy specification is listed as a percentage of the reading and an add-on number of counts. For example, the 5 digit display mode 24 hour full scale DC volts accuracy on the 30V range (see Tables 1-1 and 4-1) is:

± (.0040Jo of reading

+

3 counts) giving a full scale accuracy of ± .004% plus 3 counts (or

4-2

3478A

.001 %) for a total of

±

.005%. This is only true at full scale. The next paragraph describes the case at 1/10 scale measurement accuracy. If the same specification is used in the 4 digit display mode, the total accuracy becomes

± .007% (the percentage remains .004%, but the number of counts changes to 1 in the 4 digit mode or .003%).

•

4-15. The number of counts adder also affects the accuracy specification at less than full scale. For example, using the same specifications in paragraph 4-14, but only measuring at 1/10 of full scale gives a different total accuracy specification. The percentage remains .004% but the 3 count adder is .033% at 1/10 scale. The total accuracy at 1/10 scale becomes ± .037%, not the

± .005% at full scale.

4-16. Reference Temperature (Temperature Coefficient)

4-17. The ambient air temperature in which the 3478A was last calibrated is called its Reference Temperature.

Provided the 3478A is operated within ± 5°C ( ± 9°F) of the Reference Temperature, no correction to the accuracy specification is required. If the 3478A is operated outside this range, an adjustment to the rated specifications must be made. The adjustment is listed in Table 1-1 as a percentage of reading and a number of counts adder.

The application of the adjustment is identical with the accuracy adjustment application given in paragraphs 4-14 and 4-15.

It is recommended that the 3478A be calibrated at an ambient air temperature similar to the expected testing and operating air temperature.

4-18. Accuracy of Standards

4-19. Because the 3478A is able to make highly accurate

DC measurements, special care must be taken when calibrating or testing to ensure that the Standards used don't introduce errors. Ideally, the accuracy of the Standards used to test and calibrate the 3478A should be an order of magnitude better than the 3478A. It is important to be aware of the ambiguities caused by the Standards used. The next paragraph gives an example of the ambiguities introduced by the measurement standard.

4-20. As an example of the ambiguities caused by the

Standard used to measure the performance of the 3478A, consider the following case. The 3478A's 30V full scale

DC accuracy is to be tested with a certain Standard to its 90 day specification. The 3478A accuracy specification is

±

.0063% and the Standard used has an ideal accuracy of

±

.0006%.

If the 3478A indicates a full scale voltage of 30.0021 (.007% high), the reading is within the ambiguous region.

If the Standard's output is .0006% high (30.0018 Vdc), the 3478A's actual reading is 30.0003

V de which is within the 90 day specification limit.

If the

Standard's output is right on 30.0000 Vdc, the 3478A reading is too high and out of tolerance. In both cases the Standard is within specification, but may show the

3478A to be in or out of tolerance. This vagueness in the

•

•

3478A

• test specifications is call the ambiguous region and is graphically shown in Figure 4-1. The ambiguous region grows larger when either the 3478A tolerance limits are set tighter (as with the 24 hours specification) or when the accuracy of the Standard decreases. It is important to know the specifications of the Standard and their effect on the ambiguous region of the 3478A specifications when testing or calibrating.

DVM spec~~~::~

t

%Error

+

Readings above this point show that

+DVM is definitely out of specs

DVM spec_ std spec l - f-- _

- }

Ae~dings in thi~

_ _ _ _ _ _ _ regmn are amb1guous

r

Readings in thi~ region guarantee that DVM is within specs

DVM•p!·,.d'P"

I--

DVM

DVM spec+ std

5 ec

~ec

_l_------}

Readings in this t-- _ _ _ _ _ _ _ _ _ region are ambiguous

-

~

DVM is definitely out of specs

3455- 8-4738

Figure 4·1. Ambiguous Regions

4·21. PERFORMANCE TESTS

•

4-22. The Performance Tests are separated into five main tests by function: DC Volts, DC Current, AC Volts, AC

Current, and Ohms. For a complete Performance Test, the five main tests should be done in the order they are given in this section. The 3478A to be tested should be turned on and allowed to warm-up for at least one hour before testing. The Performance Tests are: a. DC Volts Test - paragraph 4-23 b. DC Current Test - paragraph 4-28 c. AC Volts Test - paragraph 4-33 d. AC Current Test - paragraph 4-38 e. Ohms Test - paragraph 4-43

Performance

NOTE

Leakage paths on the 3478A 'sfront panel area surrounding the input terminals can affect the input impedance. The paths can be removed by gently washing the area using a cotton swab dipped in isopropyl alcohol.

4·23. DC Volts Test

4-24. The DC Volts test limits are printed on the appropriate DC Volts Test Card at the back of this section and in Table 4-3. The Test Card also summarizes the instrument set-up for the test. Each step on the test card corresponds to a step in the test procedure. In the following test procedure the Test Card step numbers are shown in parenthesis (e.g., Step

#1).

4-25. Unless otherwise specified, all test signals are applied to the 3478A's HI and LO INPUT terminals.

4·26. Equipment Required. The following test equipment is required for the DC Volts Performance Test. The equipment is summarized with the critical specifications in

Table 4-2.

DC Volts Standard- Datron Model4000A or 4707

4·27. Test Procedure. Ensure that the 3478A to be tested has been turned on and allowed to warm-up for at least one hour. Then do the following: a. (Step

#I)

Reset the 3478A by pressing the blue shift button and then the SOL/TRIG (TEST /RESET) button.

All segments of the display will be turned on as long the button is held. Check for missing display segments. When

•

3478A

Input

Short

Short

Short

Short

Short

+ 30 mV

+300 mV

+300 mV

+1V

-1 v

-3 v

+3 v

+3

+3 v v

+

3V

+ 10 v

+ 30 v

+ 30 v

+300 v

Table 4·3. DC Volts Test Limits

3478A

Range

3478A

Set Up

High

24 Hour Limits

Low

High

90 Day Limits

Low

30 mV

300 mV

3V

30

300 v v

30 mV

300 mV

3V

3V

3V

3V

3V

DCV +00.0040 mV -00.0040 mV

+000.004 mV -000.004 mV

+0.00002

+00.0040 mV -00.0040 mV

+000.005 mV -000.005 mV v

-0.00002 v

+0.00002 v

-0.00002 v

+00.0003

+000.002 v

-00.0003 v

+00.0004 v

-00.0004 v v

-000.002 v +000.002 v

-000.002 v

+30.0115 mV +29.9885 mV

+30.0123 mV +29.9877 mV

+300.016 mV +299.984 mV

+0.30003

+ 1.00005 v

+0.29997 v

+300.020 mV +299.980 mV

+0.30003 v

+0.29997 v v

+0.99995 v + 1.00006 v

+0.99994 v

-0.99995

-2.99989

+3.00011

3V

AZ Off

+3.00014 v

-1.00005 v

-0.99994 v

-1.00006 v v

-3.00011 v

-2.99986 v

-3.00014 v v

+2.99989 v +3.00014 v

+2.99986 v v

+2.99984 v +3.00017 v

+2.99983 v

3V

AZ On,

4 Digit +3.0002

3 Digit +3.001 v v

+2.9998

+2.999 v v

+3.0002

+3.001 v v

+2.9998

+2.999 v v v

5 Digit +03.0004 v

+02.9996 v

+03.0006 v

+02.9994 v

30

30

30

30

300 v v

+ 10.0007

+30.0015 v

+09.9993 v

+ 10.0009 v

+09.9991 v v

+29.9985 v

+30.0019 v

+29.9981 v v

AZ Off

+30.0026 v

+29.9974 v +30.0030 v

+29.9970 v v

AZ On

+300.014 v

+299.986 v +300.017 v

+299.983 v

High

I Year Limits

Low

+00.0040 mV -00.0040 mV

+000.005 mV

-000.005 mV

+0.00002 v

-0.00002 v

+00.0004 v

-00.0004 v

+000.002 v

-000.002 v

+30.0145 mV +29.9855 mV

+300.026 mV +299.974 mV

+0.30004 v

+0.29996 v

+ 1.00008

-0.99992 v

+0.99992 v v

-1.00008 v

-2.99980 v

-3.00020 v

+3.00020 v

+2.99980 v

+3.00023 v

+2.99977 v

+3.0003

+3.001 v v

+03.0006

+2.9997

+2.999 v v v

+02.9994 v

+ 10.0011

+30.0025

+30.0036

+300.023 v

+09.9989 v v

+29.9975 v v

+29.9964 v v

+299.977 v

4-3

Performance 3478A the button is released, the 3478A will perform it's internal self-test. The display must show the words SELF

TEST OK for a few seconds. Do not attempt to perform the DC Volts Performance Test if this display message is not obtained. If the self-test should fail, refer to Section

VII of this manual for troubleshooting procedures. h. Check the 3478A 30mV range full scale accuracy by setting the DC Volts Standard to output 30 m V .

Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table 4-3.

NOTE

i. Uprange the 3478A to the 300m V range. Set the DC

Volts Standard to output 300m V and check the 3478A full scale accuracy. Record the reading on the Test Card.

Ensure the reading is within the limits on the Test Card and in Table 4-3.

Following the reset/self-test, the 3478A is placed in the DC Volts function, Autorange

On, Internal Trigger, and 5 digit display mode.

j. (Step #9) Uprange the 3478A to the 3V range. Set the DC Volts Standard for an output of 300mV (the same output as in step i). Record the reading on the Test Card.

Ensure the reading is within the limits on the Test Card and in Table 4-3. b. (Step #2) Short the 3478A's HI and LO INPUT terminals. The instrument should auto range to the 30m V range. k. (Step #10) Leave the 3478A as set and change the

DC Volts Standard output to

+

1 V. Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table 4-3. c. Record the displayed reading on the Test Card.

Ensure the reading is within the limits shown on the Test

Card and in Table 4-3. d. (Step #3, 4, 5, and 6) Set the 3478A to the 300mV,

3V, 30V, and 300V Ranges by pressing the up range button once for each range. Record the 3478A reading at each range and ensure that the readings are within the limits marked on the Test Card and in Table 4-3.

If any of the readings are out of tolerance, attempt the DC Volts

Calibration Procedure given in paragraph 4-57.

I. (Step #11) Set the DC Volts Standard to output -1V

(change the output polarity or reverse the leads to the

3478A). Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table

4-3. m. (Step #12) Using the same set-up in step I (negative input voltage to the 3478A), set the DC Volts Standard to output -3V. Record the reading on the Test Card.

Ensure the reading is within the limits on the Test Card and in Table 4-3. e. (Step #7 and 8) Remove the short from the 3478A

INPUT terminals and set the multimeter to the 30m V range by pressing the downrange button. f. Set the DC Volts Standard for zero volts output.

The 3478A should be set in the 5 digit display mode of the DC Volts function on the 30m V range. n. (Step #13) Set the DC Volts Standard for an output of

+

3V (change the DC Volts Standard output polarity or reverse the leads as in step 1). Record the reading on the Test Card. Ensure that reading is within the limits on the Test Card and in Table 4-3. g. Connect the DC Volts Standard output to the 3478A input terminals as shown in Figure 4-2. o. (Step #14) With the

+

3V applied to the 3478A, turn

Autozero off by pressing the blue shift button and then

-

-

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IEJEJEJEJEJEJEJEJEJI

[8]

IEJElElElElElElEll

II

.

·,__

HI

a

DDDDDDD ol~

LO

DDDDDDD

0

y

~

HP

3478A

,.

,_ ....,

(!)(!)(!)

/

}/}

~

IEJEJEJEJEJEJI IEJEJEJI [ElEJEJEl[

DC VOLTS STANDARD

Figure 4-2. DC Voltage Test and Calibration Connections

4-4

8

•

•

•

3478A Performance

WARNING '

• the INT /TRIG (AUTO ZERO) button. Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table 4-3. p. (Step #15) Turn Autozero on by pressing the blue shift button and then the INT /TRIG (AUTO ZERO) button.

Potentially lethal voltages are used in the next

3 tests. Do not touch the DC Volts Standard's output terminals or the 3478A 's input terminals. Ensure that the DC Volts Standard's output is turned off before moving any connections.

q. (Step # 16) With the

+

3V applied to the 3478A, set the 3478A to the 4 digit display mode by pressing the blue shift button and then the uprange (4) button. Record the reading on the Test Card. Ensure the reading is within the,.limits on the Test Card and in Table 4-3. w. (Step #24) Set the 3478A to the 300V range by pressing the uprange button. Set the DC Volts Standard to output

+

300V. Record the reading on the Test Card.

Ensure the reading is within the limits on the Test Card and in Table 4-3. r. (Step #17) With the

+

3V applied to the 3478A, set the 3478A to the 3 digit display mode by pressing the blue shift button and then the AUTO/MAN (3) button.

Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table 4-3. x. (Step #25) Turn off the DC Volts Standard output.

Disconnect the DC Volts Standard test leads from the

3478A INPUT terminals. s. (Step #18) Return the 3478A to the 5 digit display mode by pressing the blue shift button and then the uprange (5) button. y. (Step #26) Perform the DC Common Mode Rejection test (DC CMR test). To perform the test:

• t. (Step #19, 20 and 21) Set the 3478A to the 30V range by pressing the uprange button. Check the 3478A accuracy at 1110, 1/3, and full scale by setting the DC

Volts Standard to output

+

3V,

+

IOV, and

+

30V respectively. At each setting record the 3478A reading on the Test Card. Ensure the readings are within the limits on the Test Card and in Table 4-3.

I. Set the 3478A to the 30mV range.

2. Connect a IK ohm resistor between the 3478A's HI and LO INPUT terminals.

3. Note the reading on the 3478A. This reading will be used in step 5. u. (Step #22) With the

+

30V still applied to the 3478A, turn Autozero off by pressing the blue shift button and then the INT /TRIG (AUTO ZERO) button. Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table 4-3.

4. Ensure the DC Volts Standard's output is turned off. Connect the Standard so that the HI output lead is connected to the 3478A HI INPUT terminal.

Connect the Standard LO output lead to the 3478A chassis (use the BNC shield on the rear panel). The connection is shown in Figure 4-3. v. (Step #23) Turn Autozero on by pressing the blue shift button and then the INT /TRIG (AUTO ZERO) button.

5 . Set the DC Volts Standard for an output of

+

450V.

Record the reading on the 3478A. Ensure that this reading is within 450m V of the reading obtained in step 3.

-

-

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IEJEJElElElElElElEll

8

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[ rllj~p

HI

~ DDDDDDD

DDDDDDD

0

LO

,.

1-

....,

@@@

IEJEJEJEJEJEJEJEJI

/

}/2

~

IEJEJEJEJEJEJI IEJEJEJI IEJEJEJEJI

DC VOLTS STANDARD

TO CHASSIS GROUND

HP 3478A

Figure 4·3. DC Common Mode Rejection Test

[EiJ

HP3478.F.4.3

4-5

3478A

Performance z. Turn the DC Volts Standard's output off. Disconnect the leads from the 3478A. This completes the DC

Volts Performance Test. If any test result was outside the limits on the Test Card or in Table 4-3, try calibrating the DC Volts function of the 3478A. Calibration procedures for the DC Volts function begin in paragraph

4-57. If recalibration will not cure the problem, see Section VII of this manual for troubleshooting procedures.

4·28. DC Current Test

4-29. The DC Current Test limits are listed on the DC

Current Test Card (located at the end of this section) and in Table 4-4. The Test Card also summarizes the instrument set-up for each test. Each step on the Test Card corresponds to a step in the test procedure. In the following procedure the Test Card step numbers are shown in parenthesis (e.g., Step #1).

4-30. Unless otherwise specified, all signals are applied to the 3478A front panel LO and A INPUT terminals.

4·31. Equipment Required.

The following test equipment is required for the DC Current Performance Test. The equipment is summarized with the critical specifications in Table 4-2.

DC Current Standard - Datron Model4000A or 4707

4·32. Test Procedure. Ensure the 3478A will pass the DC

Volts Performance Test (paragraph 4-23) before attempting the DC Current Performance Test. The 3478A should have been turned on and allowed to warm-up for at least one hour before testing. Then do the following: a. (Step #1) Reset the 3478A by pressing the blue shift button and then the SGLITRIG (TEST /RESET) button. b. (Step #2) Set the 3478A to the DC Current function. Install a short between the LO and A INPUT terminals on the front panel. The 3478A should autorange to the 300mA range. c. Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table

4-4. d. (Step #3) Set the 3478A to the 3A range by pressing the uprange button. Record the reading on the Test Card.

Ensure the reading is within the limits on the Test Card and in Table 4-4.

3478A

Input

Short

Short

+ 100mA

+1A e. (Step #4) Remove the short from the LO and A IN-

PUT terminals. Set the 3478A to the 300mA range by pressing the downrange button. f. Connect the DC Current Standard output to the

3478A LO and A INPUT terminals as shown in Figure

4-4. Set the DC Current Standard for an output of

+

100mA. g. Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table

4-4. h. (Step #5) Set the 3478A to the 3A range by pressing the uprange button. Set the DC Current Standard for an output of

+

1A. i. Record the reading on the Test Card. Ensure the reading is within the limits on the Test Card and in Table

4-4. j. Turn the DC Current Standard's output off. Disconnect the test leads. This completes the DC Current

Performance Test. If any test result was outside the limits on the Test Card or in Table t-4, try calibrating the DC

Current function of the 3478A. Calibration procedures for the DC Current function begin at paragraph 4-61.

If recalibration will not cure the problem, see Section VII of this manual for troubleshooting information.

4·33. AC Volts Test

4-34. The AC Volts test limits are printed on the appropriate Test Card at the back of this section and in

Table 4-5. The Test Card also summarizes the instrument set-up for the test. Each step on the Test Card corresponds to a step in the test procedure. In the following test procedure the Test Card step numbers are shown in parenthesis (e.g., Step #1).

4-35. Unless otherwise specified, all test signals are applied to the 3478A HI and LO INPUT terminals.

4·36. Equipment Required. The following test equipment is required for the AC Volts Performance Test. The equipment is summarized with the critical specifications in

Table 4-2.

AC Volts Standard- Datron Model4200 or 4707

4·37. Test Procedure. Ensure that the 3478A passes the DC

Volts Performance Test before attempting the AC Volts

Table 4·4. DC Current Test Limits

3478A 3478A

90 Day Limits

1 Year Limits

Ranga Sat Up

300m A DCI

3A

300m A

3A high low high low

+000.040mA -000.040mA +000.040mA -000.040mA

+0.00006A -0.00006A +0.00006A -0.00006A

+ 100.150mA +099.850mA + 100.190mA +099.810mA

+ 1.00146A +0.99854A + 1.00176A +0.99824A

4-6

•

•

•

3478A Performance

•

3478A

Input

Table 4-5. AC Volts Test Limits

.028 V,20 KHz 300 mV ACV 028.176 mV 027.824 mV

0.28 V,20 KHz 300 mV

0.28 V,20 KHz

1.5 V,20 KHz

2.8 V,20 KHz

2.8 V,20 KHz

28 V,20 KHz

28 V,20 KHz

280 V,20 KHz

3478A

Range

3V

3V

3V

30 v

30 v

300 v

300 v

0.28 V,50 KHz 300 mV

2.8 V,50 KHz

28 V,50 KHz

280 V,50 KHz

3V

30 v

300 v

3478A

Sat Up High

1 Yaar Limits

Low

280.680 mV 279.320 mV

0.28126

1.50370 v v

0.27874 v

1.49630 v

2.80630 v

02.8126 v

28.0630

028.137

280.742 v

281.269 v

2.80868

28.0868

281.316 v v v v v

2.79370

02.7874

27.9370 v

027.863 v

279.258

278.731 v v v v

2.79132 v

27.9132 v

278.684 v d. (Step #3 and 4) Record the reading. Ensure the reading is within the limits shown on the Test Card and in Table 4-5. Check the full scale accuracy by setting the

AC Volts Standard for an output of 0.28V at 20KHz.

Record the reading. Ensure the reading is within the limits shown on the Test Card and in Table 4-5. e. (Step #5, 6, and 7) Set the 3478A to the 3V range by pressing the uprange button. Check the 11IO, \12 and full scale accuracy of the 3V range by applying 0.28V,

1.5V, and 2.8V at 20KHz respectively. At each setting record the reading and ensure the reading is within the limits shown on the Test Card and in Table 4-5. f. (Step #8, and 9) Set the 3478A to the 30V range by pressing the uprange button. Check the 1110 and full scale accuracy by applying 2.8V and 28V at 20KHz respectively. Record the readings and ensure the readings are within the limits shown on the Test Card and in Table 4-5.

0.28 V,100 KHz 300 mV

0.28 V, 100KHz

2.8 V,100 KHz

15 V,100 KHz

28 V,100 KHz

280 V, 100KHz

25 V,300 KHz

2.8 V,50 Hz

2.8 V,20 Hz

3V

3V

30 v

30 v

300 v

30 v

3V

3V

284.200 mV 275.800 mV

0.29024 v

2.83216V

0.26976 v

2.76784 v

15.2085 v

28.3216V

283.524 v

14.7915 v

27.6784 v

276.476 v

28.8970 v

2.81391 v

2.83294 v

22.1030 v

2.78609 v

2.76706 v

I

WARNING

I

Potentially lethal voltages are used in the next

3 steps. Do not touch the AC Volts Standard's output terminals or the 3478A input terminals. Ensure the AC Volts Standard's output is turned off before installing or removing the test leads .

•

Performance Test. The 3478A should be turned on and allowed to warm-up for at least one hour. The do the following: a. (Step #I) Reset the 3478A by pressing the blue shift button and then the SOL/TRIG (TEST /RESET) button. g. (Step #IO and II) Set the 3478A to the 300V range by pressing the uprange button. Check the 11IO and full scale accuracy by applying 28V and 280V at 20KHz respectively. Record the readings and ensure the readings are within the limits shown on the Test Card and in Table

4-5. b. (Step #2) Set the 3478A to the AC Volts function and the 300mV range. c. Connect the AC Volts Standard output to the 3478A

HI and LO INPUT terminals as shown in Figure 4-5. Set the AC Volts Standard for an output of 0.028V at 20KHz. h. (Step #I2, 13, I4, and I5) Set the AC Volts Standard output frequency to 50KHz. Check the 300V, 30V,

3V, and 300mV ranges full scale accuracy by applying

280V, 28V, 2.8V, and 0.28V respectively. Always ensure

-

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DC CURRENT STANDARD

[8]

Figure 4-4. DC Current Test and Calibration Connections

4-7

Performance 3478A the AC Volts Standard's output is turned off or downranged before the 3478A is downranged. Record the readings at each voltage and range. Ensure the readings are within the limits shown on the Test Card and in Table

4-5. i.

(Step #16) Set the AC Volts Standard for an output of 0.28V at 100KHz. Set the 3478A to the 300m V range.

Check the full scale accuracy. Record the reading. Ensure the reading is within the limits shown on the Test Card and in Table 4-5. j. (Step #17 and 18) Set the 3478A to the 3V range by pressing the uprange button. Record the 1110 scale reading. Set the AC Volts Standard output for 2.8V at

100KHz. Record the full scale reading. Ensure both readings are within the limits shown on the Test Card and in Table 4-5.

Ensure the reading is within the limits shown on the Test

Card and in Table 4-5. Turn off the AC Volts Standard's output. m. (Step #22) Set the 3478A to the 30V range by pressing the downrange button. Set the AC Volts Standard for an output of 28V at 300KHz. Record the reading.

Ensure the reading is within the limits on the Test Card and in Table 4-5. n. (Step #23 and 24) Set the AC Volts Standard's output for 2.8V at 50Hz. Set the 3478A to the 3V range by pressing the downrange button. Record the reading. Set the AC Volts Standard's output for 2.8V at 20Hz. Record the reading. Ensure both readings are within the limits on the Test Card and in Table 4-5. o. Turn off the AC Volts Standard. Remove the test connections. This completes the AC Volts Performance

Test.

If any test results was outside the limits shown on the Test Card or in Table 4-5, try recalibrating the 3478A.

Calibration procedures for the AC Volts function begin at paragraph 4-66. If recalibration will not cure the problem, see Section VII of this manual for troubleshooting procedures. k. (Step #19 and 20) Set the 3478A to the 30V range by pressing the uprange button. Set the AC Volts Standard output for 15V at 100KHz. Record the \12 scale reading. Set the AC Volts Standard output for 28V at

100KHz. Record the full scale reading. Ensure both readings are within the limits shown on the Test Card and in Table 4-5.

I

WARNING

I

4·38. AC Current Test

The next test uses potentially lethal voltage.

Do not touch the AC Volts Standard's output terminals or the 3478A input terminals.

Ensure AC Volts Standard's output is off before installing or removing test leads.

I.

(Step #21) Set the 3478A to the 300V range by pressing the uprange button. Set the AC Volts Standard for an output of 280V at 100KHz. Record the reading.

4-39. The AC Current test limits are printed on the appropriate Test Card at the back of this section and in

Table 4-6. The Test Card also summarizes the instrument set-up for the test. Each step on the Test Card corresponds to a step in the procedure. In the following procedure the Test Card step numbers are shown in parenthesis (e.g., Step #1).

Table 4·6. AC Current Test Limits

3478A

Input

.03A,5KHz

0.1A 5KHz

1A,5KHz

3478A

Range

300m A

300m A

1A

3478A

Set Up

ACI high

1 Year Limits low

030.379mA

100.883mA

1.01583A

029.621mA

099.117mA

0.98417A

4-8

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HP

3478A

AC VOLTS STANDARD

Figure 4·5. AC Voltage Test and Calibration Connections.

•

•

•

3478A

Performance

•

4-40. Unless otherwise specified, all signals are applied to the 3478A front panel A and LO INPUT terminals.

4·41. Equipment Required.

The following test equipment is required for the AC Current Performance Test. The equipment is summarized with the critical specifications in Table 4-2. g. Turn off the AC Current Standard's output.

Disconnect the test leads. This concludes the AC Current Performance Test. If If any test result was outside the limits on the Test Card or in Table 4-6, try recalibrating the instrument. Calibration procedures for the AC Current function begin at paragraph 4-72.

If recalibration will not cure the problem, see Section VII of this manual for troubleshooting procedures.

AC Current Standard - Datron Model 4200 or 4707

4-43. Ohms Test

4-42. Test Procedure.

Ensure that the 3478A passes the AC

Volts Performance Test before attempting the AC Current Performance Test. The 3478A should be turned on and allowed to warm-up for at least one hour. Then do the following: a. (Step #1) Reset the 3478A by pressing the blue shift button and then the SOL/TRIG (TEST /RESET) button.

4-44. The Ohms Performance Test limits are printed on the Test Card at the back of this section and in Table

4-7. Two sets of limits are shown, full scale and 'IJ scale, to allow for different Standards. The Test Card also summarizes the instrument set-up for each test. Each step on the Test Card corresponds to a step in the test procedure.

In the following test procedure the Test Card step numbers are shown in parenthesis (e.g., Step #1). b. (Step #2) Set the 3478A to the AC Current function and the 300mA range.

4-45. There are several important considerations for performing the Ohms Performance Test. These considerations are: c. (Step #3) Set the AC Current Standard for an output frequency of 5KHz. This output frequency will be used for all steps in this test. Connect the AC Current

Standard to the 3478A front panel A and LO INPUT terminals as shown in Figure 4-6.

1) The Ohms Performance Test is only valid in the

Ohms function last calibrated. For example, if the

3478A was last calibrated in the 4-Wire ohms function, the Ohms Performance Test should also be performed in the 4-Wire ohms function.

• d. Set the AC Current Standard for an output of

30mA. Record the reading. Ensure the reading is within the limits shown on the Test Card an in Table 4-6. e. (Step #4) Set the AC Current Standard for an output of 0.1A. Record the reading. Ensure the reading is within the limits shown on the Test Card and in Table 4-6.

2)

If possible, the same test leads used to calibrate the

3478A ohms function should be used in the Ohms

Performance Test. This is especially important in the 2-Wire ohms function where the impedance of the test leads is compensated during calibration.

Different test leads will have different impedances and so create invalid readings. f. (Step #5) Set the 3478A to the 3A range by pressing the uprange button. Set the AC Current Standard for an output of 1A. Record the reading. Ensure the reading is within the limits on the Test Card and in Table 4-6.

3) The best results will be obtained when the test leads are as short as possible. Longer test leads are more susceptible to noise and can cause invalid readings.

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3478A

Figure 4·6. AC Current Test and Calibration Connections

IEJEJEJI IEJEJEJEll

AC CURRENT STANDARD

[8]

4-9

Performance

347BA 3478A

Input Ranga

Short 30

Short 300

Short

Short

3K

30K

Short 300K

Short 3M

Short

30

(10)

30M

30

300

(100)

3K

(1 K)

300

3K

30K

(10K)

30K

300K

300K

(100K)

3M

(1M)

30M

(10M)

3M

30M

347BA

Sat Up

Ohms

Table 4·7. Ohms Test Limits

24 Hour Limits 90 Day

Limits 1 Yaar Limits high low

00.0035

000.004

-00.0035

-000.004

0.00002K -0.00002K

00.0002K -00.0002K

000.002K -000.002K

0.00002M -0.00002M

00.0002M -00.0002M

30.0104

10.0058

29.9896

09.9942

300.018

100.009

3.00013K

299.982

099.991

2.99987K

0.99994K 1.00006K

30.0013K

10.0006K

29.9987K

09.9994K

300.013K 299.987K

100.006K 099.994K

3.00018M 2.99982M

1.00007M

0.99993M

30.0110M

29.9890M

10.0038M 09.9962M high low high low

00.0041 -00.0041

00.0041 -00.0041

000.004 -000.004

000.005 -000.005

0.00002K -0.00002K 0.00002K

-0.00002K

00.0002K -00.0002K 00.0002K -00.0002K

000.002K -000.002K 000.002K

-000.002K

0.00002M -0.00002M 0.00002M

-0.00002M

00.0002M -00.0002M 00.0002M

-00.0002M

30.0122

10.0068

300.041

100.017

3.00035K

29.9878 30.0143

09.9932 10.0075

299.959 300.056

099.983

100.022

2.99965K 3.00050K

1.00013K 0.99987K

1.00018K

30.0035K 29.9965K 30.0050K

10.0013K

300.035K

100.013K

09.9987K 10.0018K

299.965K 300.050K

099.987K 100.018K

29.9857

09.9925

299.944

099.978

2.99950K

0.99982K

29.9950K

09.9982K

299.950K

099.982K

3.00035M 2.99965M 3.00050M 2.99950M

1.00013M 0.99987M 1.00018M 0.99982M

30.0200M 29.9800M 30.0236M 29.9764M

10.0068M 09.9932M 10.0080M

09.9920M

3478A

•

4) The Ohms Performance Test can be performed at either full scale or YJ scale. Because of this, two sets of test limits are shown on the Test Card and in

Table 4-7. The YJ scale limits are shown in parenthesis in the step number on the Test Card and in the input to the 3478A in Table 4-7.

5) This Ohms Performance Test is written to support the recommended Resistance Standard. Figure 4-7 shows the test connections for 2-Wire ohms. Figure

4-8 shows the test connections for 4-Wire ohms.

6) If the 4-Wire ohms function is to be tested, shorting the INPUT terminals requires that both the sense and input terminals be shorted as shown in

Figure 4-9.

4·46. Equipment Required. The following test equipment is required to perform the Ohms Performance Test. The equipment is summarized with the critical specifications in Table 4-2.

Resistance Standard- Datron Model 4000A or 4707

4-47. Test Procedure. Ensure the 3478A passes the DC Volts

Performance Test before attempting the Ohms Performance Test. The 3478A should be turned on and allowed to warm-up for at least one hour. Then do the following: a. (Step #I) Reset the 3478A by pressing the blue shift button and then the SGL/TRIG (TEST /RESET) button. b. (Step #2) Set the 3478A to the desired ohms function (see paragraph 4-45). Apply a short to the INPUT terminals (in the 4-Wire ohms function you must short

4-10 both the input terminals and the sense terminals as shown in Figure 4-9). Record the reading. Ensure the reading is within the limits shown on the Test Card and in Table

4-7. c. (Step #3, 4, 5, 6, 7, and 8) With the input to the

3478A still shorted, set the 3478A to the 3000, 3KO,

30KO, 300KO, 3MO, and 30MO ranges by pressing the uprange button once for each range. At each range, record the reading. Ensure the readings are within the limits shown on the Test Card and in Table 4-7. If any readings are not within the limits, perform the Ohms

Calibration procedure beginning at paragraph 4-86. d. (Step #9) Remove the short from the 3478A INPUT terminals. Set the 3478A to the 300 range. Connect the

Resistance Standard to the 3478A INPUT terminals (using either the connection shown in Figure 4-7 or 4-8, as appropriate). e. Set the Resistance Standard for an output of 300

(may also be 100 as described in paragraph 4-45). Record the reading. Ensure the reading is within the limits shown on the Test Card and in Table 4-7.

•

NOTE

The test limits shown on the Test Card and in Table 4-7 assume a nominal value for the

Resistance Standard. If the actual value of the

Resistance Standard used differs from this nominal value, the test limits will need to be adjusted to compensate.

•

3478A Performance

• f. (Step #10, 11, 12, 13, 14, and 15) Check the 3000,

3KO, 30KO, 300K0Hm, 3MO, and 30MO ranges of the

3478A by applying the following resistances to the IN-

PUT terminals: 3000 (or 1000), 3KO (or 1KO), 30KO (or

10KO), 300KO (or lOOKOhm), 3MO (lMO), and 30MO

(or lOMO) respectively. Record the reading at each range.

Ensure the readings are within the limits shown on the

Test Card and in Table 4-7.

• g. Remove the test leads from the 3478A. This concludes the Ohms Performance Test. If any of the test results were outside the test limits, try recalibrating the

Ohms function of the 3478A. Calibration procedures begin at paragraph 4-78.

If recalibration does not cure the problem, see Section VII of this manual for troubleshooting information.

-

4-48. CALIBRATION PROCEDURES

4·49. General

\ElElElEll

4-50. The 3478A is electronically calibrated by storing calibration constants in non-volatile memory. There are no mechanical adjustments. Calibration requires access to the 3478A front panel.

4-51. Internally, during calibration, the 3478A averages ten readings of the signal applied to the input terminals and uses this average to compute a calibration constant.

Once indicated by the user, this calibration constant is stored in non-volatile memory and then used to adjust all future measurements in that range and function.

4-52. The general procedure for calibration is to first set the offset by applying a short to the INPUT terminals and then set the gain by applying a full scale signal to the INPUT terminals. This procedure is repeated for each range in each function. (Some functions and ranges only require a

\13

scale input to set the gain.)

-

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8

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HP 3478A

RESISTANCE STANDARD

Figure 4-7. 2-Wire Ohms Test and Calibration Connections

-

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HP3478.F.4. 7

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DDDDDDD

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0

HP 3478A

RESISTANCE STANDARD

Figure 4-8. 4-Wire Ohms Test and Calibration Connections

HP3478.F.4.8

4-11

Performance

LO

3468-4-6

er-

A

Figure 4-9. 4·Wire Ohms Short

4-53. When calibration is enabled, the 3478A display will first show the currently set value of the offset. This is indicated in the display by a zero (or approximately zero) reading followed by the letter "C". When a new calibration is requested, the "C" is replaced by "?".

4-54. When calibrating the gain (full scale), the reading in the display can be changed to the exact input value by using the uprange and downrange buttons. The reading displayed will increment or decrement as long as the button is pressed. When the exact value is reached the new value is stored by pressing the SOL/TRIG button. Note that this is only necessary and desirable when the exact value of the input signal is known. If the calibration Standard used has a high enough accuracy, this adjustment is not necessary.

4·55. Calibration Messages

4-56. The 3478A display can show a variety of messages when calibrating. The following list contains the messages that may be displayed and describes the meaning of each message. a. UNCALIBRATED - This message is typically displayed following a self-test when the calibration RAM checksum is incorrect. The accuracy of the 3478A is always in doubt if this message is displayed. b. ENABLE CAL - This message indicates that a calibration was attempted without the front panel calibration switch set to the correct position. (The slot of the switch must be set vertically to allow calibration.) c. CAL ABORTED- This message is displayed when an incorrect front panel button is pushed during the calibration procedure. The message can also occur if an input overload is detected or an AID error occurs. d. VALUE ERROR - This message will be displayed when any of the following conditions are true.

1. A zero (offset) calibration is attempted and the

3478A is reading a value greater than

±

1000 counts

4-12

3478A

(e.g., I Ohm on the 30 Ohm range).

2 . A full scale or

Y3

scale (gain) calibration is attempted in the DC Volts function and a negative input signal is applied. Always calibrate the DC Volts function with a positive polarity input signal.

3 . A full scale or

Y3

scale (gain) calibration is attempted and the input signal is outside the calibration range ( ± 70Jo ). For example, a full scale calibration of the 3V range is attempted and the input signal is

+

3.22V.

4. An AC Volts function calibration is attempted with an input signal other than 3Vac. e. ACI VAL ERROR -This message is displayed when the 3478A is unable to calculate an AC Current calibration constant. This condition can exist if the calibration constants for the 300mA and 3A DC ranges are incorrect.

Always ensure the DC Current function is calibrated before calibrating the AC Current function. f.

CAL FINISHED - A calibration cycle has been successfully completed. g. CALIBRATING- This message is displayed when the 3478A is calculating calibration constants.

4·57. DC Volts Calibration

4-58. Unless otherwise stated, all calibration signals are applied to the 3478A HI and LO INPUT terminals.

4·59. Equipment Required.

The following test equipment is required for the DC Volts Calibration procedure. The equipment is summarized with the critical specifications in Table 4-2.

DC Volts Standard Datron 4000A or 4707

4·60. Calibration Procedure.

Turn on the 3478A and allow a one hour warm-up period. Then, do the following: a. Reset the 3478A by pressing the front panel blue shift button and then the SOL/TRIG (TEST /RESET) button.

•

•

NOTE

Following the reset/self-test, the 3478A is placed in the DC Volts junction, Autorange

On, Internal Trigger, and 5 digit display mode.

b. Use a small, flat blade screwdriver to set the front panel CAL ENABLE Switch to the Cal Enable position

(the slot of the switch must be in the vertical position to allow calibration).

•

Performance 3478A

• c. Set the 3478A to the single trigger mode by pressing the SOL/TRIG button. Take the 3478A out of Autorange by pressing the downrange button (set the 3478A to the

30m V range). d. Install a short across the 3478A's HI and LO

INPUT terminals. e. Press the blue shift button and then the LOCAL

(CAL) button. f. Press the SOL/TRIG button once. When the display shows CAL FINISHED, remove the short from the input. g. Connect the DC Volts Standard output terminals to the 3478A INPUT terminals as shown in Figure 4-2.

Set the DC Volts Standard for an output of 30mV. h. Press the blue shift button and then the LOCAL

(CAL) button. i.

If the actual output value of the DC Volts Standard is known, use the 3478A uprange or downrange buttons to set the 3478A display to the same value. Then press the SOL/TRIG button.

If the actual output is not known or if the Standard has a high enough accuracy, just press the SOL/TRIG button.

• j. Remove the DC Volts Standard input from the

3478A. Set the 3478A to the 300mV range by pressing the uprange button. Install a short across the 3478A HI and LO INPUT terminals. k. Repeat steps e through j on the 300mV range (the

DC Volts Standard output should be set to 300mV).

I

WARNING

I

The next step uses potentially lethal voltages.

Do not touch the DC Volts Standard's output terminals or the 3478A 's input terminals.

Ensure the DC Volts Standard's output is turned off before moving any connections.

1. Repeat steps e through j on each of the remaining

3478A ranges, increasing the value of the DC Volts Standard output accordingly. The ranges to be calibrated are:

3V, 30V and 300V.

4-61. DC Current Calibration

4-62. The DC Volts Calibration or DC Volts Performance Test should be performed before attempting the

•

DC Current Calibration. The 3478A should be turned on and allowed at least a one hour warm-up .

4-63. Unless otherwise specified, all input signals are applied to the front panel LO and A INPUT terminals.

4·64. Equipment Required.

The following test equipment is required for the DC Current Calibration. The test equipment is summarized with the critical specifications in

Table 4-2.

4707

DC Current Standard Datron Model 4000A or

4-65. Calibration Procedure.

Do the following: a. Reset the 3478A by pressing the blue shift button and then the SOL/TRIG (TEST /RESET) button. b. Set the 3478A front panel CAL ENABLE Switch to the Calibration Enable position (the slot must be vertical to allow calibration). c. Set the 3478A to the Single Trigger mode, DC Current function, and the 300mA range (take the 3478A out of the Autorange function by pressing the downrange button). d. Leave the 3478A INPUT terminals open. Press the blue shift button and then the LOCAL (CAL) button. e. Press the SOL/TRIG button once. Wait for the display to show the message CAL FINISHED. f. Uprange the 3478A to the 3A range. Repeat steps d and e. g. Connect the DC Current Standard's output to the

3478A LO and A INPUT terminals as shown in Figure

4-4. h. Set the 3478A to the 300mA range. Set the DC Current Standard for an output of

+ lOOmA. i.

Press the blue shift button and then the LOCAL

(CAL) button. j. If the actual output value of the DC Current

Standard is known, use the 3478A uprange or downrange buttons to set the 3478A display to the same value. Then press the SOL/TRIG button. If the actual output is not known or if the DC Current Standard has a high enough accuracy, just press the SOL/TRIG button. k. Uprange the 3478A to the 3A range. Set the DC

Current Standard for an output of

+ lA.

1. Repeat steps i and j. m. Turn off the DC Current Standard's output.

Disconnect the test leads. This concludes the DC Current calibration procedure.

4-66. AC Volts Calibration

4-67. The AC Volts function is calibrated using only one input signal. The signal required is 3V at 1KHz. During

4-13

Performance the calibration cycle the 3478A will automatically set the gain at full scale on the 3V range and at 1110 scale on the 30V range. These two gain adjustments are then applied to all other ranges in the AC Volts function.

4-68. The DC Volts Calibration or DC Volts Performance Test should be performed before attempting the

AC Volts Calibration. The 3478A should be turned on and allowed to warm-up for at least one hour.

4-69. Unless otherwise stated, all input signals are applied to the 3478A HI and LO INPUT terminals.

4·70. Equipment Required.

The following test equipment is required for the AC Volts Calibration. The test equipment is summarized with the critical specifications in

Table 4-2.

AC Voltage Standard Datron 4200 or 4707

4·71. Calibration Procedure.

Do the following: a. Reset the 3478A by pressing the blue shift button and then the SOL/TRIG (TEST /RESET) button. b. Set the front panel CAL ENABLE switch to the

Calibration Enable position (the slot must be vertical to allow calibration). c. Set the 3478A to the AC Volts function and the 3V range. d. Set the Single Trigger mode by pressing the

SOL/TRIG button. e. Connect the AC Volts Standard's output to the

3478A HI and LO INPUT terminals as shown in Figure

4-5. f.

Set the AC Volts Standard for an output of 3V at

1KHz. g. Press the blue shift button and then the LOCAL

(CAL) button. h. If the actual output value of the AC Volts Standard is known, use the 3478A uprange or downrange buttons to set the 3478A display to the same value. Then press the SOL/TRIG button. If the actual output value is not known or if the AC Volts Standard has a high enough accuracy, just press the SOL/TRIG button. i.

Wait for the 3478A display to show the message

CAL FINISHED. Turn off the AC Volts Standard's output. Disconnect the test leads. This concludes the AC

Volts function calibration.

4·72. AC Current Calibration

4-73. The AC Current Calibration Constants are calculated using the DC Volts, DC Current, and AC Volts

4-14

3478A calibration constants. For this reason, no AC Current calibration is required provided the DC Volts, DC Current, and AC Volts functions have been calibrated. The following procedure is provided for cases where only the

AC Current function is to be calibrated or for cases where the AC Current Performance Test (see paragraph 4-38) has failed.

4-74. Unless otherwise stated, all signals are applied to the 3478A front panel LO and A INPUT terminals.

4-75. The AC Current function can only be calibrated using full scale inputs.

4·76. Equipment Required.

The following test equipment is required for the AC Current calibration procedure. The test equipment is summarized with the critical specifications in Table 4-2.

AC Current Standard - Datron Model4200 or 4707

4·77. Calibration Procedure.

Make sure the 3478A has been turned on and allowed to warm-up for at least one hour.

Then do the following: a. Reset the 3478A by pressing the blue shift button and then the SOL/TRIG (TEST /RESET) button. b. Set the 3478A front panel CAL ENABLE Switch to the Calibration Enable position (the slot must be vertical to allow calibration). c. Set the 3478A to the Single Trigger mode, AC Current function and 300mA range (take the 3478A out of the Autorange function by pressing the downrange button). d. Connect the AC Current Standard's output to the

3478A LO and A INPUT terminals as shown in Figure

4-6. e. Set the AC Current Standard for an output of

300mA at 1KHz. f. Press the blue shift button and then the LOCAL

(CAL) button. g. If the actual value of the AC Current Standard is known, use the 3478A uprange or downrange buttons to set the 3478A display to the same value. Then press the

SOL/TRIG button. If the actual output is not known or if the Standard accuracy is high enough, just press the

SOL/TRIG button. h. Turn off the AC Current Standard output. Disconnect the test leads. This concludes the AC Current

Calibration Procedure.

4·78. Ohms Calibration

4-79. The 3478A can be calibrated in either the 4-Wire

•

•

•

3478A

• or 2-Wire Ohms function.

It cannot be calibrated in both.

The 3478A should be calibrated in the function in which it will be used.

4-80. If the calibration is to be done in the 2-Wire Ohms function, the Resistance Standard is connected to the HI and LO INPUT terminals as shown in Figure 4-7. If the calibration is to be done in the 4-Wire Ohms function, the Resistance Standard must be connected to the HI and

LO INPUT terminals and the HI and LO SENSE terminals as shown in Figure 4-8.

4-81. The 3478A's Ohms function can be calibrated using either full scale or

Y3

scale inputs. In the following procedure the

Y3

scale inputs are shown in parenthesis.

4·82. Equipment Required. The following test equipment is required for the Ohms Calibration Procedure. The test equipment is summarized with the critical specifications in Table 4-2.

Resistance Standard - Datron Model 4200 or 4707

4-83. Calibration Procedure. Ensure the 3478A has been turned on and allowed to warm-up for at least one hour. Then do the following:

• a. Reset the 3478A by pressing the blue shift button and then the SGL/TRIG (TEST /RESET) button. b. Set the front panel CAL ENABLE Switch to the

Calibration Enable position (the slot must be vertical to allow calibration). c. Set the 3478A to the Single Trigger mode, 2-Wire or 4-Wire Ohms function (see paragraphs 4-80 and 4-81), and the 300 range (take the 3478A out of the Autorange function by pressing the downrange button). d. Install a short across the 3478A HI and LO INPUT terminals. If in the 4-Wire Ohms function, also short the

SENSE terminals to the INPUT terminals (see Figure

4-9). e. Press the blue shift button and then the LOCAL

(CAL) button. f. Press the SGL/TRIG button once. Wait for the display to show the message CAL FINISHED. g. Remove the short and connect the Resistance Standard to the 3478A. The 2-Wire Ohms connection is shown in Figure 4-7 and the 4-Wire Ohms connection is shown in Figure 4-8. h. Set the Resistance Standard for 300 (100).

• i. Press the blue shift button and then the LOCAL

(CAL) button. j. If the actual value of the Resistance Standard is known, use the 3478A uprange or downrange buttons to

Performance set the 3478A display to the same value. Then press the

SGL/TRIG button. If the actual value is not known or if the Standard has a high enough accuracy, just press the SGLITRIG button. Wait for the display to show the message CAL FINISHED. k. Remove the Resistance Standard test leads from the

3478A INPUT (and SENSE) terminals. Uprange the

3478A to the 3000 range.

I. Repeat steps d through j increasing the value of the

Resistance Standard in step h to 3000 (1000). m. Repeat steps d through k on each of the remaining

3478A ranges, increasing the value of the Resistance Standard accordingly. The ranges to be calibrated are: 3KO,

30KO, 300KO, 3MO, and 30MO. n. Remove the test leads. This concludes the Ohms

Calibration Procedure.

4·84. REMOTE CALIBRATION

4·85.

General

4-86. The 3478A can be remotely calibrated using the

HP-IB (Hewlett-Packard Interface Bus). This is accomplished by using a computer to setup the 3478A to the required range, function, and calibration mode instead of doing it from the front panel.

4-87. Remote calibration uses the same test equipment, including connections to the 3478A, as is used in local calibration. In addition, both remote and local calibration procedures are basically the same in that zero scale and full or 1/3 scale calibration signals are used. It is therefore necessary to know how to calibrate the 3478A locally. Read the calibration procedures in paragraphs

4-48 to 4-83 before attempting to calibrate remotely.

4-88. The following paragraph has an example on how to remotely calibrate the 3478A. In the example, the

3478A is calibrated on the 3V Range by remotely sending the appropriate program codes. Then the value of the calibration signal is remotely sent to the 3478A's display.

Once this is done, the program code to calibrate the instrument is sent. The example shows how to send the program codes using a Model HP-85B Computer. For information on programming the 3478A, refer to the

3478A Operator's Manual or Section III of this manual.

4·89. Remote Calibration Example

4-90. Connect the 3478A to the HP-IB and make sure the instrument's HP-IB address is set to "23" (see Section

II of this manual to set the address). Using a small flat blade screwdriver, set the front panel CAL ENABLE switch to the calibration enable position (the slot of the switch is in the vertical position). A "C" should now appear on the right end of the numbers in the 3478A's

4-15

4-16

Performance display indicating that calibration is now enabled.

Calibrate the 3478A on the 3V Range and DC Volts Function by doing the following steps. a. The 3478A is first set to Remote and Listen by the computer. Then program codes "F1RON5Z1 T1" are sent to the 3478A to set the instrument to the DC Volts Function (F1), 3V Range (RO), 5 1/2 Digits Displayed (N5),

Autozero On (Zl), and Internal Trigger (Tl). This is shown as follows:

OUTPUT 723 ;"FlRON5Z1Tl"

The "OUTPUT 723" statement sets the 3478A to Remote and Listen, and "F1RON5Z1T1" are the program codes sent to the instrument to setup the instrument. b. After the 3478A is setup to the desired function and range, apply the zero volts calibration signal to the instrument. This is done by shorting the HI and LO

INPUT Terminals. Once this is performed, the value in the 3478A's display has to be set to the value of the calibration signal (i.e., OV). This is done by sending program codes "D2 + 000000". Code "D2" enables the display to receive "()()()()()()". Since the 3478A is calibrated in the 5 1/2 Digit Mode, make sure that six zeroes (i.e.,

"000000") are sent instead of five or less zeros. Also, the " +" between D2 and 000000 needs to be there for the display to accept the numbers correctly. The program codes are sent as follows:

OUTPUT 723 ;"D2+000000"

3478A c. The 3478A is now calibrated by sending program code "C" to the instrument. The 3478A will then display

"CALIBRATING", while it is calculating the zero offset calibration constant. When finished, "CAL

FINISHED" will be displayed for about two seconds.

Zero calibration is then completed. Program code "C" is sent as follows:

OUTPUT 723 ;"C" d. After zero calibration is completed, apply either a full scale (3V) or 1/3 scale (1V) calibration signal to the

3478A's INPUT Terminals. Then set the display to the applied value. Since in this example the applied value is

+ 2.99998V, send program codes "D2 + 2.99998" to the

3478A as follows:

OUTPUT 723 ;"D2+2.99998" e. Calibrate the 3478A by sending program code "C"

(see step c). After the calibration constants are calculated,

"CAL FINISHED" will be displayed by the 3478A. f. The 3V Range in the DC Volts Function is now calibrated. Calibration of the rest of the ranges and functions is similar. Remember, the same rules that apply for local calibration (e.g., AC Volts is calibrated on only one range, etc.) also apply for remote calibration. Also, when calibrating at full or 1/3 scale, make sure the 3478A receives the correct information. For example, to calibrate the gain by applying 1 V, send program codes

''D2 + 1.00000'' to the 3478A. The decimal point included in the number is not necessary; it is only there to show the value of the calibration source.

•

•

•

•

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

DC Volts Test

Step# Input to

3478A

Set-Up and

Configuration

PERFORMANCE TEST CARD

24 HOUR LIMITS

High

Limit

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

6

7

8

4

5

2

3

Open

Short

Short

Short

Short

Short

+30mV

+300mV

Press TEST /RESET

30mV Range

300mV Range

3V Range

30V Range

300V Range

30mV Range

300mV Range

+00.0040mV

+000.004mV

+0.00002V

+00.0003V

+000.002V

+30.0115mV

+300.016mV

-00.0040mV

-000.004mV

-0.00002V

-00.0003V

-000.002V

+29.9885mV

+299.984mV

+300mV

3V Range

+0.30003V 9

10 3V Range

+0.29997V

+0.99995V

+1V + 1.00005V

•

11

12

13

-1V

-3V

+3V

3V Range

3V Range

3V Range

-0.99995V

-2.99989V

+3.00011V

-1.00005V

-3.00011V

+2.99989V

14

+3V

Autozero Off

+3.00014V +2.99986V

15 Autozero On

16

17

18

19

+3V

+3V

4 Digit Disp

3 Digit Disp

+3.0002V

+ 3.001 v

+2.9998V

+2.999V

24

25

26

20

21

22

23

+3V

+10V

+30V

+30V

+300V

Open

See Below

5 Digit Disp

30V Range

30V Range

30V Range

Autozero Off

Autozero On

300V Range

30mV Range

CMR Test

+03.0004V

+ 10.0007V

+30.0015V

+30.0026V

+300.014V

+02.9996V

+09.9993V

+29.9985V

+29.9974V

+299.986V

Test

Pass

Test

Fail

•

1. Connect a 1 K Ohm resistor between the HI and LO INPUT

Terminals of the 3478A

2. Note the 3478A's reading.

CMR Test

3 . Apply 450V de between the 34 78A's chassis (rear panel) and HI INPUT Terminal.

4. The 3478A should remain within .045mV of the reading in step 2.

PERFORMANCE TEST CARD

90 DAY LIMITS

2

9

10

7

8

11

12

5

6

3

4

13

14

15

16

17

+3V

+3V

18

19

20

21

+3V

+10V

+30V

+30V 22

23

24

+300V

25 Open

26 See Below

Open

Short

Short

Short

Short

Short

+30mV

+300mV

+300mV

+1V

-1V

-3V

+3V

+3V

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

DC Volts Test

Step# Input to

3478A

Set-Up and

Configuration

Press TEST/RESET

30mV Range

300mV Range

3V Range

30V Range

300V Range

30mV Range

300mV Range

3V Range

3V Range

3V Range

3V Range

3V Range

Autozero Off

Autozero On

4 Digit Disp

3 Digit Disp

5 Digit Disp

30V Range

30V Range

30V Range

Autozero Off

Autozero On

300V Range

30mV

CMR Test

High

Limit

+00.0040mV

+000.005mV

+0.00002V

+00.0004V

+000.002V

+30.0123mV

+300.020mV

+0.30003V

+ 1.00006V

-0.99994V

-2.99986V

+3.00014V

+3.00017V

+3.0002V

+3.001V

+03.0006V

+ 10.0009V

+30.0019V

+30.0030V

+300.017V

Reading Low

Limit

-00.0040mV

-000.005mV

-0.00002V

-00.0004V

-000.002V

+29.9877mV

+299.980mV

+0.29997V

+0.99994V

-1.00006V

-3.00014V

+2.99986V

+2.99983V

+2.9998V

+2.999V

+02.9994V

+09.9991V

+29.9981V

+29.9970V

+299.983V

Test

Pass

Test

Fail

1. Connect a 1 K Ohm resistor between the HI and LO INPUT

Terminals of the 3478A.

2. Note the 3478A's reading.

CMR Test

3. Apply 450V de between the 34 78A's chassis (rear panel) and HI INPUT Terminal.

4. The 3478A should remain within .045mV of the reading in step 2.

•

•

•

2

•

11

12

13

14

15

16

17

8

9

6

7

10

4

5

2

3

22

23

24

25

26

18

19

20

21

•

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

DC Volts Test

Step# Input to

3478A

Set-Up and

Configuration

Open

Short

Short

Short

Short

Short

+30mV

+300mV

+300mV

+1V

-1V

-3V

+3V

+3V

+3V

+3V

+3V

+10V

+30V

+30V

+300V

Open

See Below

Press TEST/RESET

30mV Range

300mV Range

3V Range

30V Range

300V Range

30mV Range

300mV Range

3V Range

3V Range

3V Range

3V Range

3V Range

Autozero Off

Autozero On

4 Digit Disp

3 Digit Disp

5 Digit Disp

30V Range

30V Range

30V Range

Autozero Off

Autozero On

300V Range

30mV Range

CMR Test

PERFORMANCE TEST CARD

1 YEAR LIMITS

High

Limit

+00.0040mV

+000.005mV

+0.00002V

+00.0004V

+000.002V

+30.0145mV

+300.026mV

+0.30004V

+ 1.00008V

-0.99992V

-2.99980V

+3.00020V

+3.00023V

+3.0003V

+3.001V

+03.0006V

+ 10.0011V

+30.0025V

+30.0036V

+300.023V

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

-00.0040mV

-000.005mV

-0.00002V

-00.0004V

-000.002V

+29.9855mV

+299.974mV

+0.29996V

+0.99992V

-1.00008V

-3.00020V

+2.99980V

+2.99977V

+2.9997V

+2.999V

+02.9994V

+09.9989V

+29.9975V

+29.9964V

+299.977V

Test

Pass

Test

Fail

•

1. Connect a 1 K Ohm resistor between the HI and LO INPUT

Terminals of the 3478A.

2. Note the 3478A's reading.

CMR Test

3. Apply 450V de between the 34 78A's chassis (rear panel) and HI INPUT Terminal.

4. The 34 78A should remain within .045mV of the reading in step 2.

3

Hewlett-Packard Model 3478A

Digital Multimeter

PERFORMANCE TEST CARD

90 DAY LIMITS

Test Performed

•

DC Currant Test

2

3

4

5

Step#

Input to

3478A

Sat-Up and

Configuration

High

Limit

Open Press TEST/RESET

Open DCI Function

+000.040mA

Open 3A Range

+0.00006A

+ 100mA

300mA Range

+ 100.150mA

+1A

3A Range

+ 1.00146A

Reading Low

Limit

-000.040mA

-0.00006A

+099.850mA

+0.99854A

Test

Pass

1 YEAR LIMITS

Test Performed

Hewlett-Packard Model 34 78A

Digital Multimeter

Test

Fail

•

DC Currant Test

2

3

4

5

Step#

Input to

3478A

Sat- Up and

Configuration

High

Limit

Open Press TEST /RESET

Open

DCI Function

Open

3A Range

+000.040mA

+0.00006A

300mA Range

+ 100mA

+1A 3A Range

+ 100.190mA

+ 1.00176A

Reading Low

Limit

-000.040mA

-0.00006A

+099.810mA

+0.99824A

Test

Pass

Test

Fail

•

4

•

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

AC Volts Test

Input to

3478A

Sat-Up and

Configuration

Step#

PERFORMANCE TEST CARD

1 YEAR LIMITS

High

Limit

Reading

Test Performed

By

Date

Reference Temperature

Low

Limit

'2

5

6

3

4

7

8

9

Open

Open

.028V,20KHz

0.28V,20KHz

0.28V,20KHz

1.5V,20KHz

2.8V,20KHz

2.8V,20KHz

28V,20KHz

Press TEST/RESET

ACV Function

300mV Range

300mV Range

3V Range

3V Range

3V Range

30V Range

30V Range

028.176mV

280.680mV

0.28126V

1.50370V

2.80630V

02.8126V

28.0630V

027.824mV

279.320mV

0.27874V

1.49630V

2.79370V

02.7874V

27.9370V

10 28V,20KHz 300V Range 028.137V 027.863V

11 280V,20KHz 300V Range 280.742V 279.258V

•

12 0.28V,50KHz 300mV Range 281.269mV 278.731mV

13

14

2.8V,50KHz

28V,50KHz

3V Range

30V Range

2.80868V

28.0868V

2.79132V

27.9132V

15 280V,50KHz 300V Range 281.316V 278.684V

300mV Range 284.200mV 275.800mV

19

20

21

22

16 0.28V, 100KHz

17

0.28V, 100KHz

18

2.8V, 100KHz

23

24

15V, 100KHz

28V, 100KHz

280V, 100KHz

25V,300KHz

2.8V,50Hz

2.8V,20Hz

3V Range

3V Range

30V Range

30V Range

300V Range

30V Range

3V Range

3V Range

0.29024V

2.83216V

15.2085V

28.3216V

283.524V

28.8970V

2.8139V

2.83294V

0.26976V

2.76784V

14.7915V

27.6784V

276.476V

22.1030V

2.78609V

2.76706V

Test

Pass

Test

Fail

•

5

PERFORMANCE TEST CARD

1 YEAR LIMITS

Hewlett- Packard Model 34 78A

Digital Multimeter

AC Current Test

2

3

4

5

Step# Input to

3478A

Open

Open

.03A,5KHz

0.1A,5KHz

1 A, 5KHz

Set-Up and

Configuration

Press TEST/RESET

ACI Function

300mA Range

300mA Range

3A Range

High

Limit

030.379mA

100.883mA

1.01583A

Reading Low

Limit

029.621mA

099.117mA

0.98417A

Test

Pass

Test

Fail

•

•

•

6

•

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

4-Wire

Ohms Test

Step# Input to

3478A

Set-Up end

Configuration

2

5

6

7

3

4

•

(10)

9

(9)

10

8

30 ohm

10 ohm

11

( 11)

300 ohm

100 ohm

3K ohm

1K ohm

12

(12)

13 300K ohm

(13)

100K ohm

14

(14)

3M ohm

1M ohm

15

(15)

30K ohm

10K ohm

30M ohm

10M ohm

Short

Short

Short

Short

Short

Open

Short

Short

Press TEST/RESET

Ohms Function

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

30 Range

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

PERFORMANCE TEST CARD

24 HOUR LIMITS

High

Limit

00.0035

000.004

0.00002K

00.0002K

000.002K

0.00002M

00.0002M

30.0104

10.0058

300.018

100.009

3.00013K

1.00006K

30.0013K

10.0006K

300.013K

100.006K

3.00018M

1.00007M

30.0110M

10.0038M

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

-00.0035

-000.004

-0.00002K

-00.0002K

-000.0002K

-0.00002M

-00.0002M

29.9896

09.9942

299.982

099.991

2.99987K

0.99994K

29.9987K

09.9994K

299.987K

099.994K

2.99982M

0.99993M

29.9890M

09.9962M

Test

Pass

Test

Fail

•

7

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

4-Wire

Ohms Test

Step#

3K ohm

1K ohm

30K ohm

10K ohm

300K ohm

100K ohm

3M ohm

1M ohm

30M ohm

10M ohm

Input to

3478A

Open

Short

Short

Short

Short

Short

Short

Short

30 ohm

10 ohm

300 ohm

100 ohm

10

(10)

11

( 11)

12

(12)

13

(13)

6

7

8

9

(9)

4

5

2

3

14

(14)

15

(15)

Set-Up and

Configuration

Press TEST/RESET

Ohms Function

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

30 Range

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

PERFORMANCE TEST CARD

90 DAY LIMITS

High

Limit

00.0041

000.005

0.00002K

00.0002K

000.002K

0.00002M

00.0002M

30.0122

10.0068

300.041

100.017

3.00035K

1.00013K

30.0035K

10.0013K

300.035K

100.013K

3.00035M

1.00013M

30.0200M

10.0068M

Test Performed By

Date

Reference Temperature

Reading Low

Limit

-00.0041

-000.005

-0.00002K

-00.0002K

-000.002K

-0.00002M

-00.0002M

29.9878

09.9932

299.958

099.983

2.99965K

0.99987K

29.9965K

09.9987K

299.965K

099.987K

2.99965M

0.99987M

29.9800M

09.9932M

Test

Pass

Test

Fail

•

•

•

8

•

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

PERFORMANCE TEST CARD

1 YEAR LIMITS

Test Performed By

Date

Reference Temperature

4-Wire

Ohms Test

Step# Set-Up and

Configuration

Press TEST/RESET

Ohms Function

300 Range

3K Range

30K Range

High

Limit

Reading Low

Limit

4

5

2

3

Input to

3478A

Open

Short

Short

Short

Short

00.0041

000.005

0.00002K

00.0002K

-00.0041

-000.005

-0.00002K

-00.0002K

-000.002K

6 Short 300K Range 000.002K

7 Short

3M Range 0.00002M -0.00002M

•

8 Short 30M Range 00.0002M

-00.0002M

9

(9)

30 ohm

10 ohm

30 Range 30.0143

10.0075

29.9857

09.9925

10 300 ohm 300 Range 300.056 299.944

(10)

11

( 11)

12

(12)

13

(13)

100 ohm

3K ohm

1K ohm

30K ohm

10K ohm

3K Range

30K Range

100.022

3.00050K

1.00018K

30.0050K

10.0018K

099.978

2.99950K

0.99982K

29.9950K

09.9982K

14

(14)

300K ohm lOOK ohm

3M ohm

1M ohm

30M ohm

10M ohm

300K Range

3M Range

30M Range

300.050K

100.018K

3.00050M

1.00018M

30.0236M

10.0080M

299.950K

099.982K

2.99950M

0.99982M

29.9764M

09.9920M

15

(15)

Test

Pass

•

9

Test

Fail

PERFORMANCE TEST CARD

24 HOUR LIMITS

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

2Wire

Ohms Test

Step#

Input to

3478A

Set-Up and

Configuration

8

9

(9)

6

7

4

5

2

3

Short

Short

30 ohm

10 ohm

10

(10)

300 ohm

100 ohm

3K ohm

11

( 11) 1K ohm

30K ohm 12

(12) 10K ohm

13

300K ohm

(13)

100K ohm

14

(14)

15

(15)

3M ohm

1M ohm

30M ohm

10M ohm

Open

Short

Short

Short

Short

Short

Press TEST/RESET

Ohms Function

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

30 Range

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

High

Limit

00.2035

000.204

0.00022K

00.0004K

000.002K

0.00002M

00.0002M

30.2104

10.2058

300.218

100.209

3.00033K

1.00026K

30.0015K

10.0008K

300.013K

100.006K

3.00022M

1.00008M

30.0113M

10.0046M

Reading

Test Performed

By

Date

Reference Temperature

Low

Limit

Tast

Pass

-00.0035

-000.004

-0.00002K

-00.0002K

-000.0002K

-0.00002M

-00.0002M

29.9896

09.9942

299.982

099.991

2.99987K

0.99994K

29.9987K

09.9994K

299.987K

099.994K

2.99982M

0.99993M

29.9890M

09.9962M

Test

Fail

•

•

•

10

•

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

2-Wire

Ohms Test

•

(10)

9

(9)

10

8

11

( 11)

12

(12)

4

5

2

3

6

7

13

(13)

14

(14)

15

(15)

Step# Input to

3478A

Open

Short

Short

Short

Short

Short

Short

Short

30 ohm

10 ohm

300 ohm

100 ohm

3K ohm

1K ohm

30K ohm

10K ohm

300K ohm

100K ohm

3M ohm

1M ohm

30M ohm

10M ohm

Set-Up and

Configuration

Press TEST/RESET

Ohms Function

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

30 Range

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

PERFORMANCE TEST CARD

90 DAY LIMITS

High

Limit

00.2041

000.205

0.00022K

00.0004K

000.002K

0.00002M

00.0002M

30.2122

10.2068

300.241

100.217

3.00055K

1.00033K

30.0038K

10.0015K

300.035K

100.013K

3.00039M

1.00015M

30.0225M

10.0076M

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

-00.0041

-000.005

-0.00002K

-00.0002K

-000.002K

-0.00002M

-00.0002M

29.9878

09.9932

299.958

099.983

2.99965K

0.99987K

29.9965K

09.9987K

299.965K

099.987K

2.99965M

0.99987M

29.9800M

09.9932M

Test

Pass

Tast

Fail

•

11

PERFORMANCE TEST CARD

1 YEAR LIMITS

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

2-Wira

Ohms Tast

Stap#

2

3

Input to

3478A

Open

Short

Short

6

7

4

5

Short

Short

Short

Short

8

9

(9)

Short

30 ohm

10 ohm

300 ohm 10

(10)

100 ohm

3K ohm 11

( 11)

1K ohm

30K ohm 12

(12) 10K ohm

13

300K ohm

(13)

100K ohm

14

(14)

15

(15)

3M ohm

1M ohm

30M ohm

10M ohm

Sat-Up and

Configuration

Press TEST/RESET

Ohms Function

300 Range

3K Range

30K Range

300K Range

3M Range

30M Range

30 Range

300 Range

3K Range.

30K Range

300K Range

3M Range

30M Range

High

Limit

00.2041

000.205

0.00022K

00.0004K

000.002K

0.00002M

00.0002M

30.2143

10.2075

300.256

100.222

3.00070K

1.00038K

30.0052K

10.0020K

300.050K

100.018K

3.00055M

1.00019M

30.0260M

10.0088M

Test Performed By

Date

Reference Temperature

Reading Low

Limit

-00.0041

-000.005

-0.00002K

-00.0002K

-000.002K

-0.00002M

-00.0002M

29.9857

09.9925

299.944

099.978

2.99950K

0.99982K

29.9950K

09.9982K

299.950K

099.982K

2.99950M

0.99982M

29.9764M

09.9920M

Test

Pass

Test

Fail

•

•

•

12

•

5·1. INTRODUCTION

SECTION V

REPLACEABLE PARTS

parts by their Hewlett-Packard Part Numbers. Include instrument model and serial number.

5·6. NON-LISTED PARTS

5-2. This section has information for ordering replacement parts. Table 5-3 lists the parts in alphameric order of their reference designators and indicates the description, -hp- Part Number of each part, together with any applicable notes, and provides the following:

5-7. To obtain a part that is not listed, include: a. Total quantity used in the instrument (QTY column). The total quantity of a part is given the first time the part number appears. a. Instrument Model Number b. Instrument Serial Number c. Description of the part. d. Function and location of the part.

5·8. PARTS CHANGES b. Description of the part. (See abbreviations listed in Table 5-l.) c. Typical manufacturer of the part is a five-digit code. (See Table 5-2 for list of manufacturers.) d. Manufacturers part number.

5-9. The parts listed in Tables 5-3 and 5-4 pertain to

3478A's with serial prefix 2619. Always refer to Section

VI, Backdating, in this manual if repairing or ordering parts for instruments with a prefix earlier than 2619. Parts changes for instruments with serial prefixes above 2619 are documented on a separate manual change sheet.

5-3. Miscellaneous and Chassis Parts are listed at the

• end of Table 5-3. A disassembly procedure of the instrument is also included with the Miscellaneous and

Chassis Parts listing.

5·4. ORDERING INFORMATION

5-5. To obtain replacement parts, address order or inquiry to your local Hewlett-Packard Office. (Office

Locations are listed at the back of this manual.) Identify

•

A.

B

BT. c.

CR.

DL.

OS.

E ..

F.

Ag.

AI

A.

Au. c. cer. coef com. camp. dep.

OPDT ..

OPST. elect. encap.

F

FET. fxd.

GaAs.

GHz. gd

Go. gnd

H.

Hg.

5·1 D. 3478A DISASSEMBLY PROCEDURE

5-11. The following disassembly procedure applies to

3478A's with serial prefix 2619 and above. For serial prefixes earlier than 2619, refer to Section VI of this manual.

. assembly motor battery

. capacitor

.. diode or thyristor

. . delay line

. . lamp

. mise electronic part

. fuse

FL.

HR.

IC.

J

K.

L .

M .

MP . p .

DESIGIATDRS filter

. heater

. integrated circuit jack

. relay

. . . . . . . . . inductor meter

. . . mechanical part

. . plug

Q.

OCR

Alp!

RT s .

T

TB.

TC .

TP .

5-12. In the following procedure, all directions are referenced to the front of the instrument. That is,

Table 5·1. Standard Abbreviations silver

. . . . . . . . aluminum

... ampere(s)

... gold

"'·

10. impg incd ins . . . . . . . capacitor

. . . . . ceramic

. coefficient kD. kHz.

. . composition

... connection L lin. log. ... deposited

. . . . double-pole double-throw

. double-pole single-throw

. . electrolytic encapsulated mA.

MHZ.

MO . metflm. mfr.

. farad(s)

. field effect transistor m• mtg fixed mV.

•'

. . . . gallium arsenide

. gigahertz

=

10 + 9 hertz

,v.

. . . . . . . guard(edl

"' my

. germanium ground(ed)

. henry(ies)

. . . . . . . . . . mercury nA.

NC.

No.

NO.

ABBREVIAnDIS

. . . hertz (cycle(s) per second) NPO .

. . . . . inside diameter

.. impregnated incandescent

. . . . . . insulationledl

. kilohm(s) = 1Q+3ohms

0 . obd.

00 .

. . . . . . . . kilohertz= 1Q+3 hertz inductor p pA. pc.

... . milliampere(sl

...

. . . megahertz

.

. megohm(s)

10- 3 amperes

.

10+6 hertz

1Q+6ohms

.metal film pF. piv . p/o . pos . poly . pot.

. . . . . . manufacturer millisecond

. . . . .. mounting

.. millivolt(s)

= 10- 3 volts p-p. ppm. prec.

...

. . microfaradlsl

.... microsecond(s) R

.. microvolt(s)

10-6 volts

Rh.

•m•

. nanoampere(sl

. . . . . Mylar@

.

1 0- 9 amperes

. . normally closed

'"

So . neon

... normally open sect . s,.

. negative positive zero

. . nenosecondfs)

.

1 0- 9 seconds

.. not separately replaceable

. ohm(s)

.order

.. outside diameter . by description peak

.. picoampere(s)

. .. picofaradtsl 10- 1 2 farads

. peak inverse voltage

. part of

. . . . position(s)

. . . . . . polystyrene

. . . . . . potentiometer

. . peak-to-peak

. parts per million

.. precision (temperature coefficient, long term stability and/or tolerance) resistor

. rhodium

. . . . root-mean-square rotary

. .. selenium

. . . . . . . section(&) silicon

. . . . . . . . transistor

..... transistor-diode resistor(pack)

. ...... thermistor

. switch transformer

. terminal board

. . . . . thermocouple

. . . . . . . . . test point sl.

SPOT.

SPST.

Ta.

TC.

Ti02. tog. tol trim.

TSTR v. var . vdcw.

W. w/. wiv. w/o .

•.

..slide

. single-pole double-throw

. .. single-pole single-throw

. . tantalum

. temperature coefficient

. titanium dioxide

. toggle

. . . tolerance

. ... trimmer

. . . . . . . . transistor

.~~

. alternating current working voltage

. . . . . . . . . . variable

. ... direct current working voltage

. . . . . . . . . , . . . . . . . . . . with

. .. working inverse voltage

. ... without

. . . . . wirewound

. . optimum value selected at factory, average value shown (part may be omitted)

.. no standard type number assigned selected or special type

@

Dupont de Nemours

Tti . . . . . . . . terminal strip

U . ... microcircuit

V . . . . . . . vacuum tube, neon bulb, photocell, etc.

W

X.

XDS

XF. y. z.

.. cable

. socket tampholder

. . fuseholder

. crystal

. . . . . . . . . . network

5-1

3478A

Replaceable Parts

Table 5-2. Code List of Manufacturers

Mfr.

No.

0049D

01121

01295

0192B

03888

04713

06665

07263

07716

11236

12969

14936

24355

24546

27014

28480

56289

75915

Manufacturer Nama

United Chemicon Inc

Address

Allen·Bradley Co Milwaukee WI 53204

Texas lnstr Inc Semicond Cmpnt Div Dallas TX 75222

RCA Corp Solid State Div Somerville NJ OB876

KDI Pyrofilm Corp

Motorola Semiconductor Products

Precision Monolithics Inc

Fairchild Semiconductor Div

Whippany NJ 07981

Phoenix AZ 8 5062

Santa Clara CA 9 5050

Mountain View CA 94042

TRW Inc Burlington Div

Cts of Berne Inc

Burlington lA 52 60 1

Berne IN 46711

Unitrode Corp Watertown MA 02172

General lnstr Corp Semidon Prod Gp Hicksville NY 11802

Analog Devices Inc Norwood MA 02062

Corning Glass Works (Bradford)

National Semiconductor Corp

Hewlett·Packard Co Corporate Hq

Sprague Electric Co

Littlefuse Inc

Bradford PA 16701

Santa Clara CA 9 50 51

Palo Alto CA 94304

North Adams MA 01 24 7

Des Plaines IL 60016 references to the right side of the instrument refer to the right side as seen when looking straight-on at the front panel. k. Locate and remove the four wires from the rear input terminals. a. Locate the cover mounting screw at the bottom rear of the instrument. Loosen and remove the screw.

I. Locate the two cable clamps on the right side of the chassis. Open the clamps and remove all the wires. b. Locate the two mounting screws on the rear bezel.

Loosen the two screws and remove the bezel. The screws are captive in the rear bezel. m. The motherboard and front panel can now be removed from the chassis as an assembly. Set the 3478A on its side with the front pane! facing you. c. Remove the cover by sliding it off the rear of the instrument chassis. Most troubleshooting and repair can be accomplished with the instrument in this condition. n. Gently pry the top and bottom of the front bezel apart so that the molded tabs on the front bezel clear the front panel. d. Locate and unplug W502 (the HP-IB Cable) from the motherboard. W502 is located between the power transformer and the rear chassis. o. While holding the front bezel apart, gently push the motherboard and front panel assembly out through the front bezel. Do apply excessive force. The front bezel can be released when the front panel has cleared the molded tabs. The front panel and motherboard assembly will now slide clear of the chassis, out through the front bezel. e. Locate and unplug J530 and J531 from the motherboard. J530 is the purple VM COMP wire and J531 is the yellow EXT TRIG wire. Both J530 and J 531 are located near the rear chassis. p. Remove the front bezel from the chassis by gently bending the chassis sides together until the threaded inserts clear the front bezel molded holes. f. Locate and remove the screw holding the greenyellow ground wire to the outside rear left-side of the chassis. After the screw is removed, place the wire inside the chassis. q. The front panel assembly can now be removed from the motherboard. Locate and unplug the four wires from the front panel input terminals. r. Locate and unplug the front panel brown ground wire from the motherboard. g. Locate and remove the screw holding the brown ground wire to the outside right front-side of the chassis.

After the screw is removed, place the wire inside the the chassis. h. Unplug W3 from U760. U760 is the regulator IC and is mounted inside the chassis on the left-side. Leave

U760 mounted to the chassis. s. Unplug the ribbon display cable from the display board. Be careful. The ribbon connector is delicate. t. Locate and unplug the yellow amps input terminal wire from the motherboard. i. Locate the power switch mounting screws on the left side chassis. Loosen, but do not remove the screws. When loose, slide the power switch assembly up and out of the chassis. j.

Locate the power transformer mounting screws and nuts. Remove the screws and nuts. The transformer is mounted to the motherboard and will stay in place.

5-2 u. Loosen and remove the two screws in the bottom of the front panel connector. The motherboard and front panel can now be separated. v. To remove the display assembly from the front panel, loosen and remove the two screws holding the plastic display clamps.

•

•

•

H.eplaccahle Parts

Replaceable Parts

•

Reference

Designation

HP Part

c

Number

D

AI 03478-66501 2

AIEtT701

1420-0278 7

AICIOI

AIC102

AIC103

A1C105

AIC106

AIC107

AI Cl 08

AIC201

At C202

AIC203

AIC204

AIC205

AtCJO!

A1C302

AIC304

A1C305

AtC306

AIC307

AI C308

AIC309

AI CJ! 0

AIC311

AI C312

AIC313

AI C314

A1C401

0160-6839

0160-6839

0160-6839

0160-4571

01&0-4571

0160-4571

0160-4571

0160-4801

0160-3847

0160-3847

0160-6396

0160-6386

0160-5386

0160-5384

0180-0228

0160-4803

0180-0228

0!60-5385

0180-2205

0180-0373

0180-0291

0160-4571

0160-4571

0180-0291

0160-4571

0!60-4571

8

8

B

8

7

7

0

9

7

5

5

5

8

8

3

8

8

6

4

3

2

3

5

3

6

9

AI C402

A1C404

0160-4571

0160-4571

•

AIC405

A1C410

AtC411

AIC412

At C430

AIC431

AtC432

0160-4571

0160-5391

0160-4814

0!60-4830

0160-4823

AIC433

0160-4831

0160-4571

0160-4571

0160-Lo807 a

2

2

2

3

3

9

9

AtC463

AIC464

A1C465

AIC466

At C467

0160-3847

0160-3847

8

8

8

3

3

8

0160-4807

0160-4571

B

Atr.4'-8

AIC501

AIC502

A1C503

AIC504

AIC506

AtC507

AIC508

AI C509

AlC510

A1C511

0160-4571

0160-3847

0160-3335

0160-4571

0160-3335

0160-3847

0160-3a47

0160-4571

0160-4571

0180-0291

0160-4571

8

8 a

3 a

9

0

8

0

9

9

AIC512

A1C514

AIC515

At CSta

AIC519

AIC702

AIC703

AIC704

AIC70 5

AIC70(,

A!C711

A1C720

AIC721

AIC760

AtC761

AIC762

AIC763

A1C764

AIC765

A1C766

0160-4571

0160-4807

0!60-4807

0160-4571

0160-4571

0180-3871

0180-3871

01&0-0291

0180-0291

0180-0291

0180-3876

0160-4183

0160-4183

0160-4571

0180-3879

0180-0374

0180-0291

0160-4571

0160-4048

0160-4048

•

AICR201

AICR202

AlCR401

AlCR402

AICR500

AICR501

1901-0849

1902-0184

1902-0945

1902-0945

1901-vo5o

1901-0050

8

6

7

7

3

3

I

I

3

8

B

9

3

3

3

6

8

3

8

2

2

B

3

3 a

8

Oty

3

23

7

7

2

2

I

2

1

1

2

1

I

4

7

7

1

1

7

4

1

1

1

1

1

I

7

2

I

I

1

I

2

I

1

1

1

7

Table 5·3. Replaceable Parts

Description

~C

ASSEMBLY-MOTHER BOARD

BATTERY 3V .95A-HR LI/5-DIOX W-FLEX

CAPAC!TOR-FXD 470PF +2% 630VDC

CAPACITOR-FXD 470PF +2% 630VDC

CAPACITOR-FXD 470PF

~2%

630VDC

CAPACITOR-FXD .!UF +80-20:11:

~OVDC CER

CAPACITOR--FXD .!UF +80-20:11: 50VDC CER

CAPACITOR-FXD .!UF +80-20:11: 50VDC CER

CAPACITOR-FXD ,!UF +80-20:11: 50VDC CER

CAPACITOR-FXD IOOPF +-5:11: !OOVDC CER

CAPACITOR-FXD

.OIUF +100-0% 50VDC CER

CAPACITOR-FXD .OIUF +100-0% 50VDC CER

CAPAC!TOR-FXD 470PF + 10% 200VDC

CAPACITOR-FXD 24PF ±lPF 630VDC

CAPACITOR-FXD . 15UF 630VDC

CAPACITDR-FXD 2.7PF 400VDC

CAPACITOR-FXD 22UF+-IOX 15VDC TA

CAPACITOR-FXD 68PF +-5X !OOVDC CER 0+-30

CAPACITOR-FXD 22UF+-!OX !SVDC TA

CAPAClTOR-FXD 1.8UFIOOVDC

CAPACITOR -FXD .33UF+-10X 35VDC TA

CAPACITOR-FXD .68UF+-10X 35VDC TA

CAPACITOR-FXD IUF+-!OX 35VDC TA

CAPACITOR-FXD , IIJF +80-20:11: 50VDC CER

CAPACITOR -FXD .tUF +80-20:11: 50VDC CER

CAPACITOR-FXD tUF+-tOX 35VDC TA

CAPACITOR-FXD .tUF +80-20X 50VDC CER

CAPACITOR-FXD .!UF +80-20X 50VDC CER

CAPACITOR -FXD .tUF +80-20X 50VDC CER

CAPACITOR-FXD .tUF +80-20X 50VDC CER

CAPACITOR-FXD .tUF +80-20X 50VDC CER

CAPACITOR-FXD IOOOPF tOOVDC

CAPACITOR-FXD 150PF +-5X !OOVDC CER

CAPACITOR-FXD 2200PF +-!OX IOOVDC CER

CAPACITOR-FXD 820PF +-5X tOOVDC CER

CAPACITOR-FXD 4700PF +-lOX IOOVDC CER

CAPACITOR-FXD .!UF +80-20:11: 50VDC CER

CAPACITOR-FXD .!liF +B0-20X 50VDC CER

CAPACITOR-FXD .OtUF +100-0X 50VDC CER

CAPACITOR-FXD .O!UF +100-0X 50VDC CER

CAPACITOR-FXD 33PF +-5X !OOVDC CER 0+-30

CAPACITOR-FXD 33PF +-5X IOOVDC CER 0+-30

CAPACITOR -FXD .tUF +80-20X 50VDC CER

CAPACITOR-FXD .!UF +80-20X 50VDC CER

CAPAC ITOR-FXD .OIUF +100-0% 50VDC

CAPACITOR-FXD 470PF +-lOX IOOVDC CER

CAPACITOR-FXD .tUF +80-20:11: 50VDC CER

CAPACITOR-FXD 470PF +10% IOOVDC CER

CAPACITOR-FXD .OlUF +100-0% 50VDC CER

CAPACITOR-FXU .OIUF +100-0X 50VDC CER

CAPACITOR-FXD .llJF +80-20% 50VDC CER

CAPACITOR-FXD .tUF +B0-20X 50VDC CER

CAPACITOR-FXD lUF ±10% 35VDC

CAPACITOR-FXD ,!UF +80-20X 50VDC CER

CAPACITOR-FXD .!LJF +B0-20X 50VDC CER

CAPACITOR-FXD 33PF +-5X IOOVDC CER 0+-30

CAPACITOR-FXD 33PF +-5X 1 OOVDC CER 0+-30

CAPACITOR-FXD .tUF

+80-~0X SOVDC CER

CAPAC ITOR-FXD .lUF +80 -20% 50VDC

CAPACITOR-FXD 330UF +20% 50VDC

CAPAC !TOR- FXD 330UF +20% 50VDC

CAPACITOR-FXD lUF +-lO% 35VDC TA

CAPACITOR-FXD IUF +-10% 35VDC TA

CAPACITOR-FXD lUF +-10% 35VDC TA

CAPAC !TOR- FXD IOOOUF ±20t 25VDC

CAPACITOR-FXD 1000PF +-20% 2SOVAC(R~S)

CAPAC !TOR- FXD lOOOPF +-20% 250VAC(RMS)

CAPACITOR-FXD .tUF +80-20% 50VDC CER

CAPACITOR-FXD 3300UF ±20% 25VDC

CAPACITOR-FXD IOUF+-tOX 20VDC TA

CAPACI.TOR·FXD IUF+-!OX 35VDC TA

CAPAC!TOR-FXD .IUF +80-20% 50VDC CER

CAPACITOR .022UF 250V

CAPAC I TOP. .022UF 250V

DIODE-PWR RECT IN4007 IKV !A D0-41

DIODE-ZNR 16.2V 5% D0-35 PD=.4W

D IODE-ZNR 3V 5% D0-35 PD=.4W TC=-.043%

DIODE-ZNR 3V 5% D0-35 PD=.4W TC=-.043%

DIODE SWITCHING BOY 200MA 2NS D0-35

DIODE-SWITCHING BOY 200MA 2NS D0-35

Mfr

Code

28480

28480

28480

28480

28480

2a4BO

28480

28480

28480

29480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

56ny

56289

56289

28480

28480

28480

28480

28480

56289

56289

28480

28480

28480

14936

28480

28480

28480

See introduction to this section for ordering information

*Indicates factory selected value

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

56289

28480

56289

~~8480

56289

56289

56289

28480

284aO

56289

28480

28480

284aO

28480

284aO

28480

28480

28480

2a480

28480

28480

28480

Mfr Part Number

03478-66501

1420-0278

0160-6839

0160-6839

0160-6839

0160-4571

0160-4571

0160-4571

0160-4571

0160-4801

0160-3847

0160-3847

0160-6396

0160-6386

0160-5386

0160-5384

150D226X9015B2

0160-4803

150D226X90!5B2

0160-5385

150D334X9035A2

150Db84X9035A2

150D105X9035A2

0160-4571

0160-4571 t50Dt05X9035A2

0160-4571

0160-4571

0160-4571

0160-4571

0160-4571

0160-5391

0160-4814

0160-4830

0160-4823

0160-4831

0160-4571

0160-4571

0160-3847

0160-3847

0160-4807

0160-4807

0160-4571

0160-4571

0160-3847

0160-3335

0160-4571

0160-3335

0160-3847

01 b0-3847

0160-4571

0160-4571

0180-0291

0160-4571

0160-4571

0160-4807

0160-4807

0160-4571

0160-4571

0180-3871

0180-3871

150DI05X9035A2

150D105X9035A2

150D105X9035A2

1080-3876

0160-4183

0160-4183

0160-4571

0180-3879

150D106X9020E!2

150D105X9035A2

01~0-4571

0160-4048

0160-4048

1N4007

1902-0184

1902-0945

1902-0945

1901-0050

1901-0050

5-3

Replaceable Parts

Replaceable Parts

A1RI01

A1R102

A1 RI03

AIR104

A1RI05

A1R106

A1RI07

A1R108

AIR109

AIR11 0

A1R201

AIR202

A1 R203

A1R204

A1R205

AIR206

AIR2071>1

A1R302

A1R303

A1R304

AIR305

A1 R306

A1R307

A1R308

AIR401

A1R402

AIXF760

A1FX760

A!HSK701

AIHSK702

AIHSK703

A1 J504

AIJ70?

A1 JH403

AIJII501

A1 JH502

AIJH503

A1KIOI

AIKI02

A1KI03

A1KI04

AIL201

A1Q201

AIQ202

A1 Q203

AIQ204

A1Q205

Reference

Designation

AICR502

At CR503

AICR504

AI CR505

AICR507

AICR508

AICR701

A1 CR702

AICR703

A1 CR704

AICR705

A1CR706

AICR711

A1CR712

AICR713

AICR714

AICR715

A1 CR760

AICR7bl

AICR7b4

A1CR766

AIE101

AIF760

AIF760

Table 5-J. Replaceable Parts

HP Part

Number

c

0

Oty

1901-0050

1901-0050

1901-0050

1901-0050

1902-0945

1902-0945

1901-0743

1901-0743

1901-0743

1901-0743

1901-0743

1901-0743

1902-0632

1902-0936

1902-0632

1902-1000

1902-1000

1901-0743

1901-0743

7

7

1

1

1

1

9

6

9

3

3

3

3

?

7

I

1

I

1

8

2

2

2

Description

DIODE-SWITCHING 80V 20011A 2NS D0-35

DIODE-SWITCHIN~ 80V 20011A 2NS D0-35

DIODE-SWITCHING 80V 200HA 2NS D0-35

DIDOE-SWITCHING 80V 200HA 2NS D0-35

DIODE-ZNR 3V 5% D0-35 PD=.4W TC=-.043%

DIODE-ZNR 3V 5:C D0-35 PD=.4W TC=-.043X

DIODE-PWR RECT IN4004 400V 1A D0-41

DIODE-PWR RECT 1N4004 400V 1A D0-41

DIODE-PWR RECT IN4004 400V 1A D0-41

DIODE-PWR RECT 1N4004 400V 1A D0-41

DIODE-PWR RECT 1N4004 400V 1A D0-41

DIODE-PWR RECT 1N4004 400V 1A D0-41

DIODE-ZNR 1N5354B 1?V 5X PD=5W TC=+75X

DIODE-ZNR 6V PD=5W IR=300UA

DIODE-ZNR IN5354B 17V 5X PD=5W TC=+75%

DIODE-ZNR 1N5366B 39V 5% PD:SW IR=500NA

DIODE-ZNR 1N53b6B 39V 5% PD=SW IR=500NA

DIODE-PWR RECT 1N4004 400V 1A D0-41

DIODE-PWR RECT 1N4004 400V 1A D0-41

1901-0050

1902-0936

1970-0100

3

6

9

DIODE-SWITCHING BOV 200HA 2NS D0-35

DIODE-ZNR 6V PD=5W IRa300UA

SURGE V PROTECTOR

2110-0201

2110-0318

2110-0642

2110-0565

1205-0309

1205-0355

1205-0318

1200-0583

1251-4743

1258-0141

1258-0141

1258-0141

1258-0141

0490-1556

0490-1555

0490-1555

0490-1555

9100-1666

1853-0510

1853-0510

1853-0510

1853-0510

1855-0298

3

9

9

2

0

1

0

8

8

8

8

I

9

7

7

7

7

2

I

I

2

4

I

4

FUSE .25AT250V 1.25X.25 UL

<FOR 100V,120Vl

FUSE .125AT 250BV 58 1.25X.25 UL

<FOR 220V,240Vl

FUSEHOLDER-BOARD HOUNT

FUSEHOLDER CAP 12A HAX FOR UL

HEAT SINK SGL T0-220-CS

HEAT SINK SGL T0-220-CS

HEAT SINK SGL T0-220-CS

SOCKET-IC 24-CONT DIP DIP-SLDR

CONNECTOR-AC PWR HP-9 HALE REC-FLG THRHP

JUHPER-REH

JUIIPER-REII

JUHPER-REH

JUHPER-REII

RELAY-REED 2A 250MA 400VDC 5VDC-COIL

RELAY-REED 2A 250MA 400VDC 5VDC-COIL

RELAY-REED

~A-

250MA 400VDC 5VDC-COIL

RELAY-REED 2A 250MA 400VDC 5VDC-COIL fNDUCTOR RF-CH-MLD 3.6MH 5%

TRANSISTOR-2N6520 <SELl

TRANSISTOR-2N6520 <SELl

TRANSISTOR-2N5b20 <SELl

TRANSISTOR-2N6520 <SELl

TRANSISTOR J-FET N-CHAN D--·IIODE T0-92

Mfr

Code

28480

28480

28480

28480

28480

28480

01295

01295

01295

01295

01295

01295

04?13

12969

04?13

04?13

04713

01295

01295

Mfr Part Number

1901-0050

1901-0050

1901-0050

1901-0050

1902-0945

1902-0945

1N4004

1N4004

1N4004

1N4004

1N4004

1N4004

I N53548

TVS505

IN5354B

1N5366B

1N5366B

1N4004

1 N40 04

28480

12969

28480

1901-0050

TVS505

1970-0100

28480

29480

2110-0201

2110-0318

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

28480

2110-0642

2110-0565

1205-0309

1205-Q355

1205-0318

1200-0583

1251-4743

1258-0141

1258-0141

1258-0141

1258-0141

0490-1556

0490-1555

0490-1555

0490-1555

9100-1666

1853-0510

1853-0510

1853-0510

1853-0510

1855-0298

0686-5135

0686-5135

0686-5135

0686-5135

0686-5135

0686-5135

0811-3435

0686-1025

0683-1655

0698-8777

0698-8093

0757-0472

0757-0472

0683-1035

0683-4325

0683-4325

0683-1035

0698-66?0

0698-6520

0683-2435

075?-045?

0683-1005

0683-1005

0683-3015

0683-1655

0698-8353

1

0

7

6

6

5

5

I

8

8

I

5

5

1

I

1

b

2

5

I

3

6

b b

6

b

6

1

I

2

4

RESISTOR 51K 5% .SW CC TC=0+765

RESISTOR 51K 5% .5W CC TC=0+765

RESISTOR 51K 5% .5W CC TC=0+?65

RESISTOR 51K 5% .5W CC TC=0+765

RESISTOR 51K 5% .5W CC TC=0+765

RESISTOR 51K 5% .5W CC TC=0+?65

RESISTOR .1 .1X 3W PW TC=0+-90

RESISTOR 1K 5% .SW CC TCa0+647

RESISTOR 1.6M 5% .25W

RESISTOR IK 5% .25W

RESISTOR 40K .1% .IW F TC=0+-5

RESISTOR 200K 1% .125W

RESISTOR 200K 1% .125W

RESI~fOR 10K 5% .25W FC TC=-400/+700

RESISTOR 4.3K 5%.25W

RESISTOR 4.3K 5% .l5W FC TC=-400/+700

RESISTOR RESISTOR !OK 5% .25W

RESISTOR IK .5X .125W F TC=0+-25

RESISTOR 24K .25% .125W F TC=0+-25

RESISTOR 24K 5% .25W FC TC=-400/+800

RESISTOR 47.5K IX .125W F TC=0+-100

.RESISTOR 10 5:C .25W FC TC=-400/+500

RESISTOR 10 5:C .25W FC TC=-400/+500

RESISTOR 300 5:C .25W FC TC=-400/+600

RESISTOR 1.611 5% .25W FC TC=-900/+1100

RESISTOR 806K IX .125W F TC=0+-100

07716

28480

28480

01121

28480

01121

28480

28480

28480

01121

24546

01121

01121

01121

01121

28480

01121

01121

01121

01121

01121

01121

28480

01121

28480

28480

EB5135

EB5135

EB5135

EB5135

EB5135

EB5135

0811-3435

EBI 025

068.S-1655

0698-8777

HAR5-1/10-T16-4002-B

0757-0472

0757-0472

CBI035

0683-4325

CB4325

0683-1035

0698-6670

0698-6520

CB2435

C4-1/8-T0-4752-F

CB1005

CBI 0 05

CB3015

CB1655

0698-8353

See introduction to this section for ordering information

*Indicates factory selected value

5-4

•

•

•

Replaceable Parts

Replaceable Parts

•

Reference

Designation

HP Part

c

Number

D

AIR403

AtR404

0698-4539

0757-0472

7

5

0757-0465 6

A1R405

A1R406

0698-3228

0683-8255

9

I A1R407

Oty

I

I

1

I

I

A1R408

A1R409

AtR460

A1R461

A1R4b2

AIR463

AI R464

AIR465

AIR466

A1R467

A1R468

A1R469

AIR470

AIR471

AIRSOI

AIR503

AIR504

AI R506

AIR509

AIR510

A1R517

0683-1 DOS

0757-0415

0683-1525

0683-1525

0683-4335

0683-4715

0683-4715

0683-4335

0683-5125

0683-5125

0757-0283

0757-0472

0683-5125

069~-8777

0757-0472

1810-0560

0698-3359

0698-8777

1810-0126

1810-0126

0683-1525

AIR518

AIR519

AI R520

AIR521

AIR522

0683-1525

0683-4715

0683-4715

0683-4335

0683-4335

AIR523

0683-5125

0683-5125 A1R524

•

AIR528

A1R529

A1R531

A1R532

AIR534

AIR538

A1R539

0683-5125

0683-5125

0683-5125

0683-5125

0696-1015

0686-1015

0683-5125

8

8

8

8

3

3

AI R540

A1R553

AlR554

AIR555

A1R761

0683-5125

0698-8777

0698-8768

0698-8767

0698-4482

8

8

3

2

I

9

A1R762

0698-3226

8

8

7

7

0

2

2

AIR763

AIR765

AlR766

AIR767

0698-3226

0683-4715

0698-8768

0698-8768

AIR768

AIR769

0683-1035

0698-3444

1

1

4

0

0

0

0

6

5

8

3

I

I

4

3

5

7

7

0

0

0

8

8

5

6

4

4

0

I

6

4

II

I

5

I

I

2

2

1

2

3

Table 5·3. Replaceable Parts

Description

RESISTOR 402K IX .125W F TC=0+-100

RESISTOR 200K IX .125W F TC=0+-100

RESISTOR I ODK IX .125W F TC=0+-100

RESISTOR 49,9K IX .125W F TC=0+-100

RESISTOR 8.2M 5X .25W FC TC=-900/+1100

RESISTOR 10 5X .25W FC TC=-400/+500

RESISTOR 475 IX .125W F TC=0+-100

RESISTOR I. 5~X .25W FC TC=-400/+700

RESISTOR I. 5~X .25W FC TC=-400/+700

RESISTOR 43K SX .25W FC TC=-400/+800

RESISTOR 470 sx .25W FC TC=-400/+600

RESISTOR 470 5X .25W FC TC=-400/+600

RESISTOR 43K 5X .25W FC TC=-400/+800

RESISTOR 5 .IK 5X .25W FC TC=-400/+700

RESISTOR S.IK 5X .25W FC TC=-400/+700

RESISTOR 2K 1% . 125W

RESISTOR 2ooK a

.125W

RESISTOR 5 .IK 5X .25W FC TCa-400/+700

RESISTOR IK 5% .25W

RESISTOR

2~0K

II .125W

RESISTIVE NETWORK- 8 X 5.6K OHM

RESISTOR 12.7K IX .125W F TC=0+-100

RESISTOR IK 5X .25W

NETWORK-RES 14-DIPID.OK OHM X 13

NETWORK-RES 14-DIPIO.OK OHM X 13

RESISTOR 1. 5K5X .25W FC TC=-400/+700

RESISTOR I. 5K5X .25W FC TC=-400/+700

RESISTOR 470 SX .25W FC TC=-400/+600

RESISTOR 470 5X .25W FC TC=-400/+600

RESISTOR 43K 5X .25W FC TC=-400/+800

RESISTOR 43K SX .25W FC TC=-400/+800

RESISTOR S.IK sx .25W FC TC=-400/+700

RESISTOR 5 .1K 5X .25W FC TC=-400/+700

RESISTOR 5.1K sx .25W FC TC=-400/+700

RESISTOR 5.1K 5X .

25~!

FC TC=-400/+700

RESISTOR 5.1K sx .25W FC TC=-400/+700

RESISTOR 5.1K SX .25W FC TC=-400/+700

RESISTOR 100 sx .SW CC TC=0+529

RESISTOR 100 5X .5W CC TC=0+529

RESISTOR 5.1K 5X .25W FC TC=-400/+700

RESISTOR 5.1K 5X .25W FC TC=-400/+700

RESISTOR lK 5% .25W

RESISTOR 100 5% . 25W

RESISTOR 200K 5% .25W

RESISTOR 17.4K IX .125W F TC=0+-100

RESISTOR 6. 49K IX .125W F TC=0+-100

RESISTOR 6 . 49K IX . 125W F TC=0+-100

RESISTOR 470

5% .25W FC TC=-400/+600

RESISTOR 100 5% .25W

RESISTOR 100 5% .. 25W

RESISTOR !OK 5% .25W

RESISTOR 31b OHM 1% . 125W

Mfr

Code

Mfr Part Number

28480

24546

24546

28480

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

01121

28480

28480

28480

03888

24546

24546

01121

28480

28480

28480

28480

01121

24546

01121

011 ?.I

01121

01121

01121

01121

01121

01121

28480

284~0

01121 n48o

28480

28480

24546

28480

11236

11236

01121

0698-4539

C4-I/8-TD-2003-F

C4-1/8-T0-1003-F

0698-3228

Cll8255

CB100'5

C4-I/8-T0-475R-F

CB 152 5

CB 15 2 5

CB4335

CB4715

CB4715

CB4335

CB5125

CB5125

0751-0283

0757-0472

CB5125

0698-~777

0757-0472

1810-0560

C4-I/8-T0-1272-F

0698-8777

760-1-R I OK

760-1-RIOK

CB1525

CB1525

CB4715

CB4715

CB4335

CB4335

CB5125

CB5125

CB5125

CB5125

CB5125

CB5125

EBI 015

Ell!OIS

CB5125

CB5125

0698-8777

0698-8768

0698-8767

PME55-1/S-T0-1742-F

C4-1/8-T0-6491-F

C4-I/8-T0-6491-F

CB4715

0698-8768

0698-8768

0683-1035

0698-3444

AIRP527 1810-0307 0

I

1810-0307

NETWORK-CNDCT MODULE DIP; 16 PINS; 0. 100

AIRT507

AIS501

AIT401

AI TSO 1

A1T760

AI TP403

AITP501

AI TP502

AITP503

A1U101

A1U102

A1U201

A1U202

A1U203

0837-0223

3101-2243

9100-2616

9100-2616

9100-4201

1251-5835

1251-4682

1251-4367

1251-5394

1826-1056

IQF7-0067

1826-0493

1826-0493

1826-0072

A1U301

At UJ02

A1U303

A1U401

A1U402

1826-0887

1826-1010

1826-0893

1826-0311

1826-0635

AIU403

AIU404

AI U40S

At U462

1 QF6-0066

1826-0271

1826-0635

1820-2726

•

A1U461 1826-1249

4

3

0

0

2

4

7

2

9

0

I

6

8

8

9

4

6

1

1

4

3

6

4

9

1

I

2

I

1

1

1

I

1

2

1

1

1

I

1

1

1

1

1

I

2

THERMISTOR-PTC 10.30

SWITCH-RKR DIP-RKR-ASSY 8-IA .Q5A 30VDC

TRANSFORMER-PULSE 8IFILAR WOUND; 18.0 MM

TRANSFORMER-PULSE BIFILAR WOUND; 18.0 HM

TRANSFORMER-POWER

CONNECTOR 6-PIN H POST TYPE

CONNECTOR 3-·PIN H POST TYPE

CONNECTOR 8-PIN H POST TYPE

CONNECTOR 4-PIN M POST TYPE

IC UP AMP PRCN T0-99 PKG

PCB HYBRID INPUT

IC OP AHP LOW-BIAS-H-IHPD 8-DIP-P PKG

IC OP AMP LOW-BIAS-H-IMPD 8-DIP-P PKG

IC LIN LM208H

IC-LF412CN<SEU

IC LINEAR

IC-GIJNV, AU\;36

IC 201A

IC OP-07CP

PCB HYBRID AID

IC OP AMP GP 8-DIP-·P PKG

IC OP AMP LOW-OFS 8-DIP-P PKG

IC LINEAR RGLTR-V-REF-FXD 6.8/7.1V

IC-MICROPROCESSOR

See introduction to this section for ordering information

*Indicates factory selected value

28480

28480

28480

28480

29480

28480

28480

28480

28480

28480

28480

04713

04713

28480

28480

28480

28480

28480

28480

28480

01295

06665

28480

28480

28480

0837-0223

3101-2243

9100-2616

9100-2616

9100-4201

1251-5835

1251-4682

1251-4367

1251-5394

1826-1056

1 QF7-0 067

MLM308API

HLM308AP1

1826-0072

1826-0887

1826-1010

1826-0893

1826-0311

1826-0635

1QF6-0066

SN72741P

OP-07CP

1826-1249

1820··~2726

5-5

Replaceable Parts Replaceable Parts

Table 5·3. Replaceable Parts

A1U465

A1U41>6

A1U46?

A1 U468

A1U501

A1 U502

A1U503

A1U504

A1U505

A1U50&

A1U507

A1U508

A1U510

A1U512

A1U513

A1U514

A1U51:S

At U550

A1U?01

A1 U?02

A1U?03

A1W501

A1X52?

A1Y460

A1Y501

Reference HP Part

c

Designation Number

D

Oty

1820-2258

1820-0935

1820-1144

182&-0 138

1820-2718

03478-65501 u

1820-2549 7

1820-2485

1820-2483

1820-15?8

0

8

0

1820-2?02

1820-1199

1820-1?94

1818-1 ?54

1820-2102

4

1

2

9

8

1820-1212

1820-3080

1826-0138

1826-055!

1826-0214

9

3

8

9

1

1826-039&

0

5

1

b

8

2

8120-34?9

1200-08:53

0410-1331

0410-1330

7

8

3

2

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

2

2

1

Description

IC FF CHOS D-TYPE POS-EDGE-TRIG COH

IC CNTR CHOS BIN NEG-EDGE-TRIG 14-BIT

IC GATE TTL LS NOR QUAD 2-INP

IC COMPARATOR GP QUAD 14-DIP-P PKG

IC-INS 8039LN-11

ROM

64K

IC-8291A P HPIB

IC RCVR TTL LS BUS OCTL

IC RCVR TTL LS BUS OCTL

IC SHF-RGTR CHOS D-TYPE PRL-IN PRL-OUT

IC NHOS 16384-BIT COUNTER

IC INV TTL LS HEX 1-INP

IC BFR TTL LS NON-INV OCTL

IC-RAH HOS 5101L

IC LCH TTL LS D-TYPE OCTL

IC FF TTL LS J-K NEG-EDGE-TRIG

IC 74HC20N

IC COMPARATOR CP QUAD 14-DIP-P PKC

IC 340LA V RGLTR T0-92

IC V RCLTR T0-220

IC ?81:S V RGLTR T0-220

CABLE-RIBBON 11>P H/H

SOCKET-IC 11>-CONT DIP DIP-SLDR

CRYSTAL-10.980 HHZ

CRYSTAL-:S.B56 HHZ

Mfr

Code

Mfr Part Number

04713

01928

01295

01295

28480

28480

28480

01295

01295

0192B

28480

01295

27014

28480

0129:S

01295

28480

01295

27014

04713

0?263

28480

28480

28480

28480

HC14174BCP

CD4020BE

SN74LS02N

LH339N

1820-2718

03478-65501

1820-2549

SN75160N

SN75161N

CD40?1>BE

1820-2702

SN?4LS04N

DH81LS95N

1818-1?54

SN74LS3?3N

SN74LS112AN

1820-3080

LH339N

LI1340LAZ-5

11C?915CT

?815UC

8120-34?9

1200-0853

0410-1331

041 c

-1330

•

•

5-6

See introduction to this section for ordering information

*Indicates factory selected value

•

Replaceable Parts Replaceable Parts

•

Reference

HP Part

c

Designation Number

D

Oty

C406

MP501

C764

S760

U760

FlO!

51

W502

MP202

DSPl

FC 101

0160-0576

1600-0273

5

4

0160-4571

8

03478-61905 0

1826-0551 9

211 0-0003 0

03478-61902 7

8120-3280

8

03478-60202 8

5061-1166

6

5061-1163 3

Table 5·3. Replaceable Parts

Description

I

I

I

I

1

1

1

1

1

AI HISCELLANEOUS PARTS

CAPAC!TOR-FXD .lUF 50V

SHIELD-RF

CHASSIS MOUNTED PARTS

CAPACITOR -FXD .IUF +80-20X 50VDC

CER

SWITCH ASSEMBLY, POWER

I C LM340AT-5

HISCELLANEOUS PARTS

FUSE 3A 2SOV NTD 1.25X.25 UL

FRONT/REAR SWITCH ASSY

CABLE ASSY- 28 PVCRBN

FRONT PANEL ASSEMBLY

DISPLAY ASSY

JACK ASSY-FUSED

Mfr

Code

Mfr Part Number

28480

28480

0160-0576

1600···0273

28480

28480

28480

0160-4571

03478-61905

1826-0551

75915

28480

28480

28480

28480

28480

312003

03478-61902

8120-3280

03478-60202

5061-1166

5061-1163

•

•

See introduction to this section for ordering information

*Indicates factory selected value

5-7

5-8

Replaceable Parts

Table 5-4. 3478A Mechanical and Miscellaneous Parts

Ref.

Des.

Part

Number CD

C764

CVR1

CVR3

DSP1

FC101

FRM1

HDW1

HDW2

HDW3

HDW4

HDW5

HDW8

HDW9

HSK701

HSK702

HSK703

KYC1

LBL35

LBL83

MP2

MP3

MP6

MP7

MP12

MP13

MP1 5

0160·3622 8

034 78-041 1 1

0

5001-0438

5061·1166

5061-1163

03478-001 11

0380-0072

7

6

3

2

2

0535-0007

2190-0004

2190-0577

2950-0043

2190-0918

2190-0016

1205-0309

1205-0355

1205-0318

0370-0603

7120-4835

7124-2083

1250-0083

1510-0124

4320-0370

5040-7201

1460-1345

8

4

3

9

5

0

4

0

4

1

2

9

1

3

1

8

5

5061-1164 4

03478-88301 6

MP16

MP26

034 78-88302 7

1400-1 122 0

MP30 4135-0415 2

MP202 03478-60202 8

MP505

SCW2

SCW3

SCW4

4135-0416

0515-0367

0515-0368

0515-0430

SCW5

SCW6

STD3

U760

W3

W501

W502

0515-0431

0515-0458

0380-1289

1826-0551

03478-61601

8120-3479

8120-3280

4

5

5

9

3

3

5

6

3

7

8

Oty.

1

1

1

2

2

7

1

1

2

2

4

1

4

2

4

1

1

2

1

1

1

1

1

1

2

2

2

2

2

3

2

1

1

2

2

2

1

1

2

1

1

Description

. 1 pF (Included with W3 Assembly)

Cover

Trim Strip

Display Assembly

Jack Assembly-Fused

Chassis Assembly

Spacer (Power Switch Mounting)

Nut (HP·IB Connector)

Lock Washer (Power Switch Mounting)

Lock Washer (HP-IB Connector)

Nuts (for BNC Connectors)

Lock Washer

Lock Washers (for BNC Connectors)

Heats ink

'Heatsink

Heatsink

Pushbutton

Label, CSA Usage (not shown)

Label, Information (not shown)

BNC Connectors

Bushing (for Binding Post)

Elastomer

Foot

Tilt Stand

Binding Post

Front Bezel

Rear Bezel

Cable Clamp

Push Rod (Power Switch)

Front Panel Assembly

Push Rod (Front/Rear Switch)

Screw, Power Switch Mounting

Screw, Motherboard to Front Panel

Screw

Screw, Bottom Cover

Screw (attaches display to front panel)

Stud (HP-IB Connector fastener)

Regulator IC LM340AT-5

Regulator Cable Assembly

Display Cable Assembly

HP-IB Cable Assembly

3478A

•

•

•

~

e e

DiM

:t'!Mf1-~~F

MP202

'0-f!:tWOC 1t;!'ltf

KYC1

Figure 5-1. 3478A Front Panel View

FC101

MP15 CVR3 SCW4

Figure 5·2. 3478A Left Side View

MP13

MP3

STD3

HDW4

HDW2

Figure 5-3. Rear Panel View

SCW4

HDWB

HDW2

SCW2

HDW3

HDW1

Figure 5·4. Right Side View

sews

(not shown)

e

MP13

e

Figure 5-3. Rear Panel View

e

SCW4

HDW8

HDW2

SCW2

HDW3

HDW1

Figure 5·4. Right Side View

SCW5 (not shown)

I

I

Iii

-~1

I

MP26

Figure 5-5. Top View With Cover Removed

; j "'

L

JJ

~

j

i

!

~

Figure 5·6. Regulator Detail View

Figure 5-7. Motherboard and Front Panel Assembly

HSK701

SCW3 (not shown)

SCW3 (not shown)

Figure 5-8. Front Panel Assembly, Rear View

5-915-10

MP202

i

.. "oN···

.&OF~

UNE

KYC1

Figure 5-1. 347BA Front Panel View

FC101

MP15 CVR3 SCW4

Figure

5-2.

3478A Left Side View

MP13

MP3

HDW5

HDW9

Figure 5·3. Rear Panel View

•

SCW4

HDW8

HDW2

SCW2

HDW3

HDW1

Figure

5·4.

Right Side View

SCW5 (not shown)

~I

I

Figure 5-5. Top View With Cover Removed

Figure 5-6. Regulator Detail View

Figure 5-7. Motherboard and Front Panel Assembly

SCW6 DSP1 SCW6

HSK701

Figure 5-B. Front Panel Assembly, Rear View

5-9/5-10

•

6-1. INTRODUCTION

SECTION VI

BACKDATING

6-2. This section contains information used to adapt this manual to instruments with serial number prefixes lower than that listed on the title page. Parts listed in this section are recommended for direct replacement in the instruments affected. Parts not specifically listed in this section should be replaced with the part presently shown in Table 5-3 and on the schematics.

6-7. 2301A08635 & below. Instruments with this serial number and below have a different side frame and plastic shield. Table 6-9 and Figures 6-6 through 6-13 show the mechanical breakdown of these instruments. For replacement purposes, substitute the parts listed in Table 6-2 for the parts in Table 6-9.

Ref.

Des.

MP14

MP23

Table 6-2. Changes to Table 6-9

Part

Number c

D Oty.

Description

034 78-61201

9

034 78-00603 7

2

Side Frame

1 Plastic Shield

6-3. The following serial numbers and lower are affected by backdating information:

Serial Number

Information Begins

•

2136A03480

2301A08635

2301A18860

2520A19795

2520A20970

2520A22585

2545A24740

2545A26015

2619A26305

2619A32988

2619A37719

2619A37794

Paragraph 6-4

Paragraph 6-7

Paragraph 6-8

Paragraph 6-9

Paragraph 6-10

Paragraph 6-11

Paragraph 6-15

Paragraph 6-16

Paragraph 6-20

Paragraph 6-22

Paragraph 6-26

Paragraph 6-27

6-4. 2136A03480 & below. Instruments with this serial number and below use a Revision B 03478-66501 printed circuit board. Figure 6-1 shows the component locator for the Revision B boards. Figure 6-2 shows schematic

4 of the Revision B boards.

6-5. Other changes are as follows: Schematic 1 Figure 6-4, delete R207. Schematic 3 Figure 6-5, delete CR500 and change the power supply connection for U512 (pin 22) from CR764 to Q701.

6-8.

2301A 18860 & below. Instruments with this serial number and below use INCH rack mounting hardware.

The METRIC hardware used in higher serial numbers is not compatible. Table 6-9 and Figures 6-6 through 6-13 show the mechanical breakdown of these instruments.

For replacement purposes, substitute the parts listed in

Table 6-3 for the parts in Table 6-9.

Ref.

Des.

MP4

MP6

MP10

MP13

MP14

MP15

MP18

Table 6-3. Changes to Table 6-9

Part

Number

5060-9905

5060-9829

5060-9841

5020-8813

5

2

8

8

034 78-61203 4

2510-0192 6

5020-8814 c

D

Oty.

Description

9

2

Side Cover

1 Top Cover

1

Bottom Cover

1 Front Frame

2 Side Frame

5 Screw (Side

Frame)

1 Rear Frame

6-6. Material list changes for the revision B printed circuit boards are shown in Table 6-1.

•

Table 6·1. Changes to Table 5-3 (Revision B Boards)

Ref. Desig.

·hp· Part

Number c

D Changes

A1C765

A1C766

0160-4048

4 DELETE FROM TABLE

0160-4048 4 DELETE FROM TABLE

A1CR500 1901-0518

8 DELETE FROM TABLE

A1R207

A1R766

0683-1035

0698-8768

1

2

DELETE FROM TABLE

DELETE FROM TABLE

A1R767

A1R768

0698-8768 2 DELETE FROM TABLE

0683-1035 1 DELETE FROM TABLE

A1CR762 1901-0050 3 ADD DIODE

A1Q701 1854-0071

7 ADD TRANSISTOR NPN

A1R760

A1R764

0683-2025 1 ADD 2K 5% RESISTOR

0683-4705 8 ADD 47 5% RESISTOR

6-9. 2520A19795 & below. Instruments with this serial number and below used a capacitor and voltage suppresser in the input circuit. A different voltage suppresser and a surge protector were added and the capacitor deleted for later instruments. Figure 6-4 shows the schematic that applies to these serial numbers. For replacement purposes, substitute the parts listed in Table

6-4 for the parts in Table 5-3.

Ref.

Des.

C104

E101

Table 6·4. Changes to Table 5-3

Part

Number

0150-0012

1970-0090 c

D Oty. Description

3

6

1 CAPACITOR-

FXD .01 uF 1 KV

1 Tube ELCTRN

630V

6-10. 2520A20970 & below. The value of R469 was changed from 200K to 1.6M in later instruments. For replacement purposes use the higher value part listed in table 5-3.

6-1

Backdating

3478A

6-11. 2520A22585 & below. The voltage reference, U461, was <.:hanged in later instruments. The new reference allowed the 3478A to meet better specifications for DC and AC voltage measurements. Instruments with this serial number and below will nor meet the new s peci fica t ions.

6-12. l\·1ake the following changes to the specifications in Table 1-1.

Table 6-5. Changes to Table

1-1

DC Volts Measurement Accuracv

5 'h Digit Mode:

Range

Cal. Temp ~

1°C

24 Hours

Cal. Tamp. go oav

±5°C

1 Year

30mV 0.027

I

35 0.030 j

41

0.040

+

41

300mV

3

0.005

+

4 0.007

~

5 0.020

+

5 v

0.0034

I

2 0.006

I

2 0.019

+

2

30

300 v

0.005

+ 3

0.007

+ 2

0.020 + 3 v

0.0055 + 2 0.008

•

2 0.020 l·

2

AC Volts Measurement Accuracv

Froquoncy JOOmV

20Hz-50Hz

50Hz·· 100Hz

100Hz- 20kHz

20kHz- 50kHz

50kHz- 10 0 kHL

100<HZ- 300kHL

1 14 - 1

6 3

0.46 163

0.29 163

0.56 - 247

1 .74 - 8 8 2 fla ngas

3V. JOV

1.14

+

102

0.46

+

1 0 3

0.26 + 102

0 .41 + 180

1.0,;

+

825

10.1

-

3720

1 0V r nnye only)

300V

1.18

0.50

+

102

+

102

0.33 + 102

0.55 + 180

1.26

+

825

6-13. Performance Test Cards for the older instruments are provided at the end of this section. Use these Performance Test Cards when calibrating or rcrformancc testing the 347HA. The Performance Test procedure and

<.:alibration procedure given in Section IV of this manual still applies. The Performance Test Cards can be reproduced without written permission from Hewlett -

Packard.

6-14. :\lake the following changes to the tables indicated in Section IV.

Table 6-6. Changes to Table 4-1

IAbbreviated Specifications Table)

DC Volts Function !accuracy

=

±I ' ~ of reading

+ number of counts))

Rang•

24 Hour

30mV 0.027

+

35

300mV 0.005

+

4

3V 0.0034

~

2

30V 0.005

I

3

300V 0.0055

+

2

90 Day 1 Year

0.030 - 41

0.007

0.040

+

41

-

5 0.020

+

5

0.006 2 0.019

I

2

0.007

I

2

0.008

0.020

4

3

-

2 0.020

I

2

DC Current Function !accuracy ~ ±(% of reading

+ numbar of counts))

Range

300m A

3A<1A

3A::-1A

90 Day

0 11 + 40

0.14

1.0

+

6

+

30

1 Year

0.15 - 40

0.17 6

1.0 + 30

Ohms Function (accuracy ~ ±I% of reading

+ numbar of countsll

Range

30 ohm

300 ohm

3K ohm

30K ohm

300K ohm

3M oh,.,.,

30M ohm

24 Hour

0.023

0.0045

+

+

35

4

0.0035 + 2

0.0035

I

2

0.0035

·I

2

0.0052 ~ 2

0.036

I

2

1 Year

90 Day

0.027 - 41

0.012

0.034 +

41

-

5 0.017 + 5

0.011 2 0.016 2

,

0.011 2 0.016

I

2

0.011

I

2

0.01

1

I

2

0.066

I

2

0.016

·I

2

0.016 + 2

0.078

I

2

AC Voln Function 1 Year Limits (accurecy ~ ±I% ol raading + number of counts))

Frequency

20Hz 50Hz

50Hz-100Hz

100Hz-20KHz

20KHz-50KHz

50KHz· 1OOKHz

1OOKHz-300KHz

300mY Ran111

JV,JOV Range

1.14

0.46

+

163 1.14

+

102

+ 163 0.46 + 103

0.29

I

163 0.26 102

0.56

I

247

1.74

I

882

041

1.05

10.1

180

• 825

3720

130V Range

Only I

300V Rango

1.18

0.50

+

102

+ 102

0.33

+

102

0.55

1.26

'

180

•

825

AC Current Function 1 Year Limits laccur.cy

=

t

1% of reading

+ numbor of countsll

Frequency

20Hz-50Hz

50Hz·1 KHz

1KHz-10KHz

1OKHz- 20KHz

JOOmA Range

1.54

+

163

0.81

0.72

0 .86

+ 163

+

163

+

163

JA RanAB

2.24

+

163

1.50

~

163

1.42

1.56

+

163

+

163

6-2

Backdating

3478A

•

Short

Short

Short

Short

Short

+30mV

+300mV

+300mV

+1V

-1V

-3V

+3V

+3V

+3V

3478A

Input

+3V

+3V

+10V

+30V

+30V

+300V

3478A 3478A

Range Set Up

Table 6·7. Changes to Table 4·3

DC Volts Test Limits high

24

Hour Limits low high

90 Day Limits low high

1 Year Limits low

30mV

DCV +00.0035mV -00.0035mV

300mV +000.004mV -000.004mV

3V +0.00002V -0.00002V

30V

300V

30mV

300mV

3V

+00.0003V -00.0003V

+000.002V

-000.002V

+30.0116mV +29.9884mV

+300.019mV +299.981mV

+0.30003V +0.29997V

3V

3V

3V

+ 1.00005V +0.99995V

-1.00005V -0.99995V

- 3.00012V -2.99988V

3V

3V

+ 3.00012

AZ Off

+ 3.00015

+2.99988V

+2.99985V

3V AZ On,

4 Digit

+3.0002V

3V 3 Digit +3.001V

+2.9998V

+ 2.999V

30V 5 Digit

+03.0005V

+02.9995V

30V

30V

+ 10.0008V +09.9992V

+30.0018V +29.9982V

30V

300V

AZ Off +30.0029V +29.9971V

AZ On

+ 300.019V

+299.981V

+00.004tmV

-00.0041mV

+00.0041mV -00.0041mV

+000.005mV -000.005mV +000.005mV -000.005mV

+0.00002V -0.00002V +0.00002V -0.00002V

+00.0003V

+000.002V

-00.0003V

-000.002V

+00.0003V -00.0003V

+000.002V -000.002V

+30.0131mV +29.9869mV +30.0161mV +29.9839mV

+300.027mV +299.973mV

+300.065mV -299.935mV

+0.30004V

+ 1.00008V

+0.29996V

+0.99992V

+0.30008V

+ 1.00021V

+0.29992V

+0.99979V

-1.00008V

-3.00020V

+3.00020V

+3.00023V

-0.99992V

-2.99980V

+2.99980V

+ 2.99977V

-1.00021V

-3.00058V

+3.00058V

+3.00061V

-0.9979V

-2.99942V

+ 2.99942V

+2.99939V

+3.0003V

+3.001V

+03.0005V

+ 10.0010V

+30.0025V

+30.0036V

+300.025V

+2.9997V

+2.999V

+02.9995V

+09.9990V

+ 29.9975V

+29.9964V

+ 299.975V

+3.0007V +2.9993V

+3.002V +2.998V

+03.0009V +02.9991V

+ 10.0023V +09.9977V

+30.0063V +29.937V

+30.0074V + 29.9926V

+300.062V + 299.938V

•

Table 6-8. Changes to Table 4·5

AC Volts Test Limits

3478A

Input

3478A

Range

3478A

Set Up high

1 Year limits

.028V,20KHz

0.28V,20KHz

0.28V,20KHz

1.5V,20KHz

2.8V,20KHz

2.8V,20KHz

28V,20KHz

28V,20KHz

280V,20KHz

0.28V,50KHz

2.8V,50KHz

28V,50KHz

280V,50KHz

300mV

ACV 028.244mV

300mV

280.975mV

3V

3V

3V

0.28175V

1.50492V

2.80830V

30V

30V

02.8175V

28.0830V

028.194V

300V

300V

300mV

281.026V

281.815mV

2.81328V

3V

30V

300V

0.28V, 100KHz 300mV

0.28V,100KHz

2.8V,100KHz

15V,100KHz

28V,100KHz

280V, 1OOKHz

25V,300KHz

2.8V,50Hz

2.8V,20Hz

3V

3V

30V

30V

300V

30V

3V

3V

28.1328V

281.720V

285.754V

0.29449V

2.86765V

15.2400V

28.3765V

284.353V

28.8970V

2.81391V

2.83294V low

027.756mV

279.025mV

0.27825V

1.49508V

2.79170V

02.7825V

27.9170V

027.806V

278.947V

278.185mV

2.78672V

27.8672V

278.280V

274.246mV

0.26881V

2.76235V

14.7600V

27.6235V

275.647V

22.1030V

2.78609V

2.76706V

6-15. 2545A24740 & below. Instruments above this serial number changed the value of C501 and R501 from .luF and lOOK to .OluF and 200K respectively. The change allows the display segments to be lit while the front panel

Test/Reset button is held by changing the RC time constant. The new parts are recommended for replacement purposes.

It is recommended that both parts be replaced ed replacement parts are listed in Table 5-3 .

• to ensure the correct RC time constant. The recommend-

6-16. 2545A26015 & below. These instruments have a different cover and frame design. The new parts are not compatible with these instruments. A Mechanical and

Miscellaneous Parts list for these instruments is given in

Table 6-9. Figures 6-6 through 6-13 show the disassembly and mechanical parts for these instruments. The following paragraphs give a disassembly procedure for these instruments.

6-17. 3478A Disassembly Procedure (Serial Prefix 2545 and below)

6-18. The following is the disassembly procedure for the

3478A. a. Refer to Figure 6-7. Loosen the screw on the

3478A's top cover (MP6). Turn the instrument over and loosen the screw on the bottom cover (MPIO). b. Remove the bottom cover by pulling the cover toward the rear of the 3478A and away from the multimeter. c. Turn the 3478A right side up. Remove the top cover by pulling the cover toward the rear of the 3478A and away from the multimeter. d. See Figure 6-11. Remove the front and rear panel wires from clamp MP26. e. See Figure 6-9. Loosen and remove the screws on both the left and right side side covers (MP4). Remove the covers.

6-3

Backdating f.

Refer to Figure 6-10. Loosen and remove screws

MP21 on the bottom plastic shield (MP23). Remove the shield. g. Refer to Figure 6-9. Loosen and remove screws

MP17 on the left side frame of the 3478A. h. Refer to Figure 6-9. Loosen and remove screws

MP 17 at the 3478A's side frames (on both the left and right side). Remove the side frames. i. Unplug the HP-IB, Voltmeter Complete, External

Trigger, and Rear Panel Terminal Cables from the mother board (A I assembly). j. Carefully remove the rear frame (MP 18) and rear panel (MP7) by pulling the frame toward the rear and away from the imtrument.

3478A k. Refer to Figure 6-11. Using a smaii flat blade screwdriver, insert the scewdriver blade into one slot of the top trim (MP29) and remove the trim. Then loosen and remove screws MP20 from the rop side of the front frame (MP13).

I.

Refer to Figure 6-10. Loosen screws YIP20 from the bottom side of the front frame (MP13). m. Remove the front frame (\1P 13) by pulling the frame toward the rear and away from the instrument. Be careful that the casting does not get tangled up in the wires going to the front and rear terminals. n. Refer to Figure 6-12. Loosen and remove screws

MP32 (also see Figure 6-13), from the bottom front panel bracket (MP33) and remove the bracket. o. Unplug the cable from the display.

Raf.

Des.

MP16

MP17

MP18

MP19

MP20

MP21

MP21

MP22

MP23

MP24

MP25

MP26

MP27

MP28

MP29

MP1

MP2

MP3

MP4

MP5

MP6

MP7

MP8

MPB

MP8

MP9

MP9

MP9

MP10

MP11

MP12

MP13

MP14

MP15

MP30

MP31

MP32

MP33

MP34

MP35

Table 6-9. 3478A Mechanical and Miscellaneous Parts

(Prefix 2545

&

below}

Dty.

7

1

6

4

2

8

2

2

2

1

1

1

2

2

2

2

4

1

1

2

1

1

1

2

2

1

4

2

1

1

1

1

1

1

1

2

6

2

2

1

Part

Number c

0

0370-0603 4

0370-0604 5

034 7 8-60202 8

5061-9505

5061-1164

5061-9429

3

4

0

034 7 8-00202

2

03801289

2190-0918

20900577

1250-0083

5

4

1

1

2190 0016

2950-0043

5061 9441

5040-7201

1460·1345

3

8

6

8

4

5021 5813 6

03478-61205

3

0515·1331

5001-0438

5

7

051 5-0212

5021-5814

0403-0164

0515 0211

0515-0217

3050-0222

7120 8607

9

5

3

8

5

8

2

034 78 00604 8

7120-3185 1

7120-3530

1400-1122

034 78-61 902

7

4135 0416 3

5040-7203

4135 0415

0624-0034

0

0

0

2

4

0624-0333

6

03478-01204 6

051 5-0226 4

5061 1166 6

Description

Pushbutton (Power Switchl

Pushbutton !Front/Rear Switch)

Front Panel Assembly

Side Cover

Binding Post

Top Cover

Rear Panel

Stud (HP-IB Connector!

Washer (HP-18 Connector!

Nut fHP-18 Connector)

Connector RF BNC fVM Complete, Ext. Trig.)

Washer (BNC Connector)

Nut (BNC Connector!

Bottom Cover

Feet

Tilt Stand

Front Frame

Side Frame

Screw

Trim

Screw

Rear Frame

Guide PC Board

Screw

Screw ( Plastic Shieldl

Washer (Plastic Shield)

Metric Label

Plastic Shield

Warning Label

Warning Label

Cable Clamp

Front / Rear Switch Assembly

Push Rod (Front/Rear Switch)

Top Trim

Push Rod (Power Switch)

Screw

Screw

Front Panel Bracket

Screw

Display

6-4

3478A

• p. Refer to Figure 6-12. Loosen and remove screws

MP34 from the front panel connector. Remove the front panel assembly from the mother board (A1 assembly).

This completes the disassembly of the 3478A. If the display is to be removed, continue with the next step. q. To remove the display from the front panel, loosen and remove screws MP32 (see Figure 6-13) from the front panel assembly. Remove the display. This completes the front panel disassembly.

6-19. The front panel assembly was changed to the part number shown in Table 6-9 and 5-4. On these instruments, if replacing the front panel assembly, it is necessary to keep the old front panel mounting brackets and screws. The front panel assembly part number shown in Table 6-9 and 5-4 does not include these parts. If the old brackets and screws are not available use the following part numbers. The original front panel assembly is no longer available.

Bracket (2 required) 03478-01204

Screws (4 required) 0624-0333

•

6-20. 2619A26305 & below. These instruments use a Revision C 03478-66501 printed circuit board. Figure 6-4 shows schematic 1 for the Revision C circuit boards.

Figure 6-5 shows schematic 3 for the Revision C circuit boards. Schematics 2 and 4 do not change .

6-21. For replacement purposes on Revision C printed circuit boards, substitute the parts listed in Table 6-10 for the parts in Table 5-3.

Table 6·1 0. Changes to Table 5·3

Ref.

Des.

Part

Number co

Oty. Description

C510 0160-4571 8 1 CAPACITOR-FXD .1 uF

+

80-20

C761 0180-2394 1 1

CAPACITOR-FXD 3000uF 20V

CR500 1901-0518 8 1 DIODE 70V 41 OmW

L201 9100-1641 0 1 COIL-CHOKE 240uH

R109 0686-2245 3 1 RESISTOR 220K 5%)

R202 0683-2445 9 1 RESISTOR 220K .05

R203 0683-2445 9 1 RESISTOR 240K .05

205 0683-4715 0

1

RESISTOR 4 70 .05

R553 0683-5125 8 1 RESISTOR 5100 .05

RT706 0837-0223 4 1 THMS-PTC 10.30

RT707 0837-0223 4 1 THMS-PTC 10 .30

U515 1820-1144 6 1 IC SN74LS02N

Ref.

Des.

U502

Table 6-11. Changes to Table 5·3

Part

Number

1818-1752

CD

7

Oty.

1

Description

IC MK36000N5 64K

•

Backdating

6-22. 2619A32988 & below. These instruments use a Revision D 03478-66501 printed circuit board. The schematics given in section VII of this manual apply to these instruments with the following changes.

6-23. Changes to schematic 3. Delete R471. Delete C519.

6-24. Changes to schematic 4. Delete R769.

6-25. U502 was changed to a 28 pin part from a 24 pin part. The pin numbers of the 24 pin part are shown on schematic 3 in Figure 6-5. Use the part listed in Table

6-11 for replacement on Revision D printed circuit boards.

6-26. 2619A37719

& below. The aluminum cover and chassis were modified after this serial number. The new parts are not compatible with these older instruments. For replacement purposes, substitute the parts listed in Table

6-12 for the parts in Table 5-4.

6-27. 2619A37794 & below. Instruments with this serial number and below were manufactured using Pozidriv screws. To facilitate the production process, later instruments were manufactured using Torxdriv screws. If the Torxdriv screws are not desired for replacement purposes, substitute the parts listed in Table 6-13 for the parts in Table 5-4.

Ref. Des.

Table 6·12. Changes to Table 5·4

Part Number CD Oty.

Description

FRM1

CVR1

03478-00101 0

03478-04101 8

1 Chassis Assembly

1

Cover

Table 6·13. Changes to Table 5·4

Ref. Des. Part Number CD Oty Description

SCW2 0515-0063 8 2 Screw, Power Switch

Mounting

SCW3

0515-0226 5 2 Screw, Motherboard to

Front Panel

SCW4 0515-0918 2 7 Screw

SCW5 0515-1146 0

1 Screw, Bottom cover

SCW6 0624-0333 6 2 Screw, Display to Front

Panel

6-516-6

JW'501

JW503

;~g~~

JIIO

R108·

LO

=

EIOI

HI

C301

KIOI

UIOZ

Rl03

__ ,,,

RID7

- -

I

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JIOJ

~

-alW}--

--~ ~

'~ ~

CIOJ

~

.d3i''(j'"

~

0 "'

"''-~

RIOZ

LJ

CRZ02

--EZDr-

~ ~m d"'

=Q:::

Figure 6· · t Locator for

(Rev1s1on

1

j __ ,____

IP/tJ

A 1

POWER SUPPLy

1--____:__:_:::_j

03476-66501

- - - - - - - - - 1

T760

- = = = = = = = = = = = = = = = ANALOG SECTION = = = = = = = = = = = = = = : : : : : : : ;

I'

FLOATING COMMON

CR715

39V

_].

L~

11.;

w

~

CR703

RT707

10

C703

+

330 t t" f

U703

REGULATOR t

'*

CR7111

¢

17V

I

+1

C705 t

1

JM703

+15V

1+14.4V TO +15.6Vl

CR704 t

C711

1000

U701

REGULATOR t

*

CR712 t1

JM701

.r---. :r

C704

! > - - - - - -

+SV

1+4.9V TO +5.1VI

J702

F760 ft

.25A

240V

(~

0

220V

<~

I

I

j_C721

~

1000pF

1

E

!.125A AT 2ZoV OR 240Vl

" -

S760 OFF

C720 I""''

~-

J

1

0

- - " " - - - - ( " '

~~

!

I

I i

I

I

I l

I

I

I

I

I

I

I

REVISION B /

CIRCUITRY - -

rh

RT706

•i

t '

10

CR714

39V

---Jot

I

I

JM702

CR713

17V

-15V

1-14.4V TO -15.6Vl

12

13

~

14

r

- - = = = = = = = = = = = = = = = DIGITAL SECTION==============:::::::;

CHASSIS COMMON

Kf60

2K

CR762

R 7 6 4 ( »

47

0701

CR760

I

.....

I

--

C760

0.1

+SV CMOS-RAM

+---TO U512122l

3

+5V UNREGULATED

CR761

+..l..

C761 l3000

CR764

-T"

C764

I

L . . . - -

. 1

U760

REGULATOR

1

- - - - - - '

I

I

<

~---.....--+---

*

+..l..

C762 l l O

I

POWER ON

TO U50114l

U5121171

3

+5V

1+4.9V TO +5.1VJ

I

I

U__ --

COPYRIGHT 1961 BY HEWLETT-PACKARD COMPANY

- - -

- - - -

- 1 - - - - -

BT701 _j_

3.0V

--

.=... l

R765

470

--

------

--

--

--

-----

3478-1A/1

Figure 6-2. Schematic 4 (Revision B Boards)

6-7

[!]~

·C502 R529

R506 . R532 .

o

C104

· R531

R528

TPG

[!]

. csoo

·CRS01·

-C518-

-R504-

-RT505-

-C503-

-R553-

[!]W

TPlOOo

TPlOto

R501

J110

RlOB

LO

D

HI

E101

~

.JP1501

~ 1'~"1 (:.~·,

I

C512

~

YSOI

JMSC3

..,. cc

I t tf") en

I I -

(\.J

1-

0

:g~i~

I

° o o o

MP501

I

~

I

a:

;;:;

'

m

0

~~

-CSOB-

C762

[]

CR766

-R765-

8

tJ

C765

·CR760·

-C760-

·CR764

-R768-

-~7ji3-

=Rt~~=

0

T760

~

R523

_:~Rsg?·

-R524-

-R521-

00

[!]

~

=li!!ll!i:

5 s 1 o\~

- R 5 3 8 ·C.fi;\O.f!_:

-cRsas- =c!'ia§-

JM502 c=__i~

-

C31 0

-

~~

C101 -

R110

J201

I

K103

1

D

R107

J104 czot

L201

R307

C305

R302 R303

R306

_ C'30 4

. J 3 0 1 D

C313

R305

U302

C312

0

~

C306 _

C311

0-

I .,, ,,, "" -

~i::

, "'"

·

", a,

o"":,~,,

R201

UlOl

D

R205

. R204

R202

Gla4Glaz r:-<:> r:-<:>

CR201 R203 \.9_203\.Q_ZOl

1

U203

D

Glos

R206

"CR202

R207

C203

GND·

Cl'OG

Jt1302

.JH101

C105

J103 ClO? -

ClOB

C103 - Rl05 -

C102 A101 -

R106

R102

JHlOZ

-C467·-

-R406-

-R405-

-::f:tfN~

-R403-

-R404-

U404 U402

DD

R408

C431

· R466

C430

~4@

· C433 ·

C432

JM401

R407

U405

D

R469

-R463-

C464

C463 ·

· C411

· C401

C402

[!]

C405

· C404

C410

D

J401

oo-

,__ l!J

R465

R462

R466

R467

R409

~

~

:::::>

C412 m

[!]

-R47Q-

:E~~s:

Y460

~ ~

~ u

....

.... u

J702

-R4\12_:

U 703

8

COHP

~§~~~t

6

~

0 ~

:0

JM403 . m

U702

F/R SW

RT707

WRTH

LJNE

-csa

1

EXT.

:~~G. ~

-R540-

- R 5 3 4 -

-

~

-C763-VI1

-CR711-

-CR7lS-

-CR713-

-CR714~

Jl1702

Jt1703

-C468-

·CR504·

-CR712-

Jt1701

-C706-

VI

-

I

j.

A

I

B

I c

I

D

I

E

I

3478

7-G-8

FIG I HI

J

I

K

I

Figure 6-3. Revision C Component Locator

6-8

/""""-.

COMPONENT LOCATOR TABLE FOR SCHEMATIC 1 !INPUT CIRCUITRY)

Component

C101

C102

C103

C104

C105

C106

C107

C108

C201

C202

C203

C301

C314

CR201

Col.

c c c

A

E,F

E,F c c c

E

E

B

D c

Component

CR202

E101

JM101

JM201

K101

K102

K103

K104

L201

0201

Col.

E

A

F

E

B

B

B

B c

D

Component

0202

0203

0204

0405

R101

R102

R103

R104

R105

R106

R107

R108

R109

R110

Col.

D

D

D

E

D

E

B

B,C

D

E

B

A

A

B

~

SHOWN IN

OUT

POSITION

(FRONT TERMINALS)

SWITCH S1

18 17 15 15 14 13 12

11

10

0

0

1 2 3 4 5

5

7

8

9

Component

R201

R202

R203

R204

R205

R206

R207

TP100

TP101

U101

U102

U201

U202

U203

A

A

C,D

C,D

E

E

E

Col.

c

D

D

D

D

E

E

I

I

03478-66501

3

FM

U40~~~0,~~~

JM201 '

R206

4. 3K

OSENSE r4w n 1

0

l

[HI]

INPUT rzw n

1

0

[i;"O]

..,

"'

&

~

'-"

I

[fi-s-ENSE:

(4\.J 0]

1

0 ~ B~ ~

:-r-NPUT-:

, rz\J n

1 ,

"'

0

ILDI

..,

~

,~

OPVREOR;vEOC\TtoGNE

~

INPUT S W I T C H I N G = = = = = = = = = = = = = = = = = \ r

P£10

1 lB •

17

REA.A

)6'

1~ t....L

J101

I

I

I

,__L JlOB

RllO lK

Rl03

51K w..-

.£!_Ql

<>"""

·tt

2

TO U301 ~ 81 · -

~ 8

3oa

T .

1

R106

Rtos

51K

51K

~

~

4------

...

15V

W -1sv4--1sv

12

L201

Z40uH

C103

~

8

K101

GUARD

----------,

1 c:

~

J ! ; ,

1

!

I

~

~ ~~ w

'

3? '

,I:

I

J

'i: i

"::

I

I

<>

f

•SV

.

"'

1'

,_!,

/_

~ '~i=----------t------------"-~~~-jl_

t

__

•

:

...

Rt02

Rl01

SlK a

~ 51K

"

'

JlOO t

470pf

(it

I TP100 TP101

1 11.

0 c 5 MP~UcT

2

I

J~~SPG:l t OF 4 RELAY CRIVERS

;-Kl01,Kt02.,K103,K104~

) ,

R!OB

'

'

:

'

NOTE

I

TEST POINTS SPG

ARE USE I'IS fl

SP/IAK GAP. tK

K104

C301

0.15

2

+15Y +SV +15\1 d r}-

~n

TO U102 f27,2.6.Z9.'30l

42 1

:

TO Rl\.l

AC INPUT

Z7.1

1 1

•SV

CR201

F

I~Pc:ToH:MsP. =._

+lSV

02.0'3

RDZ3

233K

RD90

90K

ROOS

9K

ROO! lK

0201

R205

470

CLI(~FHU4G213213

3

' '

COPYRIGHT 1961 sY

Hf:wLETT-PACKARD COMPANY

R2.01

40K

CR202 lG, 2V

F=

OUTP:T----t--:

FET

R207

.61

- - - G

P/0

U102

OHMS CURRENT SOUJ~R~CE;-:::::::::::~-;:,::-==:::::::::::::::::::::~-~-~::::::::::::::::::::~-;:,::-~::::::-

~NBGU[FRElsttta~

+15V

:~a f

:ri6K f

:~~ f

:~s

JM101

TC~g31Z5J 3

-----o=3478-1..V3

I

Figure 6-4. Input Circuitry and Ohms Current Source

6-9/6-10

Col.

J c c

J

J

E

B

B,C

B,C

A

F

J

A

A

A

K

F

F

G

G

H

H

F,G

F,G

G

G

G

F,G

H

F

F

H

H

A

Component

C401

C402

C404

C405

C410

C411

C412

C430

C431

C432

C433

C463

C464

C465

C466

C467

C468

C501

C502

C503

C504

C506

C507

C508

C509

C510

C511

C512

C514

C515

C518

CR401

CR402

CR500

COMPONENT LOCATOR TABLE FOR SCHEMATIC 3 (LOGIC)

A

J

F

H c

A,B

B

F

F

F

G

H

H

G,H

G

E

F

F

F

F

G

G,H

G,H

G,H

F

Col.

A

J

J

J,K

H

H

H

Component

CR501

CR502

CR503

CR504

CR505

CR507

CR508

J501

J504

JM401

JM403

JM501

JM502

JM503

R401

R402

R403

R404

R405

R406

R407

R408

R409

R460

R461

R462

R463

R464

R465

R466

R467

R468

A c

K

G

H

B

Col.

F

H

A

A

A

A

D

B

H

H

H

H

A

A

J

J

H

H

A

A

K

H

J

A

Component

R521

R522

R523

R524

R528

R529

R531

R532

R534

R538

R539

R553

R469

R470

R501

R503

R504

R506

R509

R510

R517

R518

R519

R520

RT505

RP527

5501

T401

T501

TP2

A

A

D c

B

J

H

B c

D,E

E,F

E

A

G

G

F

G

F

F

F

G,H

G

H

G,H

H

B

Col.

B

B

D

A

E

B

B

Component

TP3

TP4

TP5

TP6

TP7

TP8

TP9

U401

U402

U403

U404

U405

U461

U462

U465

U466

U467

U468

U501

U502

U503

U504

U505

U506

U507

U510

U512

U513

U514

U515

U550

Y460

Y501

I

I

I

~§

I

I'

~-

H i: : i}

I

I

I

I

I

I

'~'

.~

I f--2>

I

I

I~

,;s

I~

n

SENSE'

!<1 W!~F.!

INPUT

MP5

MP3

Figure 6-6. 3478A Front Panel View

MP2

MP6

MP7 MPB

MP4

MP10

Figure 6-7. 3478A Rear Panel View

MP9

MP11

MP12

/

MP13

Figure 6-il. 347BA Bottom View

MP14 MP15

MP17

MP4 figure

!HL 347BA teft

Side View

MP24

/

MP20

-------

MP13

MP~

I

I

I

I,.

MP~

I

MP19

Figure 6·1 0. Bottom View with Cover Removed

MP27 MP28

0

/

MP20

MP13

MP31

Figure 6-11. Top View With Cover Removed

MP29

MP32

MP33

Figure 6-12. Front Panel Bracket View

MP33

Figure 6-13. Front Panel Assembly

6-13/6-14

•

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

DC Volts Test

(Serial Prefix 2520A and below)

Set-Up and

Configuration

Step# Input to

3478A

•

11

12

13

14

15

10

4

5

6

7

2

3

8

9

16

17

+3V

+3V

18

19

20

21

22

+3V

+10V

+30V

+30V

23

24 +300V

Open 25

26 See Below

Open

Short

Short

Short

Short

Short

+30mV

+300mV

+300mV

+1V

-1V

-3V

+3V

+3V

Press TEST/RESET

30mV Range

300mV Range

3V Range

30V Range

300V Range

30mV Range

300mV Range

3V Range

3V Range

3V Range

3V Range

3V Range

Autozero Off

Autozero On

4 Digit Disp

3 Digit Disp

5 Digit Disp

30V Range

30V Range

30V Range

Autozero Off

Autozero On

300V Range

30mV

CMR Test

PERFORMANCE TEST CARD

90 DAY LIMITS

High

Limit

+00.0041mV

+000.005mV

+0.00002V

+00.0003V

+000.002V

+30.0131mV

+300.027mV

+0.30004V

+ 1.00008V

-0.99992V

-2.99980V

+3.00020V

+3.00023V

+ 3.0003V

+3.001V

+03.0005V

+ 10.0010V

+30.0041V

+30.0041V

+300.029V

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

-00.0041mV

-000.005mV

-0.00002V

-00.0003V

-000.002V

+29.9869mV

+299.973mV

+0.29996V

+0.99992V

-1.00008V

-3.00020V

+2.99980V

+2.99977V

+2.9997V

+2.999V

+02.9995V

+09.9990V

+29.9959V

+29.9959V

+299.971V

Test

Pass

Test

Fail

•

1. Connect a 1 K Ohm resistor between the HI and LO INPUT

Terminals of the 34 78A.

2. Note the 34 78A's reading.

CMR Test

3. Apply 450V de between the 3478A's chassis (rear panel) and HI INPUT Terminal.

4. The 34 78A should remain within .045mV of the reading in step 2.

Page 1

PERFORMANCE TEST CARD

24 HOUR LIMITS

9

10

11

12

13

14

15

7

8

5

6

2

3

4

16

17

18

19

+3V

+3V

20

21

22

+3V

+10V

+30V

+30V

23

24 +300V

Open 25

26 See Below

Open

Short

Short

Short

Short

Short

+30mV

+300mV

+300mV

+1V

-1V

-3V

+3V

+3V

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

DC Volts Test

(Serial Prefix 2520A and below)

Step# Input to

3478A

Set-Up and

Configuration

Press TEST/RESET

30mV Range

300mV Range

3V Range

30V Range

300V Range

30mV Range

300mV Range

3V Range

3V Range

3V Range

3V Range

3V Range

Autozero Off

Autozero On

4 Digit Disp

3 Digit Disp

5 Digit Disp

30V Range

30V Range

30V Range

Autozero Off

Autozero On

300V Range

30mV Range

CMR Test

High

Limit

+00.0035mV

+000.004mV

+0.00002V

+00.0003V

+000.002V

+30.0116mV

+300.019mV

+0.30003V

+ 1.00005V

-0.99995V

-2.99988V

+3.00012V

+3.00015V

+3.0002V

+3.001V

+03.0006V

+ 10.0008V

+ 30.0018V

+30.0029V

+ 300.019V

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

-00.0035mV

-000.004mV

-0.00002V

-00.0003V

-000.002V

+29.9884mV

+299.981mV

+0.29997V

+0.99995V

-1.00005V

-3.00012V

+2.99988V

+2.99983V

+2.9998V

+2.999V

+02.9994V

+09.9992V

+29.9982V

+29.9971V

+299.981V

Test

Pass

Test

Fail

CMR Test

1. Connect a 1 K Ohm resistor between the HI and LO INPUT

Terminals of the 3478A

2. Note the 3478A's reading.

3. Apply 450V de between the 3478A's chassis (rear panel) and HI INPUT Terminal.

4. The 34 78A should remain within .045mV of the reading in step 2.

Page 2

•

•

•

•

11

12

13

14

10

15

9

20

21

22

23

24

25

26

16

17

18

19

2

3

4

5

6

7

8

•

Hewlett-Packard Model 34 78A

Digital Multimeter

Serial Number

DC Volts Test

(Serial Prefix 2520A and below)

Step# Input to

3478A

Set-Up and

Configuration

+300mV

+300mV

+1V

-1V

-3V

+3V

+3V

Open

Short

Short

Short

Short

Short

+30mV

+3V

+3V

+3V

+10V

+30V

+30V

+300V

Open

See Below

Press TEST/RESET

30mV Range

300mV Range

3V Range

30V Range

300V Range

30mV Range

300mV Range

3V Range

3V Range

3V Range

3V Range

3V Range

Autozero Off

Autozero On

4 Digit Disp

3 Digit Disp

5 Digit Disp

30V Range

30V Range

30V Range

Autozero Off

Autozero On

300V Range

30mV Range

CMR Test

PERFORMANCE TEST CARD

1 YEAR LIMITS

High

Limit

+00.0041mV

+000.005mV

+0.00002V

+00.0003V

+000.002V

+30.0161mV

+300.065mV

+0.30008V

+1.00021V

-0.99979V

-2.99942V

+3.00058V

+3.00061V

+3.0007V

+ 3.002V

+03.0009V

+ 10.0023V

+30.0063V

+30.0074V

+300.062V

Reading

Test Performed By

Date

Reference Temperature

Low

Limit

-00.0041mV

-000.005mV

-0.00002V

-00.0003V

-000.002V

+29.9839mV

+299.935mV

+0.29992V

+0.99979V

-1.00021V

-3.00058V

+2.99942V

+ 2.99939V

+2.9993V

+2.998V

+02.9991V

+09.9977V

+29.9937V

+29.9926V

+299.938V

Test

Pass

Test

Fail

•

1. Connect a 1 K Ohm resistor betwee·n the HI and LO INPUT

Terminals of the 34 78A.

2. Note the 3478A's reading.

CMR Test

3. Apply 450V de between the 3478A's chassis (rear panel) and HI INPUT Terminal.

4. The 34 78A should remain within .045mV of the reading in step 2.

Page 3

20

21

22

23

24

Open

Open 2

3 .028V,20KHz

0.28V,20KHz 4

5 0.28V,20KHz

1.5V,20KHz 6

7 2.8V,20KHz

2.8V,20KHz 8

9 28V,20KHz

28V,20KHz 10

11

280V,20KHz

0.28V,50KHz 12

13 2.8V,50KHz

14 28V,50KHz

280V,50KHz

15

16 0.28V, 1OOKHz

17 0.28V, 1OOKHz

18 2.8V, 100KHz

19 15V, 100KHz

28V, 100KHz

280V, 1OOKHz

25V,300KHz

2.8V,50Hz

2.8V,20Hz

Hewlett-Packard Model 3478A

Digital Multimeter

Serial Number

AC Volts Test

(Serial Prefix 2520A and below)

Step# Input to

347BA

Sat-Up and

Configuration

Press TEST/RESET

ACV Function

300mV Range

300mV Range

3V Range

3V Range

3V Range

30V Range

30V Range

300V Range

300V Range

300mV Range

3V Range

30V Range

300V Range

300mV Range

3V Range

3V Range

30V Range

30V Range

300V Range

30V Range

3V Range

3V Range

PERFORMANCE TEST CARD

1 YEAR LIMITS

High

Limit

Reading

028.244mV

280.975mV

0.28175V

1.50492V

2.80830V

02.8175V

28.0830V

028.194V

281.026V

281.815mV

2.81328V

28.1328V

281.720V

285.754mV

0.29449V

2.86765V

15.2400V

28.3765V

284.353V

28.8970V

2.8139V

2.83294V

Test Performed By

Date

Reference Temperature

Low

Limit

027.756mV

279.025mV

0.27825V

1.49508V

2.79170V

02.7825V

27.9170V

027.806V

278.974V

278.185V

2.78672V

27.8672V

278.280V

274.246mV

0.26881V

2.76235V

14.7600V

27.6235V

275.674V

22.1030V

2.78609V

2.76706V

Test

Pass

Test

Fail

•

•

•

Page 4

•

SECTION VII

SERVICE

7-1. INTRODUCTION

7-2. This section of the manual has information on how to troubleshoot and repair the 3478A multimeter with the information given in Service Groups. Preliminary troubleshooting procedures to select an appropriate group are also given in Paragraph 7-27. It is recommended to use the procedures first, before going to a service group. Section VII also has the 3478A's complete Theory of Operation (in Service Group F), the complete schematics (in Service Group G), and the necessary safety considerations. The section is separated as follow:

NOTE

The 3478A 's Theory of Operation is in Service Group F (next to the last group) .

• a. Safety Considerations - paragraph 7-3. b. Recommended Test Equipment- paragraph 7-8. c. Miscellaneous Information - paragraph 7-10.

1. Instrument Disassembly (PC Board

Replacement) - see Section V.

2. Fuse Replacement - paragraph 7-13. d. Troubleshooting - paragraph 7-15.

1. Introduction - paragraph 7-16.

2. 3478A Self-Test- paragraph 7-18.

3. Service Group Selection - paragraph 7-27.

7·3. SAFETY CONSIDERATIONS

7-4. The 3478A has been designed with international safety standards. To maintain these standards, the cautions, warnings, and other safety related information in this manual must be followed when servicing the instrument. Servicing should only be done by qualified service personnel.

•

7-5. Calibration, maintenance, or repair of the instrument with covers removed while any power or voltage is applied, should be avoided as much as possible.

If any work is done while power and/or voltage is applied, the work should be carried out by a skilled person who is aware of the hazards involved.

WARNING

I

Any interruptions of the protective grounding conductor (inside or outside the instrument) or disconnections of the protective earth terminal can make the instrument dangerous. Intentional interruption of the protective grounding conductor is strictly prohibited.

7-6. It is possible for capacitors inside the instrument to remain charged when the instrument has been turned off or its power source disconnected.

7-7. Make sure that only the recommended fuse type

(fast blow, correct current rating, etc.) is used for replacemant. The use of repaired fuses and the shortcircuiting of fuse holders must be avoided.

WARNING

I

The service information given in this manual is normally used with the instrument's protective covers removed and with power applied. Voltage or signals at many points may, if contacted, result in personal injury.

7-8.

RECOMMENDED TEST EQUIPMENT

7-9. The recommended test equipment is listed in Table

4-2 in Section IV of this manual.

7-10. MISCELLANEOUS INFORMATION

7-11. Instrument Disassembly (PC Board Replacement)

7-12. To replace the 3478A's main printed circuit board, the instrument must be completely disassembled.

The procedure to disassemble the instrument is in Section V (Replaceable Parts) of this manual.

7-13.

Fuse Replacement

7-14. The 3478A has two fuses, one fuse is the main power fuse and the other one is to protect the instrument in the DC and AC Current Functions. The fuses are replaced as follows:

7-1

Service a. Main Power Fuse. To replace the main power fuse, first remove power from the 3478A. With a flatblade screwdriver rotate the fuse terminal (at the rear panel) counterclockwise. Remove the fuse and reinstall with a replacement (refer to this manual's Section II or Table 5-3 for the correct value). Reinstall the terminal. b. Amps Fuse. The Amps Fuse is located inside the

3478A's A (Amps) terminal (on the front panel). To replace the fuse, first remove any cables connected to the A terminal and then turn the instrument off. Use the side slots on the A terminal to rotate the terminal counterclockwise. The terminal and fuse will then protrude from the front panel. Remove the terminal and fuse, and replace the fuse with a 3A at 250V fast blow fuse (-hp- Part No. 2110-0003). Return the terminal and fuse to the front panel.

NOTE

3478A

7-21. Control ROM Fails (U .C. ROM FAIL). This indicates that the 3478A has failed its internal ROM self test. The Control ROM (U502) is the most likely cause.

Go to Service Group D, paragraph 7-D-19, for further troubleshooting.

7-22. Calibration RAM Fails (CAL RAM FAIL). If this test fails, an attempt made to calibrate the RAM was unsuccessful. Go to Service Group D, paragraph

7-D-23 (Calibration Ram Failure) to check the CMOS

RAM.

•

7-15. TROUBLESHOOTING

The instrument contains CMOS Integrated

Circuits which are susceptible to failure due to static discharge. It is especially important that grounded tools and wrist straps be used when handling or troubleshooting these components.

7 ·16. Introduction

7-17. The following paragraphs and Service Groups have troubleshooting information and procedures for the -hp- Model 3478A Digital Multimeter. Before troubleshooting and repairing the 3478A, make sure the failure is in the instrument rather than from any external connections. Also make sure the instrument is calibrated.

7·18. 3478A Self-Test

7-19. The 3478A Self-Test is designed to make sure that most of the instrument's internal logic circuitry is operational. The test is selected when the 3478A is first turned on or by pressing the blue Shift button and then the

SGL/TRIG (TEST /RESET) button. The following paragraphs have the Self-Test Failures and some troubleshooting information.

7-20. U501 RAM Fails (U.C. RAM FAIL). This test shows that the Chassis Common CPU's (Main Controller U501) RAM has failed its internal self test. The failure is normally caused by a defective U501. To make sure U501 is the cause, go to Service Group D, paragraph 7-D-21, for further troubleshooting.

7-2

The CAL ENABLE Switch on the front panel should not be in the CALIENABLE position under normal use. It should only be in that position to calibrate or troubleshoot the instrument.

7-23. Uncalibrated Instrument (UNCALIBRATED).

Calibrate the 3478A.

7-24. A/D Link Fails (A:D LINK FAIL). The failure shows that the Chassis Common Processor (Main Controller, U501) is unable to communicate with the

Floating Common Processor

(AID

Controller, U462).

Go to Service Group D, paragraph 7-D-44 (Isolation

Circuitry Troubleshooting) for troubleshooting.

7-25. A/D Slope Error (A:D SLOPE ERR). If the

AID

Converter is unable to do a proper conversion, this test fails. Go to Service Group D, paragraph 7-D-35

(AID

Converter Troubleshooting) for troubleshooting.

7-26. A/D Test Fails (A:D TEST FAIL). This shows that the

AID

Converter has failed its internal self test.

Go to Service Group D, paragraph 7-D-35

(AID

Converter Troubleshooting) for troubleshooting.

7-27. Service Group Selection

Table 7-1. 3478A Service Groups

Service

Group

Title

A DC Volts and DC Current Troubleshooting

B AC Volts and AC Current Troubleshooting c

Ohms Troubleshooting

D

AID Converter and Logic Troubleshooting

E Power Supplies and Reference Troubleshooting

F Theory of Operation

G Schematics

7-28. The Service Groups have the Troubleshooting Information, Theory of Operation, and Schematics for the 3478A. Service Group F has the Theory of Operation and Service Group G has the Schematics. The rest of the groups have troubleshooting information.

•

•

Service

•

3478A

7-29. The correct Service Group is selected according to failure. Once the failure has been determined, go to the recommended group. The following paragraphs lists possible failures, general troubleshooting information, and corresponding Service Group(s). The Service

Groups are also listed in Table 7-1.

7-30. DC Volts and DC Current Failure (Service Group

A). Typical DC Volts and DC Current Failures are

Overload, Inaccurate, Constant Zero, Floating, or

Noisy Readings. Troubleshooting information for these failures is in Service Group A. The following explains the failures. a. Overload. An overload is caused when the reading taken by the instrument appears to be larger than the input actually is. This can be caused by a saturated

DCIOhms Input Amplifier or by the

AID

Converter. b. Inaccurate Readings. Inaccurate readings are normally caused when the measurement circuitry is not linear. This is because the 3478A is calibrated using zero and full scale inputs. Therefore, the full scale and zero readings must be good, but any other reading can be inaccurate.

• c. Constant Zero Reading. A constant zero reading is normally caused when either the input to the DCIOhms

Input Amplifier or the input to the

AID

Converter is shorted to ground (common). It can also be caused if no runup is done by the

AID

Converter. d. Floating Reading. A floating reading is when the

3478A displays a certain reading (with no input applied) which does not change, after an input is applied to the multimeter. This can be caused by the

AID

Converter and if there is an open in the Input Circuitry. e. Noisy Readings. Noisy readings can be caused by the Input Circuitry and

AID

Converter.

7-31. AC Volts and AC Current Failures (Service

Group B). AC Volts and AC Current Failures can be

Overload, Inaccurate, Floating, or Noisy Readings.

Troubleshooting information for these failures is in Service Group B. Before going to the service group, check and make sure the DC Volts and DC Current Function is operating correctly. The DC Volts and DC Current failures are explained in paragraph 7-30. The following explains the AC Volts and AC Current Failures. a. Overload. An overload is caused when the reading taken by the instrument appears to be larger than the in-

• put actually is. This can be caused by a saturated ACto

DC Converter or the

AID

Converter . b. Inaccurate Readings. Inaccurate readings are normally caused when the AC to DC Converter has poor frequency response. c. Floating Reading. A floating reading is when the

3478A displays a certain reading (with no input applied) which does not change, after an input is applied to the multimeter. This can be caused if there is an open circuit in the AC to DC Converter or

AID

Converter. d. Noisy Readings. Noisy readings can be caused by the amplifiers and the RMS Converter in the AC to DC

Converter.

7-32. Ohms Failures (Service Group C). Typical Ohms

Failures can be Overload, Inaccurate, Floating, or

Noisy Readings. Troubleshooting information for these failures is in Service Group C. Before going to the service group, check and make sure the DC Volts and DC

Current Functions are operating correctly. The DC

Volts and DC Current failures are explained in paragraph 7-30. The following explains the Ohms

Failures. a. Overload. An overload is caused when the reading taken by the instrument appears to be larger than the input actually is. This can be caused if the ohms current is too large. Since the DCIOhms Input Amplifier or the

AID

Converter can also cause an overload, make sure the DC Volts Function is operating correctly (go to paragraph 7-30, if the function fails). b. Inaccurate Readings. Inaccurate ohms readings can be caused if the ohms current changes value under different loads. Inaccuracy can alo be caused if the measurement circuitry is not linear. Make sure the DC

Volts Function is operating correctly (go to paragraph

7-30, if the function fails). c. Constant Zero Reading. A constant zero reading is normally caused when the Ohms Current Source does not supply any ohms current. The failure can also be caused when either the input to the DCIOhms Input

Amplifier or the input to the

AID

Converter is shorted to ground (common). Make sure the DC Volts Function is operating correctly (go to paragraph 7-30, if the function fails). d. Floating Reading. A floating reading is when the

3478A displays a certain reading (with no input applied) which does not change, after an input is applied to the multimeter. This can also be caused by the

AID

Converter and the Input Circuitry. Since this is not an ohms failure, make sure the DC Volts Function is operating correctly (go to paragraph 7-30, if the function fails). e. Noisy Readings. Noisy readings can be caused by a noisy ohms current.

7-33. Chassis Common Logic Failures (Service Group

D).

Chassis Common Logic Failures consists of Turn-

On, Display, Keyboard, Control ROM, Calibration

RAM (CMOS RAM), HP-IB Failures, and miscellaneous failures (e.g. Voltmeter Complete, Exter-

7-3

7-4

Service nal Trigger, etc). Go to Service Group D, paragraph

7-D-5, if any of the failures are detected. The following explains the failures. a. Turn-On Failure. A Turn-On Failure is when the

3478A's Keyboard Display, and HP-IB is dead (i.e., the

3478A is completely inoperative). This is most likely caused by the Main Controller (U501) and associated circuitry. b. Inoperative Display. An Inoperative Display is when part or all of the 3478A's display is inoperative.

This can be caused by the display itself or the Main Controller Circuitry. c. Inoperative Keyboard. An Inoperative Keyboard is when part or all of the 3478A's keyboard is inoperative. This can be caused by the keyboard itself or the Main Controller Circuitry. d. Control ROM Failure. A failure caused by the

Control ROM normally shows up as a "U.C, ROM

FAIL" (after the 3478A's Self-Test). The ROM (U502) itself can be the cause in addition to the Main Controller

(U501) and latch U513. A defective ROM can also show up as a Turn-On Failure. e. U.C. RAM Fails. This failure shows up as a "U.C.

RAM FAIL" after the 3478A's Self-Test routine. It shows that the Main Controller's internal RAM has failed its self-test. f. Calibration RAM (CMOS RAM) Failure. This failure can show up as a "CAL RAM Fail" after the

3478A's Self-Test routine. The RAM (U512) itself can be the cause or the Main Controller Circuitry. g. HP-IB (Remote) Failure. This failure is most likely caused by the HP-IB Chip (U503), but can also be caused by other circuitry in the Chassis Common Logic

Circuitry.

Reference Circuitry.

3478A

7-34. Floating Common Logic Failures (Service Group

D). Floating Common Logic Failures are normally caused by the AID Converter or the AID Controller (U462).

Go to Service Group D, paragraph 7-D-31 for troubleshooting. The following explains the failures. a. Overload, Constant Zero, Floating, or Noisy

Readings. Any one of these failures can be caused by the

AID Converter or the 3478A's Input Circuitry (Input

Switching or

DCIOhms Input Amplifier). Since both circuitry can cause a failure, a procedure to isolate the circuitry is in both Service Group D and Group A. For a definition of the failures, go to paragraph 7-30 (DC

Volts Failures). b.

AID Slope Error. This failure can be caused by the AID Converter or the AID Controller and shows up as an "A:D SLOPE ERR", after a Self-Test routine. c. AID Test Fails. This failure can also be caused by the AID Converter or the AID Controller. It shows up as an "A:D TEST FAIL", after a Self-Test routine. d. Input Hybrid (U102) Failure. Since the Input

Hybrid receives its set up information from the

AID

Controller, the controller can cause the hybrid to fail.

•

7-35. Isolation Circuit Failure (Service Group D). This failure will normally show up as an "A:D Link Fail"

(after the 3478A's Self-Test routine). The failure can be caused by the Isolation Circuitry, or either the Main

Controller (U501) or AID Controller (U462).

Troubleshooting information is in Service Group D, paragraph 7-D-44.

7-36. Power Supplies and Reference Troubleshooting

(Service Group E). Service Group E has some information on how to troubleshoot the power supplies and

•

•

•

SERVICE GROUP A

DC VOLTS AND DC CURRENT TROUBLESHOOTING

Service Group A Contents

Title Paragraph

Introduction ................................ 7-A-1

Pre-Troubleshooting Information .............. 7-A-3

DC Volts Troubleshooting .................... 7-A-5

Overload, Floating, Constant Zero (with input applied), or Noisy Readings on All Ranges ...... 7-A-7

Constant Zero Readings (with no input applied) on

All Ranges .............................. 7-A-9

Overload, Constant Zero, Floating, or Noisy

Readings on Some Ranges ................ 7-A-11

Inaccurate Readings on All Ranges .......... 7 -A-17

Protection Circuitry Troubleshooting .......... 7-A-19

Input Circuitry Troubleshooting .............. 7-A-21

Overload Readings on All Ranges ........... 7-A-23

Constant Zero Readings on All Ranges ...... 7-A-25

Floating Readings on All Ranges ............ 7-A-27

Noisy Readings on All Ranges .............. 7-A-29

DC Current Troubleshooting ................. 7-A-31

Checking the AID Controller ................ 7-A-33

7·A·1. INTRODUCTION

•

7-A-2. This Service Group has the DC Volts and DC

Current troubleshooting information for the 3478A.

The Service Group is symptoms oriented (i.e., what fails) with two different levels of troubleshooting. The first level determines the general area of the 3478A that causes the failure and the second level has specific troubleshooting information for the area that fails.

Unless otherwise specified, refer to Schematic 1 when using the troubleshooting procedures.

The instrument contains CMOS Integrated

Circuits (e.g. U102) which are extremely susceptible to failures due to static discharge. It is especially important that grounded tools and wrist straps be used when handling or troubleshooting these components.

7·A·3. PRE-TROUBLESHOOTING INFORMATION

7-A-4. Before doing any troubleshooting procedures,

• perform the following: a. Check the 3478A's Floating Common Power Supplies and make sure they are stable, have the correct value, and are not oscillating. The power supplies are as follows (see Schematic 4):

Power

Checked

Supply at

+

5V JM701

-15V JM702

+

15V JM703

Voltage

Level

+

4.9V to

+

5.1V

- 14.4V to - 15.6V

+

14.4V to

+

15.6V b. Check and make sure the Reference Supplies are at the correct level and quiet. The

+

IOV supply can be checked at U405 pin 6, the -lOY supply at U404 pin 6, and the buffered

+

IOV supply at JM201 (see Schematic

3). c. Make sure the Front/Rear Switch is making good contact and not open.

7-A-5. DC VOLTS TROUBLESHOOTING

7-A-6. Typical DC Volts Failures are Overload, Inaccurate, Constant Zero, Floating, or Noisy Readings on all or some ranges. The following paragraphs have the failures and the troubleshooting procedures (see paragraph 7-30 for a description of these failures).

7 ·A· 7. Overload, Floating, Constant Zero (with input ap· plied), or Noisy Readings on All Ranges

7-A-8. If a failure is noted on all ranges, the failure can be caused by the Input Circuitry (Input Switching or

DC I Ohms Input Amplifier) or by the AID Converter.

To determine the inoperative circuitry, do the procedure which follows this paragraph (the same procedure is

7-A-1

Service 3478A also in Service Group D). If the procedure has been performed already, ignore the procedure and go to paragraph 7-D-21 for troubleshooting. If it has not been performed, do the following: a. Set the 3478A to the DC Volts Function and the

3V Range. b. Turn Autozero off by pressing the blue Shift button and then the INT /TRIG (AUTOZERO) button. c. Apply a stable + 3V de to the INPUT Terminals. d. With a Digital Voltmeter (like the 3456A) measure for +lOY at JM101. e. Make sure the reading on the test voltmeter is a stable + 1 OV. If the reading on the test voltmeter is a stable + IOV, the

AID Converter is at fault. Go to Service Group D for troubleshooting. f.

If the reading on the test voltmeter is wrong

(overload, constant zero, floating, or noisy), unsolder and lift the end of jumper JM101 which is connected to the AID Converter (toward the rear of the 3478A). g. If the reading on the test voltmeter is now good, the AID Converter is at fault. Go to Service Group D for troubleshooting. h.

If the reading is still wrong, the Input Circuitry

(Input Switching and DC/Ohms Input Amplifier) is at fault. Go to paragraph 7-A-21 for troubleshooting. i. Replace jumper JM101.

7-A-9. Constant Zero Readings (with no input applied) on

All Ranges

7-A-10. Since the 3478A's 30V and 300V Ranges will normally have a constant zero reading with no input applied, the other ranges will also be at zero if relay K102 is shorted. Make sure the relay is good and is not being turned on by U102 (zero volts across the coil of K102). If the relay is turned on in the 30mV through 3V Ranges, U102 may be defective. Before replacing Ul02, make sure the

AID Controller (U462) is good. Go to paragraph 7-A-33 for the SA procedure to check U462, before replacing the hybrid.

7 -A-11. Overload, Constant Zero, Floating, or Noisy

Readings on Some Ranges

7-A-12. The Input Hybrid (U102) in conjunction with the Input Relays (KlOl through K104) is used to select different paths to connect the input signals with the

DC/Ohms Input Amplifier. The hybrid is also used to select the amplifier's different gain configurations.

Because of this, a relay or U102 can make certain ranges fail.

7-A-2

7-A-13. Overload. An overload condition exists if the

DC/Ohms Input Amplifier's feedback circuitry is open.

Since the feedback circuitry is in Ul02, the hybrid is most likely defective. Before replacing U102, make sure the

AID Controller (U462) is good. Go to paragraph

7-A-33 for the SA procedure to check U462, before replacing the hybrid.

7-A-14. Constant Zero Reading. The most likely cause is the Input Hybrid (Ul02). Before replacing U102, make sure the AID Controller (U462) is good. Go to paragraph 7-A-33 for the SA procedure to check U462, before replacing the hybrid.

7-A-15. Floating Readings. A floating reading is normally caused when an input path to the DC/ Ohms Input

Amplifier is open. Check for the following: a. If the 30m V, 300m V, and 3V Ranges are defective, do the following:

1. Short across the contacts of relay KlOl.

2. If the ranges are now good, make sure KIOl is energized (5V de across the coil). If KIOl is energized, replace the relay. If not, U102 may be defective. Go to paragraph 7-A-33 before replacing U102.

3. If, after replacing KlOl, the ranges still fail,

U102 may be defective. Go to paragraph 7-A-33 before replacing U102. b. If the 30V and 300V Ranges are defective, do the following:

1. Short across the contacts of relay Kl02.

2. If the ranges are now good, make sure Kl02 is energized (5V de across the coil). If K102 is energized, replace the relay. If not, Ul02 may be defective. Go to paragraph 7-A-33 before replacing U102.

3. If, after replacing Kl02, the ranges still fail,

U102 may be defective. Go to paragraph 7-A-33 before replacing U102.

7-A-16. Noise. Noise can be caused by a FET switch internal to the Input Hybrid (U102) and UlOl. Replace

UlOl and then U102 if noise is noted on some ranges.

7-A-17. Inaccurate Readings on All Ranges

7-A-18. Inaccurate readings normally show up as other than positive full scale readings. This is because the

3478A is calibrated using zero and positive full scale (or

1/3 scale) inputs. Inaccurate readings can be caused by the Input Circuitry (Input Hybrid or DC/Ohms Input

Amplifier). Try replacing UIOl and then U102.

•

•

•

3478A

•

7-A-19. PROTECTION CIRCUITRY TROUBLESHOOTING

7-A-20. This circuitry consists of E101 and various diodes in U102. If all ranges fail, try replacing ElOl. If the ranges still fail or some ranges fail, the most likely cause is U102.

7-A-21. INPUT CIRCUITRY TROUBLESHOOTING

7-A-22. The Input Circuitry consists of the Input

Switching Circuitry and the DC

I

Ohms Input Amplifier.

Before troubleshooting the circuitry, make sure the failure is not caused by the AID Converter. Go to paragraph 7-A-5 to determine the faulty circuitry, if it has not been done already.

7-A-23. Overload Readings on All Ranges

7-A-24. An overload can be caused when the output of the DCIOhms Input Amplifier is too high. This can be caused by an excessive input to the amplifier, open feedback, or a defective amplifier. Do the following: a. Set the 3478A to the DC Volts Function and the

3V Range. b. Make sure Autozero is turned off (see paragraph

•

7-A-8 step b). c. Short the 3478A's INPUT Terminals. d. With a high impedance Digital Voltmeter (like the

3456A) measure for zero volts(± 1mV) at Ul01 pin 3

(U102 pin 10). e. If the reading on the test voltmeter is other than zero volts (i.e., above 1 m V), the Input Hybrid is defective. Replace U102. f. If the reading is good, connect pin 6 and pin 2

(U102 pin 3 and 9) of U101 to each other. Using the test voltmeter, measure for zero volts (±3m V) at pin 6 of

U101. g. If the reading is good (less than ±3m V), the amplifier feedback circuitry is defective. Replace U102. h. If the reading is wrong (greater than 3m V), the amplifier is defective. Replace U101.

7-A-25. Constant Zero Readings on All Ranges

7-A-26. A constant zero reading is normally caused when the input or output of the DCIOhms Input

Amplifier is shorted to ground. Make sure pin 1 and pin

•

13 of U102 and pin 6 of U101 are not shorting to ground. If no shorts are noted, do the following: a. Set the 3478A to the DC Volts Function and the

3V Range.

Service b. Make sure Autozero is turned off (see paragraph

7-A-8 step b) . c. Using an external power supply with a lOOK ohm resistor in series, apply

+

3V to pin 3 of UlOl. (Connect one end of the resistor to pin 3 of U101 and the other end to the power supply.) d. Using a high impedance Digital Voltmeter (like the

3456A), make sure the voltage at the resistor end connected to pin 3 of Ul01 is

+

3V. e. If the voltage is loaded down, the Input Hybrid is defective. Replace U102. f. If the voltage is

+

3V, measure (using the test voltmeter) for approximately

+

10V at U101 pin 6. g. If the voltage is incorrect, the Input Amplifier is at fault. Replace U101. h. If the voltage is good, the Input Hybrid (U102) may be defective. Before replacing U102, make sure the

AID

Controller (U462) is good. Go to paragraph

7-A-33 to check the AID Controller. If the controller is good, replace U102.

7-A-27. Floating Reading on All Ranges

7-A-28. A floating reading is normally caused when an open exists between the DCIOhms Input Amplifier and the instrument's INPUT Terminals. Before troubleshooting the Input Circuitry, make sure the wire connected from the Front/Rear Switch to J108 is not open. If the wire is good, then do the following: a. Set the 3478A to the DC Volts Function and the

3V Range. b. Make sure Autozero is turned off (see paragraph

7-A-8 step b). c. Using an external power supply, apply

3478A's INPUT Terminals.

+

3V to the d. Connect the 3478A's HI INPUT Terminal to U101 pin 3 (U102 pin 10). e. If the displayed reading on the 3478A is still a floating reading, replace UlOl. f. If the displayed reading on the 3478A is

+

3V, the

Input Hybrid (U102) may be at fault. Before replacing

U102, make sure the AID Controller (U462) is good.

Go to paragraph 7-A-33 to check the AID Controller. If the controller is good, replace U102.

7-A-29. Noisy Readings on All Ranges

7-A-30. Noisy readings can be caused by the Input

7-A-3

..

7-A-4

Service

Hybrid or the DCIOhms Input Amplifer. Do the following: a. Set the 3478A to the DC Volts Function and the

3V Range. b. Make sure Autozero is turned off (see paragraph

7-A-8 step b). c. If the reading on the 3478A is quiet with Autozero off, the Input Hybrid is defective. Replace U102. If the reading is still noisy, continue with the next step. d. Connect pin 6 and pin 2 (U102 pin 3 and 9) of

U 101 to each other. e. Apply a stable minals.

+

3V to the 3478A's INPUT Terf. Using a high impedance Digital Voltmeter (like the

3456A) measure for a stable

+

3V at UlOl pin 3. g. If the voltage is noisy, replace the Input Hybrid

(U102). h. If the voltage is stable, measure for a stable at pin 6 of UlOl.

+

3V i. If the voltage is noisy, replace UlOl. If the voltage is stable, replace U102 (Input Hybrid).

7·A·31. DC CURRENT TROUBLESHOOTING

7-A-32. Make sure the DC Volts Function is operating correctly on all ranges, before troubleshooting for de current failures. Go to paragraph 7-A-5 to troubleshoot for DC Volts Failures. If the DC Volts Function is good, the only components that can cause a current failure are an open current fuse (FlOl), a defective resistor R107, or the Input Hybrid U102. Make sure

FlOl and R107 are good. If the resistor and fuse are good, U102 may be defective. Before replacing U102, make sure the AID Controller (U462) is good. Go to paragraph 7-A-33 to check the AID Controller. If the controller is good, replace U102.

3478A

7·A·33. CHECKING THE AID CONTROLLER (U4621

7-A-34. Do the following to check the AID Controller.

Refer to Schematic 3. a. Turn the 3478A off. b. Move jumpers JM502, JM503, and JM403 to the

"D" position (JM403 pin 1 and 2), as shown in Figure

7-A-1. c. Obtain a Signature Analyzer. Set and connect as follows (shown in Figure 7-A-1):

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd:

TP401 (JM403 pin 6)

( f )

TP402 (JM403 pin 5) ( \.. )

TP403 (JM403 pin 4) ( . / )

Out

Out

Ground Pin (next to C203)

PIN

#

JM403

347[j 7 Al

4

5 5

~o----~o----~o--~ u

><: u

D

_J r r r

[]__

D

1-a:

<C

1--

1-·

(f)

(f)

Figure 7·A·1. JM403 SA Connection

d. Turn the 3478A on and check the following signatures.

U462 pin 32: 7 ACA

U462 pin 33: 20FO

U462 pin 34: 666H e. If any signatures are wrong, go to Service Group D

(Flowchart D) for troubleshooting. f. If the signatures are good, the Input Hybrid is defective.

•

•

•

•

SERVICE GROUP B

AC VOLTS AND AC CURRENT TROUBLESHOOTING

Service Group B Contents

Title Paragraph

Introduction ................................ 7-B-1

AC Volts Troubleshooting .................... 7-B-3

Overload, Floating, or Noisy Readings on

All Ranges .................................. 7-B-5

Inaccurate Readings on All Ranges ........... 7-B-8

Overload, Inaccurate, Floating or Noisy Readings on

Some Ranges .............................. 7-B-10

AC Current Troubleshooting ................. 7-B-12

Overload Protection Circuitry Troubleshooting. 7-B-14

Checking the

AID

Controller ................. 7-B-16

7-B-1. INTRODUCTION

7-B-2. This Service Group has the AC Volts and AC

Current troubleshooting information for the 3478A and is symptoms oriented (i.e., what fails). Before

• troubleshooting for AC Volts or AC Current Failures, make sure the 3478A's DC Volts and DC Current Functions are operating correctly (go to Service Group A, if the functions fail). These functions must be good, before the AC Volts and AC Current Functions can operate.

The instrument contains CMOS Integrated

Circuits (e.g. U102) which are extremely susceptible to failures due to static discharge. It is especially important that grounded tools and wrist straps be used when handling or troubleshooting these components.

7-B-3. AC VOLTS TROUBLESHOOTING

7-B-4. An AC Volts Failure can be Overload, Inaccurate, Floating, or Noisy Readings on all or some ranges. The following paragraphs have the failures and troubleshooting procedures (go to paragraph 7-31 for a description of these failures). Unless otherwise specified, refer to Schematic 2 for the following troubleshooting procedures.

Ranges

•

7-B-5. Overload, Floating, or Noisy Readings on All

7-B-6. An overload reading can be caused if one of the amplifiers or the RMS Converter in the AC to DC Converter is saturated. A floating reading can be caused if there is an open circuit in the AC to DC Converter.

Noisy readings can be caused by any of the amplifiers in the converter.

7-B-7. Before troubleshooting the AC to DC Converter, make sure relay K104 (see Schematic 1) is good and is energized (5V de across the coil). If the relay is not energized, U102 may be defective. Before replacing

U102, make sure the

AID

Controller (U462) is good.

Go to paragraph 7-B-16 to check U462.

If

K104 is good, do the following procedure. a. Set the 3478A to the AC Volts Function and the

3V Range. b. Apply a stable 3V at 1KHz sine wave to the

3478A's INPUT Terminals. c. Using a stable Digital Voltmeter (like the 3456A), measure for approximately

+

3V de at jumper JM302. d. If the reading is a stable ing:

+

3V de, do the follow-

1. Apply 1 Vat 1KHz to the INPUT Terminals.

2. If the test voltmeter now reads a stable

+

1 V de at JM302, the AC to DC Converter is good.

Make sure the DC Volts Function is operating correctly.

3. If the DC Volts Function is good, replace the

AID

Hybrid (U403). e. If the reading is other than approximately

+

3V or noisy, measure for approximately .12V ac at jumper

JM303. Make sure the reading on the test voltmeter is stable.

7-B-1

3478A

Service f. If the reading is good, do the following:

1. Measure for a stable 3V ac at pin 4 of U303.

2. If the reading is good, replace U303.

3. If the reading is wrong, lift the end of capacitor C304 which is connected to pin 4 of

U303. Then measure for a stable 3V ac at the lifted end of the capacitor.

4. If the voltage is good, replace U303.

5.

If the voltage is still wrong, make sure the voltage at pin 6 of U302 is a good stable 3V ac.

6. If the voltage is good, capacitor C304 or

C306 is defective.

7. If the voltage is unstable or wrong, connect pin 6 to pin 2 of U302 (use a very short lead to connect the pins, to prevent oscillations). If the reading at pin 6 is now a stable .12V, the feedback resistors of U302 are defective. If the .12V is wrong, replace U302. g. If the reading at JM303 is other than .12V ac or unstable, replace U301. If the AC Volts Function is still inoperative, U102 may be defective. Before replacing

U102, make sure the AID Controller (U462) is good.

Go to paragraph 7-B-16 to check the

AID Controller.

If the controller is good, replace U102.

7 ·B-8. Inaccurate Readings on All Ranges

7-B-9. Since the 3478A's AC to DC Converter is calibrated with an input voltage at a frequency of 1KHz, inaccuracy can result from poor frequency response.

Since the high frequency is compensated by C302, make sure the capacitor is good. If the capacitor is good, try replacing U301 and if still inaccurate, try U102.

7-B-1 0. Overload, Inaccurate, Floating, or Noisy

Readings on Some Ranges

7-B-11. Since all ranging of the ACto DC Converter is done in the Input Hybrid U102, the hybrid is the most likely cause for ac failures on some ranges. Before replacing U102, make sure it is not set to an incorrect mode by the AID Controller (U462). Go to paragraph

7-B-16 to check the AID Controller. If the controller is good, replace U102.

7-B-12. AC CURRENT TROUBLESHOOTING

7-B-13. Make sure the DC Current and AC Volts Functions are operating correctly on all ranges, before troubleshooting for ac current failures. Go to paragraph

7-B-3 to troubleshoot the AC Volts Failures and Service

Group A for the DC Current Failures. If the functions

7-B-2 are good, the only component that can cause a failure is the Input Hybrid U102. Before replacing Ul02, make · • sure the AID Controller is good. Go to paragraph

7-B-16 to check the AID Controller. If the controller is good, replace U102.

7-B-14. OVERLOAD PROTECTION CIRCUITRY

TROUBLESHOOTING

7-B-15. All of the ac functions overload protection circuitry is in U102. Replace the hybrid, if defective.

7-B-16. CHECKING THE A/D CONTROLLER (U462)

7-B-17. Do the following to check the AID Controller.

Refer to Schematic 3. a. Turn the 3478A off. b. Move jumpers JM502, JM503, and JM403 to the

"D" position (JM403 pin 1 and 2), as shown in Figure

7-B-1. c. Obtain a Signature Analyzer. Set and connect as follows (shown in Figure 7-B-1):

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd:

TP401 (JM403 pin 6) (

J)

TP402 (JM403 pin 5) ( ""\.. )

TP403 (JM403 pin 4) (

J )

Out

Out

Ground Pin (next to C203) d. Turn the 3478A on and check for the following signatures.

U462 pin 32: 7 ACA

U462 pin 33: 20FO

U462 pin 34: 666H e. If any signatures are wrong, go to Service Group D

(Flowchart D) for troubleshooting. f. If the signatures are good, the Input Hybrid is defective.

2

PIN

#

3

4

5

JM403

D

N do

ol

0

0 0 0

>a::

<

>-

(f) i

347!1 7 A1 u

_j

0

0<: u i i

[L

0

1-·

(f)

Figure 7-B-1. JM403 SA Connection

6

•

•

•

SERVICE GROUP C

OHMS TROUBLESHOOTING

Service Group C Contents

Title

Paragraph

Introduction ................................ 7-C-1

2-Wire and 4-Wire Ohms Troubleshooting ....... 7-C-4

Overload Readings on All Ranges ............ 7-C-6

Inaccurate Readings on All or Some Ranges ........................... 7-C-8

Constant Zero Reading on All Ranges ....... 7-C-10

Noise on All Ranges ...................... 7-C-12

Floating Readings on All or Some Ranges .......................... 7-C-14

Overload, Noise, or Constant Zero

Readings on Some Ranges ............... 7-C-16

Ohms Protection Circuitry Troubleshooting .... 7-C-18

Ohms Current Source Troubleshooting ........ 7-C-20

4-Wire Ohms Troubleshooting ................ 7-C-22

Checking the AID Controller ................. 7-C-24

•

7·C·1. INTRODUCTION

7-C-2. This Service Group has the Ohms troubleshooting information for the 3478A and is symptoms oriented (i.e., what fails). Unless otherwise specified, refer to Schematic 1 when using the troubleshooting procedures. failure on the 3K ohm Range should show up with a 3K ohm resistor applied to the input. The following paragraphs have the ohms failures and the troubleshooting procedures (go to paragraph 7-32 for a description of the failures).

7-C·&. Overload Readings on All Ranges

7-C-3. Most ohms failures will show up in both the

2-Wire and 4-Wire Ohms Function with the troubleshooting procedure given in paragraph 7-C-4.

If a failure shows up in only the 4-Wire Ohms Function, go to paragraph 7-C-22 for troubleshooting.

7-C-7. An Overload is normally caused by a high ohms current (or an open between the INPUT Terminals and the Input Circuitry). Make sure the DC Volts Function is operating correctly, before troubleshooting for an ohms failure. Do the following procedure. a. Set the 3478A to the 2-Wire Ohms Function and the 3K ohm Range. b. Connect a 3K ohm Resistor to the 3478A's INPUT

Terminals.

The instrument contains CMOS Integrated

Circuits (e.g. Ul02) which are extremely susceptible to failures due to static discharge. It is especially important that grounded tools and wrist straps be used when handling or troubleshooting these components.

•

7·C·4. 2-WIRE AND 4·WIRE OHMS TROUBLESHOOTING

7-C-5. An Ohms Failure can be Overload, Inaccurate,

Constant Zero, Floating, or Noisy Readings on some or all ranges. A failure should show up with an appropriate input applied to the 3478A. For example, an overload c. Using a high impedance Digital Voltmeter (like the

3456A), measure the voltage between pin 17 and pin 19 of Ul02. Connect the low input of the voltmeter to pin

17 and the high input to pin 19. d. If the reading on the test voltmeter is

+

4V de and the 3478A displays an overload, the Range Resistors in

Ul02 may be too low. Replace Ul02 . e. If the reading is other than

+

4V de, the Ohms

Current Source is defective. Go to paragraph 7-C-20 for troubleshooting.

7-C-1

Service

7-C-8. Inaccurate Readings on All or Some Ranges

7-C-9. This failure is normally caused when the ohms current changes value due to a load change. Do the following procedure. a. Set the 3478A to the 2-Wire Ohms Function and the 3K ohm Range. b. Connect a 3K ohm Resistor to the 3478A's INPUT

Terminals. c. Using a high impedance Digital Voltmeter (like the

3456A), measure the voltage across R205. Since the ohms current on the 3K ohm Range is 1mA, the voltage should be approximately .47V de. d. If the voltage is radically wrong, the ohms current is incorrect. Use the overload troubleshooting procedure (in paragraph 7-C-6) to determine the faulty circuitry. e.

If the voltage is good, remove the 3K ohm Resistor from the INPUT Terminals. Then short the INPUT

Terminals. f. If the voltage across R205 changes, the Output

PMOS FET in U102 may be defective. Replace U102. g. If the voltage remains the same, the failure is most likely in the Ohms Protection Circuitry. Make sure

Q201 through Q204 are good.

7-C-10. Constant Zero Reading on All Ranges

7-C-11. A Constant Zero Reading is normally caused when the Ohms Current Source supplies no ohms current (current at zero value). Since no current goes through the resistor to be measured, no voltage drop across the resistor is developed and the 3478A measures zero volts (zero reading). A no-current condition can be caused by an open circuit between the Ohms Current

Source and the INPUT Terminals, or by a defective

Current Source. Do the following procedure. a. Set the 3478A to the 2-Wire Ohms Function and the 3K ohm Range. b. Connect a 3K ohm Resistor to the 3478A's INPUT

Terminals. c. Using a clip lead, connect pin 15 of U102 to the

3478A's HI INPUT Terminal. d. If the 3478A still shows a constant zero reading, the Ohms Current Source is inoperative. Go to paragraph 7-C-20 for troubleshooting. e. If the Ohms Function is now operating correctly, do the following:

7-C-2

3478A

1. Disconnect the clip lead from pin 15 of U102 and connect it to the collector of Q204 (junction of Q204, R203, and cathode of CR201). Leave the other end of the clip lead connected to the input terminal for the checks that follow.

2.

If the Ohms Function is now operating, check for an open R205 or an open in Q201 through Q204.

3. If the Constant Zero Reading is still displayed, disconnect the clip lead from Q204 and connect it to the anode of CR201.

4.

If the Ohms Function is now operating, check for an open CR201.

5. If the Constant Zero Reading is still displayed, check for an open K103. Make sure

K103 is energized (

+

5V across the relay coil), before replacing the relay.

If the relay is not energized, U102 may be defective. Before replacing U102, make sure the A/D Controller (U462) is good. Go to paragraph 7-C-24 for the SA procedure to check U462.

7-C-12. Noise on All Ranges

7-C-13. Noise on all ranges is normally caused by a noisy ohms current. Do the following procedure . a. Set the 3478A to the 2-Wire Ohms Function and the 3K ohm Range. b. Connect a 3K ohm Resistor to the 3478A's INPUT

Terminals. c. Using a clip lead, connect pin 15 of U102 to the

3478A's HI INPUT Terminal. d. If the Ohms Function is quiet, noise is caused by the Ohms Protection Circuitry. Check Q201 through

Q204. e. If the Ohms Function is still noisy, do the following checks.

1. Using a high impedance Digital Voltmeter

(like the 3456A), make sure the voltage at U201 pin 6 is a quiet

+

8V (

<

101-'V change). Replace

U201, if noisy. If the voltage is still noisy, try

U102.

2. If the voltage at U201 pin 6 is good, measure for a quiet

+

12V at U202 pin 6 (

<

101-'V change).

Replace U202, if noisy. If the voltage is still noisy, replace U102.·

3.

If the voltage at U202 pin 6 is good, replace

U203. If the ohms function is still noisy, replace

U102.

•

•

•

3478A

•

7 -C-14. Floating Reading on All or Some Ranges

7 -C-15. A Floating Reading is normally caused by an open circuit between the INPUT Terminals and the

DC/Ohms Input Amplifier. Make sure the DC Volts

Function is operating correctly, before suspecting an ohms failure. If the failure shows up in the Ohms Function only, Ul02 may be defective. Before replacing

Ul02, make sure the AID Controller (U462) is good.

Go to paragraph 7-C-24 to check U462.

7-C-16. Overload, Noise, or Constant Zero Readings on

Some Ranges

7 -C-17. Failures on some ranges can only be caused by the Input Hybrid U 102. This is because the hybrid is used to configure the current source for the different ranges. If at least one range is good, the Ohms Current

Source is operating. Before replacing U102, make sure it receives the correct information from the AID Controller (U462). Go to paragraph 7-C-24 to check U462.

7-C-1 B. OHMS PROTECTION CIRCUITRY

TROUBLESHOOTING

•

7-C-19. The Ohms Protection Circuitry is used to protect the Ohms Current Source from excessive positive or negative input voltages. To make sure the circuitry is operational, check the following: a. To check the circuitry operation for positive input voltages, do the following:

1. Set the 3478A to the 2-Wire Ohms Function and the 3K ohm Range.

•

2. Connect a high impedance Digital Voltmeter

(like the 3456A) across R205.

3. Acquire a variable 0-lOV power supply. Set the supply for a OV output and connect it to the

3478A's INPUT Terminals.

4. Measure for approximately .47V de across

R205. If the voltage is wrong, the Current Source may be defective (go to paragraph 7-C-20 for troubleshooting).

5. While monitoring the voltage across R205, adjust the power supply until it outputs + lOY. At an output voltage of approximately + 6V, the voltage across R205 should go to OV and remain at that level.

6. If the voltage does not go to OV, replace

CR201.

7.

If the voltage does go to OV, the Ohms Protection Circuitry does protect for positive input voltages.

Service b. To check the circuitry operation for negative input voltages, do the following:

1. Leave the same set up as in step a, except bring the variable power supply down to OV. The voltage across R205 should again be .47V.

2. Reverse the power supply output leads and apply -lOY de to the 3478A's INPUT Terminals.

3. The voltage across R205 should remain at

.47V.

4. If the voltage remains the same (.47V), the

Ohms Protection Circuitry is operating correctly.

5. If the voltage changes value and/or polarity, the Ohms Protection Circuitry is inoperative.

Measure for approximately -.6V at the source and drain of Q205.

If the voltage is high or zero, replace Q205. If the voltage is good, check for a defective Q201 through Q204.

7-C-20. OHMS CURRENT SOURCE TROUBLESHOOTING

7-C-21. The Ohms Current Source consists of a Voltage

Reference, Buffer and Range Resistors, and a Gate Bias

Amplifier. Before troubleshooting the current source, make sure the +lOY reference is good at JM201. To troubleshoot the Ohms Current Source, do the following procedure. a. Set the 3478A to the 2-Wire Ohms Function and the 3K ohm Range. b. Using a high impedance Digital Voltmeter (like the

3456A), measure the voltage at pin 2 and pin 3 of U203

(U102 pins 17 and 18, respectively). Make sure the voltage on both pins is approximately + 8V. c. If the voltages are not approximately the same, replace U203. d. If the voltages on both pins are wrong (other than

+ 8V), but are approximately the same, do the following:

1. Measure for approximately + 12V at pin 6 of

U201.

2. If the voltage at pin 6 of U201 is + 12V, replace U102. Before replacing U102, make sure the AID Controller (U462) is good. Go to paragraph 7-C-24 to check U462.

3.

If the voltage at pin 6 of U201 is other than

+ 12V, measure for approximately + 8V at pin 3 of U201 .

4. If the voltage at pin 3 of U201 is wrong, replace U102. Before replacing U102, make sure

7-C-3

7-C-4

Service the AID Controller (U462) is good. Go to paragraph 7-C-24 to check U462.

5. If the voltage is good, connect pin 6 to pin 3 of U201 (U102 pin 6 to pin 7).

6. Measure for approximately

U201.

+

8V at pin 6 of

7. If the voltage at pin 6 of U201 is

+

8V, replace U102. Before replacing Ul02, make sure the AID Controller (U462) is good. Go to paragraph 7-C-24 to check U462.

8.

If the voltage is other than

U201.

+

8V, replace e. If the voltages on both pins of U203 are approximately

+

8V, do the following:

1. Measure for approximately

+

12V at pin 6 of

U202.

2. If the voltage is wrong, connect pin 6 to pin 3 of U202.

3. If the voltage is now good, replace U102.

Before replacing Ul02, make sure the AID Controller (U462) is good. Go to paragraph 7-C-24 to check U462.

4. If the voltage is still wrong, replace U202. f. If the Ohms Current Source is still inoperative, replace U203 and then Ul02.

7·C·22. 4-WIRE OHMS TROUBLESHOOTING

7-C-23. The only difference between the two ohms functions is that the 4-Wire Ohms Function uses the

Ohms SENSE Terminals and a different input path in

UI02. Make sure the Front/Rear Switch is good and that the wires from the terminals are connected correctly. Also, make sure the lead resistance of the test used in the 4-Wire Ohms Function is not excessive (

<

1/30 of full scale reading in the LO INPUT lead and

<

1/3 of full scale in the HI INPUT lead). If everything appears to be good, Ul02 may be defective. Before replacing

PIN " p

JM 40 3 dL_o _ _

N

3

'31170 7 Al

5

4

0 0

L) r i i f -

0

"'

[L

0

1-·

.-"

(/)

0:::

< f -

(/)

5

3478A

Ul02, make sure the AID Controller (U462) is good.

Go to paragraph 7-C-24 to check U462.

7-C-24. CHECKING THE A/D CONTROLLER IU4621

7-C-25. Do the following to check the AID Controller.

Refer to Schematic 3. a. Turn the 3478A off. b. Move jumpers JM502, JM503, and JM403 to the

"D" position (JM403 pin 1 and 2), as shown in Figure

7-C-1. c. Obtain a Signature Analyzer. Set and connect as follows (shown in Figure 7-C-1):

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd:

TP401 (JM403 pin 6) (

J)

TP402 (JM403 pin 5) ( \._ )

TP403 (JM403 pin 4)

(_f)

Out

Out

Ground Pin (next to C203)

•

Figure 7·C·1. JM403 SA Connection

d. Turn the 3478A on and check the following signatures:

U462 pin 32: 7 ACA

U462 pin 33: 20FO

U462 pin 34: 666H e. If any signatures are wrong, go to Service Group D

(Flowchart D) for troubleshooting. f. If the signatures are good, the Input Hybrid is defective.

•

•

SERVICE GROUP D

A/D CONVERTER AND LOGIC TROUBLESHOOTING

Service

•

3478A

Service Group D Contents

Title Paragraph

Introduction ................................ 7-D-1

Chassis Common Logic Troubleshooting and

Failures ................................. 7-D-5

Pre-Troubleshooting Information ............ 7-D-7

Turn-On Failure ............................ 7-D-9

Inoperative Display ....................... 7-D-13

Inoperative Keyboard ..................... 7-D-15

HP-IB Failure ........................... 7-D-17

U.C. ROM Fails ......................... 7-D-19

U.C. RAM Fails ......................... 7-D-21

Calibration RAM Failure .................. 7-D-23

Voltmeter Complete ...................... 7-D-25

Address Switch Failure .................... 7-D-27

External Trigger .......................... 7-D-29

Floating Common Logic Failures ............. 7-D-31

Pre-Troubleshooting Information ........... 7-D-33

AID Converter Failures and Troubleshooting. 7-D-35

Input Hybrid (U102) Inoperative ............ 7-D-40

AID Controller Troubleshooting ........... 7-D-42

Isolation Circuitry Troubleshooting ........... 7-D-44

•

7-D-1. INTRODUCTION

7-D-2. This Service Group has the AID Converter and

Logic Circuitry troubleshooting information for the

3478A. Unless otherwise specified, refer to Schematic 1 when using the troubleshooting procedures.

The instrument contains CMOS Integrated

Circuits which are extremely susceptible to failures due to static discharge. It is especially important that grounded tools and wrist straps be used when handling or troubleshooting these components.

7-D-3. The 3478A Logic Circuitry can be separated into two major circuitry: Chassis Common Logic Circuitry and Floating Common Logic Circuitry. The Chassis

Common Logic Circuitry consists of the Main Controller

(U501), Program ROM (U502), Calibration RAM

(CMOS RAM, U512), HP-IB Chip (U503), Display,

Keyboard, and associated circuitry. Its purpose is to control the operation of the instrument. The Floating Common Logic Circuitry consists of an AID Controller

(U462), AID Converter (U403, U401, etc.), and associated circuitry. Its purpose is to control the AID conversion, and to control the Input Hybrid. Communications between the circuitry are done by the Isolation Circuitry.

•

7-D-4. Most of the procedures in this Service Group require a Signature Analyzer for troubleshooting. In addition to it, a logic probe and a logic pulser are also required for some troubleshooting procedures. Obtain the required equipment, before going to the procedures.

7-D-5. CHASSIS COMMON LOGIC TROUBLESHOOTING

AND FAILURES

7-D-6. The following paragraphs have the Chassis

Common Logic Failures and Troubleshooting.

7-D-7. Pre-Troubleshooting Information

7-D-8. Before troubleshooting the Chassis Common

Logic Circuitry, check and do the following: a. Check the

+

5V Power Supply and make sure it is good. The supply should be between

+

4.9V and

+

5

.IV. If the supply is inoperative, go to Service Group

E for troubleshooting. b. Make sure the ALE line at U501 pin 11 is good, as shown in Figure 7-D-1. If the signal is missing or wrong,

7-D-1

Service

3478A make sure the CPU's clock (at pin 2 and 3 of U501) is at approximately 5.856MHz. Try replacing crystal Y501 and if the signal is still missing, try U501.

2V

IlLS Pos. Trig.

Figure 7·0·1. U501 ALE Signal

c. Make sure the RESET line at pin 4 of U501 is high.

If the line is low, try replacing U550 (see Schematic 4).

7·0·9. Turn·On Failure

7-D-10. The Turn-On Failure normally shows up if all of the following symptoms are noted. If only one symptom is noted, it is not a turn-on failure. The symptoms for a turn-on failure are as follows: a. The display is dead or inoperative. Since this can also be caused by a defective display, assume it is turnon failure before troubleshooting the display. b. The keyboard is inoperative (does not respond). If only the keyboard is inoperative, go to paragraph

7-D-15 for troubleshooting. c. HP-IB is inoperative. It may not be necessary to check for an HP-IB failure if the two previous symptoms were are noted. If only an HP-IB failure is noted, go to paragraph 7-D-17 for troubleshooting.

7-D-11. If the previous symptoms were noted, go to

Flowchart A for troubleshooting. In the flowchart, the various address lines and data lines are checked, using

Signature Analysis, to determine the faulty component.

The faulty component(s) can be the Main Controller

(U501), Program ROM (U502), CMOS RAM (U512), or the HP-IB Chip (U503).

7-D-12. Before troubleshooting for a Turn-On Failure, check the following: a. Make sure the Data Bus Break RP527 is making good contact. If the pins are bent, the signatures on the

Data Lines may be good, but the 3478A may be inoperative. b. Make sure jumpers JM501, JM502, and JM503 are in the "N" (Normal) position. The 3478A will not turn on at all or properly, if they are in a different position.

7-D-2

7·0·13. Inoperative Display

7-D-14. An inoperative display is when all or part of the display is inoperative. The failure can be caused by the display itself or part of the Chassis Common Circuitry.

Before doing any troubleshooting, make sure the 1.1 V,

2.2V, and 3.3V power supplies to the display are good.

The supplies can be checked at R503 pins 9, 3, and 15 for the 3.3V, 2.2V, and 1.1 V power supplies, respectively. If any supply is wrong, replace R503 and if still wrong, replace the display.

If the supplies are good, go to Flowchart B for troubleshooting. In the flowchart, the control lines to the display are checked, using

Signature Analysis routines, to determine if the display or another circuit is at fault.

Make sure grounded tools and wrist straps are used, when replacing or checking the display.

7 ·0·15. Inoperative Keyboard

7-D-16. An inoperative keyboard is when all or part of

3478a operations cannot be selected from the keyboard.

This can be caused by the keyboard itself or by the Main

Controller. The following procedure checks the ports of the Main controller (using Signature Analysis) that receive the information from the keyboard. From the resultant signatures it is determined if the keyboard or the Main Controller is defective. Do the following: a. Turn the 3478A off. b. Move jumpers JM502 and JM503 to the "D" position. c. Connect and set the Signature Analyzer as follows:

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd: d. Turn the 3478A on and check the following signatures.

TP7 ( \..)

TP8 (\_)

TP3

( f )

Out

Out

Chassis Ground

U501 pin 27: P6H5

U501 pin 28: PF57

U501 pin 29: 08C6

U501 pin 30: 41PA

U501 pin 31: 35PU

U501 pin 32: 62U5

U501 pin 33: 27H3

U501 pin 34: 6U19

•

•

•

NOTE

The 3478A can have either a Revision 8 (part number 1818·17528! Program ROM (U502) or a

Revision C (part number: IB18-1752C! Program

ROM which make some of the signatures in the flowchart different. If two sets of signatures are listed in the flowchart, use the signatures shown in parentheses for Revision 8 ROMs and the others for Revision

C

ROMs. If no signatures in parenthesis are given, the signatures apply to both

ROMs.

Do the following: a.

Turn the 34 78A off. b. Remove Data Bus Break

RP527. c.

Move JM502 to the

"D" psotion. d. Connect the Signature

Analyzer as follows:

1 . Start I '-- I to TP2

2. Stop

I'--

I to TP2

3. Clock I'-- Ito TP3 e. Turn the 34 78A on.

Check the Address Bus of

U 501 by checking the following signatures.

+

5V supply: 7 A 70

U501 pin 12: H62U

U501 pin 13: C21A

U501 pin 14: HA07

U501 pin 15: HOAA

U501 pin 16: P030

U501 pin 17: 4442

U501 pin 18: 4U2A

U501 pin 19: 0772

Connect the Signature

Analyzer clock to TP4 l...rl

Check ports P20 to P2 2 of U501 by checking the following signatures.

U501 pin 21: 9635

U501 pin 22: 1734

U501 pin 23: 8P54

3478 7-02

Replace USOl.

Replace U 501 .

Check latch U513 by checking the following signatures.

U513 pin 2: 4U2A

U513 pin 5: P030

U513 pin 6: HA07

U513 pin 9: H62U

U513 pin 12: C21A

U513 pin 15: HOAA

US13 pin 16:4442

U513 pin 19:0772

Move JM501 to the "D" position.

Check the ROM by check· ing the following signatures.

U502 pin 9:

U502 pin 10:

Rev C

ROM

32FC

192A

Rev B

ROM

IP5FPI

(P5FP

U502 p1n 11: 87U7 (F91FI

U502 pin 13: 65C8 IH6F31

U502 pin

14: 643H 169671

U502 pin

15:

U502 pin 16:

U502 pin

17:

5866

67H3

IPAF51

189FHI

0229 IPA7CI

Replace U 51 3

Replace U502

Check the Data Bus by checking the following signatures.

U502 p1n 9.

U502 p1n 10:

U502 p1n 11

U502 pin 13·

U502 p1n 14

U502 p1n 15

U502 p1n 16:

U502 p1n 17:

Rev C

ROM lFOC

8751

Rev B

ROM

172731

1300Hl

PHOA

8AC1

1043FI

IA74AI

4769 115AOI

A4UF IA4541

9AA 1 IA0271

476C IH2CH1

Move JM503 to the position.

··o··

Check the following signatures.

U502 pin 9: HA05

U502 pin 10: PU2A

U502 pin 11: ClUJ

U502 pin 13: 6194

U502 pin 14: 05HP

U502 pin 15: 5PC5

U502 pin 16: 9960

U502 pin 17: 16SP

Replaca U502

Replace U502 or U503

Move JM501 to the ""N" position.

Check the following signatures.

Rev B

U502 pin 9:

U502 pin 10:

U502 p1n 11:

U502 p1n 13:

U502 pin 14:

U502 pin 15:

U502 pin

16:

U502 p1n

17.

Rev C

ROM

1665

6FF4

26C5

8989

8AOA

A008

UUPA

0223

ROM ness1

18U051 iUC55J

!8F1AJ

18AOA1

IA008J

!UUPAJ

102231

Replace U502 or US03

Troubleshoot the Display,

Keyboard, and HP-IB by going to paragraph

7-0·13, 7-0·15, and

7 ·D-1 7, respectively.

Figura 7-D-2. Flowchart A

7-D-3

Service

3478A e. If any signatures are incorrect, U501 may be at fault. Replace U501. If all signatures are correct, the keyboard or keyboard connector may be defective. The keyboard can be checked by doing the following:

1. Leave the Signature Analyzer connected as in step c.

2. By pressing a certain front panel button, the signature on a port of U501 should change. For example, the signature on U501 pin 27 (port PIO) should change from "P6H5" to "U878", if the A button is pressed. From this change, it can be determined if the button (i.e., part of the keyboard) is inoperative or good. The following lists the pin numbers of U501, the button to be pressed, and the change in signature. make sure the RAM is defective, go to Flowchart A (see paragraph 7-D-11) for troubleshooting.

7-0-23. Calibration RAM Failure

7-D-24.

If the "CAL RAM FAIL" message is displayed (after a Self-Test routine), the most likely cause is a Calibration RAM (CMOS RAM, U512)

Failure. The RAM can be checked by sending data to the RAM and reading it back.

Make sure grounded tools and wrist straps are used, when replacing or checking the display.

U501 pin#

27

27

28

28

29

30

30

31

32

32

34

Press

Shift

4 WIRE

I NT/TRIG

"-A

:-::v

2 WIRE

LOCAL

Change Signature

Button From

""A

P6H5

SGL!TRIG P6H5

"-V

PF57

0

PF57

08C6

41PA

41PA

35PU

62U5

62U5

33 AUTO/MAN 27H3

33

0

27H3

34 SRO 6U19

6U19

To

U878

2F5U

A998

4132

PUF4

AHUA

CF39

1C44

2113

2718

9F9A

24HU

4F39

H083

The test in paragraph 7-D-24 cannot be made without destroying the present data in the Calibration RAM. The 3478A must be recalibrated, after doing the test.

a. Turn the 3478A off. b. Move jumpers JM502 and JM503 to the "D" position. c. Connect and set the Signature Analyzer as follows:

7-0·17. HP-18 Failure

7-D-18. Before troubleshooting for an inoperative

HP-IB, make sure the 3478A is operating correctly from the front panel. Repair the front panel operation first, before troubleshooting for an HP-IB failure. To troubleshoot an HP-IB failure, go to Flowchart C. The procedure in the flowchart checks the HP-IB Chip to determine if data can be written to or read by the chip.

7-0·19. U.C. ROM Fails

7-D-20. If the "U .C. ROM FAIL" message is displayed

(during a Self-Test routine), the most likely cause is a failure in Program ROM (U502). To make sure the ROM is defective and not the Main Controller, go to Flowchart

A (see paragraph 7-D-11) for troubleshooting.

7·0·21. U.C. RAM Fails

7-D-22.

If the "U.C. RAM FAIL" message is displayed, the failure is most likely in the Chassis Common CPU's RAM (RAM in Main Controller U501). To

7-D-4

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd:

TP8

( f )

TP7 ( \...)

TP6

( f )

Out

Out

Chassis Ground d. Turn the 3478A on and check the following signatures.

U512 pin 9: H709

U512 pin 11: C577

U512 pin 13: 4296

U512 pin 15: 8U25 e. If any signatures are wrong, something on the

Data Bus is defective. Go to Flowchart A (see paragraph

7-D-11) for troubleshooting. f.

If the signatures are good, the RAM (U512) may be defective. The RAM can be checked by continuing with the test in the next step.

•

3478A

•

Do the following: a. Turn the 3478A off. b. Move JM502 to the

"D" position. c. Move JM503 to the

"D" position. d. Connect the Signature

Analyzer as follows:

1. Start ( \.... ) to TP7 ·

2. Stop (\....)to TP8

3. Clock

(...r) to TP 3 e. Turn the 34 78A on.

Check latch U506 by checking the following signatures.

+

5V supply: HF52

U506 pin 3: 8427

U506 pin 4: 5CA6

U506 pin 5: 726U

U506 pin 6: 6PUH

YES

Check U501 by checking the following signatures.

U501 pin 21: 6FC8

U501 pin 22: H3CC

U501 pin 23: 8028

U501 pin 24: C90H

Replace Display

Replace U506

Check ports P24 and P25 b_y checking the following

Signatures.

U501 pin 35: U8HH

U501 pin 36: HF52

NO

Service

•

Figure 7-D-3. Flovvchart B

"347b 7 0"3

7-D-5

7-D-6

Service

Do the following: a. Turn the 34 78A off b. Move JM502 to the

"D" position. c. Move JM503 to the

"D" position. d. Connect the signature

Analyzer as follows:

1 . Start ( __r ) to TP7

2. Stop

I

__r) to TPB

3. Clock

L.r ) to TP6 e. Turn the 34 78A on.

Check Data Lines by checking the following signatures.

+

5V Supply: 2FCO

U503 pin 12: PC84

U503 pin 13: C312

U503 pin 14: 7P1 C

U503 pin

15: C3A8

U503 pin 16: P3P1

U503 pin 17: F114

U503 pin 18: A65F

U503 pin 19:3112

Go to Flowchart A for troubleshooting

Connect Signatures

Analyzer clock to TP5

Take the following signatures.

+

5V Supply: CC34

U503 pin 12: 96PF

U503 pin 13: P4C7

U503 pin 14: 2U6F

U503 pin 15: U06A

U503 pin 16: P288

U503 pin 1 7: 9U6U

U503 pin 18: 6679

U503 pin 1 9: 6AF5

Check the following signatures.

U503 pin 28: 2HH8

U503 pin 29: 5U83

U503 pin 30: 9458

U503 pin 31: 4C5P

U503 pin 32; 59CF

U503 pin 33: 245C

U503 pin 34: HH4H

U503 pin 35: H1U1

Replace U503

Figure 7-0-4. Flowchart C

1478 7 04

Replace U503.

3478A

•

•

•

3478A Service

• g. The RAM can be checked by reading data back from it. One caution when checking the RAM, the data in the RAM will be lost and the 3478A will need to be recalibrated. Do the following:

1. To check the RAM, leave the Start and Stop inputs of the Signature Analyzer connected as in step c, but connect the Clock to TP5 ( _f).

2. Using a flat blade screwdriver, set the front panel

CAL ENABLE Switch to the calibration enable position

(the slot of the switch is in the vertical position, as shown on the front panel).

3. Take the following signatures.

U512 pin 9: H709

U512 pin 11: C577

U512 pin 13: 4296

U512 pin 15: 8U25

4. If the signatures are wrong, the RAM may be defective. Before replacing the RAM, make sure the

RAM's R/W line reads a signature of 4296. If the signature is wrong, replace U515. If the signature is good, replace U512.

•

5. If the signatures are good, other circuitry may cause the failure. Go to Flowchart A (see paragraph

7-D-11) for further troubleshooting.

7·0·25. Voltmeter Complete

7-D-26. The Voltmeter Complete pulse is normally output after an input measurement is completed. To troubleshoot the operation, with a logic probe, check and make sure pin 25 of U501 is toggling. If the probe does not show toggling, U501 is most likely defective. If the probe shows toggling, make sure R538 is not open, and CR504 and CR505 are not shorted. If the resistor and diodes are good, replace U508.

7·0·27. Address Switch Failure

7-D-28. An address switch failure can be caused by the switch itself or U510. The address switch can easily be checked using a logic probe. With all switches of the address switch on (up), pins 9, 10, 11, 12, 13, 14, 15, and

16 of the switch are low. With all switches off (down), the pins are high. If the switch is good, replace U510.

7·0·29. External Trigger

7-D-30. An external trigger failure can be caused by a

• defective U514 or HP-IB Chip. Do the following: a. Set the 3478A to the Single Trigger mode . b. Using a logic probe, make sure pin

5 of U514 is high. If the pin is low, do the following:

1. Check for a low at pin 4 of U514.

2. If pin 4 of U514 is low, replace U514.

3. If pin 4 of U514 is high, replace U503. c. If pin 5 of U514 is high, using a logic pulser, pulse

(i.e., toggle) pin 5. d. Using a logic probe, check for a high at pin 9 of

U514. e. If pin 9 is low, replace U514. If the pin is high, while checking the pin with a logic probe, apply a trigger pulse to the 3478A's EX TRIG connector (i.e., short the input of the connector to ground). When the 3478A is triggered, pin 9 of U514 should toggle high and then low. f. If pin 9 does not toggle, replace U514. If it does toggle, U501 may be defective.

7·0·31. FLOATING COMMON LOGIC FAILURES

7-D-32. Floating Common Failures can be failures in the A/D Converter and the A/D Controller. The following paragraphs have the failures and troubleshooting information.

7·0·33. Pre·Troubleshooting Information

7-D-34. Before troubleshooting the Floating Common

Logic Circuitry and A/D Converter, perform the following: a. Check the 3478A's Floating Common Power Supplies. Make sure they are stable, are at the correct !eve and are not oscillating. The power supplies are a follows:

Power

Checked

Supply at

Voltage level

+

5V

JM701

-15V JM702

+

15V

JM703

+

4.9V to

+

5.1V

- 14.4V to - 15.6V

+

14.4V to

+

15.6V b. Check and make sure the Reference Supplies are at the correct level and are quiet. The

+ lOY suppply can be checked at U405 pin 6, the -lOY supply at U404 pin 6, and the buffered +lOY supply at JM201. c. Make sure the ALE line at TP403 (U462 pin 11) is good, as shown in Figure 7-D-5. If the signal is missing or incorrect, make sure the CPU's clock (at pin.2 and 3 of U462) is at 10.98MHz. Try replacing crystal Y460, if the signal is missing. If still missing, replace U462.

7·0·35. AID Converter Failures and Troubleshooting

7-D-36. An A/D Converter failure can show up as

Overload, Constant Zero, Floating, or Noisy Readings.

7-D·7

Service

2V

. 5p,S Pos. Trig .

Figure 7·0·5. U462 ALE Signal

Other failures are normally noted when, after doing a

Self-Test, the 3478A display's either "A:D SLOPE

ERR" or "A:D TEST FAIL". If an "A:D LINK

FAIL" is displayed, the failure is most likely in the

Isolation Circuitry (go to paragraph 7-D-44 for troubleshooting). The following paragraphs have the failures and troubleshooting information for the

AID

Converter.

7-D-37. Overload, Constant Zero, Floating, or Noisy

Readings. Before troubleshooting the AID Converter for these failures, make sure the failures are not caused by the 3478A's Input Circuitry. Do the procedure which follows this paragraph (the same procedure is also in

Service Group A). If the procedure has been performed already, ignore the procedure and go to Flowchart D for troubleshooting. If it has not been performed, do the following: a. Set the 3478A to the DC Volts Function and 3V

Range. b. Turn Autozero off by pressing the blue Shift button and then the INT /TRIG (AUTOZERO) button. c. Apply a stable + 3V de to the INPUT Terminals. d. With a Digital Voltmeter (like the 3456A) measure for +lOY at JMlOI. e. If the reading on the test voltmeter is a stable

+ lOY, the AID Converter is at fault. Go to Flowchart

D for troubleshooting. If the reading is other than

+lOY, go to Service Group A for troubleshooting.

7-D-38. A/D Slope Error. When an "A:D SLOPE

ERR" is displayed on the 3478A, the most likely cause is the AID Converter (U403 and associated circuitry) or the AID Controller (U462). Go to Flowchart D for troubleshooting. The procedure in the flowchart checks the different ports (using Signature Analysis) of the

AID Controller (U462) and also checks the DAC

(U465).

7-D-39. A/D Test Fails. If the message "A:D TEST

FAIL" is displayed, the AID Converter fails its internal test. Since this can be caused by the AID Controller

7-D-8

3478A

(U403 and associated circuitry) or the AID Controller

(U462), go to Flowchart D for troubleshooting. The procedure in the flowchart checks the different ports

(using Signature Analysis) of the AID Controller and also checks the DAC (U465).

7-0-40. Input Hybrid (U1 02)1noperative

7-D-41. An inoperative Input Hybrid can be caused by the hybrid itself or when it receives wrong information from the AID Controller. To isolate the circuitry, do the following: a. Turn the 3478A off. b. Move jumpers JM502, JM503, and JM403 to the

"D" position (JM403 pin 1 and 2), as shown in Figure

7-D-7. c. Obtain a Signature Analyzer. Set and connect as follows (shown in Figure 7-D-7):

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd:

TP401 (JM403 pin 6)

( f )

TP402 (JM403 pin 5) ( \_ )

TP403 (JM403 pin 4) ( _/ )

Out

Out

Ground Pin (next to C203)

•

• d. Turn the 3478A on and check for the following signatures:

U462 pin 32: 7 ACA

U462 pin 33: 20FO

U462 pin 34: 666H e. If any signatures are wrong, U462 may be defective. Go to Flowchart D for troubleshooting. f. If the signatures are good, the Input Hybrid is defective.

7-0-42. A/0 Controller Troubleshooting

7-D-43. Do the following to check the AID Controller

(U462). a. Using a logic probe, check and make sure the

RESET line (U462 pin 4) is high. b. If the RESET line is low, do the following:

1. Make sure pin 1 of U462 is toggling.

2. If pin 1 is not toggling, the Isolation Circuitry may be at fault. Go to paragraph 7-D-44 for troubleshooting.

3. If pin 1 is toggling, check for a low at U466 pin 3.

•

•

3478A

Do the following: a. Turn the 34 78A off. b. Move JM502 to the

"D" position. c. Move JM503 to the

"D" position. d. Move JM403 to the

"D" position, as shown in

Figure 7-D-7. e. Connect the Signature

Analyzer as follows as shown in Figure 7-D-7:

1. Start (

_r)

to

TP401 (JM403 pin 6).

2. Stop ( """\.... l to TP402

(JM403 pin 5).

3. Clock

( _ r ) to

TP403 (JM403 pin 4). f. Turn the 34 7 SA on.

•

Check the following signatures:

+

5V Supply: 666H

U462 pin 27: 27CA

U462 pin 28: 1 U96

U462 pin 29: 90HP

U462 pin 30: P4CH

U462 pin 31 : C9C6

U462 pin 32: 7ACA

U462 pin 33: 20FO

U462 pin 34: 666H

NOTE

Since the tests on this

Flowchart are performed in the Floating Common

Circuitry. make sure the

Signature Analyzer is connected to the appropriate ground (GND pin located near C203).

U462 may be defective.

Go to paragraph 7-D-42 for troubleshooting.

•

Check the input to the

DAC (U465) by checking the following signatures.

U462 pin 21 A4H7

U462 pin 22 55A1

U462 pin 23 73F6

U462 pin 24 8524

U462 pin 35 P261

U462 pin 36 2206

Set Signature Analyzer clock to ("""\.... ).

Check the following signatures:

U465 pin 2: A4H7

U465 pin 5: 55A1

U465 pin 7: 73F6

U465 pin 10: 8524

U465 pin 12: P261

U465 pin 1 5: 2206

Make sure capacitor

C41 0 is good (not open or shorted). If C41 0 is good, try replaceing U40 1 and then U403.

Figure 7-D-6. Flowchart D

"347B 7 De

Replace U462.

Replace U465

Service

7-D-9

Service

JM403

2

PIN "

0 do ol

N

0

3

3478 7 AI

4

0

D

..J u

:<: u r

0

5

D

.....

(j)

IL r

Figure 7-0-7. JM403 SA Connection

0

.....

0::

<

(j)

i

6

4. If pin 3 of U466 is high, replace U466. If low, replace U467. c. If the RESET line is high, while monitoring the line, press the 3478A's blue Shift button and then the

SGLITRIG (TEST /RESET) button. The 3478A should go through its Self-Test routine, and when the routine is finished, the RESET line toggles from high to low to high. d. If the RESET line toggles and the 3478A is still inoperative, replace U462. e. If the RESET line does not toggle, do the following:

1. Make sure pin 1 of U467 is toggling.

2. If pin 1 is not toggling, the Isolation Circuitry may be at fault. Go to paragraph 7-D-44 for troubleshooting.

3. If pin 1 is toggling, replace U466 and then U467.

7-0-44. ISOLATION CIRCUITRY TROUBLESHOOTING

7-D-45. The Isolation Circuitry transfers information from the Main Controller (U501) to the AID Controller

(U462) and also from the AID Controller to the Main

Controller. A failure in the logic is normally indicated when, after doing a Self-Test, "A:D LINK FAIL" is displayed. To troubleshoot the circuitry, first determine the inoperative circuitry and then troubleshoot the circuitry. Do the following: a. Turn the 3478A off. b. Move jumpers JM502 and JM503 to the "D" position. c. Connect the Floating Common ground to the

3478A's chassis. The LO INPUT terminal can be

3478A used as a Floating Common ground (make sure the correct terminal is used, dependent on the position of the

Front/Rear Switch). d. Connect and set the Signature Analyzer as follows:

Start:

Stop:

Clock:

Hold:

Self-Test:

Gnd:

U462 pin 1 ( \_ )

TP8

C\.)

TP3 ( . / )

Out

Out

Chassis Ground e. Turn the 3478A on and check the signature of the

Chassis Common

+

5V power supply. f. If the signature is different than "HF52" and the

SA probe is toggling, the Main Controller (U501) may be defective. Go to Flowchart A for troubleshooting

(see paragraph 7-D-11). g. If the SA probe is not toggling (the signature can be the same or different), the isolation circuitry is defective. Do the following:

1. Using a logic probe, make sure pins 2 and 4 of U508 are toggling.

2. If the pins are not toggling, replace U508.

3. If they are toggling, check for a defective transformer T501 and associated circuitry. If T501 is good, replace U468. h. If the signals at pin 38 of U501 and pin 14 of U462 are good, the isolation logic used to transfer information between U462 and U501 may be defective. Do the following:

1. Using a logic probe, make sure pin 38 of

U462 is toggling.

2. If pin 38 is not toggling, U462 may be defective. Go to Flowchart D for troubleshooting.

3. If pin 38 is toggling, make sure pin 1 and 4 of

U467 are toggling.

4. If the pins are not toggling, replace U467.

5. If they are toggling, check for a defective transformer T401 and associated circuitry. IfT401 is good, replace U550.

•

•

•

7-D-10

•

SERVICE GROUP E

POWER SUPPLIES AND REFERENCE TROUBLESHOOTING

Service Group E Contents

Title Paragraph

Introduction ................................ 7-E-1

Power Supply Troubleshooting ................ 7-E-3

Chassis Common Power Supply ............. 7-E-5

Floating Common Power Supplies ........... 7-E-7

Reference Circuitry Troubleshooting .......... 7-E-13

7-E-1. INTRODUCTION

7-E-2. This Service Group has information used to troubleshoot the 3478A's Power Supplies and Reference

Circuitry.

7-E-3. POWER SUPPLY TROUBLESHOOTING

•

7-E-4. The Floating Common Section of the 3478A has three power supplies which are: + 5Y, -15Y, and + 15Y.

The Chassis Common Section has one + 5Y supply. The following paragraphs have some troubleshooting information for the Chassis Common and Floating Common supplies (refer to Schematic 4).

7-E-5. Chassis Common Power Supply

7-E-6. A low supply can be caused if zener diode CR766 and capacitor C762 are shorted, if there is an excessive load on the supply (shorted component in the Chassis

Common Logic Circuitry), or if regulator U760 is defective. A high supply can be caused by U760.

7·E·7. Floating Common Power Supplies

7-E-8.

+ SY

Supply.

A low supply can be caused by an excess load on the supply, a shorted CR712, or a defective U701. The supply can be checked by lifting jumper

JM701. If the supply is still low, troubleshoot the supply. Otherwise, troubleshoot the Floating Common Circuitry.

7-E-9. A high supply is most likely caused by a defective U701.

7-E-10. + 15V and -15V Supplies. Since the -15V supply is a mirror image of the + 15V supply, use the following procedure for both supplies.

•

7-E-11. A low supply can be caused by an excessive load on the supply, a shorted filter capacitor or protection diode, an open temperature sensitive resistor

(RT706 or RT707), or a defective regulator. The supply can be checked by lifting jumper JM703 for the + 15Y supply or jumper JM702 for the -15Y supply.

If the supply is now good, troubleshoot the Floating Common

Circuitry. If still low, troubleshoot the supply.

7-E-12. A high supply is most likely caused by the regulators (U702 or U703).

7·E·13. REFERENCE CIRCUITRY TROUBLESHOOTING

7-E-14. The 3478A's Reference Circuitry is used to develop three reference voltages: +lOY, -lOY, and a buffered +lOY. Since the -lOY and buffered +lOY depends on the + lOY reference voltage, make sure the

+lOY is good before troubleshooting the other reference supplies. Perform the following checks (refer to Schematic 3). a. If the +lOY reference is inoperative, do the following:

1. Measure the voltage at zener diode U461.

The voltage should be quiet and at approximately

+7Y.

2. If the voltage is wrong, replace U461.

3. If the voltage is good, short across capacitor

C431. Measure pin 6 of U405.

4. If the voltage at pin 6 is approximately + 7Y and quiet, replace U403.

5.

If the voltage is still incorrect or noisy, replace U405 . b. If the +lOY is good and the -lOY is incorrect or noisy, replace U405. If still incorrect or noisy, replace

U403.

7-E-1

7-E-2

Service c. If both +lOY and -lOY voltages are good and the buffered +lOY is is low, lift jumper JM201 (see

Schematic 1). If the +lOY is now good, replace Ul02.

If still wrong, continue with the next step. d. If the buffered +lOY is wrong or noisy, do the following:

3478A

1. Check for a quiet -lOY at pin 2 of U402 .

2. If the voltage is wrong, replace U403.

3. If the voltage is good, connect pin 19 to pin

24 of U403.

4.

If the voltage at pin 6 of U402 is now at

+lOY, replace U403. If not, replace U402.

•

•

•

•

SERVICE GROUP F

THEORY OF OPERATION

Service Group F Contents

Title Paragraph

Introduction ................................ 7-F-1

General Block Diagram Theory Of Operation .... 7-F-3

Theory Of Operation ......................... 7-F-7

General .................................. 7-F-8

Input Circuitry ........................... 7-F-10

Ohms Current Source ..................... 7-F-17

ACto DC Converter ...................... 7-F-25

AID Converter ........................... 7-F-31

3478A Logic Circuitry ..................... 7-F-50

Chassis Common Circuitry ................. 7-F-55

Isolation Logic ........................... 7-F-71

Floating Common Circuitry ................ 7-F-75

Power Supplies ........................... 7-F-83

7 ·f-1. INTRODUCTION

•

7-F-2. The following Service Group has the general and detailed description of the operating circuitry of the -hp-

Model 3478A Multimeter. The general description explains the purpose of each operating block of the 3478A

Simplified Block Diagram (shown in Figure 7-F-1). The detailed description explains the circuitry in each operating block.

7-F-3. GENERAL BLOCK DIAGRAM THEORY OF

OPERATION

7-F-4. Refer to Figure 7-F-1 for the following discussion of the 3478A's General Block Diagram Theory Of

Operation.

HP-IB (remote). The information is received by the

Main Controller which then passes the information over the Isolation Circuitry to the AID Controller. The AID

Controller then sets up the measurement circuitry to do the desired measurement. The Main Controller also sends information to the display to show the selected function and range. The following takes place in the

3478A's different functions.

7-F-5. The 3478A can be separated into two major areas, Floating Common and Chassis Common. The

Floating Common has the cicuitry which does the ac, de, and ohms measurements. It consists of the Input

Circuitry, AID Converter, AID Controller, Ohms Current Source, and AC to DC Converter. The Chassis

Common is used to calculate and display readings, controls the Floating Common Circuitry, and sends and receives remote information. It consists of the Main

Controller (the main CPU used with the Control ROM) and associated circuitry. Communications between the

Chassis Common and Floating Common is done by the

Isolation Circuitry.

•

7-F-6. The following paragraphs explain a typical measurement sequence. a. Set-up. The 3478A receives range and function information from the front panel (local) or over the b. DC Volts Function. The following occurs if the

DC Volts Function is selected.

1. The Input Circuitry is set up to a certain gain configuration by the AID Controller circuitry.

The gain depends on the range selected.

2. The input voltage is amplified or attenuated

(dependent on the range) to lOV (for full scale inputs) which is then applied to the AID Converter.

3. The AID Converter changes the voltage to digital information and transfers it to the

AID

Controller. The

AID Controller then processes the information and transfers it over the isolation transformers to the Main Controller.

4. The Main Controller takes the information and calculates the correct reading. The correct reading is calculated by using the zero measurement (see step f) and the calibration constant(s)

(which are stored in the Calibration RAM).

5. The corrected reading is then sent to the front panel to be displayed and sent over the

HP-IB (if the 3478A is in remote and addressed to talk).

7-F-1

3478A

Service

I

I

I

I in~E~sEI ~:

La

V

HI

OHMS

CURRENT 1 4 - - - - - - - - - - l

SOURCE

I r

REFERENCE

AID

INPUT

SWITCHING

.----..___-.--r-_.J

INPUT

AMPLIFIER

T

:

L----------- -----------1 r--0 un-L-o t

I

.1

I

UA

AC TO DC

CONVERTER

AID

CONTROLLER

POWER

SUPPLIES

I SOLA

Tl

ON

LOGIC

1 - - - - - - - - - - - - - - - - - - - - - - - - - - lcHAssrscoMMON------------

I

~~L_~

__.J

I

I

I

I

I

I

ISOLATION

LOGIC

MAIN

CONTROLLER

I

I

I

I

I

POWER

SUPPLIES

I

HP-IB

INPUT/OUTPUT

FRONT PANEL

CONTROL

IPUSHBUTTONSl

I

DISPLAY

I

I

I

! _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

I

3478-7-F-1

Figure 7-F-1. 3478A Simplified Block Diagram c. Ohms Function.

If the Ohms Function is selected, the Ohms Current Source supplies a known de current to the unknown resistance. A voltage drop proportional to the unknown resistance and the current is applied to the Input Terminals. A regular de measurement is then made (see step b) and the ohms reading is calculated by the Main Controller circuitry using the zero measurement (see step t) and calibration constant(s).

d. AC Volts Function.

If the AC Volts Function is selected, the input is connected to the AC to DC Converter. The converter changes the voltage to its equivalent (RMS) de voltage and applies it to the AID

Converter. The AID Converter changes the voltage to digital information and applies it to the AID Controller. The AID Controller passes it on to the main controller which calculates the correct reading using the

7-F-2 zero measurement (see step t) and calibration constant(s).

e. AC Current or DC Current Function.

If the AC

Current or DC Current Functions are selected, the input current is applied to resistor R107 (.1 ohm). The resultant voltage drop across the resistor is then measured.

An ac or de volts measurement is made, dependent on the function selected (AC Current or DC Current, respectively).

f. Autozero Function.

If the 3478A's Autozero Function is enabled, an offset measurement (known as a zero measurement) is made before an input measurement.

The zero measurement is made by connecting the input of the Input Amplifier (HI INPUT Terminal is open) to ground (LO INPUT Terminal). The resultant offset of

•

•

•

Service

•

3478A the amplifier is then measured and stored into memory.

This reading is then subtracted from the DC Volts, DC

Current, and Ohms readings that follow. If the AC

Volts or AC Current Functions is selected, the zero reading is taken differently. The input to the

AID

Converter is shorted to ground instead of the DCIOhms Input Amplifier.

7-F-7. THEORY OF OPERATION

7 ·f·B. General

7-F-9. The following paragraphs give a detailed description of the operating circuitry in the 3478A. The circuitry is explained as follows: a. Input Circuitry - paragraph 7-F-10. b. Ohms Current Source- paragraph 7-F-17. c. ACto DC Converter- paragraph 7-F-25. d.

AID

Converter- paragraph 7-F-31. e. 3478A Logic Circuitry - paragraph 7-F-50. f. Chassis Common Circuitry - paragraph 7-F-55. g. Isolation Logic - paragraph 7 -F -71. h. Floating Common Logic Circuitry paragraph

7-F-75. i. Power Supplies - paragraph 7-F-83.

•

7 -F-1 0. Input Circuitry

7-F-11. General. The purpose of the Input Circuitry is to condition the de input signals to the 3478A to provide full scale 10V de input voltages to the

AID

Converter, for full scale inputs to the 3478A (the explanation for ac inputs is in paragraph 7-F-25, AC to DC Converter).

The Input Circuitry also acts as a buffer between the input and the

AID

Converter. The cicuitry can be separated (and is explained) as follows:

Overvoltage Protection

Input Switching

Autozero and Pre-Charge

Pre-Charge Stage

DCIOhms Input Amplifier

7-F-12. Overvoltage Protection. This circuitry has three parts: High Voltage Protection, Low Voltage Protection, and Current Protection. The two circuits operate as follows (refer to Schematic 1 for the explanation).

• a. High Voltage Protection. This circuit consist of a

630V Surge Voltage Protector (E101) in series with a

220K ohm resistor. The circuitry is connected between the HI and LO INPUT Terminals and conducts with a peak voltage level of 630V (

±

200fo ), which provides a

low

impedance path across the terminals. Capacitor

C104 provides a temporary low impedance path and

R109 provides current limiting, if E101 conducts continuously. b. Low Voltage Protection. This circuit consists of diodes connected to the individual input nodes (part of the HI INPUT, LO INPUT, A INPUT Paths, etc.). The diodes on each node are connected (internally in U 1 02) to

+

3.5V and -3.5V power supplies. If the voltage on a node exceeds either

+

4.2V or -4.2V, a diode conducts and keeps the level on the node to the ± 4.2V levels. The difference between the high voltage at the input terminals and the voltage at the input nodes is dropped across the resistors which are in series with the diodes and input terminals (the low pass filter). Figure 7-F-2A shows a typical protection circuit. c. Current Protection. A fuse in series with the current shunt (Rl07) protects the shunt from excessive input currents (

>

3A).

7-F-13. Input Switching. The Input Switching Circuitry consists mostly of Relay and MOSFET switches, with most FET switches located in U 102. The purposes of the switches are to provide five signal paths to the Input

Amplifier and to connect the amplifier for a zero measurement (done in the Autozero Function; see paragraph 7-F-14). The switches are controlled by circuits in U102 which receive their control information from the

AID

Controller. The following explains the various input paths. Refer to Figure 7-F-2 and

Schematic 1 for the explanation . a. Low Voltage Range Input Path (Figure 7-F-2B).

The path consists of KIOI, R103, R104, RIIO, and

SIDC (SIDC is in U102). The purpose of the path is to connect the HI INPUT Terminal (high input voltage) to the DC

I

Ohms Input Amplifier. The path is used only in the 30mV through 3V de volts Ranges and all Ohms

Ranges. b. High Voltage Range Input Path (Figure 7-F-2C).

The path consists of Rl10, K102, S2DC (in 102), and a

100:1 divider (9.9M ohm and lOOK ohm resistors, RD99 and RD98, in U102). The purpose of the path is to attenuate input voltages by a facter of 100 and to connect the attenuated voltage to the DCIOhms Input

Amplifier. The path is used only in the 30V and 300V de volts Ranges. c. Ohms High Sense Path (Figure 7-F -20). This path consists of R105, Rl06, and S4ADC and S4BDC

(S4ADC and S4BDC are in U102). The path connects the HI OHMS SENSE Terminal (high ohms input) to the DCIOhms Input Amplifier, only when the 3478A is in the 4-Wire Ohms Function. Switch S4CDC (which is also part of the path) is used to connect the junction of

S4ADC and S4BDC to ground. Switch S4CDC is closed in all functions except the 4-Wire Ohms Function and shunts any possible voltage on the S4ADC and S4BDC junction to ground.

7-F-3

Service

A.

102K

~--------~

P/0 n.sv :utoz

'

'

'

'

-3. 5V :

'

----------

'

B.

INPUT

K101

'

:

:

'

'

P/0 U102

·-----------------.

: SlDC

HC

TO

AID

c.

INPUT

'

'

·---------------------------------'

P/0 Ul 02

S2DC MC

G.

F.

INPUT

A

R1~7 f

LOO~

P/0 U102

-----------------------~

S3DC MC

'

TO

AC TO DC

CONVERTER

--,

'

TO

AID

, _______________________________________ j

'

'

3478A

•

P/0 Ul 02

TO

AID

SBO :

' ' TO

AID

•

H.

D. n

SENSE

: SiiAOC

E.

HI

S4BDC 11C :

TO

AID

Rx

.>--..,...-•~o

--,

'

'

'

·-----------------------------------'

___________________________________________

)

'

' '

I. s~coc:

-------------------------

'

'

I

I-----------------------------------,

I

I

I

I

I

I

1

SIDC fOR SZDC,

S30C, S4AOC AND

S4BOCJ

I

I

I

-I

I

I

I

I

I

I

I

I

------------------------------------------------·

3478 7-FZ

TO

AID

Figure 7 -F-2. Simplified Schematic Of The Input Switching Circuitry

7-F-4

•

3478A

• d. Ohms Low Sense Path (Figure 7-F-2E). This path consists of RlOl, R102, and. S6ADC and S6CDC

(S6ADC and S6CDC are in Ul02). The path is used to connect the LO OHMS SENSE Input Terminal (low ohms input) to ground (LO INPUT Terminal), when the

3478A is in the 4-Wire Ohms Function. In the 2-Wire

Ohms Function, the low ohms input is the LO INPUT

Terminal (which is connected to ground). e. Current Input Path (Figure 7-F -2F). This path includes R107 and S3DC (in U102). The voltage drop across R107 (which is generated by the current being measured) is connected through S3DC to the DC/Ohms

Input Amplifier. This path is used only in the DC Current Function.

7-F-14. Autozero. The Autozero Function of the 3478A is used to measure the offset (called a zero measurement) of the DC/Ohms Input Amplifier and subtract it from the input measurement. As long as the Autozero

Function is enabled, a zero measurement is taken between each input measurement. The zero measurement is done in two different ways, dependent on the function selected. The following explains the two ways to make the measurement and the circuitry used. a. Autozero (in the DC Volts, DC Current, and

•

2-Wire Ohms Functions). In the DC Volts, DC Current, and 2-Wire Ohms Functions, the zero measurement is made with switch MC (measure customer) open, and switch MZ (measure zero) and S8DC closed (see Figure

7-F-20). Switch S8DC and MZ connects the DC/Ohms

Input Amplifier to ground through a 102K ohm resistor.

After the zero measurement is made, switch S8DC and

MZ opens, and switch MC closes for the input measurement. (Note: MOSFET switches MC, MZ, and S8DC are in U102.) b. Autozero (in the 4-Wire Ohms Function). In the

4-Wire Ohms Function, the zero measurement is made with switch MC (and S8DC) open and switch MZ,

S6ADC, and S6BDC closed. The DC/Ohms Input

Amplifier is connected to ground through the Ohms

Low Sense Path (includes an externally connected lead; see Figure 7-F-2H) to the LO INPUT Terminal. This measurement is different than in the DC Volts, DC Current, and 2-Wire Ohms Functions, since the Input

Amplifier is connected to ground through the externally connected low ohms sense and lo input leads. After the offset measurement is made, switch MC and S6CDC closes and switch MZ, S6ADC, and S6BDC opens.

Switch S6CDC is used to to connect the junction of switch S6ADC and S6BDC to ground, shunting any possible voltage on the junction to ground. (Note:

MOSFET switches S6ADC, S6BDC, and S6CDC are in

•

Ul02.)

7-F-15. Pre-Charge Stage (Figure 7-F-21). A small stray capacitance exists in U102 between the input of the

DC/Ohms Input Amplifier and ground. During a zero

Service measurement (measure zero in the Autozero Function), this capacitor is at zero volts. After the zero measurement, the input to the 3478A is applied to the Input

Amplifier and the capacitor is charged to the input voltage. This charging may temporarily load down the input voltage and a wrong reading is taken. To prevent this, the input of the Input Amplifier is pre-charged to the input voltage before the input measurement is made.

This is done by the Pre-Charge Amp and MOSFET

Switch PRE (both in Ul02). The operation is as follows: a. After the zero measurement is made, switch PRE closes (switch MC is still open). b. The input voltage is connected to the Pre-Charge

Amp using the input paths. c. Since the Pre-Charge Amp is a XI gain amplifier, a voltage with the same polarity and value as the input voltage is applied through PRE to the DC/Ohms Input

Amplifier. This pre-charges the stray capacitor to the input voltage. d. Switch PRE then opens and MC closes. An input measurement is then made. e. The same takes place before the next input measurement.

7-F-16. DC/Ohms Input Amplifier. The purpose of the

DC/Ohms Input amplifier, in conjunction with the Input Switching Circuitry, is to condition the 3478A's input signals. The conditioning is done to apply the same full scale 1 OV de voltage to the AID Converter for all

DC Volts, DC Current, and Ohms full scale inputs. This is done by configuring the amplifier to a gain of X3.33,

X33.3, or X333. The gains used in the 3478A's different ranges (in the DC Volts, DC Current, and Ohms Functions) is shown in Figure 7-F-3.

7·F·17. Ohms Current Source

7-F-18. General. The purpose of the Ohms Current

Source is to provide a stable current for resistance measurements. The current is applied to the unknown resistance and the resultant voltage drop across the resistance is measured. Since this voltage drop is directly proportional to the unknown resistance, the resistance value is determined by the 3478A's Main Controller from the voltage reading.

7-F-19. The Ohms Current Source consists of the following circuitry: Voltage Splitter (Voltage

Reference), Buffer, Range Resistors, Output FET Control Amp (Gate Bias Amplifier), Output MOSFET, and

Overvoltage Protection. In addition to these, a number of MOSFETS are used as switches (to select various gain determining resistors). All the previously mentioned

FETs are inside Ul02 which also controls the FET

7-F-5

Service

30mV

RANGE

30!),

300mA

102K

-----'V'.'v-------1

X333

3

0 0 mV

RANGE

300!),

3A

3V

RANGE

3K[).-30M[).

1 02K

10K

323K

X3 3

3

X3. 33

3478A the positive terminal of Buffer U202. The reference output, which is applied to the positive terminal of the Output FET Control Amp U203, is divided down to

+

8V, irrespective of range, by feedback resistors RR3 and

RR4 in conjunction with R206. b. The output of the Buffer is

+

12V (or

+

8.4V for the 30M ohm Range only) which is applied to one side of either Range Resistor RR5, RR6, RR7, or RR8

(dependent on the selected range). The other side of the

Range Resistors is applied to the Output FET Control

Amp. c. Since the Output FET Control Amp is a high gain operational amplifier with its non-inverting terminal at

30, 300, 3K

RANGf

•

TG IJ\..lM:<

PROTECTIOt-.1 lOOK

OVERALL

>--t----

GAIN=. 333

X33.

3

• lOOK lOOK

233K

OVERALL

>--t----

GAIN=. 0333

X3 33

147B-7-F3

Figure 7-F-3. Simplified Schematic Of The DC/Ohms

Input Amplifier

switches. The following paragraphs explain how the ohms current is generated and how the ohms circuitry operates. Refer to Schematic 1 and Figure 7-F-4 for the explanation.

7-F -20. Current Generation.

The explanation on how current is generated is as follows: a. The Voltage Splitter's (U201) output is

+

12V (or

8.4V for the 30M ohm Range only) which is applied to

7-F-6 lOV

TO OHMS

PROTECTION

Figure 7·f·4. Ohms Circuitry Configuration

•

3478A

Service

•

+ 8V, its inverting terminal must also be + 8V (the inverting terminal draws little or no current). This makes the resultant voltage drop across the Range Resistors

+ 4V (or + .4V for the 30M ohm Range). d. A current is then generated with its value proportional to the value of the Range Resistor and the voltage drop across the resistor. e. The current is applied to the unknown resistor through the Output MOSFET (in U102), High Voltage

Protection Circuitry, and the HI INPUT Terminal. The

3478A's Ohms Ranges, Ohms Currents, Range

Resistors, and selected MOSFET Switches are listed in

Table 7-F-1.

7-F-21.

Voltage Splitter

(U201).

The following explains the Voltage Splitter (Reference) Circuitry. a. The Voltage Splitter is a X1.5 gain non-inverting amplifier with an output of + 12V (for the 300 ohm to

3M ohm Ranges) or + 8.4V (for the 30M ohm Range).

•

• b. The gain is determined by feedback resistors RR3,

RR4 (both in U102), and R201. Since the total value of

RR3 plus RR4 is 20K ohm and R201 is 40K ohm, the non-inverting gain is Xl.5. (The gain is:

[20K/40K] + 1

=

1.5). c. The + 12V output is generated by applying + 8V to the amplifier input (8•1.5

=

12). The + 8V is determined by the + lOY Reference (from the 3478A's

Reference Circuitry, see paragraph 7-F-49d) and voltage divider RRO, RRl, and RR2. The sum of RRl and RR2 is 200K ohm and RRO is 50K ohm resulting in a voltage drop across the resistors of + 8V and + 2V, respectively. The + 8V is applied through FET Switch SOR to

U201. d. The + 8.4V output is generated by applying

+ 5.6V to the amplifier input (5.6•1.5

=

8.4). The

+ 5.6V is also determined by the +lOY Reference (from the 3478A's Reference Circuitry) and voltage divider

RRO, RRl, and RR2. In this case the voltage drop across RR2 (which is + 5.6V developed across 140K ohm) is applied through FET Switch SlR to U201.

7-F -22. Buffer (U202) and Range Resistors (RRS to

RR8). The Buffer is a non-inverting Xl gain amplifier with its output at either + 12V or + 8.4V (on the 30M

Ohms

Range

30-3K

30K

300K

3M

30M

·ohm Range only). The gain is selected by either

MOSFET Switch pairs S6R and S7R, S8R and S9R,

SlOR and SllR, or S12R and Sl3R. The Range

Resistors are used to determine the different ohms current values. Refer to Table 7-F-1 to determine which switch and resistor is selected for the different ohms ranges.

7-F-23. The Output FET Control Amplifier (U203) and the Output MOSFET (in U102) form a feedback circuit used to boost the output impedance of the Output

MOSFET. The FET is normally biased into saturation, and in conjunction with the open loop gain of U203 and the Range Resistors, results in a high output impedance of the Ohms Current Source. A high output impedance is necessary to prevent measurement nonlinearities.

7-F-24. Overvoltage Protection Circuitry. The circuitry is used to protect the Ohms Current Source from high voltages inadvertently applied to the 3478A's Input Terminals (when the multimeter is in the Ohms Function).

The following explains the circuitry operation. a. If a large positive voltage is applied to the 3478A's

HI INPUT Terminal, the voltage is applied through

R204 and L201 to the cathode of CR201. Since the cathode voltage of CR201 is higher than the anode voltage, the diode is reverse biased. This prevents the large input voltage from damaging the current source . b. If a large negative voltage is applied to the 3478A's

HI INPUT Terminal, the voltage is dropped across

CR201, R203, and R202 to diode connected FET Q205.

This makes Q205 conduct and in turn clamps the base of

Q202 at -.7V (one diode drop). This voltage along with negative collector to base voltage forces Q201, Q202,

Q203, and Q204 to turn on. Transistors Q201 and Q203 conducts no more current than the circuit which generates the ohms current (on a given range). The circuit that generates the ohms current cannot tell the difference between a valid unknown resistance and the large negative input voltage. Most of the large input voltage is dropped across R202 and R203.

7-F-25. AC to DC Converter

7-F-26. The purpose of the AC to DC Converter is to convert the 3478A's ac inputs (volts or current) to de volts. The converter output is + 3.00000V de for all fullscale ac inputs with the output applied to the

AID

Con-

Ohms

Current

Table 7 -F-1. Ohms Current and Ranges

Range

Resistor

Resistor

Voltage

FET Switches

Enabled

1mA

.1mA

.01mA

1uA

.1uA

4K (RR5)

40K (RR6)

400K (RR7)

4M (ARB)

4M (ARB)

4V

4V

4V

4V

.4V

SOR,S2R,S3R,S6R,S7R,S14R

SOR,S2R,S3R,SBR,S9R,S14R

SOR,S2R,S4R,S1 OR,S11 R

SOR,S2R,S 12R,S 13R

S 1 R,S5R,S 12R,S 13R

7-F-7

Service 3478A verter. All ac ranging is done in the AC to DC Converter.

7-F-27. The AC to DC Converter consists of three amplifier stages and a True RMS Converter. The purpose of the amplifier stages is to provide the same full scale input voltage to the RMS Converter for all full scale ac inputs, and to be a buffer between the converter and the ac inputs. The True RMS Converter does the actual ac to de conversion. The following explains the circuitry operation.

7-F-28. Amplifier

Stages. Refer to Figure 7-F-5 and

Schematic 2 for the following explanation.

300mA RANGE"

RAZ lOOK a. The first amplifier stage (U301A) is an inverting amplifier with gains of X.OOl, X.l, or Xl (dependent on the ac range and function selected). The gains are determined by resistors RAl, RA2, RA3, and RAll (all in

U102), as shown in Figure 7-F-5. Capacitor C302 and resistor R305 are used for high frequency compensation

(for flat gains at high frequency). The gain determining resistors are selected by MOSFETS SlAC through

S6AC, and SllAC (all in Ul02) which operate as switches. The gains of the amplifier and FETs selected for the ac functions are listed in Table 7-F-2. b. The second amplifier stage (U301B) is an inverting amplifier with gains of X.4 or X4 (dependent on the ac

3A RANGE

RAZ lOOK

•

300mV RANGE

RAZ lOOK

---l

C301

X. 1

30V RANGE

RA3 lK

RAB

16K

3V RANGE

RAZ lOOK

---l

C301

RAB

16K

R303

24K

300V RANGE

RA3 lK RA7

16K

3~76-7-FS

7-F-8

R303

24K

Figure 7·F-5. AC Gain Configurations

•

R303

24K

•

3478A Service

•

Function and Range

Stage 1

Gain

ACV 300mV

ACV 3

ACV 30

ACV 300 v

.1

. 1 v

.001 v

.001

ACI 300mA 1

ACI 3 A

1

Table 7-F-2. AC Amplifier Gains

Stage 2

Gain

4

.4

4

.4

4

.4

Total

Gain

10

1

. 1

.01

100

10

Switches (FETs)

Enabled

S2AC,S4AC,S5AC,S8AC,S 1 OAC

S2AC, S4AC, S 5AC, S 7 AC. S9AC

S 1 AC,S3AC,S6AC,S8AC,S 1 OAC

S 1 AC,S3AC,S6AC,S7 AC,S9AC

S4AC,S5AC,S8AC,S 1 OAC,S11 AC

S4AC,S5AC,S7AC,S9AC,S11 AC range and function selected). The gains are determined by resistors RA5, RA6, RA7, and RA8 (all in Ul02), as shown in Figure 7-F-5. The gain determining resistors are selected by FETs S7AC to SlOAC (all in Ul02) which operate as switches (see Table 7-F-2). Resistor RA9 (in

U 102) is used for the amplifier to have the same high frequency response in X4 gain as in X.4 gain. Resistors R306 and R307, and C3l0 and C313 are used to filter the

+

l5V and -l5V power supplies, respectively. c. The third amplifier stage (U302) is a non-inverting amplifier with a gain of X25 in all ac ranges and functions. The output of the amplifier is applied to the RMS

Converter and is 3V RMS for all full scale ac inputs in all ac functions and ranges. Capacitor C305 is used for high frequency compensation (for flat gains at high fre-

• quency).

7-F-29. True RMS Converter (U303). The True RMS

Converter's output is a positive de voltage with its value equal to the true rms value of the input. For example, a sine wave input of l V RMS ac generates a put.

+

l V de out-

7-F-30. Refer to Schematic 2. The RMS Converter has one major stage that does the actual conversion and a buffer (used as an output stage). The converter stage and the buffer are externally connected by R304. Pin 9 of U303 is the input to the buffer and pin 10 is the output of the converter stage. The gain of the buffer is X1 which is internally set. Capacitor C307 is the RMS Converter's averaging capacitor and C308, C309, and resistor R304 are used with the buffer as a ripple filter.

7 -F-31. AID Converter

7-F-32. General. The

AID

Converter is used to change de voltages to digital information. The circuitry consists of an Integrator (U401 and associated circuitry),

Voltage Reference (U461 and associated circuitry), and the

AID

Hybrid (U403). The

AID

Converter operation is controlled by the

AID

Controller (U462).

•

7-F-33. The

AID

conversion method used by the 3478A is called Multi-Slope II and has two operating states:

Runup and Rundown. The 3478A's most significant digits are determined during runup (see paragraph

7-F-41) and the least significant digits are determined during rundown. The integration time depends on the selected Number Of Digits Displayed (3 112, 4 112, or 5

1/2). To help understand Multi-Slope II, first consider the operation of the Dual-Slope Conversion method.

This method is explained in the following paragraph.

7-F -34. Dual-Slope Conversion. In dual-slope conversion, an integrator capacitor charges for a fixed time period (as shown in Figure 7-F-6), which is done during runup. The charging rate and the resultant amplitude of the charge is proportional to the voltage applied to the integrator. The integrator capacitor is then discharged at a fixed rate determined by a known reference voltage and is done during rundown. Since the discharge rate is constant, the discharge time is proportional to the amplitude of the charge (input voltage). The amplitude level can then be determined by the discharge time.

7-F-35. Multi-Slope II Conversion. Multi-Slope II is similar to Dual-Slope in that a capacitor is charged and discharged by the input voltage and by known reference voltages. The following paragraphs explain the Multi-

Slope II operation (runup and rundown).

7-F-36. Simplified Explanation of Runup. The Runup operation lasts for 349

AID

counts with one

AID

count equal to 30 (36 in the 50Hz option) cycles of the ALE clock (Address Latch Enable at U462 pin 11). Each

AID

count results in one

AID

ramp (or slope) at the output of the

AID

Integrator. The same time is used in both the

5 112 and 4 1/2 digit mode (349 ramps), with lO readings taken in the 5 1/2 digit mode (making the integration time time longer, see paragraph 7-F-40). Only

34 ramps are used in the 3 112 digit mode. The ALE clock is generated by the

AID

Controller (U462, also known as the Floating Common CPU). Refer to Figure

LARGER , / / / / ' , , ' ' , , , _ .• · , ,

INPUf.l,./

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

/

' , , ,

~--

RUNUP -----iof4---RUNDOWN

---~

Figura 7-F-6. Dual Slope Conversion

3468 7-FG

7-F-9

3478A

Service

+Vref

C410

I L n

I

I

I

I

I

I

I

- - - - - - -

I

COMP OUT

---------- -----1------------------------------------------------------

1

I

U462

A/0

CONTROLLER

3478 7-F7

-Vref

Figure 7 ·f· 7. Simplified A/0 Converter

7-F-7

~nd

Figure 7-F-8 for the following simplified explanatiOn of the runup operation.

C4~0. in the opposite direction (C410 is discharged).

Thts

IS because the applied current is larger than the input current. a. When runup starts, the input voltage

(AID

Conve_rter in~ut voltage, not instrument input voltage) is appl_Ied to mtegrator U401. The resultant input current

(Im) then charges integrator capacitor C410 and a certai~ slope (output of the integrator) is then developed.

!h1s happens

~t time period T1 (see Figure 7-F-8). (The mput voltage 1s always applied during runup.) d. When time T3 is completed, the

AID

Controller determines if the output slope crossed zero. If zero crossing is detected, a current with the same value and an opposite polarity as the previously applied current is a~plied.

This current is the same current as the first applied current and is applied to the integrator for a new time period T4 (T4 is as long as T3). This current, in addition to the input current, then charges C410. Since both currents charge C410, the output slope becomes steeper and, as shown in Figure 7-F-8, crosses zero. b .. After ti~e period T1, a negative going current is apphed to the mtegrator for a set time period. This curre~t, in addition to the input current, charges C410.

Th1s generates a positive going output slope (the integrator output). The applied current makes sure that

~he output slope that follows will cross zero, whether the mput current is positive or negative. The current is applied for time period T2. e. If no zero crossing (in step c) was detected (because of a larger input voltage), the same current as the previously applied current is applied for the new time period T4. The current is reapplied until zero crossing is detected. (This is shown as the dashed lines in Figure

7-F-8).

. c. After time. period T2, the applied current (not the mput_ cu_rrent) 1s re~oved and a current of opposite pola!1ty 1_s then apphed to U401 for new time period T3

(T3 1s tw1ce as long as T2). The newly applied current is the same value as the first applied current (at time T2) but at opposite polarity. The new current then charge~

Tl

/

TZ

'

....

/1

/

...-

T3

--..

--..

--.. --..

--..

T4

------

--..

'

:

..._,--+---...,

'

'

' f. The operation in steps c and d, or in steps c and e continues until the runup operation is completed. The total runup operation lasts for 349 ALE ramps (or counts). g. During the runup operation, a counter in the

AID

Co?troller increments during the positive going slope penods and decrements during the negative going slope periods. The counter, in effect, is used to determine the amount of charge added and subtracted from the input voltage. From that information, the most significant digits of the 3478A's reading is calculated.

T3

=-2-

7-F-37. Detailed Explanation of Runup. Figure 7-F-9 illustrates the 3478A runup operation in the 4 112 digit mode. Refer to the figure (and Schematic 3) for the runup explanation in the following steps. The solid lines

(in the figure) showing the runup sequence is for a

7-F-10

Figure 7-f·B. Integrator (U401) Output Slopes

•

•

•

T5 T6 T7

Service

•

3478A

15

{ 181

5

{61

ALE CYCLES AT 60Hz!50Hz1

Figure 7-F-9. Runup Slopes (4

1/2

Digit Model)

hypothetical input value. The dashed lines are for a larger hypothetical input value. a. When runup starts, the integrator capacitor (C410) is charged by the input current (which is developed by the input voltage). The input current is applied to the negative terminal of integrator U401 (see Figure 7-F-7), and since the integrator is in the inverting configuration, the resultant output of U401 is positive (for positive input currents the slope is negative). The capacitor is

• charged for a short time period. b. During the time period when only the input current is applied, no other currents charge C410. Since no other current is applied to U401 (except the input current), it is called a no current condition and the resultant output slope is called slope S + 0.

30

{361

3478 7-F9 e. When time T2 is completed, an S + 4 current is applied for 30 ALE cycles (36 ALE cycles for the 50Hz option) during time period T3. The S + 4 current has the same value as S-4, but at opposite polarity. This charges

C410 in the other direction (i.e. the capacitor is discharged and then charged in the other direction).

Time period T3, and the T5, T7, and T9 periods that follow are twice as long as time period T1 (30 or 36 ALE cycles instead of 15 or 18 ALE cycles). f. After time T3, the S + 4 current is removed and no current (slopeS+ 0) is applied for time T4. Time T4 is as long as time period T2 (5 or 6 ALE cycles). This is also the same time for the S-0 or S + 0 slopes that follow. g. When T4 is completed, the

AID

Controller then determines if the output slope has crossed zero. Zero crossing occurs when the

AID

comparator's output

(CMP output at U403 pin 11) changes state. In the example, zero crossing is detected and current S-4 is applied for time T5 (30 or 36 ALE cycles). c. After the time period, a negative current (called

S-4) is then applied to U401. This current develops a positive going output slope which is called slope S-4.

The S-4 current is always the first current applied to the integrator after the input current is applied. The current is applied for 15 ALE cycles (18 ALE cycles in the 50 Hz option) and is for time period Tl. Since the input current and the applied current in the example have the same polarity, both charge C410. If the input current was at opposite polarity, C410 will still be charged in the same direction but the output slope will be less steep.

This is because the applied current (S-4) is normally larger than the input current. h. After time T5, current S-4 is removed and no current (slope S-0) is applied for time T6. Since zero crossing was detected (during time T5), current S + 4 is applied for time T7, after slope S-0 is completed. i. When time T7 is completed, no current (slope

S + 0) is applied for time T8. Since no zero crossing was detected, current S + 4 is reapplied for time T9 (after slope S + 0). d. After time period T1, current S-4 is removed. A no current condition (slope S-0) will then exist for 5 ALE cycles (or 6 ALE cycles for the 50Hz option) during time period T2. The charge rate of Capacitor C410 is again determined by only the input current. Slope S-0 is also a no current condition, as is slope S + 0. The major dif-

• ference is that the slopes are generated differently (see paragraph 7-F-39). Slope S-0 is selected since the previous no current condition was slope S + 0. The slopes alternate with each other (S + 0, S-0, S + 0, etc.) for each no current condition. j. Since zero crossing was detected during time T9, current S-4 is applied (after slope S + 0) for 30 (or 36)

ALE cycles. Then S + 4 is applied (since zero crossing is detected) and so on. This takes place until the runup time is completed (either currentS+ 4 or S-4 is selected, dependent upon if and when zero crossing occurs). k. Once the runup operation is completed, U462 then determines the 2 most significant digits of the reading.

For other than a zero reading, the number of S + 4 slopes will always be different than the number of S-4

7-F-11

Service 3478A

T 1 TZ T3 T5 T6 T7

T9

•

S-4 ov

INPUT

TO

1\/D

S+O generated.

15

( 181

30

(361 (61

30

(361

30

(361 (61

ALE CYCLES AT 60Hz (50Hz1

30

(361

Figure 7-F-10. Runup Slopes for Zero Inputs (4 112 Digit Model)

3478 7-F10 slopes. For a perfect zero reading, the number of S

+

4 slopes will be the same as the number of S-4 slopes. This is represented in Figure 7-F-10.

7-F -38. Slope

S

+

4 and S-4 Generation.

The following explains how the curents for slopes S

+

4 and S-4 are a. SlopeS+ 4. Refer to Figure 7-F-11. Note that both

Yl and Y2 paths are connected to ground. Since the summing node of the paths is a virtual ground and Y 1 and Y2 are also connected to ground, no current flows between the paths and the summing node. Current does flow from

+

Vref (Positive Reference Voltage) through a lOOK ohm resistor into the integrator capacitor (connected to the negative terminal of U401). This generates a negative going output slope. b. Slope S-4. Refer to Figure 7-F-12. Note that both

Yl and Y2 paths are connected to -Vref (Negative

Reference Voltage). Since the summing node is a virtual ground, current flows from

+

Vref through a lOOK ohm

+Vref

I

I

I

I

I tOOK

~ lsUMMIN~

I

N

0 0;..=-E --..;,_____..,

I C

~---H------,

I

I

Yl

I

1 OOKl OOK

YZ

: SLOPE

: S+4

3468 7-Fll

-Vref

Figure 7-F-11. Slope S+4 Generation

resistor and paths Yl and Y2 to -Vref. Current also flows from the integrator capacitor

(C) to -Vref. Thi1: current is generated because the total resistance of tht:

Yl and Y2 paths is smaller than the lOOK ohm resistor from

+

Vref. The current from

+

Vref plus the current from the capacitor equals the total current through paths Yl and Y2. Since the total resistance of paths Yl and Y2 is 50K ohms, the current from

+

Vref

(11)

and the current from the capacitor (12) is half as large as tht: total Yl and Y2 current (13). The resultant output slopt: is positive.

I

I

I

I

I

+Vref

~---

- - 12=123

I

U403

I lOoK

Il=Iz3~ ~

C---Hc·-----.

II3=Il+I~

I

I

I y 1

I lOOKlOOK

YZ

'

! SLOPE

S-4

3468 7-Fl2

Figure 7-F-12. Slope S-4 Generation

7-F-39. SlopeS+ 0 and S-0 Generation.

Refer to Figure

7-F-13. Note that one side of a lOOK ohm resistor (Yl path) is connected to ground and the other side is connected to the summing node. Since the lOOK ohm resistor from

+

Vref (Y3 path) and the lOOK ohm resistor from -Vref (Y2 path) are also connected to the summing node, no current flows from the integrator capacitor

(C).

This is because the resistance value of path Y2 and Y3 is the same and makes the current value of paths Y2 and Y3 the same (but opposite polarity).

This is true for both slopes S

+

0 and S-0. The only dif-

7-F-12

•

•

3478A

+Vref

•

:U403 rl lOOK

Y3

I

=u

Y2

Yl

I

SLOPE

S+O

3468 7-F13

Figure 7 ·F-13. Slope S

+

0 and S·O Generation

ference is that paths Y1 and Y2 are switched when the slopes are switched (Y1 to ground and Y2 to -Vref, or

Y2 to ground and Y1 to -Vref).

7-F -40. Run up Time.

The run up time changes with the number of digits selected. For the 3 1/2 Digit mode, the time is 1/600 second (for both the 60Hz and the 50Hz

• options) and is called .1 PLC (Power Line Cycles). For the 4 1/2 Digit mode, the time is 1160 second (1/50 second for the 50 Hz option) and is called 1 PLC. The 5 1/2

Digit mode is different. In this mode, 1 PLC is used for the runup time with the AID operation repeated ten times. The resultant ten readings are then averaged and the answer becomes a single reading.

7-F-41. Digit Generation.

When the 3478A is in the 4 Y2 and 5 Y2 Digit mode, the first two significant digits (of the reading) are determined during runup. In the 3 Y2

Digit mode, only the first digit is determined. In rundown, the three least significant digits are determined in all modes. A total of

5 Y2 digits are developed in both the

5

Y2 and 4 Y2 digit modes. Since only 4 Y2 digits are displayed in the 4Y2 digit mode, the last digit in the mode is rounded off to the next higher digit.

Service

7-F-42. Rundown.

When runup is completed, the voltage at the AID Converter's input is removed and the input is then connected to ground. The rundown operation then starts. Rundown is used to determine the three least significant digits of the 3478A's reading.

7-F-43. After runup, a voltage (or charge) remains on the integrator with its amplitude and polarity dependent on the last current applied (S

+

4 or S-4) and the input voltage (applied during runup). By obtaining the value of the remaining voltage, the least significant digits can then be determined. The voltage value is obtained by applying various currents to the integrator and counting the number of times the currents have to be applied for the resultant output slopes of the integrator to cross zero.

7-F-44. The currents applied to the integrator are called the S-4, S

+

4, S-3, S

+

2, S-1, and S

+

1 currents and the resultant output slopes are the S-4, S

+

4, S-3, S

+

2, S-1, and S

+

1 slopes. Each one of the currents (S-4, S

+

4, etc.) are applied (in the given order) to the integrator a set number of times until zero crossing occurs. The only exception is the first S-4 current (see paragraph 7-F-45 step c). The first and second set of currents applied are the S-4 and S

+

4 currents, respectively. These currents have the same value as the S-4 and S

+

4 currents used in the runup operation, but are applied half as long. The

S-4 and S

+

4 slopes are each 15 ALE cycles long (30

ALE cycles in runup) and are called half-ramps. The next currents applied (in order) are the S-3, S

+

2, and

S-1 currents, with S-0 slopes applied between them.

7-F-45. Rundown time is separated into five time periods, as shown in Figure 7-F-14. Refer to the figure for the following explanation on the rundown operation. a. When rundown starts, the polarity of the remaining voltage on the integrator is determined by the AID

Controller (U462). The polarity is determined by the output state of the AID comparator (CMP output at

U403 pin 11). A high output level shows a positive voltage and a low level shows a negative voltage.

Tl T2 T3

T4 T5

POSITIVE

INTEGRATOR

VOLTAGE s-o s-o

•

NEGATIVE

INTEGRATOR

VOLTAGE

Figure 7·F·14. Rundown Slopes

7-F-13

Service b. If it has been determined that the remammg voltage on the integrator is negative, S-4 currents are applied a number of times until zero crossing occurs (CMP output changes state). Since the S-4 currents can be applied (during time T1 in Figure 7-F-14) to a maximum of three ramps, the resultant output slope S-4 will normally cross zero with three or less S-4 currents applied. After zero crossing occurs, the current is removed with 15

ALE cycles (i.e. one half-ramp) after the S-4 slope crosses zero.

If

(after the current is removed) time T1 is not completed, a no current condition remains (i.e. an

S-0 slope) for the rest of time Tl. No current is applied to keep the rundown time constant. c. If the remaining voltage on the integrator is positive, current S-4 is applied for a short time and then removed. The current is applied for a short time because the current develops a positive output slope and the integrator voltage is also positive. Both the slope and the integrator voltage together could saturate the integrator. When Current S-4 is removed, no current (an

S-0 slope) is then applied for the rest of time Tl. Current S-4 is applied whether the integrator voltage is positive or negative. This is to make sure that the slopes that follow (slope S + 4) will always cross zero and that the same transitions occurs for all readings. d. The next current applied is positive S + 4 current.

Its value is the same as S-4, but in the opposite direction. The current is applied until slope S + 4 crosses zero. The current can be applied (during time T2) a maximum of three ramps. This makes time T2 the same as time T 1. The S + 4 currents are also removed within

15 ALE cycles after the S + 4 slope crosses zero. Here again, no current is applied (slope S-0) for the remainder of time T2. e. After time T2, the next current applied is negative

S-3 current (its polarity is opposite of S + 4). Because the value of an S-3 current is 1/10 the value of an S-4 current, the resultant S-3 slope is not as steep and takes longer time to cross zero. This makes the maximum number of times the currents can be applied (during time T3) seven times instead of three. The S-3 current is also removed within 15 ALE cycles after slope S-3 crosses zero. Then no current (S-0) is applied for theremainder of time T3. f.

When time T3 is completed, positive current S + 2 is applied. This current is 1/10 the value of S-3 (1/100 of

S-4) and in the opposite direction. The maximum number of times the S + 2 current can be applied is seven

(as are S-3 currents). Time T4 has the same amount of time as T3. The S + 2 currents are also removed within

15 ALE cycles after slope S + 2 crosses zero. Then no current (S-0) is applied for the remainder of time T4. g. The next current applied is negative S-1. This current is 1/10 the value of S+2 (1/1000 of S+4) and in the opposite direction. The current is applied until it

7-F-14

3478A crosses zero. The currents are also removed within 15

ALE cycles after slope S-1 crosses zero. h. Once the S-1 currents are removed a positiveS+ 1 current is applied for 5 ALE cycles and is called one sixth ramp. This current is applied instead of no current and only happens after the S-1 slope. The current has the same value as S-1, but in the opposite direction. The currents are applied until zero crossing occurs and are removed within 5 ALE cycles after crossing zero. i. After current S + 1 is removed, within 5 ALE cycles, current S-1 is reapplied. This new S-1 current is also applied until zero crossing occurs. After S-1 slope cross zero, current S + 1 is reapplied. After current S + 1 is removed, S-1 is applied, and so on. This takes place until time T5 (and rundown) is completed. j. During the rundown time, a counter in the AID

Controller counts the number of S-4, S + 4, S-3, S + 2, and S-1 slopes it takes for each set of slopes to cross zero. This is then used to calculate the three least significant digits of the 3478A's reading.

7-F -46. Integrator Offset Compensation. The AID Integrator can have offsets which prevent the S + 2 and S-1 slopes from crossing zero. To make sure the slopes will cross zero, the A/D's DAC (Digital to Analog Converter, U465 and associated circuitry) is turned on before the S + 2 currents are applied. The DAC is used to null out any offsets from the integrator. The maximum number of times the S + 2 current can be applied is seven (as are S-3 currents). Time T4 has the same amount of time as T3. The S + 2 currents are also removed within 15 ALE cycles after slope S + 2 crosses zero. Then no current (S-0) is applied for the remainder of time T4.

7-F-47. The correct DAC setting is determined during the time when the S + 1 and S-1 currents are applied.

These currents are applied after the first set of S-1 slopes have crossed zero (see paragraph 7-F-45, step g). Since both S + 1 and S-1 currents have the same amplitude, the S + 1 and S-1 slopes should have the same magnitude

(i.e. zero crossing should occur at a a certain time).

If a difference in magnitude is noted by the AID Controller, the DAC is adjusted until the magnitude of the S + 1 and

S-1 slopes are the same. This is illustrated in Figure

7-F-15.

•

•

7-F -48. Rundown Slope Generation. The S-4 and S + 4 slopes are generated the same way it is done for the runup operation (see paragraphs 7-F-38). The only difference is that they only depend on the applied S-4 and

S + 4 currents, not the input current. The S-0 slope is generated the same way as the S-0 slope in runup (see paragraph 7-F-39). The S-3 and S-1 currents use the same circuitry configuration as the S-4 current (see

Figure 7-F-12), but use different resistor values. The resistor values are such that the S-3 current is 1/10 the

•

3478A

Service

•

DAC VALUE

MUCH TOO LOW

DAC VALUE

TOO LOW

DAC VALUE

TOO HIGH

DAC VALUE

GOOD

3468 7-FlS

DAC VALUE

MUCH TOO HIGH

Figure 7-F-15. Determining the DAC Setting

S-4 current and the S-1 current is 1

I

1000 the S-4 current.

The S

+

2 and S

+

1 currents use the same circuitry configuration as the S

+

4 current (see Figure 7-F-11). In this case, resistor values chosen are such that the S

+

2 current is 1

I

100 the value of S

+

4 current and S

+

1 is

1/1000 the value of S

+

4.

26

DC IN

25

7-F-49.

AID

Converter and Reference Circuitry.

The

AID Converter Circuitry consists of the AID Hybrid

(U403), AID Integrator (U401 and associated circuitry),

AID Controller (U462), and a DAC (U465 and associated circuitry). Since the Voltage Reference Circuitry (U461, U405, U404, U402, and associated circuitry) uses part of the AID Hybrid (for stability purposes) and since it is also used by the AID Converter, it is considered part of the converter circuitry. Refer to

Schematic 3 for the following explanation on the AID

Converter Circuitry (except for the DAC, see paragraph

7-F-46 and 7-F-47 for its explanation). a. AID

Hybrid (U403).

The AID Hybrid, shown in

Figure 7-F-16, operates as follows:

1. The AID Hybrid has, internal to it, various latches, decoders, and a clock generator. The decoders receive control information from the

AID Controller, then decode the information and pass the new information to the latches. The latches then transfer the new information to the various switches in the hybrid during each clock pulse. The clock pulses are generated by the clock

27

AC IN

+

v

REF

28

24

•

•

D

5

E

G

B c

A

7

B

9

ALE

10

CMP OUT

11

3468 7 -Flo

RA13 RA14

33.35K 7.SK

23

RAll RA12 lllK

25K

STATIC

PROTECTION

DECODE

LOGJC

LATCH

----J

RAl

99. toK

RA17

30K

RA18

70K

22

21

1

LEVEL

SHIFT

----

~-----i

20

STATIC

PROTECTION

DECODE

LOGIC

LEVEL

SHIFT

LATCH

JA

SLOPE

SWJTCHES

~~'

11 OF

!; I

RA16 lOOK

RA2 lOOK

RA3 lOOK

RA15 lOOK

RAS lOOK

RA4

SOOK

RA7

RAo lOOK 112.5K

RAB

1M

RA9

1M

RA10

14.706K

~

_JEF

TTL

DRlVER

I

CLOCK

'GENERATOR

I

LATCH

2,1~.

ANALOG

~~-

DIGITAL

v

co~~

31

+SV

151

-v

REF

141

+15V

19

18

Vss

13 f---

4

CMP

IN

Figure 7 ·F-16. AID Hybrid (U403)

7-F-15

Service generator which is syncronized by the ALE clock

(from the AID Controller). The hybrid receives all its control information from ports PlO through

Pl4 of the AID Controller (U462 pins 27 to 31).

The information is transferred over the A, B, C,

D, and E lines (U403 pins

5

through

9) of the hybrid.

2. The S-4, S+4, S-3, S+2, S-1, S+ 1, S-0, and

S + 0 currents are developed using resistors RA2 through RAIO in conjunction with the slope switches.

3. The AID comparator is also inside the AID

Hybrid and its input is connected to the output of the AID Integrator. The comparator updates its output during each clock pulse. Since the comparator's output is connected to a latch, the output is transferred to a TTL driver during each clock pulse. The TTL driver is a buffer which connects the output of the latch to the

AID Controller.

4. Dependent on the function selected, the hybrid connects the DCIOhms Input Amplifier's output or the AC to DC Converter's output to the

AID Integrator's (U401) input resistor (RAl in

U403). This is done by the input switches inside the hybrid. b. AID Integrator (U401 and associated circuitry).

The AID Integrator consists of an amplifier (U401) with capacitor feedback (C410). Since the amplifier is inverting, the output slopes of the integrator will be positive for negative input currents (and vice versa). c. AID Controller (U462). The AID Controller controls the operation of the AID Converter. This includes the control of the runup and rundown operation, and selecting the correct currents (S-4, S + 4, etc.). Refer to

3478A paragraph 7-F-77 for more information on the

AID

Controller. d. Voltage Reference. The Voltage Reference provides three stable reference voltages: -lOY, +lOY, and a buffered -lOY. The circuitry, shown in Figure 7-F-17, is explained as follows:

1.

The -lOY reference voltage is used by the

AID Hybrid (U403) to develop stable and accurate S-4, S + 4, S-3, etc. currents. The reference voltage is developed by non-inverting amplifier

(U405) using feedback resistors in U403 and a 7Y reference diode (zener diode U461). The 7Y reference diode is connected to the amplifier's positive terminal and determines the stabilty of the reference voltage. The diode voltage is very stable since the case of the diode has internal heaters to keep the diode temperature as constant as possible. The feedback resistors for U405 are in U403 for good stability.

2. The buffered -lOY is used by the

AID

Hybrid as a stable -lOY power supply. The voltage is developed by Xl gain non-inverting amplifier

U404 and the -lOY reference voltage.

3. The +lOY reference voltage is used by the

AID Hybrid (in conjunction with the -lOY reference) to develop the S-4, S + 4, S-3, etc. currents. The +lOY reference voltage is also used by the Ohms Current Source to develop a stable ohms current (see paragraph 7-F-21). The reference voltage is developed using inverting amplifier

U402 and feedback resistors in U403.

7-F-50. 3478A Logic Circuitry

7-F-51. General. The 3478A Logic Circuitry can be divided into two circuit areas: Chassis Common Cir-

•

•

-7V

R468

2K

-lOV REF

70K

30K

U403 lOOK

18 lOOK

">------.!~-

+

1 0 v

•

7-F-16

3478 7-F17

Figure 7-F-17. 3478A Simplified Reference Circuitry

R761

17.4K

R762

6.49K

;====SCHEMATIC 7 ~

+5V

U501

CPU

R763

6.49K

Service

3478A

• cui try and Floating Common Logic Circuitry. Communications between the circuitry is done by the Isolation Logic. The circuitry is described as follows:

7-F-52. Chassis Common Circuitry- paragraph 7-F-55. a. Main CPU (U501) Circuitry - paragraph 7-F-57. b. Program ROM (U502) - paragraph 7-F-58. c. Power-On and Reset Circuitry- paragraph 7-F-59. d. CMOS RAM - paragraph 7-F-60. e. RAM Addressing - paragraph 7-F-61. f. Reading the RAM - paragraph 7-F-62. g. Sending Data to the RAM paragraph - 7-F-63. h. Keyboard Operation - paragraph 7-F-65.

1.

Display Operation - paragraph 7-F-66. j. HP-IB Operation - paragraph 7-F-67. k. Rear Panel Switch Circuitry - paragraph 7-F-68.

I. Voltmeter Complete - paragraph 7-F-69. m. External Tigger - paragraph 7-F-70.

7-F -53. Isolation Logic - paragraph 7-F -71.

7-F -54. Floating Common Logic Circuitry - paragraph

7-F-75.

• a.

AID Controller (U462) Operation - paragraph

7-F-77. b.

AID Converter Control- paragraph 7-F-78. c. Input Hybrid Control- paragraph 7-F-79. d. Digital to Analog Converter Operation

-paragraph 7-F-80. e. CPU Reset Operation - paragraph 7-F-81. f. Front/Rear Switch Position - paragraph 7-F-82.

7-F-55. Chassis Common Circuitry

7-F-56. The Chassis Common Circuitry controls the operation of the whole instrument, including front panel and remote operation. The major circuitry is the Main

Controller Circuitry, consisting of a CPU (U501) and a

Program ROM (U502). The operation of the Chassis

Common Circuitry is descibed in the following paragraphs. Unless otherwise specified, refer to

Schematic 3 for the explanation.

7-F-57. Main CPU (USOl) Circuitry. The operation of the CPU and associated circuitry is as follows: a. The CPU has an internall28 bytes of RAM memory and a clock. The frequency and stability of the clock is determined by 5.856 MHz crystal Y501. b. The Data Lines (DO to D7) from the CPU are used as both Data Lines and the lower 8 bits of the Address

•

Lines (AO to A7). This is done by multiplexing the lines.

The Address Lines are used to address the Program

ROM, CMOS RAM, and the HP-IB Chip. The Data

Lines send and receive data between the CPU and the

Program ROM, CMOS RAM, and HP-IB Chip. The

ALE (Address Latch Enable) line goes low to latch the lower 8 Address bits on U513. The Address bits are then sent to the Program ROM, CMOS ROM, and HP-IB

Chip. c. Other lines from the CPU are bi-directional Ports.

The ports are used to send data to the display and to send, and receive data between the Front Panel Pushbuttons and Isolation Logic. The ports used to send data to the display (P20 to P23) are also used as the upper Address bits (A8 to All).

7-F-58. Program ROM (US02). The Program ROM is addressed when its CE Line (Chip Enable at U502 pin

20) is low. The low comes from the CPU's PSEN Line

(Program Store Enable at U501 pin 9). Address AO to

A7 comes from latch U513. Address bits AS to All comes from Ports P20 to P23 (U501 pins 21 to 24). Address bit

Al2 comes from Port P26 (U501 pin 37) of the CPU.

When the ROM is addressed and enabled, data from the

ROM is transfered to the Data Lines.

7-F -59. Power-On and Reset Circuitry. The Power-On and Reset Circuitry are used to reset the CPU after the

3478A is turned on, when the front panel TEST /RESET button is pressed, and if the CPU inadvertantly goes to a non-operational state. The circuitry operates as follows: a. Power-On Circuitry. Refer to Figure 7-F-18, or

Schematic 3 and 4. The Power-On Circuitry resets the

CPU when the 3478A is turned on and when

+

5V power supply is low. The step by step operation is as follows:

1. When the 3478A is turned on, the positive input of comparator U550C goes high after the

+

5V power supply comes up.

2. Since the negative terminal of U550C is connected to BT701, the output of the comparator at-

F==-

SCHEMATIC 6

= . _

U512

CMOS

RAM

'3478 7-FtB

-

~

BT701

3V

Figure 7·F·1 B. Power-On Circuitry

7-F-17

Service tempts to go high and charges capacitor C763. The output goes high since the comparator has an open collector output and a pull-up resistor is connected between the CPU's RESET line (output of U550C and U550D) and

+

5V (the resistor is internal to the CPU).

3. During the charge time, the RESET line is held low until the capacitor is charged to a high level.

4. The RESET line goes high and the CPU resets and turns on. The 3478A is now in its turnon state.

5. As long as the RESET line is low, the CPU's

SS (Single Step) line is low (the line is connected to the RESET line). The SS line steps the CPU to its first program line. The program line sets the

PSEN line high, which disables the Control ROM

(CE high). This prevents the ROM from operating until the CPU turns on.

6. When the RESET line is low, the CE2 line of the CMOS RAM (U512) is also low and disables the RAM (see paragraph 7-F-61).

7. The CPU is also reset when the supply goes low. A low

+

5V power

+

5V sets the positive input of U550C low which makes U550C's output low. This resets the CPU. b. Reset Circuitry. Refer to Figure 7-F-19, or Schematic

3 and 4. The Reset Circuitry is used to reset the CPU when the TEST /RESET button is pressed or if the CPU inadvertently goes to a non-operational state. The step by step operation is as follows:

1. During normal operation, counter U507 is continuously incremented by the ALE clock.

2. Port Pl4 (U501 pin 31) continuously output data to the keyboard (Pl5 is one port used to scan

;====SCHEMATIC 6 = = = = -

+5V

3478A the keyboard, see paragraph 7-F-65). This resets the counter as long as the keyboard is scanned. The reset pulse is developed from Pl5 using C501 and

R528.

3. If the TEST /RESET button is pressed or the

CPU goes to a non-operational state, the keyboard scanning is stopped.

4. Since the ALE clock is still operating, the counter keeps incrementing for about 1.3 seconds.

5. After the 1.3 seconds, the Q output of U507 goes high (RESET REQ line goes high). This is because the counter is not being reset.

6. The Q output is connected to the negative terminal of comparator U550D. This brings the output of U550D low which in turn brings the RESET line low.

7. The ALE clock turns off and the counter stops incrementing.

8. The Q output goes low and the output of

U550D attemps to go high and charges C763 (see step a-2).

9. Once the capacitor is charged to the high level, the

RESET line once again goes high. The CPU then resets and turns on. The 3478A is now in its turn-on state.

7-F-60. CMOS RAM. The CMOS RAM is used to store the 3478A'S Calibration Constants. The following paragraphs explain how the RAM is addressed, how data

(constants) is read from the RAM, and how new data

(new constants) is sent to the RAM. This is done using the RAM's Address, Input, and Output Lines. The Address Lines are connected to the CPU's lower 8 Address bits (AO to A7). The RAM's input and output lines (Dl to D4) are connected to each other and to the DO to D3

Data Lines.

•

•

32

P15

11 LE

U501

CPU

+5V

R7&1

17.4K

R762

6.49K

R501 lOOK

R763

6. 4 9K

'=:SCHEMATIC 7

= f

Figure 7·f-19. Reset Circuitry

3478 7-Ft9

7-F-18

7-F-61. RAM Addressing. The RAM can only be addressed as long as line CE2 (Chip Enable 2 at U512 pin

17) is high. The line is high when the 3478A is turned on.

Line CEI (Chip Enable I at U512 pin 19) can be high or low. This line is used to read the RAM (see next paragraph).

7-F-62. Reading the RAM. The RAM can be read under the following conditions. a. Line OD (Output Disable at U512 pin 18) must be low.

It is low when the RD Line (Read at U501 pin 8) is low. b. Line CEI must also be low. It receives the low from one section of the Quad flip-flop U506 (pin 6).

•

3478A

•

The flip-flop operates like a latch and transfers data from Port P23 during each ALE cycle . c. Once the previous conditions are met (the RAM is addressed) and line CE2 is high, data from the RAM is transferred to the Data Lines.

7-F-63. Sending Data to the RAM. The RAM can receive new Data when its R/W line (Read/Write at

U 512 pin 20) is low. This can only happen if the 34 78A' s

Cal Enable Switch (located on the front panel) is on and the WR line of the CPU (Write at U501 pin 10) is low.

The following explains the operation. a. The Cal Enable Switch brings one input of NOR gate U508C low. b. The other input of the gate is a low from the WR line. c. The output of U508C goes high, and since NOR gate U508D is configured as an inverter, the output of

U508D goes low. The RAM is now ready to receive new data.

•

7-F-64. Since the 3478A's Calibration Constants are stored in the CMOS RAM, the constants must remain in the RAM when the 3478A is turned off (or power removed). This is done by battery BT701 in the

+

5V

Power Supply Circuit. In addition, the RAM should not see any possible write commands (R/W low) during the time that power is removed. The RAM must be disabled.

This is because a write command may erase some calibration constants. The RAM is disabled by comparator

U550C (part of the CPU's power-on circuit in the

+

5V power supply). The operation is as follows (refer to

Schematic 4 for the explanation): a. As long as the 3478A is on, the RAM gets its supply voltage from CR500. b. When power is off, the RAM gets its supply voltage from battery BT701 through diode CR764. The battery voltage is used for data retention. c. After turning power off, the RAM is disabled by setting line CE2low. This is done by comparator U550C

(see Schematic 4). The comparator senses a low (or no

+

5V) from voltage divider R761, R762, and R763. Since

U550C's inverting input is at the battery voltage, the output of U550C becomes low. This discharges capacitor

C763 before the power supply goes off. This makes line

CE2 low and disables the RAM.

7-F-65. Keyboard Operation. The Keyboard's pushbuttons are connected in a 4x4 matrix and are continuously

• scanned by the CPU. The operation is as follows: a. One side of the matrix is connected to Ports PIO to

Pl3 of the CPU (U501 pins 27 to 30) and the other side is connected to Ports P14 to P17 (U501 pins 31 to 34).

Service b. Before scanning starts, Ports P14 to P17 are low.

When scanning begins, starting with Port P14, each port goes sequentially high. c. During the time that the keyboard is scanned, the

CPU determines which one and if any of Ports P10 to

Pl3 are high. A high on PIO to Pl3 is used to determine the button pressed. For example, the SRQ button is pressed and turns the corresponding SRQ switch on.

This connects Port P 11 to P 17 and makes P 11 high when P17 is high. Since the CPU knows when it sets P17 high and also knows when Pll is high, the pressed button is determined.

7-F -66. Display Operation. The 3478A Display is an alphanumeric display with 12 annunciators. The CPU sends serial data to the Display Circuitry which in turn does all the necessary decoding of the data (to display readings, etc.). The operation is as follows: a. With line PWO high, the CPU can send new data to the Display Circuitry. Data is in serial form and is sent on the Data line (U506 pin 4). For the Display Circuitry to receive and decode the data, the other display lines have to send certain information to the circuitry.

This is as follows:

1. The Display Circuitry requires two clock inputs to receive data, II and 12. The inputs come from flip-flop U506 (pin3) and Port P25 for clock inputs II and 12, respectively. (Flip-flop U506 is used as a latch between the CPU and the Display

Circuitry.)

2. The ISA line (U506 pin 5) is used to give instructions to the Display Circuitry.

3. The SYNC line (U506 pin 6) is used to tell the

Display Circuitry when to look for instructions. b. With line PWO (from Port P23 of the CPU at

U501 pin 36) low, the Display Circuitry operates without receiving any data from the CPU. The circuitry can operate in this mode since it has an internal clock

(capacitor C502 is the frequency reference). With the circuitry in the internal mode, no updating of the display is done. Line PWO is controlled by the CPU.

7-F -67. HP-IB Operation. All interfacing between the

CPU and the Hewlett-Packard Interface Bus (HP-IB) is done by the HP-IB Chip (U503) and two Bus

Transceivers (U504 and U505). The HP-IB Chip is a microprocessor and changes the data sent and received by the CPU to the necessary HP-IB information (e.g.

Listen, Talk, etc.). The Transceivers transfer and receive the HP-IB information between the HP-IB Chip and the Bus. The circuitry operates as follows: a. The HP-IB Chip (U503) receives its clock signal from the CPU's TO output (U501 pin 1).

7-F-19

Service b. When U503 is addressed (by the CPU) and its

WR

(Write) line is low, data from the CPU is sent over the

Data Lines to U503. Line WR gets its low from the CPU's

WR line. With the CPU WR line low, its RD (Read) line is high (which makes U503's RD line high). Depending on the Address selected (RSO to RS2 at U503 pins 21 to

23, which are the AO to A2 Address Lines of the CPU),

U503 interprets the data as a command (ATN, SRQ, etc.) or data (DIOI to DI08) and sends the appropriate information to the HP-IB. c. When U503 is addressed (by the CPU) and its

RD line is low, U503 is enabled to send data to the CPU over the Data Lines. Line RD gets its low from the

CPU's RD line. Depending on the Address selected

(RSO to RS2, see previous step), the data may be remote data from the HP-IB (Program Codes, etc.) and status information (Remote, Local, etc.). d. The CPU continuously checks (for HP-IB data) and updates U503.

7-F -68. Rear Panel Switch Circuitry. The Rear Panel

Switch (S501) is an 8 section DIP switch used to select the 3478A's HP-IB Address, set the Power-On SRQ

Status Bit, set the 3478A to the Talk-Only Mode, and to set the multimeter to the selected power line frequency.

The switch positions are determined by the CPU when driver U510 is enabled. The switches that are on (set) will then bring the corresponding data lines low. The driver is enabled when line Gl (CPU's RD line) and G2

(from flip-flop U506) are both low. The operation of the switches is as follows: a. HP-IB Address. The switches marked AO to A4 set the 3478A's HP-IB Address. When the CPU determines the setting of the switches, it passes the information to the HP-IB Chip. (Refer to this manual's Section III for more information on addressing the 3478A.) b. Power-On SRQ Bit. The switch marked POW

SRQ is used to set the Power-On SRQ Status Bit. The setting of this switch is also passed on to the HP-IB

Chip. (Refer to Section III of this manual for information on SRQ.) c. Talk-Only Mode. When all AO to A4 switches are on, the 3478A's Talk-Only Mode is selected. Here again, the CPU sends the necessary information to the

HP-IB Chip. d. Power Line Frequency. The 50/60Hz switch is used to set the 3478A for the correct power line frequency.

The CPU determines the position of the switch and passes it on to the AID Controller (located in the

Floating Common Circuitry). Dependent on the position of the switch, the

AID Controller selects the corresponding Integration Time of the AID Converter

(1/60 second for 60Hz or 1150 second for 50Hz, etc.).

7-F-20

3478A

7-F-69. Voltmeter Complete. The Voltmeter Complete pulse is connected to inverter U508C from the PROG line of U501. The output of U508C is connected to inverters U508D, E, and F with their outputs connected to the Voltmeter Complete Terminal. Inverters U508D, E, and F are used as output buffers and CR504, CR505, and R538 is the protection circuitry. The voltmeter complete output is a negative going TTL pulse with a duration of approximately lp.S.

•

7-F-70. External Trigger. An external trigger pulse

(connected to the External trigger Input) is used to trigger the 3478A, when the multimeter is in the External

Trigger mode. The operation is as follows: a. When an external trigger pulse is received, J-K flip-flop U514B is clocked and its Q output goes high.

Since the Q output is connected to the INT input of the

CPU,

iN'F

goes high. b. If the 3478A is configured to a trigger mode other than the External Trigger mode, no action is taken. INT remains high. c. If the 3478A is in the External Trigger mode, the

CPU checks the state of the INT line. If the line is high, the 3478A is triggered. If the line is low, the CPU keeps on checking the line until INT goes high or the 3478A is configured to another trigger mode. d. When INT goes high (and the 3478A is in the External Trigger mode), the 3478A triggers and initiates a measurement cycle. e. During that time, the HP-IB Chip is addressed and sends out a trigger pulse (from its TRIG output at U503 pin 5). f. The pulse is inverted by flip-flop U514A (which is configured as an inverter) and resets flip-flop U514B.

The 3478A is now ready for a new trigger pulse.

7 .f. 71. Isolation Logic

7-F-72. The 3478A's Isolation Logic is used to communicate between the CPU (U501) in the Chassis Common Circuitry and the CPU (U462) in the Floating

Common Circuitry. The serial data from U501 (going to

U462) is used to control the operation of Floating Common Circuitry. This includes instrument set-up information (Function, Range, etc.) and AID information (like changing the integration time). The serial data from

U462 to U501 is the multimeter's measurement data and certain self-test data (AID test information). The following explains the circuitry operation.

7-F-73. The data from U501 is output from Port P27

(U501 pin 38) and applied to drivers U508A and U508B.

The drivers apply the data to the input (primary) of transformer T501. The output of T501 is applied to

•

•

3478A

• comparators U468A and U468B. The comparators are used to bring the low level output of T501 up to a TTL level. The output of the comparators is applied to the TO input of U462 (U462 pin 1), which is the same data as the data sent by U501. This makes the output waveform of U501 the same as the input waveform of U462.

7-F-74. Serial data from U462 to U501 is sent using drivers U467 A and U467B, transformer T401, and comparators U550A and U550B. The circuitry operation is the same as sending data from U501 to U462 (see previous paragraph). The difference is that the data is input to the Tiline of U501 (U501 pin 39) instead of TO, as is the case with U462.

7·f·75. Floating Common Logic Circuitry

7-F-76. The main parts of the Floating Common Logic

Circuitry are the A/D Controller and the AID Converter. The A/D Controller consists of CPU U462 and the A/D Converter is U403 and associated circuitry.

Other circuitry includes an Digital to Analog Converter

(U465 and associated circuitry) and a Voltage Reference

Supply (U404, U405, and U461). For the explanation on the A/D Converter and Voltage Reference refer to paragraph 7-F-49. The operation of the AID Controller, the Digital to Analog Converter, and other logic

• circuitry is explained in the following paragraphs.

7-F-77. A/D Controller (U462) Operation. The purpose of U462 is to control the AID operation, set up the

Digital to Analog Converter, and to send set-up (Range and Function) information to the Input Hybrid U102

(see paragraph 7-F-13 for its operation and purpose).

The CPU also determines measurement data from the

AID Converter and sends the data (readings) to the

Chassis Common CPU (U501). The CPU (U462) has an internal 128 bytes of RAM memory, 2K bytes of ROM memory, and a clock. The frequency and stability of the clock is determined by a 10.98MHz crystal Y460. The

ROM is used to control the CPU operation and the

RAM is used to store Autozero constants (see paragraph

7-F-14). Since the U462 has an internal ROM, all addressing and data transfer is done using bidirectional

Ports P10 to P17 (U462 pins 27 to 34) and P20 to P27

(U462 pins 27 to 34, 21 to 24, and 35 to 38).

7-F-78. A/D Converter Control. The AID Converter receives control data from the CPU Ports PlO to P14

(U462 pins 27 to 31). The data is used to select the various slopes (see paragraph 7-F-49) in the converter.

The output of the AID Converter (CMP, the Comparator Output) is applied to the T1 input of the CPU

(at U462 pin 1). The ALE output (Address Latch Enable at U462 pin 11) is used as the converter's clock. Refer to

• paragraph 7-F-31 for more information on the

AID

operation .

7-F-79. Input Hybrid Control. The control lines to the

Input Hybrid (Ul02) which come from Ports P15 to P17

Service of the CPU and are: Data, Mode, and Clock. The lines do the following: a. When the Clock input (U102 pin 24) is low, no data is transferred into the hybrid. b. When the clock input is high, the following occurs:

1. When the Mode input (U 102 pin 25) is low, data on the Data line (U102 pin 26) is transferred into the hybrid (into an internal shift register).

2. When the Mode input is high, the data in the hybrid (in its shift register) is used to set-up the switches in the hybrid.

7-F-80. Digital to Analog Converter Operation. The

3478A's AID Converter requires a certain offset voltage

(see paragraph 7-F-46 for more information). This offset is applied to the negative input of the AID Integrator

(U401) and comes from the Digital to Analog Converter

(DAC). The offset voltages are developed by resistors

R401 to R406, which are selected by Hex D flip-flop

U465. Each time the flip-flop is clocked by the ALE line, its QO to Q5 outputs are set either high or low. This depends on the position (high or low) of Ports P20 to

P25. The outputs in conjunction with resistors R401 to

R406 generates a certain offset voltage .

7-F-81. CPU Reset Operation. The Chassis Common

CPU (U501) can reset the Floating Common CPU

(U462) whenever needed. This is normally done when the 3478A is turned on. The operation is as follows. a. Counter U466 increments each time it is clocked by the ALE line (U462 pin 11). b. As long as the Chassis Common sends data bytes over the Isolation logic, the counter is reset each time the data byte has a high (a high resets the counter). c. If the counter's Reset line stays low (e.g. no high level from the data bytes), the counter keeps on incrementing for about 11mS. The counter's Q14 output then goes high. d. The Q14 output is inverted by NOR gate U467C

(connected like an inverter) and sets the CPU's RESET line (U462 pin 14) low. The CPU turns off. e. The CPU remains off until the counter's Reset line receives a high from the data bytes. This resets the counter and its Q14 output goes low. The RESET line of the CPU goes high and U462 resets and turns on to a predefined condition.

7-F-82. Front/Rear Switch Position. The 3478A's

Front/Rear Switch position is determined by the state

(high or low) of Port P26. A low state is when the port is

7-F-21

Service connected to ground (by the switch). This state shows that the Front/Rear Switch is in the rear position.

7-F-83. Power Supplies

7-F-84. General. The 3478A has one set of power supplies for the Floating Common Circuitry and another set of supplies for the Chassis Common Circuitry. The

Floating Common Circuitry has three supplies: + 15V,

-15V and + 5V. The Chassis Common Circuitry has one

+ 5V supply and a + 3V lithium battery (BT701). The supply is used by the Chassis Common logic circuitry and the battery is used by the CMOS RAM (U512) to supply the RAM when the battery is off. Unless otherwise noted, refer to Schematic 4 for the following explanation on the

3478A's power supplies.

7-F-85. + 15V and -15V Power Supplies (Floating Common). A full-wave bridge rectifier, consisting of CR701,

CR702, CR705, and CR706, develops the raw

(unregulated) voltages for the supplies. The regulated

+ 15V is developed by voltage regulator U703 and the

-15V by U702. Breakdown diodes CR711 and CR713 are used for overvoltage protection. Overvoltage protection of regulators U702 and U703 is by diodes CR715 and

CR714, respectively. The diodes conduct if the raw

(unregulated) voltage is too large. Capacitors C702, C703,

C705, and C706 are filter capacitors. Temperature sensitive resistor RT706 and RT707 are used to protect supplies from excessive output currents. The protection circuitry operates as follows: a. If the output current of the + 15V supply is excessive, RT707 heats up. If the -15V has excessive current, RT706 heats up.

3478A b. Since RT706 and RT707 have positive temperature coefficients, their resistance increases to a large value due to high temperature. c. The high resistance causes most of the supply voltage to drop across RT706 and RT707, shutting down the respective supply. d. The large resistance value remains until RT706 or

RT707 cool down (the supply draws normal current).

7-F -86. + 5V Power Supply (Floating Common). This power supply receives its raw (unregulated) voltage from full-wave rectifiers CR703 and CR704. The + 5V is developed by voltage regulator U701. Breakdown diode

CR712 is used for overvoltage protection. Capacitor C704 and C711 are filter capacitors.

7-F-87. +5V Power Supply (Chassis Common). This power supply receives its raw (unregulated) voltage from full-wave rectifier CR760 and CR761. The + 5V is developed by voltage regulator U760. Breakdown diode

CR766 is used for overvoltage protection and capacitor

C761 and C762 are filter capacitors. Comparators U550C and U550D are used to reset the Chassis Common CPU

(U501). Refer to paragraph 7-F-59 for information on the comparators operation.

7-F-88. +3V Power Supply (CMOS RAM). As long as the 3478A is turned on with ac power applied, the CMOS

RAM (U512) receives its supply voltage from the + 5V power supply through diode CR500 (see Schematic 3).

When power is off, the battery (BT701) supplies the voltage to the RAM through diode CR764. This circuit maintains the supply voltage on the CMOS RAM to keep the 3478A's calibration constants in the RAM's memory.

•

•

•

7-F-22

•

SERVICE GROUP G

SCHEMATICS

Service Group G Contents

n~ ~~

General Schematic Notes ..................... 7-G-1

3478A Block Diagram ........................ 7-G-2

Input Circuitry and Ohms

Current Source (Schematic

1) ................

7 -G-3

ACto DC Converter (Schematic 2) ............. 7-G-4

AID Converter and Control

Logic (Schematic 3) ........................ 7-G-5

Power Supplies (Schematic 4) ................. 7-G-6

7·G·1. INTRODUCTION

7-G-2. This Service Group has the 3478A's Block

Diagram and Schematics. In addition, general schematics notes are also included to gain an understanding on how to use the schematics.

•

GENERAL SCHEMATIC NOTES

1. RESISTANCE IN OHMS, CAPACITANCE IN MICROFARADS, INDUCTANCE IN MICROHENRIES UNLESS OTHERWISE NOTED.

8.

9.

2. ASTERISK DENOTES A FACTORY-SELECTED VALUE. VALUE SHOWN ON SCHEMATIC TYPICAL

3.

4.

ENCLOSES FRONT PANEL MARKING. c· ::

J

ENCLOSES REAR PANEL MARKING.

5. - - - - - - - -

CIRCUIT ASSEMBLY BORDERLINE.

6.

OTHER ASSEMBLY BORDERLINE. ALSO USED TO INDICATE MECHANICAL INTERCON-

NECTIONS (GANGING).

7.

DENOTES WIRE COLOR CODE. CODE USED IS SAME AS THE RESISTOR OR COLOR CODE. FIRST NUMBER

IDENTIFIES THE BASE COLOR. SECOND NUMBER IDENTIFIES THE NARROWER STRIPE.

E.G.

~DENOTES w

DENOTES GROUND ON FLOATING COMMON CIRCUITRY.

m

DENOTES GROUND ON CHASSIS COMMON CIRCUITRY. CONNECTED TO INSTRUMENT FRAME GROUND.

Figure 7·G·1. General Schematic Notes

•

7-G-1/7-G-2

- - - - - - - - - - - - - ,

FLOATING COMMON

- - - - - -

I

I

I

I

In

~~~sE

I

~I

I

!____()

HI

I

I

I r--0

LO

I

I

I

1

~

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I o

I j~j

,-----

OHMS

CURRENT

SOURCE

INPUT

SWITCHING

INPUT

AMPLIFIER

"':" ~

-------------

---------------

'

REFERENCE

~

A/D

,--------.. CONVERTER

~

.1\C TO DC

CONVERTER ~--------J

______________________________

SWITCH CONTROL

;

A/D

CONTROLLER

I

POWER

SuPPLIES

I

I

I

.

-

ISOLATION

LOGIC

-

I

I

-

-

-

- -

I CHASSIS COMMON

I

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

ISOLATION

LOGIC

MAIN

CONTROLLER

3478-7-F-1

HP-IB

INPUT/OUTPUT

L _ _ _ _ _ _ - - - - - - - -

FRONT PANEL

CONTROL

(PUSHBUTTONSJ

-

DISPLAY

-

- - - - -

------~

Figure 7-G-2. 3478A Block Diagram

7-G-3

~l!J

C502

RSOG

R529 .

R532

. R531

R528

-RSS4-

. csoo

CRSOl

A SOl

-C51B-

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-R555-

- R T 5 0 5 -

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-m-

TPlOOo

TPlOto

J110

R108

R109 -

LO

HI m

C512

.JM503

.JM502·

[

=

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C301

R103

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I

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~

~

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I

K101

I

R104 c~~

-

R110

J

.J104

J103

C310 -

: . J 3 0 1 D

C313

[101 -

U201

D

C201

L201

C107

ClOB -

R307

C302

R305

C305

R302

R308 l_,,:2

R201

U101

0

-R205-

-C204-

C103

C102 -

C312

R105

R101 -

R303

U302

· R204

C314

R202

0

~

=

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TP7 0

Wo4CQ1oz

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00

-csaa-

C762

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R306

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C304

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C306 _ 0

-

C308 - U303

0

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C303 -

U202

D

U203

R304

G".io3G".io1 Glos

I -~0-;

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C202

R206

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A207

C203

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A102 - .JMlOZ

GND o

CR766

-R765-

ClOG

C105

8

R40B

C431

JM4Ql·

R407

C765

-C467·-

- R 4 0 6 -

-R405-

-R401-

-R402-

- R 4 0 3 -

-R4Q4-

U404 U402

D D

JM302

JM101

U405

D

R469

R4G8

C430

U4@

C433

C432

C401

C402

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·CR76-4·

-R768-

[411

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C404

C410

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T760

C412

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0

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-CR760-

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C464

C463 oo~

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R523

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·CR508·

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R462

R466

R467

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=~~5\l:

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U702

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RT706

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-C706-

3478 7-G-B

I

A

I

B

I c

I

DIE I FIG I HI j

I

K

I

Component Locator for Input Circuitry and Ohms Current Source

7-G-4

COMPONENT LOCATOR TABLE FOR SCHEMATIC 1 (INPUT CIRCUITRY)

Component

C101

C102

C103

C104

C105

C106

C107

C108

C201

C202

C203

C301

C314

CR201

Col.

E,F c c c

E

E c c c

A

E,F

B

D c

Component

CR202

E101

JM101

JM201

K101

K102

K103

K104

L201

0201

Col.

E

B

B

B

B c

D

A

F

E

Component

0202

0203

0204

0405

R101

R102

R103

R104

R105

R106

R107

R108

R109

R110

Col.

D

D

D

E

D

E

B

B,C

D

E

B

A

A

B

~

SHOWN IN

OUT

POSITION

(fRONT TERMINALS)

SWITCH S1

18 17 16 15 14 13 12 11

10

0

0

2 3 4 5

6

7 8

9

Component

R201

R202

R203

R204

R205

R206

R207

TP100

TP101

U101

U102

U201

U202

U203

A

A

C,D

C,D

E

E

E

Col.

c

D

D

D

D

E

E

[P7o -A

Ti"NPi

CrRCu"i'TRY AND""'HMs-cURRENT sO..iRc_E_ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

~

- - - - - - - - - - - - - - -- - - - - - - - - - -

Ct!MS CURRENT SOURCE

03478-1515501 ERC: 2717

JM201

,==

R~~~f~~6E

==_

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I

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R206

4. 3K

-~~ t=RA~~[filsl~TDOO~

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R201

40K

;===============

INPUT SWITCHING

================-

CR202

16.2V

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& 0

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INPUT

(2WD)

I

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.

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8

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Rll0 lK

R109

1. 6M

~

RHl3

51K

2

TO U301 (8)

---w-

R308

300

I

C314

~

1

R106

51K

R105

51K

33 ~

+H!V

~

-15V~-15V

12:

K101

~

R104

51K

_l_Ct03

+

470pF

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i

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Kl02

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----

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6

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r=

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JM101

TOA~3(25) 3

Rl!il2

51K

R101

51K u:

J100

!

)

!

TP100 TP101

J110 SPG

J

I

(~ ~Rl08

NOTE lK

TEST POINTS SPG

A~A~Eo!~.A

C102

~

m

+5\I~+SV

R000

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3

C..K~FMU462(32l3

K104

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42 :

27:

TA~ RI~T

2

1 C!IF 4 RELAY DRIVERS

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(27,28,29,3€1)

l_----------------------------------------------~--------~~=~~=~~=~~--------------~---------------------------------_j

CCPYRIGHT 1981 BY HEWLETT-PACKARD CCMPANY MCOlFlED 3478-lA/3

1

Figure 7-G-3. Input Circuitry and Ohms Current Source

7 -G-517 -G-6

)

C50'2

11500

0~

R5'29

R5'3'2

115'31

R5'28

-R554-

-C518-

-R553-

-R555-

-11T505-

-C50'3-

-R504csoo

CR501

R501

JllO

- R108

~

(512

Jrt503

LO

HI

D

EIOI

JH502

0 m

¥501

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Q

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-R~OG-

-R405-

-R401-

-R402-

-R403-

-R404-

[-~~

C302

R305

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C312

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0

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- C309 -

U~04 U402

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R201

U101

U202

[202

U

203

R304

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L_j

R206

LR202

R207

RllO

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J104

C201

L201

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D

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-C204-

R204

R202

Q,,GJ,

0

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[203

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U405

R468

[430

[433

[432

R407

D

R4b9

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C108

0 ':;:,

R307

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C'305

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8

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C301

C302

C304

C305

C306

C307

C308

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E

E

E

B c

E

D

E

Component

C310

C311

C312

C313

C314

JM301

JM302

Col. c

E

D c

D

E

F

Component

JM303

R302

R303

R304

R305

R306

R307

Col.

D

D

D

E

C,D

D,E c

Component

R308

U102

U301

U302

U303

Col.

D

C,D c

D

E

+Vs

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I

OUT

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1

FROM S3

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1

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1M

I

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I

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COPYRIGHT 1981 BY HEWLETT-PACKARD COMPANY

, = = = = = =

STAGE 2

RA2 lOOK

:

:

----------------------

C302

I

2. 7pf

I

I

I

37

39

R305

47.5K

RA6

4K

RA3 lK

RAB

16K

+15V

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I

34

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I_ - - - - - - - - - - - - - - - - - _ I

RA7

16K

I

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40K

RA9

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\

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=

\

+15V

C305

68pf t

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I

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R3D3

R302 24K lK

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22

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TO AID

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Figure 7-G-4. AC to DC Converter

7-G-7

0~

[502

R506

R529

· R532

RS31

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C306 -

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R206

CR202

R207

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=-'i.":,lb~-=-

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[765

U402

DD

U405

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R-469

R4G8

C430

U4W

C433

C432

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-CR760-

C411

C401

C402

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CR764

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-R761-

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C464

C463

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R462

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R467

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C404

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U703

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~CRA551o~­

·CA502

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-CR711-

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FIG

I HI j

I

K

I

Component Locator for AID Converter and Control Logic

7-G-8

)

Col.

F,G

F,G

G

G

G

F,G

H

F

F

F

F

G

G

H

H

F j

A

A

A

K j j

E j c c

B

B,C

B,C

A

H

H

A

Component

C466

C467

C46B

C501

C502

C503

C504

C506

C507

C508

C509

C510

C511

C512

C514

C515

C518

C401

C402

C404

C405

C410

C411

C412

C430

C431

C432

C433

C463

C464

C465

CR401

CR402

CR500

COMPONENT LOCATOR TABLE FOR SCHEMATIC 3 (LOGIC)

Component

Col.

CR501

CR502

CR503

CR504

CR505

CR507

CR50B

A j j

J,K

H

H

H

J501

J504

A j

JM401

JM403

JM501

JM502

JM503

R401

R402

R403

R404

R405

R406

R407

R40B

R409

R460

R461

R462

R463

R464

R465

R466

R467

R468

F

H c

A,B

B

F

F

G

H

H

G,H

F

F

F

E

F

F

G

G

G,H

G,H

G,H

F

A c

K

Col. j

H

H

H

H

A

A

A

A

K

H j

A j

A

A

D

B

F

H

A

A

H

H

G

H

B

Component

R51B

R519

R520

R521

R522

R523

R524

R52B

R529

R469

R470

R501

R503

R504

R506

R509

R510

R517

R531

R532

R534

R53B

R539

R553

RT505

RP527

S501

T401

T501

TP2

~

SHOWN IN

OUT

POSITION

!FRONT TERMINALSl

SWITCH S1

18 17 16 15 14 13 12 11 10

0

0

1 2 3 4

5

6

7

8

9

Component

Col.

TP3

TP4

TP5

TP6

TP7

TPB

TP9

B

B

D

A

E

B

B

U401

U402

U403

U404

U405

U461

U462

U465

U466

U467

U46B

U501

U502

U503

U504

U505

U506

U507

U510

U512

U513

U514

U515

U550

B c

D,E

E,F

E

A

A

D c

B

G

F

G

F

F

F

G,H

G

H

G,H

H j

A

G

Y460

Y501

H

B

FA-~-~AlDCoNvERTERAND-~LOGIC----

03478-66501 ERC 2717

1

I

1

TO Ul02(24)

1

TO UHI2(26)

1

TO UHl2(25)

+15V

TP401 TP402

;::::::::::=:=

INTEGRATOR~

" •

.

':'"

~ '[""'"

R407

B. 2M

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- -

+5V

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I

I

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COMMON ... CHASSI_S_COMM<iJ- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

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- - - - - - - -

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12

1 a.J<

I

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R 11

13

•

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I s

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CR505

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17

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0

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36

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P23

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05

:

1

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n

l

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I : jR509

R532. R.531 4 t0K u oe

5. lK 5. lK

1

12

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177

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12 H 18 2 1 3 5 j 20

5. lK

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: :R503 i

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~···~

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10K ;;

I :

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3: l.lV

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I

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I

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1

I

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1

I

I

I

I

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1

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1

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CR501

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A3

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AI

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3

Figure 7-G-5.

AID

Converter and Control Logic

7-G-9/7-G-10

A

B

Co'"po-1

BT701

C702

C703

C704

C705

C706

C71 1

C720

C760

C761

C76 2

C763

C765

Col.

J

K

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K

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G

F

F

J.K

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G

c

D

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COMPONENT LOCATOR TABLE FOR SCHEMATIC 4 IPOWER SUPPLYI

Campanant

C766

CR701

CR702

CR703

CR704

CR705

CR706

CR711

CR712

CR713

CR714

CR715

CR760

Col.

G

J j

J

J

J

G

J

J

K

J

J

J

Carapoa•nt

CR761

CR762

CR764

CR767

FX760

J702

JM701

JM702

JM703

R761

K

J

J

G

Col.

G

G

G

E , F

J,K

K

H

Companl!lnt

R762

R763

R765

R766

R767

R768

RT706

RT707

U550

U701

U702

U703

J

J

G

K

J

J

1:.1.

G

G

G

F

F

G

J

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K

J702

I

I

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I

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CR715

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10

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470

R768

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Figure 7-G-6. Power Supplies

7-G-1117-G-12

•

A·1. Introduction

APPENDIX A

A-2. This appendix contains a general description of the Hewlett-Packard Interface Bus (HP-IB). HP-IB is

Hewlett-Packard's implementation of IEEE Standard

488-1978, "Standard Digital Interface for Programmable Instrumentation". The information is noncontroller dependent but, where appropriate, is dependent on the 3478A.

A·3. General HP·IB Description

A-9. HP·IB System Overview

A-10. The following paragraphs define the terms and concepts used to describe HP-IB (Bus) system operations.

A-11. HP-18 System Terms a. Address: The characters sent by a controlling device to specify which device will send information on the

HP-IB and which device(s) will receive that information. Addressing may also be accomplished by hardwiring a device to only send information or only receive information.

A-4. The Hewlett-Packard Interface Bus (HP-IB) is a carefully defined interface which simplifies the integration of various instruments, calculators, and computers into systems. The interface provides for messages in digital form to be transferred between two or more

HP-IB compatible devices. A compatible device can be an instrument, calculator, computer, or peripheral device that is designed to be interfaced using the HP-IB.

•

A-5. The HP-IB is a parallel bus of 16 active signal lines grouped into three sets, according to function, to interconnect up to 15 instruments. A diagram of the Interface Connections and Bus Structure is shown in Figure

A-1.

A-6. Eight Signal lines, termed as DATA Lines, are in the first set. The Data Lines are used to transmit data in the form of coded messages. These messages are used to program the instrument function, transfer measurement data, coordinate instrument operation, and to manage the system. This allows you to set-up the instrument and read its measurement data. Input and Output of messages, in bit parallel byte serial form, are also transferred in the Data Lines. A 7-bit ASCII code normally represents each piece of data. b. Byte: A unit of information consisting of 8 binary digits (bits). c. Device: A unit that is compatible with the IEEE

Standard 488-1978. d. Device Dependent: An action a device performs in response to information sent over the HP-IB. The action is characteristic of an individual device and may vary from device to device. e. Polling: This process typically is used by a controller to locate a device that needs to interact with the controller. There are two types of polling, as follows:

1. Serial Poll: This method obtains one byte of operational information about an individual device in the system. The process must be repeated for each device from which information is desired.

2. Parallel Poll: This methods obtains information about a group of devices simultaneously.

The 3478A does not respond to a Parallel Poll.

A-7. Data is transferred by means of an interlocking

"handshake" technique which permits data transfer

(asynchronously) at the rate of the slowest active device used in that particular transfer. The three DATA BYTE

CONTROL lines coordinate the transfer and form the second set of lines.

A-8. The remaining five GENERAL INTERFACE

MANAGEMENT lines are used to manage the devices on the HP-IB. This includes activating all connected

• devices at once, clearing the interface, and others. A condensed description is available in the Condensed

Description of the Hewlett-Packard Interface Bus

Manual, -hp- part number 59401-90030. The manual is available through your local -hp- Sales and Service Office.

A-12. Basic Device Communication Capabilities

A-13. Devices which communicate along the interface bus can be classified into three basic categories: a. Talker: Any device that is able to send information over the HP-IB when it has been addressed. Only one talker may be active at a time; usually the one that is currently directed to send data. All HP-IB type calculators and computers are generally talkers.

A-1

Appendix

3478A

DEVICE A

ABLE TO TALK,

LISTEN AND CONTROl

L--,...-----,~J=f-==*l#l=i=D

I e .

q.

CALCULATOR)

I

c

f:;-,___,oe_::AT.:_A

,aus'---,--~-

r

1 ..._ 18 SIGNAL LINES I

DEVICE B

ABLE TO TALK

AND LISTEN le.q. DIGITAL VOLTMETER!

I HANDSHAKE I l I NES

•

ONLY ABLE TO LISTEN

II.Q.

SIGNAL

GENERATOR! c

DEVICE 0

ONLY ABLE TO TALK

=_

~::j::j:::J::::W t 1.

q.

TAPE READER J

~010

1-8

L _ _ _ O A V

'=====

NRFO

NOAC

I

L

I

====="c

REN

' - - - - - - - - - - E O I

Figure A-1. Interface Connection and Bus Structure b. Listener: Devices which receive information over the HP-IB, when they have been addressed. A device may or may not be both a talker and a listener.

Calculators and computers are generally both a talker and a listener (at different times). c. Controller: The device that can specify which device(s) on the bus is a talker or listener. There can be two types of controllers, an· Active Controller and a

System Controller. The Active Controller is the current controlling device. The System Controller can, however, take control of the HP-IB even if it is not the

Active Controller. There can also be only one Active

Controller at a time, even if several controllers are on the Bus.

A-14. HP-18 Messages

A-15. Different types of information can be passed over the HP-IB to one or more devices. Some of this inforamtion is in the form of messages, most of which can be separated into two parts. One part can be classified as the address portion specified by the controller and the information that comprises the messages. The second part can be classified as HP-IB management messages.

These message are comprised of twelve messages and are called Bus messages.

A-2 a. Data: The actual information (binary bytes) sent by a talker to one or more listener. The information

(data) can either be in numeric form or a character string. b. Trigger: The Trigger message causes the listening device or devices to perform a device dependent action when addressed. c. Clear: The Clear message causes the listening device(s) or all the devices on the HP-IB to return to their predefined device-dependent state. d. Remote: This message causes the listening device(s) to switch from local front panel control to remote program control when addressed to listen. e. Local: This message clears the REMOTE message from the listening device(s) and returns the device(s) to local front panel control. f. Local Lockout: This message prevents a device operator from manually inhibiting remote program control. g. Clear Lockout and Set Local: With this message, all devices are removed from the local lockout mode and revert to local. The remote message is also cleared for all devices.

•

•

3478A

• h. Require Service: A device can send this message at any time to signify the device needs some type of interaction with the controller. This message is cleared by the device's STATUS BYTE message if the device no longer requires service. i.

Status Byte: A byte that represents the current status of a single device on the HP-IB. One bit indicates whether the device sent the require sevice message and the remaining seven bits indicate optional conditions defined by the device. This byte is sent from the talking device in response to a "Serial Poll" operation performed by the controller. j. Status Bit: A byte that represents the operational conditions of a group of devices on the HP-IB. Each device responds on a particular bit of the byte thus identifying a device dependent condition. This bit is typically sent by deviCes in response to a parallel poll operation. k. Pass Control: The bus management responsibility is transferred from the active controller to another controller by this message.

•

I. Abort: The system controller sends this message to unconditionally assume control of the HP-IB from the active controller. The message will terminate all bus communication but does not implement the CLEAR message.

A-16. 3478A Bus Capabilities

A-17. The 3478A interfaces to the HP-IB as defined by

Appendix the IEEE Standard 488-1978. The interface functional subset which the 3478A implements is specified in Table

A-1.

SH 1

AH 1

T5

Table A-1. 3478A Device Capability

Source Handshake complete capability

Acceptor Handshake complete capability

Basic talker, with serial poll, talk only mode, and unaddress with MLA.

TEO

L4

LEO

SR1

RL 1

PPO

DC 1

DT1

CO

No extended talker

Basic listener, unaddress when MTA

No extended listener

Service request complete capability

Remote-Local complete capability

No parallel poll capability

Device Clear complete capability

Device Trigger complete capability

No controller capability

A·18. HP·IB Worksheet

The HP-IB worksheet (Table A-2) can be used to determine the HP-IB capabilities of the other HP-IB compatible instruments in a system. The sheet may be filled in with the bus message applicability for your controller and for each HP-IB device. The bus capability for the

3478A has already been filled in. Refer to your controller manual and the manual(s) of your other device(s) for their Bus Message capabilities. Once the sheet is filled out, you should then have the HP-IB capabilities of your device(s) .

•

A-3

A-4

Appendix

DATA

TRIGGER

CLEAR

LOCAL

REMOTE

LOCAL

LOCKOUT

CLEAR LO &

SET LOCKOUT

REQUIRE

SERVICE

STATUS

BYTE

STATUS

BIT

PASS

CONTROL

ABORT

Message

INSTRUMENT

IDENTIFICATION

AND

HP-IB

ADDRESS

MODEL

3478A

LISTEN

YES

TALK

YES

5 BIT

VALUE 23

S&R

R

R

R

R

Table A·2 HP-18 Worksheet

Device

MODEL

LISTEN

TALK

5 BIT

VALUE 23

R

R s s

N

N

N

S

=

SEND ONLY

R

=

RECEIVE ONLY S & R

=

SEND AND RECEIVE N

=

NOT IMPLEMENTED MODEL LISTEN

3478A

•

•

•

•

•

11111111111111111111111111111111111111111111111111111111111111111

034 78-90008

FJ/o-

HEWLETT

li:~

PACKARD

•

Printed in U.S.A.