Emerson 755A Instruction manual

Instruction Manual
748183-K
April 2002
Model 755
Oxygen Analyzer
http://www.processanalytic.com
ESSENTIAL INSTRUCTIONS
READ THIS PAGE BEFORE PROCEEDING!
Rosemount Analytical designs, manufactures and tests its products to meet many national and
international standards. Because these instruments are sophisticated technical products, you
MUST properly install, use, and maintain them to ensure they continue to operate within their
normal specifications. The following instructions MUST be adhered to and integrated into your
safety program when installing, using, and maintaining Rosemount Analytical products. Failure to
follow the proper instructions may cause any one of the following situations to occur: Loss of life;
personal injury; property damage; damage to this instrument; and warranty invalidation.
• Read all instructions prior to installing, operating, and servicing the product.
• If you do not understand any of the instructions, contact your Rosemount Analytical
representative for clarification.
• Follow all warnings, cautions, and instructions marked on and supplied with the product.
• Inform and educate your personnel in the proper installation, operation, and
maintenance of the product.
• Install your equipment as specified in the Installation Instructions of the appropriate
Instruction Manual and per applicable local and national codes. Connect all products to
the proper electrical and pressure sources.
• To ensure proper performance, use qualified personnel to install, operate, update, program,
and maintain the product.
• When replacement parts are required, ensure that qualified people use replacement parts
specified by Rosemount. Unauthorized parts and procedures can affect the product’s
performance, place the safe operation of your process at risk, and VOID YOUR WARRANTY.
Look-alike substitutions may result in fire, electrical hazards, or improper operation.
• Ensure that all equipment doors are closed and protective covers are in place, except
when maintenance is being performed by qualified persons, to prevent electrical shock
and personal injury.
The information contained in this document is subject to change without notice.
Teflon and Viton are registered trademarks of E.I. duPont de Nemours and Co., Inc.
Paliney No.7 is a trademark of J.M. Ney Co., Hartford, CT
SNOOP is a registered trademark of NUPRO Co.
Emerson Process Management
Rosemount Analytical Inc.
Process Analytic Division
1201 N. Main St.
Orrville, OH 44667-0901
T (330) 682-9010
F (330) 684-4434
e-mail: gas.csc@EmersonProcess.com
http://www.processanalytic.com
Instruction Manual
748183-K
April 2002
Model 755
TABLE OF CONTENTS
PREFACE...........................................................................................................................................P-1
Definitions ...........................................................................................................................................P-1
Intended Use Statement.....................................................................................................................P-2
Safety Summary .................................................................................................................................P-2
General Precautions For Handling And Storing High Pressure Gas Cylinders .................................P-4
Documentation....................................................................................................................................P-5
Compliances .......................................................................................................................................P-5
1.0
1-1
1-2
1-3
1-4
1-5
1-6
1-7
2.0
2-1
2-2
2-3
2-4
A.
2-5
2-6
2-7
2-8
DESCRIPTION AND SPECIFICATIONS..............................................................................1-1
Overview................................................................................................................................1-1
Range Options.......................................................................................................................1-1
a. Standard Zero-Based Range Options ............................................................................1-1
b. Standard Zero-Suppressed Range Options ...................................................................1-3
c. Special Range Options ...................................................................................................1-3
Isolated Current Output Options............................................................................................1-3
Alarm Option..........................................................................................................................1-3
Case Mounting Options .........................................................................................................1-3
Electrical Options...................................................................................................................1-3
Specifications ........................................................................................................................1-5
a. General ...........................................................................................................................1-5
b. Sample ............................................................................................................................1-5
c. Electrical..........................................................................................................................1-6
d. Physical – General Purpose Enclosure ..........................................................................1-6
e. Physical – Explosion-Proof Enclosure ............................................................................1-6
INSTALLATION ....................................................................................................................2-1
Unpacking..............................................................................................................................2-1
Location .................................................................................................................................2-1
a. Location and Mounting....................................................................................................2-1
voltage requirements .............................................................................................................2-1
Electrical Connections ...........................................................................................................2-2
Line Power Connections........................................................................................................2-2
b. Recorder Output Selection and Cable Connections .......................................................2-2
c. Output Connections, Initial Setup for Dual Alarm Option................................................2-6
Calibration Gases ..................................................................................................................2-10
a. Downscale Standard Gas ...............................................................................................2-11
b. Upscale Standard Gas....................................................................................................2-11
Sample Handling ...................................................................................................................2-11
a. Sample Temperature Requirements...............................................................................2-11
b. Sample Pressure Requirements: General ......................................................................2-11
c. Normal Operation at Positive Gauge Pressures.............................................................2-13
d. Operation at Negative Gauge Pressures ........................................................................2-13
e. Sample Flow Rate...........................................................................................................2-13
f. Corrosive Gases .............................................................................................................2-14
Leak Test ...............................................................................................................................2-14
Purge Kit (Optional) ...............................................................................................................2-15
Rosemount Analytical Inc.
A Division of Emerson Process Management
Contents
i
Instruction Manual
748183-K
April 2002
3.0
3-1
3-2
3-3
3-4
3-5
3-6
4.0
4-1
4-2
4-3
OPERATION .........................................................................................................................3-1
Start-up Procedure ................................................................................................................3-1
Calibration..............................................................................................................................3-1
a. Calibration with Downscale and Upscale Standard Gases ............................................3-4
b. Alternative Calibration Procedure Using Upscale Standard Gas Only ...........................3-4
Compensation for Composition of Background Gas .............................................................3-5
a. Oxygen Equivalent Values of Gases ..............................................................................3-5
b. Computing Adjusted Settings for Zero and Span Controls .............................................3-7
Routine Operation .................................................................................................................3-8
Effect of Barometric Pressure Changes on Instrument Readout ..........................................3-8
Calibration Frequency ...........................................................................................................3-8
THEORY................................................................................................................................4-1
Principles of Operation ..........................................................................................................4-1
a. Magnetic Displacement Force ........................................................................................4-1
b. Physical Configuration of Detector/Magnet Assembly....................................................4-3
Variables Influencing Paramagnetic Oxygen Measurements ...............................................4-5
a. Pressure Effects..............................................................................................................4-5
b. Temperature Effects .......................................................................................................4-5
c. Interferents ......................................................................................................................4-5
d. Vibration Effects ..............................................................................................................4-6
Electronic Circuitry.................................................................................................................4-6
a. Detector/Magnet Assembly.............................................................................................4-6
b. Control Board and Associated Circuitry ..........................................................................4-6
c. Case Board Assembly ....................................................................................................4-7
d. Isolated Current Output Board (Optional) .......................................................................4-8
e. Alarm Option ...................................................................................................................4-8
5.0
5-1
5-2
5-3
5-4
5-5
5-6
5-7
CIRCUIT ANALYSIS.............................................................................................................5-1
Power Supply ±15 VDC........................................................................................................5-1
Case Heater Control Circuit...................................................................................................5-1
Detector Heater Control Circuit .............................................................................................5-6
Detector Light Source Control Circuit....................................................................................5-7
Detector With First Stage Amplifier .......................................................................................5-8
Final Output Amplifier ............................................................................................................5-10
Zero Suppression Module For Zero Adjustment ...................................................................5-12
6.0
6-1
6-2
6-3
MAINTENANCE AND SERVICE ..........................................................................................6-1
Initial Checkout with Standard Gases ...................................................................................6-1
Checkout at Test Points on Case Circuit Board ....................................................................6-2
Detector component Checkout ..............................................................................................6-4
a. Detector...........................................................................................................................6-4
b. Source Lamp...................................................................................................................6-4
c. Photocell .........................................................................................................................6-4
d. Suspension .....................................................................................................................6-4
Detector Component Replacement .......................................................................................6-4
a. Detector Replacement and Calibration ...........................................................................6-4
b. Source Lamp Replacement and Adjustment ..................................................................6-7
c. Photocell Replacement and Adjustment.........................................................................6-9
Heating Circuits .....................................................................................................................6-10
a. Case Heater Control Circuit ............................................................................................6-10
b. Detector/Magnet Heating Circuit.....................................................................................6-10
6-4
6-5
ii
Model 755
Contents
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
7.0
7-1
7-2
7-3
7-4
REPLACEMENT PARTS ......................................................................................................7-1
Circuit Board Replacement Policy.........................................................................................7-1
Matrix – Model 755 General Purpose Enclosure...................................................................7-2
Matrix – Model 755 Explosion Proof Enclosure.....................................................................7-3
Replacement Parts ................................................................................................................7-4
8.0
8-1
8-2
8-3
RETURN OF MATERIAL ......................................................................................................8-1
Return Of Material .................................................................................................................8-1
Customer Service ..................................................................................................................8-1
Training..................................................................................................................................8-1
9.0
INDEX....................................................................................................................................9-1
LIST OF ILLUSTRATIONS
Figure 1-1.
Figure 1-2.
Figure 2-1.
Figure 2-2.
Figure 2-3.
Figure 2-4.
Figure 2-5.
Figure 2-6.
Figure 2-7.
Figure 2-8.
Figure 2-9.
Figure 3-1.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 5-4.
Figure 5-5.
Figure 5-6.
Figure 5-7.
Figure 5-8.
Figure 6-1.
Figure 6-2.
Figure 6-3.
Figure 6-4.
Figure 6-5.
Figure 6-6.
Model 755 - Front View ...................................................................................................1-2
Model 755 - Location of Major Components.................................................................1-4
Electrical Interconnection................................................................................................2-3
Control Board – Adjustment Locations ...........................................................................2-4
Potentiometric Recorder with Non-Standard Span.........................................................2-5
Model 755 Connected To Drive Current Output-Activated Output Devices ...................2-5
Typical Alarm Settings ....................................................................................................2-7
Relay Terminal Connections...........................................................................................2-7
Alarm Relay Option Schematic Diagram ........................................................................2-9
Connection of Typical Gas Selector Panel to Model 755 ...............................................2-12
Installation of Purge Kit ...................................................................................................2-16
Control Board - Adjustment Locations ............................................................................3-2
Functional Diagram of Model 755 Paramagnetic Oxygen Measurement System ..........4-2
Spherical Body in Non-Uniform Magnetic Field ..............................................................4-3
Detector/Magnet Assembly.............................................................................................4-4
Two-Comparator OR Circuit ...........................................................................................5-2
Case Heater Control Circuit ............................................................................................5-3
Ramp Generator .............................................................................................................5-3
Detector Heater Control Circuit.......................................................................................5-6
Detector Light Source Control Circuit .............................................................................5-7
Detector with First Stage Amplifier..................................................................................5-8
Final Output Amplifier......................................................................................................5-11
Zero-Suppression Module...............................................................................................5-12
Voltage Test Points .........................................................................................................6-2
Locations of Case Board Test Points A, B, C and D ......................................................6-3
Detector/Magnet Assembly Wiring..................................................................................6-7
Modification of 633689 Connector Board for Compatibility with Replacement Lamp.....6-8
Lamp Alignment ..............................................................................................................6-9
Photocell Adjustment Voltmeter Lead Location ..............................................................6-9
Rosemount Analytical Inc.
A Division of Emerson Process Management
Contents
iii
Instruction Manual
748183-K
April 2002
Model 755
LIST OF TABLES
Table 1-1.
Table 1-2.
Table 2-1.
Table 3-1.
Table 3-2.
Front Panel Controls ........................................................................................................1-1
Range Options .................................................................................................................1-3
Calibration Range for Various Operating Ranges............................................................2-10
Control Board - Adjustment Functions .............................................................................3-3
Oxygen Equivalent of Common Gases ............................................................................3-6
DRAWINGS (LOCATED IN REAR OF MANUAL)
617186
620434
624549
632349
638277
643127
652188
iv
Contents
Schematic Diagram, Case Board
Schematic Diagram, Isolated Current Output Board
Pictorial Wiring Diagram, Model 755
Installation Drawing, Model 755 General Purpose
Schematic Diagram, Alarm
Installation Drawing, Model 755 Explosion Proof
Schematic Diagram, Control Board
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
PREFACE
The purpose of this manual is to provide information concerning the components,
functions, installation and maintenance of the 755.
Some sections may describe equipment not used in your configuration. The user should
become thoroughly familiar with the operation of this module before operating it. Read
this instruction manual completely.
DEFINITIONS
The following definitions apply to DANGERS, WARNINGS, CAUTIONS and NOTES found throughout
this publication.
DANGER .
Highlights the presence of a hazard which will cause severe personal injury, death, or substantial
property damage if the warning is ignored.
WARNING .
Highlights an operation or maintenance procedure, practice, condition, statement, etc. If not
strictly observed, could result in injury, death, or long-term health hazards of personnel.
CAUTION.
Highlights an operation or maintenance procedure, practice, condition, statement, etc. If not
strictly observed, could result in damage to or destruction of equipment, or loss of effectiveness.
NOTE
Highlights an essential operating procedure,
condition or statement.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Preface
P-1
Instruction Manual
748183-K
April 2002
Model 755
INTENDED USE STATEMENT
The Model 755 is intended for use as an industrial process measurement device only. It is not intended for
use in medical, diagnostic, or life support applications, and no independent agency certifications or
approvals are to be implied as covering such application.
SAFETY SUMMARY
If this equipment is used in a manner not specified in these instructions, protective systems may be
impaired.
AUTHORIZED PERSONNEL
To avoid explosion, loss of life, personal injury and damage to this equipment and on-site
property, all personnel authorized to install, operate and service the this equipment should be
thoroughly familiar with and strictly follow the instructions in this manual. SAVE THESE
INSTRUCTIONS.
DANGER.
ELECTRICAL SHOCK HAZARD
Do not operate without doors and covers secure. Servicing requires access to live parts which can
cause death or serious injury. Refer servicing to qualified personnel. For safety and proper
performance this instrument must be connected to a properly grounded three-wire source of power.
WARNING.
PARTS INTEGRITY
Tampering or unauthorized substitution of components may adversely affect safety of this product.
Use only factory documented components for repair.
WARNING.
POSSIBLE EXPLOSION HAZARD
Ensure that all gas connections are made as labeled and are leak free. Improper gas connections
could result in explosion or death.
P-2
Preface
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
WARNING .
POSSIBLE EXPLOSION HAZARD
The general purpose Model 755 Oxygen Analyzer, catalog number 191102, is for operation in nonhazardous locations. It is of a type capable of analysis of sample gases which may be flammable.
If used for analysis of such gases, the instrument must be protected by a continuous dilution purge
system in accordance with Standard ANSI/NFPA-496-1086 (Chapter 8) or IEC Publication 79-2-1983
(Section Three).
The explosion-proof Model 755 Oxygen Analyzer, catalog number 632440, is for operation in
hazardous locations. The enclosure must be properly secured with all flange bolts in place and
tightened, lens cover fully engaged, all factory installed flame arrestor assemblies are properly
installed in sample inlet and outlet and any unused openings plugged with approved threaded
plugs properly secured in place. Installation must be made in accordance with applicable parts of
the NEC, especially Articles 501-4(a) and 501-5(a)(1).
If explosive gases are introduced into this analyzer, the sample containment system must be
carefully leak-checked upon installation and before initial start-up, during routine maintenance and
any time the integrity of the sample containment system is broken, to ensure the system is in leakproof condition. Leak-check instructions are provided in Section 2-7.
Internal leakage of sample resulting from failure to observe these precautions could result in an
explosion causing death, personal injury, or property damage.
CAUTION .
PRESSURIZED GAS
This module requires periodic use of pressurized gas. See General Precautions for Handling and
Storing High Pressure Gas Cylinders, page P-4
Rosemount Analytical Inc.
A Division of Emerson Process Management
Preface
P-3
Instruction Manual
748183-K
April 2002
Model 755
GENERAL PRECAUTIONS FOR HANDLING AND STORING HIGH
PRESSURE GAS CYLINDERS
Edited from selected paragraphs of the Compressed Gas Association's "Handbook of Compressed
Gases" published in 1981
Compressed Gas Association
1235 Jefferson Davis Highway
Arlington, Virginia 22202
Used by Permission
1. Never drop cylinders or permit them to strike each other violently.
2. Cylinders may be stored in the open, but in such cases, should be protected against extremes of weather
and, to prevent rusting, from the dampness of the ground. Cylinders should be stored in the shade when
located in areas where extreme temperatures are prevalent.
3. The valve protection cap should be left on each cylinder until it has been secured against a wall or bench, or
placed in a cylinder stand, and is ready to be used.
4. Avoid dragging, rolling, or sliding cylinders, even for a short distance; they should be moved by using a
suitable hand-truck.
5. Never tamper with safety devices in valves or cylinders.
6. Do not store full and empty cylinders together. Serious suckback can occur when an empty cylinder is
attached to a pressurized system.
7. No part of cylinder should be subjected to a temperature higher than 125°F (52°C). A flame should never be
permitted to come in contact with any part of a compressed gas cylinder.
8. Do not place cylinders where they may become part of an electric circuit. When electric arc welding,
precautions must be taken to prevent striking an arc against the cylinder.
P-4
Preface
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
DOCUMENTATION
The following Model 755 instruction materials are available.
representative to order.
Contact Customer Service Center or the local
748183 Instruction Manual (this document)
COMPLIANCES
Model 755 Oxygen Analyzer - General Purpose Enclosure
The Model 755 Oxygen Analyzer (general purpose enclosure), catalog number 191102, has been designed
to meet the applicable requirements of the U.S. Occupational Safety and Health Act (OSHA) of 1970 if
installed in accordance with the requirements of the National Electrical Code (NEC) of the United States in
non-hazardous areas and operated and maintained in the recommended manner.
®
Model 755 Oxygen Analyzer - Explosion-Proof Enclosure
The Model 755 Oxygen Analyzer (explosion-proof enclosure), catalog number 632440, is approved by
Factory Mutual (FM) for installation in Class I, Groups B, C, and D, Division 1, hazardous locations as
defined in the National Electrical Code (NEC) of the United States (ANSI/NFPA 70).
FM
APPROVED
Rosemount Analytical Inc.
A Division of Emerson Process Management
Preface
P-5
Instruction Manual
748183-K
April 2002
P-6
Preface
Model 755
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 1
DESCRIPTION AND SPECIFICATIONS
1-1 OVERVIEW
1-2 RANGE OPTIONS
The Model 755 Oxygen Analyzer provides
continuous read-out of the oxygen content of
a flowing gas sample. The determination is
based on measurement of the magnetic
susceptibility of the sample gas. Oxygen is
strongly paramagnetic, other common gases
are weakly diamagnetic, with few exceptions.
The instrument provides direct read-out of
oxygen concentration on a front-panel meter.
In addition a field-selectable voltage output is
provided as standard. An isolated current
output of 4 to 20 mA or 0 to 20 mA is
obtainable through plug-in of the optional
circuit board. Current and voltage outputs
may be utilized simultaneously, if desired.
The basic electronic circuitry is incorporated
into two boards designated the Control Board
and the Case Board, see Figure 1-2, page 14. The Control Board has receptacles that
accept optional plug-in circuit boards thus
permitting inclusion of such features as
current output and alarms, and facilitating
conversion from one range option to another.
The analyzer is available in a general purpose
enclosure or an explosion proof enclosure.
See Figure 1-1, page 1-2.
CONTROL
Meter
%RANGE switch
ZERO Adjust
SPAN Adjust
The Model 755 is supplied, as ordered, with
four switch-selectable ranges: an overall
range and three sub-ranges, each covering a
portion of the overall range. The standard
range options are of two general types: zerobased (Section 1-2a, page 1-1) and zerosuppressed (Section 1-2b, page 1-3). In
addition, special range options incorporating
combinations of zero-based and zerosuppressed ranges are available on factory
special order, refer to Section 1-2c, page 1-3.
All range options utilize a front-panel meter
with left-hand zero. See Figure 1-1 (page 1-2)
and Table 1-1 (page 1-1).
a.
Standard Zero-Based Range Options
In a zero-based range option, the lower
range-limit for all four ranges is 0% oxygen.
There are five standard zero-based range
options:
•
•
•
•
•
Range Option
Sub-Range A
Sub-Range B
Sub-Range C
Overall Range
Refer to Table 1-2, page 1-3.
FUNCTION
Indicates oxygen content of sample, provided the analyzer has been calibrated by
appropriate adjustment of % RANGE switch, ZERO control, and SPAN control.
Meter face is calibrated with scales covering the operating ranges provided.
Select percentage oxygen range for meter and recorder
Used to establish downscale calibration point on meter scale or recorder chart.
With suitable downscale standard gas flowing through the analyzer, the ZERO
Control is adjusted for appropriate reading on meter or recorder.
Used to establish downscale calibration point on meter scale or recorder chart.
With suitable downscale standard gas flowing through the analyzer, the ZERO
Control is adjusted for appropriate reading on meter or recorder.
Table 1-1. Front Panel Controls
Rosemount Analytical Inc.
A Division of Emerson Process Management
Description and Specifications
1-1
Instruction Manual
748183-K
April 2002
Model 755
A. General Purpose Enclosure
Meter
ZERO Adjust
SPAN Adjust
RANGE Switch
Model 755
Oxygen Analyzer
Rosemount Analytical
B. Explosion-Proof Enclosure
Meter
ZERO Control
SPAN Adjust
RANGE Switch
Rosemount Analytical
Model 755
Oxygen Analyzer
Controls have slotted shafts for
screwdriver adjustment from
outside the enclosure.
Figure 1-1. Model 755 - Front View
1-2
Description and Specifications
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
RANGE
OPTION
01
02
03
04
06
SUB-RANGE A
SUB-RANGE B
SUB-RANGE C
OVERALL RANGE
0 to 1%
0 to 5%
0 to 10%
0 to 1%
90 to 100%
0 to 2.5%
0 to 10%
0 to 25%
0 to 2.5%
80 to 100%
0 to 5%
0 to 25%
0 to 50%
0 to 5%
60 to 100%
0 to 10%
0 to 50%
0 to 100%
0 to 25%
50 to 100%
Table 1-2. Range Options
b.
Standard Zero-Suppressed Range
Options
1-4 ALARM OPTION
If equipped with the alarm option:
With any zero-suppressed range the 0%
oxygen point lies off-scale below the lower
range-limit. In a zero-suppressed range
option the four ranges have the same upper
range-limit, but different lower range-limits.
There is a standard zero-suppressed range
option, as shown in Table 1-2 (page 1-3).
c.
Special Range Options
1. On the Control Board there are two
comparator amplifiers, one each for the
ALARM l and ALARM 2 functions. Each
amplifier has associated set-point and
dead-band adjustments, set-point is
adjustable from l% to l00% of fullscale.
The dead-band is adjustable from l% to
20% of fullscale.
On factory special order, the analyzer may
be provided with a special range option
incorporating any desired combination of
zero-based and zero-suppressed ranges,
arranged in ascending order according to
span.
2. Alarm relay assembly, containing two
single-pole double-throw relays, one for
each of the alarm contacts. These
relays may be used to drive external,
customer-supplied alarm and/or control
devices.
1-3 ISOLATED CURRENT OUTPUT OPTIONS
An isolated current output is obtainable by
installation of the optional Current Output Board,
either during factory assembly or subsequently
in the field. The maximum load resistance for
this board is 850 ohms.
1-5 CASE MOUNTING OPTIONS
General Purpose Enclosure, see drawing
632349.
Explosion Proof Enclosure, see drawing
643127.
1-6 ELECTRICAL OPTIONS
The analyzer is supplied, as ordered, for
operation on either 120 VAC, 50/60 Hz, or
240 VAC, 50/60 Hz.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Description and Specifications
1-3
Instruction Manual
748183-K
April 2002
Model 755
Control Board
Current Output
Board (Option)
R
R R2
R
8
I G
1
2
U
U
U
C C
UC
I
G
U
I G
U
C3
J
Door
Case Board
Alarm Relay
Assembly
(Alarm Option)
Recorder Output
TB2
Case Heater
Assembly
NO. 1
NO
COM
HOT
NC
RESET
NO. 2
MA
+ -
NO
MV
+ COM
TB2
COM
NC
RESET
Fuse
Case
Heater
Fuse
AC Power
TB1
N
GND E
U
T
AC Power
TB1
Transformer, Power
T1
(Behind TB1)
H
O
T
Detector/Magnet
Assembly Shock
Mount
Detector/Magnet
Assembly
General Purpose enclosure shown. Components mounted in same locations in Explosion-Proof enclosure.
Figure 1-2. Model 755 - Location of Major Components
1-4
Description and Specifications
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
1-7 SPECIFICATIONS
a.
General1
Catalog Number ............................ 191102 General Purpose for operation in non-hazardous locations
632440 Explosion-Proof for operation in hazardous locations
Standard Range Options
(% oxygen fullscale) 2 .................... 0 to 1, 2.5, 5, and 10% fullscale
0 to 5, 10, 25, and 50% fullscale
0 to 10, 25, 50, and 100% fullscale
0 to 1, 2.5, 5 and 25% fullscale
0 to 1, 5, 10, and 25% fullscale
50 to 100, 60 to 100, 80 to 100, and 90 to 100% fullscale
Response Time (90% of fullscale) Factory set for 20 seconds; adjustable from 5 to 25 seconds.
Reproducibility ............................... ±0.01% Oxygen or ±1% of fullscale, whichever is greater
Ambient Temperature Limits ......... Maximum: 49°C (120°F)
Minimum: -7°C (20°F)
Zero and Span Drift 3 ..................... ±1% of fullscale per 24 hours, provided that ambient temperature
does not change by more than 11.1°C (20°F).
±2.5% of fullscale per 24 hours with ambient temperature change
over entire range.
b.
Sample
Dryness ......................................... Sample dewpoint below 43°C (110°F), sample free of entrained
liquids.
Temperature Limits ....................... Maximum: 66°C (150°F)
Minimum: 10°C (50°F)
Operating Pressure ....................... Maximum: 69 kPa (10 psig).
Minimum: 88.1 kPa absolute (660 mm Hg absolute pressure)
Flow Rate 4 .................................... Maximum: 500 cc/min
Minimum: 50 cc/min
Recommended: 250 ±20 cc/min
Materials in Contact with
Sample Gas................................... 316 stainless steel, glass, titanium, Paliney No. 7, epoxy resin,
Viton-A, platinum, nickel.
1
Performance specifications based on recorder output.
For applications requiring suppressed ranges other than those provided, we recommend the Model 755A Oxygen Analyzer,
Catalog Number 617720. This instrument includes automatic correction for barometric pressure variations and provides
maximum accuracy for suppressed ranges. This particularly important at high level suppressed ranges such as 99 to 100%
where a barometric pressure change from standard 29.90 inches Hg (101 kPa) to 31.5 inches Hg (106 kPa) would result in
an actual oxygen change in the order of 5%. The Model 755A provides automatic barometric pressure correction and optimum accuracy for such suppressed ranges. The Model 755A also provides direct readout from 0.00% to 100.00% oxygen
on a digital display. Optimum resolution of the oxygen reading is provided.
3
Zero and span drift specifications based on following conditions: Operating pressure constant; ambient temperature change
from initial calibration temperature, less than 11.1 Celsius degrees (20 Fahrenheit degrees); deviation from set flow held to
within ±10% or ±20 cc/min, whichever is smaller.
4
Deviation from set flow would be held to within ±10% or ±20 cc/min, whichever is smaller. If so, zero and span drift will be
within specifications, provided that operating temperature remains constant.
2
Rosemount Analytical Inc.
A Division of Emerson Process Management
Description and Specifications
1-5
Instruction Manual
748183-K
April 2002
c.
Model 755
Electrical
Supply Voltage and Frequency
(selectable when ordered)............ Standard: 115 VAC ±10 VAC, 50/60 Hz
Optional: 230 VAC ±10 VAC, 50/60 Hz
Power Consumption ...................... Maximum: 300 watts
Outputs .......................................... Standard: Field selectable voltage output of 0 to 10mV, 0 to
100mV, 0 to 1V, or 0 to 5VDC
Optional: Isolated current output of 0 to 20mA or 4 to 20mA (with
Current Output Board)
Alarm Option.................................. High-Low Alarm
Contact Ratings ..................... 5 amperes, 240V AC, resistive 3 amperes, 120 VAC inductive
1 amperes, 24V DC, resistive
5 amperes, 30 VDC resistive
5 amperes, 120V AC, resistive 3 amperes, 30 VDC inductive
Setpoint ......................................... Adjustable from 1% to 100% of fullscale
Deadband ...................................... Adjustable from 1% to 20% of fullscale (Factory set at 10% of
fullscale)
d.
Physical – General Purpose Enclosure
Mounting........................................ Standard: Panel mount
Optional: Surface or stanchion mount accessory available
Enclosure Classification ................ Meets requirements for NEMA 3R
Air Purge Option1: NFPA 496 (1989) Type Z purge
Refer to Installation Drawing 632349 in the rear of this manual.
e.
Physical – Explosion-Proof Enclosure
Mounting........................................ Surface or wall
Enclosure Classification ................ Class I, Groups B, C, and D, Division 1 hazardous locations
(ANSI/NFPA 70)
Refer to Installation Drawing 643127 in the rear of this manual.
1
When installed with user supplied components, meets requirements for Class I, Division 2 locations per National Electrical
Code (ANSI/NFPA 70) for analyzers sampling nonflammable gases. Analyzers sampling flammable gases must be protected by a continuous dilution purge system in accordance with Standard ANSI/NFPA 496-1986, Chapter 8. Consult factory
for recommendations.
1-6
Description and Specifications
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 2
INSTALLATION
2-1 UNPACKING
2-3 VOLTAGE REQUIREMENTS
Carefully examine the shipping carton and
contents for signs of damage. Immediately
notify the shipping carrier if the carton or its
contents are damaged. Retain the carton and
packing materials until the instrument is
operational.
2-2 LOCATION
a.
DANGER
ELECTRICAL SHOCK HAZARD
For safety and proper performance this
instrument must be connected to a
properly grounded three-wire source of
power.
Location and Mounting
Shock and mechanical motion can reduce
instrument accuracy; therefore, mount the
instrument in an area that is as vibration
free as possible
General Purpose Enclosure
The analyzer is designed to meet NEMA
3R enclosure requirements and may be
mounted outdoors. Permissible ambient
temperature range is 20°F to 120°F (-7°C
to 49°C).
The analyzer is designed for either
surface or stanchion (optional kit)
mounting. Avoid mounting outside in
direct sunlight, or inside in a closed
building, where ambient temperature may
exceed the allowable maximum.
Explosion-Proof Enclosure
The analyzer can be either surface or wall
mounted and meets (ANSI/NFPA 70)
Class 1, Groups B, C, and D, Division 1
Hazardous Locations.
DANGER
ELECTRICAL SHOCK HAZARD
Do not operate without doors and covers
secure. Servicing requires access to live
parts which can cause death or serious
injury. Refer servicing to qualified
personnel.
CAUTION
ENCLOSURE INTEGRITY
With reference to Installation Drawing
632349 or 643127, any unused cable
conduit openings must be securely sealed
by permanent closures in order to provide
enclosure integrity in compliance with
personnel safety and environmental
protection requirements. The plastic
closures provided are for shipping
protection only.
NOTE
Refer to Installation Drawing 632349 or
643127 at the rear of this manual for
recommended cable conduit openings.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Installation
2-1
Instruction Manual
748183-K
April 2002
Model 755
NOTE
For NEMA 3R service, all conduit must be
connected through approved fittings.
The analyzer is supplied, as ordered, for
operation on 120 VAC or 240 VAC, 50/60 Hz.
Make sure that the power source conforms to
the requirements of the individual instrument,
as noted on the name-rating plate.
2-4 ELECTRICAL CONNECTIONS
a.
Line Power Connections
Electrical power is supplied to the
analyzer via a customer-supplied threeconductor cable, type SJT, minimum wire
size 18 AWG. Route power cable through
conduit and into appropriate opening in
the instrument case. Refer to Installation
Drawing (632349 or 643127). Connect
power leads to HOT, NEUT, and GND
terminals on TB1, Figure 2-1. Connect
analyzer to power source via an external
fuse or breaker, in accordance with local
codes.
NOTE
Do not draw power for associated
equipment from the analyzer power
cable.
b.
Recorder Output Selection and Cable
Connections
If a recorder, controller, or other output
device is used, connect it to the analyzer
via a 22 or 24 AWG two-conductor
shielded cable. Route the cable through
conduit to the analyzer, and into the case
through the appropriate opening shown in
Installation Drawing (632349 or 643127).
Connect the shield only at the recorder
end.
NOTE
Route recorder cable through a
separate conduit, not with power cable
or alarm output cable.
2-2
Installation
Cable connections and output selection
for potentiometric and current-actuated
devices are explained below.
NOTE
Do not allow internal cable service
loop to touch the shock-mounted
detector assembly or associated
sample inlet and outlet tubing. This
precaution ensures against possible
transmission of mechanical vibration
through the cable to the detector,
which could cause noisy readout.
Potentiometric Output
1. Insert RECORDER OUTPUT Selector
Plug (Figure 2-2, page 2-4) in position
appropriate to the desired output: 10
mV, 100 mV, 1 V, or 5 V.
2. On TB2 (Figure 2-1, page 2-3)
connect leads of shielded recorder
cable to MV+ and COM terminals.
3. Connect free end of output cable to
appropriate terminals of recorder or
other potentiometric device:
a. For device with a span of 0 to
10mV, 0 to 100mV, 0 to 1V, or 0 to
5V, connect cable directly to input
terminals of the device, making
sure polarity is correct.
b. For device with intermediate span,
i.e., between the specified values,
connect cable to device via a
suitable external voltage divider, as
shown in Figure 2-3, page 2-5.
Isolated Current Output (Option)
The isolated current output board (Figure
2-2, page 2-4) is optional, and can be
adjusted for either 0 to 20 mA or 4 to 20
mA. The adjustments made on this board
are for zero and span. To set output:
1. With analyzer meter at zero, adjust
R1 for desired zero level (typically 0
for 0 to 20 mA, 4 for 4 to 20 mA).
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
6. For the set up of optional boards, the
isolated current output board
(optional) can be adjusted for either
0 to 20 mA or 4 to 20 mA. The
adjustments made on this board are
for zero and span.
2. With analyzer at fullscale, adjust R2
for desired fullscale current (typically
20 mA).
3. To connect current activated output
devices:
4. On TB2 (Figure 2-1, page 2-3)
connect leads of shielded recorder
cable to MA+ and " - " terminals.
a. With analyzer meter at zero, adjust
R1 for desired zero level, typically
0 for 0 to 20 mA, and 4 for 4 to 20
mA..
5. Connect free end of output cable to
input terminals of recorder or other
current-actuated device, making sure
that polarity is correct. If two or more
current-actuated devices are to be
used, they must be connected in
series, see Figure 2-4, page 2-5. Do
not exceed the maximum load
resistance (see Section 1-3, page 13).
b. With analyzer meter at fullscale,
adjust R2 for desired fullscale
current (typically 20 mA).
7. Current and voltage outputs may be
utilized simultaneously, if desired.
Optional Alarm Kit
Explosion-Proof
Enclosure
General Purpose
Enclosure
NO. 1
NO
COM
HOT
NC
RESET
NO. 2
MA
NO
TB2
COM
MV
+ - + COM
NC
+ mV Recorder
-
RESET
+ mA Recorder
TB1
N
GND E
U
T
120 VAC CONFIGURATION
Jumpers
H
O
T
TB1
GND
Power Connections
(see detail)
N
E
U
T
H
O
T
240 VAC CONFIGURATION
Jumper
TB1
Figure 2-1. Electrical Interconnection
Rosemount Analytical Inc.
A Division of Emerson Process Management
N
GND E
U
T
H
O
T
Installation
2-3
Instruction Manual
748183-K
April 2002
Model 755
R63
R64
R73
RECORDER OUTPUT
Selector Plug
R78
5V
1V
100mV
10mV
R68
R67
R3
R4
R8
R9
CR2
R5
R6
R2
R1
R1
U6
I G O
1
2
3
4
U3
U2
C5
I
G
O
R2
C4
C2
U4
U1
U5
I G O
C3
CR1
C1
J1
Current Output Board
Figure 2-2. Control Board – Adjustment Locations
2-4
Installation
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
755
Analyzer
Potentiometric
Recorder
Input
Terminals
Voltage Divider
(Customer Supplied)
(Make sure polarity
is correct)
Position of Recorder Output
Selector Plug
Minimum Permissible
Resistance for R1 + R2
10 mV
100 mV
1V
5V
1K Ohm
10K Ohm
100K Ohm
2K Ohm
Figure 2-3. Potentiometric Recorder with Non-Standard Span
+
mA 755
Analyzer
+
-
Recorder
+
- Controller
+
-
Remote
Indicator
Figure 2-4. Model 755 Connected To Drive Current Output-Activated Output Devices
Rosemount Analytical Inc.
A Division of Emerson Process Management
Installation
2-5
Instruction Manual
748183-K
April 2002
c.
Model 755
Output Connections, Initial Setup for
Dual Alarm Option
If so ordered the analyzer is factoryequipped with alarm output. Alternatively
the alarm feature is obtainable by
subsequent installation of the Alarm Kit.
Alarm 1 Relay
The alarm output provides two sets of
relay contacts for actuation of alarm or
process-control functions. Leads from the
customer-supplied external alarm system
connect to terminals on the Alarm
Assembly, see Figure 2-1 page 2-3.
The Alarm I relay coil is de-energized
when the meter needle moves downscale
through the value that corresponds to
setpoint minus dead-band. This relay coil
is energized when the needle moves
upscale through the value that
corresponds to setpoint plus dead-band.
See Figure 2-5A, page 2-7.
Note the following recommendations:
Alarm 2 Relay
Alarm Output Connections
1. A fuse should be inserted into the line
between the customer-supplied power
supply and the alarm relay terminals
on the Alarm Relay Assembly.
2. If the alarm contacts are connected to
any device that produces radio
frequency interference (RFI), it should
be arc-suppressed. The 858728 Arc
Suppressor is recommended.
3. If at all possible, the analyzer should
operate on a different AC power
source, to avoid RFI.
Alarm Relay Characteristics
The Alarm 1 and Alarm 2 outputs of the
638245 Alarm Relay Assembly are
provided by two identical single-pole
double-throw relays. Relay contacts are
rated at:
5 amperes, 240 VAC resistive
1 ampere, 240 VAC inductive
5 amperes, 120 VAC resistive
3 amperes, 120 VAC inductive
5 amperes, 30 VDC resistive
3 amperes, 30 VDC inductive
2-6
Removal of AC power from the analyzer,
as in power failure, de-energizes both
relays, placing them in alarm condition.
Switching characteristics of the Alarm 1
and Alarm 2 relays are as follows:
Installation
Relay The Alarm 2 relay coil is deenergized when the meter needle moves
upscale through the value that
corresponds to the setpoint plus deadband. This relay coil is energized when
needle moves downscale through the
value that corresponds to setpoint minus
dead-band, see Figure 2-5B, page 2-7.
Alarm Reset
Normally both the ALARM 1 and ALARM
2 functions incorporate automatic rest.
When the meter reading goes beyond the
selected limits, the corresponding relay is
de-energized; when the meter reading
returns within the acceptable range, the
relay is turned on.
The desired ALARM 1 or ALARM 2 alarm
function may be converted to manual
reset. The conversion consists of
substituting an external push-button or
other momentary-contact switch for the
jumper that normally connects the RESET
terminals on the Alarm Relay Assembly,
see Figure 2-1 page 2-3. If the
corresponding relay is now de-energized,
i.e., in alarm condition, the relay remains
de-energized until the operator
momentarily closes the switch.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
A. Typical ALARM 1 Setting
When input signal moves upscale through this point, the coil of
ALARM 1 relay (K1) is energized, providing continuity between the
common and normally-closed contacts of the relay.
40
INPUT SIGNAL
Percent of Fullscale 30
DEADBAND SET FOR
20% OF FULLSCALE
ALARM 1 Setpoint
When input signal moves downscale through this point, the coil of
ALARM 1 relay (K1) is de-energized, providing continuity between the
common and normally-open contacts of the relay.
20
B. Typical ALARM 2 Setting
When input signal moves upscale through this point, the coil of
ALARM 2 relay (K2) is de-energized, providing continuity between the
common and normally-open contacts of the relay.
55
INPUT SIGNAL
Percent of Fullscale 50
DEADBAND SET FOR
10% OF FULLSCALE
ALARM 2 Setpoint
When input signal moves upscale through this point, the coil of ALARM
2 relay (K2) is energized, providing continuity between the common
and normally-closed contacts of the relay.
45
Figure 2-5. Typical Alarm Settings
REQUIREMENT
TYPICAL CONNECTIONS
No. 1
NO
Low Alarm,
Fail-Safe
Alarm Bell
or Lamp
TYPICAL CONNECTIONS
No. 1
N
COM
NC
REQUIREMENT
H
115 VAC
RESET
Low Control
Limit,
Fail-Safe
NO
COM
NO
COM
H
NC
N
115 VAC
RESET
NO
COM
NC
NC
RESET
No. 2
No. 1
RESET
No. 2
NO
Lower
Low Alarm
Indicator,
Fail-Safe
COM
NC
High Alarm,
Fail-Safe
RESET
NO
NC
RESET
No. 1
NO
Alarm Bell
or Lamp
H
115 VAC
NC
RESET
NO
Low Control,
Fail-Safe
No. 2
N
COM
N
COM
Alarm Bell
or Lamp
H
115 VAC
Solenoid
Valve
COM
H
NC
N
115 VAC
RESET
No. 2
No. 1
No. 1
NO
High Control,
Fail-Safe
COM
NC
Low Control
Limit,
Fail-Safe
Solenoid
Valve
RESET
NO
Solenoid
Valve
COM
H
NC
N
115 VAC
RESET
Solenoid
Valve
COM
H
NC
N
115 VAC
RESET
NO
No. 2
Higher
High Alarm
Indicator,
Fail-Safe
NO
N
COM
H
115 VAC
NC
RESET
Alarm Bell
or Lamp
No. 2
Figure 2-6. Relay Terminal Connections
Rosemount Analytical Inc.
A Division of Emerson Process Management
Installation
2-7
Instruction Manual
748183-K
April 2002
Model 755
Fail-Safe Applications
By appropriate connection to the doublethrow relay contacts, it is possible to
obtain either a contact closure or a
contact opening for an energized relay.
Also either a contact closure or a contact
opening may be obtained for a deenergized relay. It is important that for failsafe applications, the user understand
what circuit conditions are desired in
event of power failure and the resultant
relay de-energization. Relay contacts
should then be connected accordingly,
see Figure 2-6 page 2-7.
Alarm Setpoint Adjustment
The ALARM 1 and ALARM 2 circuits have
independent setpoint and dead-band
adjustments. Before the ALARM 1 and
ALARM 2 setpoints can be set, the alarm
dead-band must be calibrated according
to the following procedure.
1. Set the front panel TEST switch to
position 1.
2. Introduce upscale span gas through
analyzer at a flow rate of 50 to 500
cc/min.
3. Verify that ALARM 1 and ALARM 2
dead-band adjustments, R73 and R78
(Figure 2-2, page 2-4) are turned fully
counter-clockwise to set the deadband at minimum. Normally these
potentiometers are factory-set for
minimum dead-band. Both
potentiometers must remain at this
setting throughout calibration of the
alarm setpoint adjustments.
4. Connect an ohmmeter to relay
terminals on 638254 Alarm Relay
Assembly to verify when alarms have
been energized.
5. Calibration of ALARM 1, HIGH.
a. Rotate setpoint adjustment, R64,
fully counter-clockwise.
2-8
Installation
b. Adjust SPAN control to give a
display or recorder reading exactly
fullscale. If the fullscale setting
cannot be reached, set to a reading
higher than the desired alarm
setpoint.
c. Set ALARM 1 calibration
adjustment, R63, to its clockwise
limit (Figure 2-2, page 2-4). Rotate
R63 counter-clockwise the
minimum amount required to
energize ALARM 1, relay K1. Verify
that the alarm has been energized
with the ohmmeter on the relay
contacts (Figure 2-7, page 2-9).
6. Calibration of ALARM 2, LOW.
a. Rotate setpoint adjustment, R68,
fully counter-clockwise.
b. Adjust SPAN control for display or
recorder reading exactly fullscale. If
the fullscale setting cannot be
reached, then set to a reading
higher than the desired alarm
setpoint.
c. Set ALARM 2 calibration
adjustment, R67, to its clockwise
limit. Rotate R67 counterclockwise, the minimum amount
required to energize ALARM 2,
relay K2. Verify that the alarm has
been energized with the ohmmeter
on the relay contacts (Figure 2-7,
page 2-9).
7. Setpoint adjustment of ALARM 1,
HIGH.
a. With span gas flowing, adjust SPAN
control to read desired alarm
setpoint on display or recorder.
b. Rotate setpoint adjustment, R64,
clockwise to energize relay.
c. Check this setting by adjusting the
SPAN control to lower the output
below the setpoint. This will deenergize the relay. Rotating R64
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
above the setpoint will energize the
relay.
b. Rotate setpoint adjustment, R68,
clockwise to energize relay.
8. Setpoint adjustment of ALARM 2,
LOW.
c. Check setting by adjusting the
SPAN control to lower the output
below the setpoint. This will
energize the relay. Rotating R68
above the setpoint will de-energize
the relay.
a. With span gas flowing, adjust the
SPAN control to read desired alarm
setpoint on display or recorder.
1
+15V
J5
1
5
CR1
2
ALARM 1
COM-
4
13
12
COM
NC
8
K1
RESET
1
9
5
CR2
NO
COM
NC
ALARM 2
14
K2
ALARM 2
COM-
NO
ALARM 1
14
-15V
9
13
12
8
RESET
6
2. RELAYS SHOWN IN ENERGIZED POSITION.
1. CR1 AND CR2 ARE ANY 600 V, 1 AMP DIODE.
NOTES:
Figure 2-7. Alarm Relay Option Schematic Diagram
Rosemount Analytical Inc.
A Division of Emerson Process Management
Installation
2-9
Instruction Manual
748183-K
April 2002
Model 755
2-5 CALIBRATION GASES
WARNING
HIGH PRESSURE GAS CYLINDERS
Calibration gas cylinders are under
pressure. Mishandling of gas cylinders
could result in death, injury, or property
damage. Handle and store cylinders with
extreme caution and in accordance with
manufacturer instructions. Refer to
General Precautions for Handling and
Storing High Pressure Gas Cylinders, page
P-4.
Analyzer calibration consists of establishing a
downscale calibration point and an upscale
calibration point.
Downscale calibration may be performed on a
range that will be used during sample
analysis. For maximum precision, however, it
should be performed on the range of highest
sensitivity, i.e., most narrow span.
RANGE % O2
0 to 1
0 to 2.5
0 to 5
0 to 10
0 to 25
0 to 50
0 to 100
RANGE % O2
90 to 100
80 to 100
60 to 100
50 to 100
Preferably upscale calibration should be
performed on a range to be used in sample
analysis. In some applications, however, it
may be desirable to perform upscale
calibration on a range of higher sensitivity,
i.e., more narrow span, and then move the %
RANGE switch to the desired operating range.
For example, if the operating range is to be 0
to 50% oxygen, upscale calibration may be
performed on the 0 to 25% range to permit
use of air as the upscale standard gas.
Recommendations on calibration gases for
various operating ranges are tabulated in
Table 2-1, page 2-10, and are explained in
Sections 2-5a (page 2-11) and 2-5b (page 211).
Each standard gas should be supplied from a
cylinder equipped with dual-stage metaldiaphragm type pressure regulator, with
output pressure adjustable from 0 to 50 psig
(0 to 34.5 kPa).
A. ZERO BASED RANGES
RECOMMENDED DOWNSCALE
RECOMMENDED UPSCALE
STANDARD GAS
STANDARD GAS
Nitrogen
0.9% O2, balance N2
Nitrogen
2.3% O2, balance N2
Nitrogen
4.5% O2, balance N2
Nitrogen
9% O2, balance N2
Nitrogen
Air (20.93% O2)
Nitrogen
0.45% O2, balance N2
Nitrogen
100% O2
B. ZERO SUPPRESSED RANGES
RECOMMENDED DOWNSCALE
RECOMMENDED UPSCALE
STANDARD GAS
STANDARD GAS
91% 0.5% O2, balance N2
High-purity O2
82% 1% O2, balance N2
100% O2
62% 1% O2, balance N2
100% O2
52% 1% O2, balance N2
100% O2
NOTE
Each standard gas used should have a composition within the specified limits, and should have a
certified analysis provided by the supplier.
Table 2-1. Calibration Range for Various Operating Ranges
2-10
Installation
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
a.
• Provision for selecting sample,
downscale standard, or upscale
standard gas for admission to
the analyzer, and for measuring
the flow of the selected gas.
Typically these functions are
provided by a gas selector panel
available as an accessory. A
typical gas selector panel is
shown in Figure 2-8, page 2-12.
Downscale Standard Gas
In the preferred calibration method described in Section 3-2a (page 3-4), a suitable downscale standard gas is used to
establish a calibration point at or near the
lower range-limit. Composition of the
downscale standard depends on the type
of range:
A zero based range normally uses an
oxygen-free zero gas, typically nitrogen.
A zero-suppressed range uses a blend
consisting of a suitable percentage of
oxygen contained in a background gas.
typically nitrogen.
An alternative calibration method, described in Section 3-2b (page 3-4), uses
an upscale standard gas only and does
not require a downscale standard gas.
b.
Upscale Standard Gas
Many different sample-handling systems are
available depending on the requirements of
the individual user. Most sample-handling
systems have copper or brass components;
however stainless-steel components are
available for applications involving corrosive
gases. With corrosive gases, complete drying
of the sample is desirable, as most of these
gases are practically inert when totally dry.
For specific corrosive applications, consult the
factory.
a.
Sample temperature at the analyzer inlet
should be in the range of 50°F to 150°F
(10°C to 66°C).
A suitable upscale standard gas is required to establish a calibration point at or
near the upper range limit. If this range
limit is 215% or 25% oxygen, the usual
upscale standard gas is air (20.93% oxygen).
With a thoroughly dry sample, entry temperature can be as high as 150°F (66°C)
without affecting readout accuracy. Normally however a maximum entry temperature of 110°F (43°C) is recommended
so that the sample temperature will rise
during passage of the sample through the
analyzer. This precaution ensures against
cooling of the sample and possible condensation of moisture. Such condensation
should be avoided as it may damage the
detector.
2-6 SAMPLE HANDLING
Basic requirements for sample handling are:
• Particulate filter, inserted into the
sample line immediately upstream from the analyzer inlet. A
2-micron filter is recommended
to ensure against damage to the
test body and associated internal
diffusion screen within the detector assembly.
• Provision for pressurizing the
sample gas to provide flow
through the analyzer. Special
applications may use a suction
pump to draw sample through
the analyzer.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Sample Temperature Requirements
b.
Sample Pressure Requirements: General
Operating pressure limits are as follows:
Maximum, 10 psig (69 kPa gauge pressure); minimum, 660 mm Hg absolute
(88.1 kPa absolute pressure).
Installation
2-11
Instruction Manual
748183-K
April 2002
Model 755
CAUTION
OPERATION LIMITS
Operation outside the specified limits may
damage the detector, and will void the warranty.
The basic rule for pressure of sample and
standard gases supplied to the inlet is to
calibrate the analyzer at the same pressure that will be used during subsequent
operation, and to maintain this pressure
during operation. The arrangement re-
quired to obtain appropriate pressure
control will depend on the application.
When inputting sample or calibration
gases, use the same pressure that will be
used during subsequent operation, refer
to Section 2-6c 2.6.3 Normal Operation
at Positive Gauge Pressures page 2-13;
or Section 2-6d 2.6.4 Operation at Negative Gauge Pressures page 2-13.
Needle
Valves
Model 755
Oxygen Analyzer
Sample In
Two Micron
Filter
Downscale
Standard
Gas
To Vent
(via back-pressure
regulator if required)
Flowmeter
Upscale
Standard
Gas
Figure 2-8. Connection of Typical Gas Selector Panel to Model 755
2-12
Installation
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
c.
Normal Operation at Positive Gauge
Pressures
d.
Operation at negative gauge pressures is
not normally recommended but may be
used in certain special applications. A
suction pump is connected to the analyzer
exhaust port to draw sample into the inlet
and through the analyzer. Such operation
necessitates special precautions to ensure accurate readout. There is the basic
consideration of supplying the standard
gases to the analyzer at the same pressure that will be used for the sample during subsequent operation. In addition, any
leakage in the sample-handing system
will result in decreased readout accuracy
as compared with operation at atmospheric pressure.
Pressure at Sample Inlet
Normally the sample is supplied to the
analyzer inlet at a positive gauge pressure in the range of 0 to 10 psig (0 to 69
kPa).
CAUTION
HIGH PRESSURE SURGES
High pressure surges during admission of
sample or standard gases can damage the
detector.
Sample Exhaust
With positive sample pressure, the proper
choice of arrangement for sample exhaust
depends principally on whether the analyzer has zero-based or zero-suppressed
ranges. as explained below.
Sample Exhaust Arrangements for
Zero-Based Ranges
With zero-based ranges, the analyzer exhaust port is commonly vented directly to
the atmosphere, and any change in
barometric pressure results in a directly
proportional change in the indicated percentage of oxygen.
EXAMPLE
Range, 0% to 5% O2
Barometric pressure change after
calibration, 1%
Instrument reading, 5% O2
Readout error = 0.01 x 5% O2 =
0.05% O2
Fullscale span is 5% O2, therefore
the 0.05% O2 error is equal to 1%
fullscale.
Thus if the exhaust is vented to the atmosphere, the pressure effect must be
taken into consideration. This may be accomplished in various ways: manual
computation, computer correction of data.
etc.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Operation at Negative Gauge Pressures
The minimum permissible operating pressure is 660 mm Hg absolute (88.1 kPa
absolute). Operation below this limit may
damage the detector and will void the
warranty.
e.
Sample Flow Rate
Operating limits for sample flow rate are
as follows: Minimum, 50 cc/min; maximum, 500 cc/min. A flow rate of less than
50 cc/min is too slow to sweep out the
detector and associated flow system efficiently, it will therefore allow the incoming
sample to mix with earlier sample, causing an averaging or damping effect. Too
rapid a flow will cause a back pressure
that will affect the reading. The optimum
flow rate is between 200 and 300 cc/min.
Deviation from the set flow should be held
to within ±10% or ±20 cc/min, whichever
is smaller. If so, zero and span will be
within the limits given on the specifications page, provided that operating pressure remains constant.
Bypass Flow
Preferably the analyzer should be installed near the sample source to minimize transport time. Otherwise time lag
may be appreciable. For example, assume that sample is supplied to the ana
Installation
2-13
Instruction Manual
748183-K
April 2002
Model 755
lyzer via a 100-foot (30.5 m) length of 1/4inch (6.35 mm) tubing. With a flow rate of
100 cc/min, sample transport time is approximately 6 minutes.
Sample transport time may be reduced by
piping a greater flow than is required to
the analyzer and then routing only the appropriate portion of the total flow through
the analyzer. The unused portion of the
sample may be returned to the stream or
discarded.
f.
Corrosive Gases
In applications where the sample stream
contains corrosive gases. a complete
drying of the sample is desirable. as most
of these gases are practically inert when
totally dry. For corrosive applications,
consult the factory.
WARNING
RADIOACTIVE SAMPLE GASES
Radioactive sample gases will attack the
rubber sample tubing within the analyzer,
causing deterioration at a rate proportional
to the level of radioactivity. In applications
involving radioactive samples, the internal
tubing should be examined periodically
and replaced as required. Failure to observe this precaution can result in leakage
of radioactive sample into the ambient atmosphere.
2-14
Installation
2-7 LEAK TEST
Supply air or inert gas such as nitrogen at 10
psig (69 kPa) to analyzer via a flow indicator
with range of 0 to 250 cc/min. Set flow at 125
cc/min. Plug sample outlet. Flow reading
should drop to zero. If not, the system is
leaking.
DANGER
POSSIBLE EXPLOSION HAZARD
If explosive gases are introduced into this
analyzer, the sample containment system
must be carefully leak-checked upon installation and before initial start-up, during
routine maintenance and any time the integrity of the sample containment system
is broken, to ensure the system is in leakproof condition. Internal leakage of sample resulting from failure to observe these
precautions could result in an explosion
causing death, personal injury, or property
damage.
Leakage must be corrected before introduction of flammable sample or application of
electrical power. Liberally cover all fittings,
seals, and other possible sources of leakage
with suitable leak test liquid such as Snoop
(P/N 837801). Bubbling or foaming indicates
leakage. Checking for bubbles will locate most
leaks but could miss some because some areas are inaccessible to application of Snoop.
For positive assurance that system is leakfree, use the flow stoppage test.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
2-8 PURGE KIT (OPTIONAL)
The optional 643108 Purge Kit is designed to
equip the Model 755 General Purpose enclosure with Type Z Air Purge per National Fire
Protection Association Standard NFPA 4961986, Chapter Two. The kit, along with usersupplied components, when installed as described in these instructions, is designed to
reduce the classification within the enclosure
from Division 2 (normally non-hazardous) to
non-hazardous.
not cover protection from possible abnormal
release (leakage) of flammable gases intentionally introduced into the enclosure.
This kit consists of the following items:
PART NO.
190697
045835
002787
856156
DESCRIPTION
Purge Inlet Fitting
Purge Outlet Fitting
Warning label
Sealant (Duxseal)
NOTE
DANGER
POSSIBLE EXPLOSION HAZARD
The general purpose Model 755 Oxygen
Analyzer, catalog number 191102, is for
operation in non-hazardous locations. It is
of a type capable of analysis of sample
gases which may be flammable. If used
for analysis of such gases, the instrument
must be protected by a continuous dilution
purge system in accordance with Standard
ANSI/NFPA-496-1086 (Chapter 8) or IEC
Publication 79-2-1983 (Section Three).
If explosive gases are introduced into this
analyzer, the sample containment system
must be carefully leak-checked upon installation and before initial start-up, during
routine maintenance and any time the integrity of the sample containment system
is broken, to ensure the system is in leakproof condition.
Internal leakage of sample resulting from
failure to observe these precautions could
result in an explosion causing death, personal injury, or property damage.
To conform to NFPA Type Z requirements,
the warning label must be applied to the
analyzer front cover. If the analyzer is ordered factory equipped with purge kit, this
label is applied at the factory.
Installation options are shown in Figure 2-9,
page 2-16. Use only clear dry air or suitable
inert gas for the purge supply. Recommended
supply pressure is 20 psig (138 kPa, which
provides a flow of approximately 8 cubic feet
per hour (approximately 4 liters per minute),
and a case pressure of approximately 0.2 inch
of water (approximately 50 Pa). With a flow
rate of four liters per minute, four case volumes of purge gas pass through the case in
ten minutes.
All conduit connections through the case must
be sealed thoroughly with a sealant (supplied
in kit). The sealant, to be applied from the interior of the case, must thoroughly cover all
exiting leads as well as the conduit fitting.
This kit is designed only for protection against
the invasion of flammable gases into the enclosure from the outside atmosphere. It does
Rosemount Analytical Inc.
A Division of Emerson Process Management
Installation
2-15
Instruction Manual
748183-K
April 2002
Model 755
A. Option with Flow Indicator
B. Option with Pressure Indicator or Alarm
Affix Warning
Label
Affix Warning
Label
Analyzer
Door
Analyzer
Door
190697 Purge
Inlet Fitting
Flow
Indicator
190697 Purge
Inlet Fitting
645835 Purge
Outlet Fitting
Purge
Supply
Purge Supply
Pressure
Indicator or
Alarm
645835 Purge
Outlet Fitting
Components in dashed line are supplied by customer.
Figure 2-9. Installation of Purge Kit
2-16
Installation
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 3
OPERATION
Preparatory to start-up and calibration, a familiarization with Figure 1-1 (page 1-2), Figure 1-2
(page 1-4), Figure 3-1 (page 3-2), and Table 3-1
(page 3-3) is recommended. These figures give
locations and summarized descriptions of components and operating adjustments of the Model
755.
Open analyzer door and verify that circuit boards
are properly installed and connected. Verify
proper connection of electrical cables, see Figure
2-1 (page 2-3).
3-1 START-UP PROCEDURE
DANGER
POSSIBLE EXPLOSION HAZARD
If explosive gas samples are introduced
into the analyzer, it is recommended that
sample containment system fittings and
components be thoroughly leak checked
prior to initial application of electrical
power, routinely on a periodic basis
thereafter, and after any maintenance
which entails breaking the integrity of
the sample containment system. Leakage of flammable sample gas could result in an explosion.
Pass suitable on-scale gas (not actual
sample) through the analyzer. Turn on
power. If meter drives off-scale in either direction, the probable cause is hang-up of
the suspension within the detector assembly. To correct this condition, turn off power,
tap detector compartment with fingers, wait
30 seconds, then again apply power.
When on-scale reading is obtained, allow
analyzer to warm up for at least one hour
with gas flowing. This warm-up is necessary because a reliable calibration is obtainable only after the analyzer reaches
temperature stability. Moreover the resultant elevated temperature will ensure
Rosemount Analytical Inc.
A Division of Emerson Process Management
against condensation within, and possible
damage to, the detector assembly.
After analyzer warm-up, the meter or recorder should give stable,, drift-free readout. If so, proceed to Section 3.2
Calibration, page 3-1. Otherwise refer to
Section 6 Maintenance and Service.
3-2 CALIBRATION
Calibration consists of establishing a downscale calibration point and an upscale calibration point, see Table 3-2 (page 3-6).
Downscale calibration may be performed
on the range that will be used during sample analysis. For maximum precision however, it should be performed on the range
of highest sensitivity, i.e., most narrow
span. Preferably upscale calibration should
be performed on the range that will be used
during sample analysis. In some applications however, it may be desirable to perform upscale calibration on a range of
higher sensitivity, i.e., more narrow span,
and then move the % RANGE Switch to the
desired operating range. For example, if the
operating range is to be 0 to 50% oxygen
upscale calibration may be performed on
the 0 to 25% range, to permit use of air as
the upscale standard gas.
It is necessary to calibrate the instrument at
the same pressure that will be used during
subsequent operation and to maintain this
pressure during operation.
The preferred calibration method uses both
a downscale and an upscale standard gas,
as described in Section 3-2a, page 3-4. An
alternative method using an upscale standard gas only is described in Section 3-2b,
page 3-4.
Operation
3-1
Instruction Manual
748183-K
April 2002
Model 755
R63 15
16 R64
17 R73
Meter
14 R78
13 R68
2
12 R67
R38
R3
R4
R8
R9
CR2
R2
R5
R6
R1
10 R1
U6
1
I G O
1
2
3
4
U3
U2
C5
I
G
O
SPAN potentiometer
11 R2
C4
C2
U4
U1
U5
I G O
R33
R45
C3
CR1
C1
J1
7
Current Output Board
8
ZERO potentiometer
%RANGE switch
R92
5
R20
9
3
R89
4
R90
Numbered items, see
Table 3-1, page 3-3.
Figure 3-1. Control Board - Adjustment Locations
3-2
Operation
Rosemount Analytical Inc.
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Instruction Manual
Model 755
748183-K
April 2002
1. RECORDER OUTPUT (Selector Plug)
Provides selectable output of 10 mV 100 mV, 1 V, or 5 V for a voltage recorder.
2. Meter adjustment (R38)
Used to set meter to agree with recorder.
3. Amplifier AR3 Zero adjustment (R89)
Used for initial factory zeroing of amplifier AR3. (With slider of front-panel SPAN potentiometer R4 connected to ground, R89 is adjusted for zero.)
4. Amplifier AR4 Zero Adjustment (R90)
Used for initial factory zeroing of amplifier AR4. (With R10 connected to ground, R90 is adjusted for
zero.)
5. Response time adjustment (R20)
Provides adjustment range of 5 to 25 seconds for electronic response time (0 to 90% of fullscale).
Clockwise adjustment decreases response time.
6.
7. +5 VDC fullscale output adjustment (R33)
Used to set fullscale for basic analyzer output at +5 VDC.
8. Zero suppression adjustment (R45)
Used to set appropriate zero offset for suppressed-zero ranges.
9. Detector Coarse Zero Adjustment (R92)
Provides coarse adjustment of detector zero by shifting the position of the detector within the magnetic
field. It is adjusted during factory checkout, and does not require readjustment except after replacement
of detector.
10. Current output zero adjustment (R1)
Used to set zero-level current output, i.e., 4 mA for 4 to 20 mA board, 0 mA for 0 to 20 mA board, or 10
mA for 10 to 50 mA board.
11. Current output span adjustment (R2)
Used to set fullscale current output at 20 mA for 4 to 20 or 0 to 20 mA board, or at 50 mA for 10 to 50
mA board.
12. ALARM 2 calibration adjustment (R67)
Used for initial calibration of ALARM 2 circuit.
13. ALARM 2 set-point adjustment (R68)
Provides continuously variable adjustment of setpoint for ALARM 2 circuit on optional alarm accessory, for actuation of external, customer-supplied alarm and/or control device(s). Adjustment range is 0
to 100% of fullscale span.
14. ALARM 2 Deadband Adjustment (R78)
Permits adjusting deadband of ALARM 2 circuit from 1% of fullscale (counterclockwise limit) to 20% of
fullscale (clockwise limit). Deadband is essentially symmetrical with respect to setpoint.
15. ALARM 1 Calibration Adjustment (R63)
16. ALARM 1 Setpoint Adjustment (R64)
17. ALARM 1 Deadband Adjustment (R73)
Functions identical to the corresponding adjustment for ALARM 2 circuit.
See Figure 3-1 (page 3-2) for adjustment locations.
Table 3-1. Control Board - Adjustment Functions
Rosemount Analytical Inc.
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Operation
3-3
Instruction Manual
748183-K
April 2002
a.
Model 755
standard gas. Allow gas to purge
analyzer for minimum of three
minutes.
Calibration with Downscale and Upscale Standard Gases
1. Set downscale calibration point as
follows:
c.
a. Set % RANGE Switch in a position appropriate to the selected
standard gases. The switch may
be set for the range to be used
during sample analysis. For
maximum precision however, it
should be set for the range of
highest sensitivity, i.e., most narrow span.
b. Pass downscale standard gas
through analyzer at suitable flow
rate preferably 250 cc/min. Allow
gas to purge analyzer for minimum of three minutes.
c.
Adjust ZERO Control so that
reading on meter or recorder is
appropriate to the downscale
standard gas. (The required
reading may be the actual oxygen content of the downscale
standard gas, or may be an adjusted value, depending on the
relative magnetic susceptibilities
involved, and the range and
span used, see Section 3-3b
(page 3-7.) If proper reading is
unobtainable by an adjustment of
the ZERO Control, refer to Section 6, Maintenance and Service.
d. If previous reading was obtained
on a recorder, set Meter Adjustment R38 (see Figure 3-1, page
3-2) so that meter reading
agrees with recorder setting.
2. Set upscale calibration point as follows:
a. Set % RANGE Switch in position
appropriate to the selected upscale standard gas.
b. Pass upscale standard gas
through analyzer at same flow
rate as was used for downscale
3-4
Operation
b.
Adjust SPAN Control so that
reading on meter or recorder is
appropriate to the upscale standard gas. (The required reading
may be the actual oxygen content of the upscale standard gas,
or may be an adjusted value,
depending on the relative magnetic susceptibilities involved,
and the range and span used,
see Section 3-2b, page 3-4.) If
proper reading is unobtainable
by adjustment of the SPAN Control, refer to Section 6, Maintenance and Service.
Alternative Calibration Procedure Using Upscale Standard Gas Only
The following calibration procedure, using
an upscale standard gas only, is an alternative to the calibration procedure described in Section 3-2a (page 3-4), which
requires both a downscale and an upscale standard gas.
Throughout the procedure it is preferable
to use recorder readout for all oxygen
readings.
If a recorder is not available, use the
front-panel meter.
1. Set % RANGE Switch for range of
highest sensitivity, i.e., most narrow
span.
2. Set ZERO and SPAN Controls at midrange.
3. Pass upscale standard gas through
analyzer at suitable flow rate, preferably 250 cc/min. Allow gas to purge
analyzer for minimum of three minutes.
4. With % RANGE Switch set for mostsensitive range, obtain reading equal
to the oxygen content of the upscale
Rosemount Analytical Inc.
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Instruction Manual
Model 755
748183-K
April 2002
90% to 100% oxygen. Verify that the
recorder indicates the correct value.
standard gas by adjustment of the
appropriate control:
a. If the most-sensitive range is zerosuppressed, obtain the correct
reading by adjustment of internal
Zero Suppression Potentiometer
R45, see Figure 3-1 (page 3-2).
b. If the most-sensitive range is zerobased, or if a stable reading is unobtainable by adjustment of R45,
obtain correct reading by adjustment of ZERO control.
5. Set % RANGE Switch for leastsensitive range, i.e., widest span.
Then adjust SPAN Control to obtain
reading equal to the oxygen concentration of the upscale standard gas.
Return % RANGE Switch to mostsensitive range.
6. Repeat Steps 4b and 5 as many
times as necessary until no readjustment is required after switch-over
from one range to the other.
7. To verify accurate calibration, admit
an on-scale gas other than the upscale standard. and check that the indicated oxygen concentration is
correct.
EXAMPLE
Range, 90% to 100% oxygen
Upscale Standard Gas, 99.7% oxygen
8. Set % RANGE Switch for 90% to
100% oxygen. Then adjust SPAN
Control for recorder reading of 99.7%
oxygen. Return % RANGE Switch to
99% to 100% range.
9. Repeat Steps 4b and 5 as many
times as necessary until recorder
reads 99.7% oxygen regardless of
position of % RANGE Switch.
10. Admit a gas containing a known concentration of oxygen in the range of
Rosemount Analytical Inc.
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11. Pass upscale standard gas through
analyzer at 250 cc/min. Allow gas to
purge analyzer for minimum of 3
minutes.
12. Obtain recorder reading of 99.7%
oxygen, by adjustment of (a) R45
and, if necessary, (b) ZERO Control.
3-3 COMPENSATION FOR COMPOSITION OF
BACKGROUND GAS
Any gas having a composition other than
100% oxygen contains background gas. The
background gas comprises all non-oxygen
constituents. Although instrument response to
most gases other than oxygen is comparatively slight, it is not in all cases negligible.
Contribution of these components to instrument response is a function of the span and
range used, and can be computed for each
individual case.
If the downscale and upscale standard gases
contain the same background gas as the
sample, the routine standardization procedure
automatically compensates for the background components: therefore, they introduce
no error.
If the background gas in the sample is different from that in the downscale and/or upscale
standard gas(es) background effects must be
taken into consideration to ensure correct
readout. During adjustment of the front-panel
ZERO and SPAN Controls, the instrument is
set to indicate not the true oxygen content of
the downscale and upscale standard gases,
but slightly different values, calculated to provide correct readout during subsequent analysis of the sample gas. The calculations are
explained in Section 3-3b, page 3-7.
a.
Oxygen Equivalent Values of Gases
For computation of background corrections, the analyzer response to each
component of the sample must be known.
Table 3-2 (page 3-6) lists the percentage
oxygen equivalent values for many common gases. The percentage oxygen
equivalent (POE) of a gas in the instru
Operation
3-5
Instruction Manual
Model 755
748183-K
April 2002
ment response to the given gas compared
to the response to oxygen, assuming that
both gases are supplied at the same
pressure, can be calculated using the following equation:
To select a random example from Table
3-2, if analyzer response to oxygen is
+100%, the response to xenon would be 1.34%.
Oxygen Equivalents of Gas Mixtures
The oxygen equivalent of a gas mixture is
the sum of the contributions of the individual gas components.
Example: Zero-based range
At lower range-limit, i.e., 0% oxygen
composition of sample is: 80% CO2,
20% N2.
From Table 3-2, the % oxygen equivalents are: CO2, -0.623%, N2, -0.358%.
% oxygen equivalent of mixture
= 0.8 x (-0.623) + 0.2 x (-0.358)
= (-0.4984) + (-0.07l6)
= 0.570% O2
Example: Zero-suppressed range
Range 50% to 100% oxygen
At lower range-limit, i.e., 50% oxygen
composition of sample is: 50% oxygen:
30% CO2: 20% N2.
From Table 3-2, the % oxygen equivalents are: O2 + 100%, CO2, -0.623%;
N2, -0.358%
% oxygen equivalent of mixture
= 0.5 x (+100) + 0.3 x (-0.623) + 0.2
x (-0.358)
= +50.00 + (-0.187) + (-0.072)
= +49.7415% O2
GAS
Acetylene, C2H2
Allene, C3H4
Ammonia, NH3
Argon, A
Bromine, Br2
1,2-Butadiene C4H6
1,3-Butadiene C4H6
n-Butane, C4H10
iso-Butane, C4H10
Butene-1, C4H8
cis Butene-2, C4H8
iso-Butene, C4H8
trans butene-2, C4H8
Carbon Dioxide CO2
Carbon Monoxide, CO
Ethane, C2H6
Ethylene, C2H4
Helium, He
n-Heptane, C7H16
n-Hexane, C6H12
cyclo-Hexane, C6H12
Hydrogen, H2
Hydrogen Bromide, Hbr
Hydrogen Chloride, HC1
Hydrogen Fluoride, HF
Hydrogen Iodide, HI
Hydrogen Sulphide, C2S
Kryton, Kr
Methane, CH4
Neon, Ne
Nitric Oxide, NO
Nitrogen, N2
Nitrogen Dioxide, NO2
n-Octane, C8H18
Oxygen, O2
n-Pentane, C5H12
iso-Pentane, C5H12
neo-Pentane, C5H12
Propane, C3H8
Propylene, C3H6
Water, H2O
Xenon, Xe
EQUIV. % AS
-0.612
-0.744
-0.479
-0.569
-1.83
-1.047
-1.944
-1.481
-1.485
-1.205
-1.252
-1.201
-1.274
-0.623
-0.354
-0.789
-0.553
-0.059
-2.508
-2.175
-1.915
-0.117
-0.968
-0.651
-0.253
-1.403
-0.751
-0.853
-0.512
-0.205
+44.2
-0.358
+28.7
-2.840
+100.0
-1.810
-1.853
-1.853
-1.135
-0.903
-0.381
-1.340
Table 3-2. Oxygen Equivalent of Common Gases
3-6
Operation
Rosemount Analytical Inc.
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Instruction Manual
748183-K
April 2002
b.
Model 755
the magnetic susceptibility of the background gas. The quantities are defined as
follows (see Table 3-2):
Computing Adjusted Settings for Zero
and Span Controls
During instrument calibration, adjusted
values may be required in setting the
ZERO and SPAN Controls, to correct for
BGGst
BGGs
PO
=
=
=
Oxygen equivalent of background gas in standard gas
Oxygen equivalent of background gas in sample
Operating pressure
Use the following equation to compute the adjusted settings for the ZERO and SPAN Controls:
Adjusted % oxygen for standard gas =
[true % O2 of standard gas] [100 + (BGGs - BGGst)] - 100 [BGGs - BGGst]
100
Use the following equation to compute the adjusted settings for the ZERO and SPAN Controls, see
equation below.
Example
Background gas in sample is CO2, oxygen equivalent = -0.623%.
Downscale standard gas is 100% N2.
Upscale standard gas is air: 21% O2, 79% N2.
Background gas in downscale and upscale standard gases is N2, oxygen equivalent = -0.358%.
With N2 downscale standard gas flowing, ZERO control is adjusted so meter reads:
0 [100 + (-0.623 - (-0.358)] - 100 [-0.623 - (-0.358)]
= 0.265 % O2
100
With air flowing SPAN control is adjusted so meter reads:
21 (100 - 0.265) - 100 (-0.265)
= 21.209 % O2
100
3-7
Operation
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
Model 755
748183-K
April 2002
In two limiting cases, the general equation
reduced to simpler forms.
1. If the upscale standard gas is 100%
oxygen, the adjusted oxygen value for
setting the SPAN Control is the same
as the true value, i.e., 100% oxygen.
2. If the downscale standard is an oxygen-free gas, the adjusted value for
setting the ZERO Control = BGGst BGGs. (If the oxygen-free zero gas is
more diamagnetic than the background gas in the sample, this difference is negative. The meter scale is
not calibrated with negative values;
however, a negative value may be set
on the recorder if provided with below-zero capability.)
3-4 ROUTINE OPERATION
After the calibration procedure of Section 3-2
(page 3-1), admit sample gas to the analyzer
at the same pressure and the same flow rates
as used for the downscale and upscale gases.
The instrument will now continuously indicate
the oxygen content of the sample gas.
If desired, the % RANGE Switch may be
moved to a setting of lower sensitivity, i.e., of
wider span, than was used during calibration.
At this time an adjustment of instrument response time via R20 (Figure 3-1, page 3-2)
may be desirable to obtain the optimum compromise between response speed and noise.
3-5 EFFECT OF BAROMETRIC PRESSURE
CHANGES ON INSTRUMENT READOUT
If the analyzer exhaust port is vented through
a suitable absolute back-pressure regulator
barometric pressure changes do not affect the
percent oxygen readout. However, if the analyzer exhaust port is vented directly to the
atmosphere, any change in barometric pressure after instrument standardization will re-
3-8
Operation
sult in a directly proportional change in the indicated percentage of oxygen. This effect may
be compensated in various ways. If desired,
correction may be made by the following
equation:
Where:
Pst = Operating pressure during standardization
Pan = Operating pressure during sample
analysis
Example (U.S. Units)
Pst = 760 mm Hg
Pan = 740 mm Hg
Indicated % O2 = 40%
True % O2 = 40% = 41.1% O2
Example (S.I. Units)
Pst = 101 kPa
Pan = 98.2 kPa
Indicated % O2 = 40%
True % O2 = 101/98.2 x 40% = 41.1% O2
3-6 CALIBRATION FREQUENCY
The appropriate calibration interval will depend on the accuracy required in the particular application, and is best determined by
keeping a calibration log. If the analyzer exhaust port is vented directly to the atmosphere, the greatest source of error is normally
the variation in barometric pressure. If desired, effects of barometric pressure variation
can be minimized by calibrating immediately
before taking readings, for example, at the
beginning of each shift.
Rosemount Analytical Inc.
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Instruction Manual
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Model 755
SECTION 4
THEORY
4-1 PRINCIPLES OF OPERATION
Compared with other gases, oxygen is
strongly paramagnetic. Other common gases,
with only a few exceptions, are weakly diamagnetic. The paramagnetism of oxygen may
be regarded as the capability of an oxygen
molecule to become a temporary magnet
when placed in a magnetic field, analogous to
the magnetization of a piece of soft iron. Diamagnetic gases are analogous to nonmagnetic substances.
With the Model 755, the volume magnetic
susceptibility of the flowing gas sample is
sensed in the Detector/Magnet Assembly. As
shown in the functional diagram of Figure 4-1
(page 4-2), a dumbbell-shaped nitrogen-filled
hollow glass test body is suspended on a
platinum/nickel alloy ribbon in a non-uniform
magnetic field. Because of the "magnetic
buoyancy" effect, the spheres of the test body
are subjected to displacement forces, resulting in a displacement torque that is proportional to the volume magnetic susceptibility of
the gas surrounding the test body.
Measurement is accomplished by a nullbalance system, where the displacement
torque is opposed by an equal, but opposite,
restorative torque. The restorative torque is
due to electromagnetic forces on the spheres,
resulting from a feedback current routed
through a titanium wire conductor wound
lengthwise around the dumbbell. In effect,
each sphere is wound with a one-turn circular
loop. The current required to restore the test
body to null position is directly proportional to
the original displacement torque, and is a linear function of the volume magnetic susceptibility of the sample gas.
The restoring current is automatically maintained at the correct level by an electro-optical
feedback system. A beam of light from the
source lamp is reflected off the square mirror
attached to the test body, and onto the dual
photocell. The output current from this combination is equal to the difference between the
signals developed by the two halves of the
photocell. This difference, which constitutes
Rosemount Analytical Inc.
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the error signal, is applied to the input of an
amplifier circuit that provides the restoring current. When the test body is in null position,
both halves of the photocell are equally illuminated; the error signal is zero; and the amplifier output remains constant. As soon as the
test body begins to rotate, however, the
amounts of light become unequal. resulting in
application of an error signal to the input of
the amplifier circuit. The resultant amplifier
output signal is routed through the current
loop, thus creating the electromagnetic forces
required to restore the test body to null position. Additionally the output from the amplifier
is conditioned as required to drive the meter,
and recorder if used. The electronic circuitry
involved is described briefly in Section 4-3
(page 4-6) and in greater detail in Section 5.
a.
Magnetic Displacement Force
Because the magnetic forces on the
spherical ends of the test body are the
basis of the oxygen measurement, it is
worthwhile to consider the force acting on
one of these spheres alone and to disregard, for the present, the remainder of the
detector. A small sphere suspended in a
strong non-uniform magnetic field. Figure
4-2 (page 4-3), is subjected to a force
proportional to the difference between the
magnetic susceptibility of this sphere and
that of the surrounding gas. Magnitude of
the force is expressed by the following
simplified equation:
Fk = c (k - ko)
Where:
c = A function of the magnetic field
strength and gradient
k = Magnetic susceptibility of the surrounding gas
ko = Magnetic susceptibility of the
sphere
The forces exerted on two spheres of the
test body are thus a measure of the magnetic susceptibility of the sample, and
therefore of its oxygen content.
Theory
4-1
Instruction Manual
748183-K
April 2002
Model 755
Displacement
Torque
Electromagnetic
Axis
Restoring
Torque
Restoring
Current
Balancing Weight
Electromagnetic
Axis
Nitrogen-Filled Hollow Glass
Test Body
Titanium Wire Conductor
Mirror
Balancing
Weight
Restoring
Current
Platinum/Nickel Alloy
Suspension Ribbon
TEST BODY DETAIL
Displacement
Torque
Restoring
Torque
Restoring
Current
Magnet
Test Body
Source Lamp
DS1
DETECTOR/MAGNET
ASSEMBLY
CONTROL
ASSEMBLY
Shaded Pole Pieces (4)
Zero
Span
% Oxygen
Readout
Dual Photocell
BT1, BT2
Figure 4-1. Functional Diagram of Model 755 Paramagnetic Oxygen Measurement System
4-2
Theory
Rosemount Analytical Inc.
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Instruction Manual
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April 2002
Model 755
Shaded
Pole
Piece
Sphere
(Magnetic Susceptibility = ko )
Fk
Sample Gas
(Magnetic Susceptibility = k )
Note:
As percentage of oxygen in sample gas increases,
displacement force (Fk ) increases.
Figure 4-2. Spherical Body in Non-Uniform Magnetic Field
b.
Physical Configuration of Detector/Magnet Assembly
As shown in the exploded view of Figure
4-3A (page 4-4), the Detector/Magnet Assembly consists of three major subassemblies: the magnet assembly, the
detector assembly, and the optical bench
assembly.
The magnet assembly includes a sample
preheating coil. It is connected into the
sample line, upstream from the detector,
and is heated to approximately the same
temperature as the detector assembly.
For convenience in servicing, the detector
and the optical bench are self-aligning assemblies that utilize slip-on sample connections and plug-in electrical connection.
Within the detector assembly, Figure 4-3B
(page 4-4), the incoming preheated sample passes through an integral 5-micron
diffusion screen. It protects the test body
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by preventing entry of particulate matter
and/or entrained liquid mist. Additionally
the screen isolates the test body from flow
effects, ensuring that instrument readout
is relatively independent of flow rate
within the optimum range of 200 to 300
cc/min.
At the rear of the detector are an integral
temperature sensor (RTI) and an integral
heater (HR2). Another heater (HR1) is
attached to the magnet. Sensor RTI provides the input signal to the detector temperature control section of the case circuit
board assembly, Section 4-3c (page 4-7).
This section controls application of electrical power to both HR1 and HR2.
On the optical bench assembly, see Figure 4-3C (page 4-4),, the source lamp and
the photocell plate are externally accessible, permitting convenient replacement.
Theory
4-3
Instruction Manual
748183-K
April 2002
Model 755
Sample Pre-Heating Coil
Sample Inlet Tube
Sample Outlet Tube
Magnet Assembly
Detector Assembly
Optical Bench Assembly
Mounting Screws (2)
A. Exploded View of Detector/Magnet Assembly
Connector J12
➋ Integral Temperature
➋ Integral Heater
(HR2)
Sensor (RT1)
➋ Integral 5-Micron
Photocell
Lock Screws (2)
Diffusion Screen
➋ Test Body
Mirror
Dual Photocell
Lamp Retaining
Set Screw
➊ Dual Photocell
➊ Source Lamp
Lamp Viewing Hole
➊ Optical Bench Assembly
➋ Detector Assembly
B. Sectional Top View of Optical Bench
and Detector Assemblies
Source Lamp
Assembly
C. Exploded View of Optical Bench
Assembly
Figure 4-3. Detector/Magnet Assembly
4-4
Theory
Rosemount Analytical Inc.
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Instruction Manual
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April 2002
Model 755
4-2 VARIABLES INFLUENCING PARAMAGNETIC OXYGEN MEASUREMENTS
CAUTION
PRESSURE LIMITS
Variables that influence paramagnetic oxygen
measurements include: Operating pressure,
Section 4-2a below, sample temperature,
Section 4-2b below; interfering sample components, Section 4-2c below; and vibration,
Section 4-2d (page 4-6).
a.
Do not subject the sensing unit to an absolute pressure of less than 600 mm Hg
(88.1 kPa)
Operation at negative gauge pressure is
not normally recommended. but is used in
certain special applications, see Section
2-6d (page 2-13).
Pressure Effects
Although normally calibrated for readout
in percent oxygen, the Model 755 actually
responds to oxygen partial pressure. The
partial pressure of the oxygen component
in a gas mixture is proportional to the total
pressure of the mixture. Thus readout is
affected by pressure variations. For instance assume that an instrument is calibrated for correct readout with a standard
gas containing 5% oxygen, admitted at
the normal sea-level atmospheric pressure of 14.7 psia (101.3 kPa). If the operating pressure now drops to one-half the
original value, i.e., to 7.35 psia (50.65
kPa), and the calibration controls are left
at the previously established settings, the
meter reading for the standard gas will
drop to 2.5%.
It is therefore necessary to calibrate the
instrument at the same pressure that will
be used during subsequent operation,
and to maintain this pressure during operation.
Typically the sample gas is supplied to
the analyzer inlet at slightly above ambient pressure, and is discharged to ambient pressure from the analyzer outlet.
However with most applications involving
zero-suppressed ranges, and some applications of zero-based ranges, it is necessary to insert an absolute back-pressure
regulator into the exhaust line to prevent
the readout error that would otherwise result from fluctuations in exhaust pressure.
The regulator must be mounted in a temperature-controlled housing, see Section
2-6c (page 2-13).
Rosemount Analytical Inc.
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b.
Temperature Effects
Magnetic susceptibilities and partial pressures of gases vary with temperature. In
the Model 755, temperature-induced
readout error is avoided by control of
temperatures in the following areas:
Interior of the analyzer is maintained at
140°F (60°C) by an electrically controlled
heater and associated fan.
Immediately downstream from the inlet
port, prior to entry into the detector, the
sample is preheated by passage through
a coil maintained at approximately the
same temperature as the detector, see
Figure 4-3A (page 4-4).
The detector is maintained at a controlled
temperature of 150°F (66°C).
c.
Interferents
Instrument response to most non-oxygen
sample components is comparatively
slight, but is not in all cases negligible.
During initial installation of an instrument
in a given application, effects of the background gas should be calculated to determine if correction is required, refer to
Section 3-3 (page 3-5).
Theory
4-3
Instruction Manual
748183-K
April 2002
d.
Model 755
AR1 on the Control Board assembly. Amplifier AR1 drives AR2, which in turn supplies the restoring current to the titanium
wire loop on the test body, refer to Section 4-1 (page 4-1).
Vibration Effects
Instrument Design
To minimize vibration effects, the Detector/Magnet Assembly is contained in a
shock-mounted compartment (Figure 1-2,
page 1-4).
Elements of Detector Temperature
Control Circuit
Detector temperature is sensed by thermistor RT1, an integral part of the detector assembly, see Figure 4-3B (page 4-4).
The thermistor provides the input signal to
the detector temperature control section
of the case circuit board assembly. The
output from this section is applied to two
heaters within the Detector/Magnet Assembly: HR1. mounted on the top of the
magnet, and HR2, mounted permanently
on the rear of the detector assembly.
Installation
Use reasonable precautions to avoid excessive vibration. In making electrical
connections, do not allow any cable to
touch the shock-mounted detector assembly or the associated internal sample
inlet and outlet tubing. This precaution
ensures against possible transmission of
mechanical vibration through the cable to
the detector, which could cause noisy
readout.
Electronic Response Time
If readout is noisy despite observance of
the precautions mentioned, obtain slower
electronic response by counter-clockwise
adjustment of R20, Figure 3-1 (page 3-2).
4-3 ELECTRONIC CIRCUITRY
Electronic circuitry is shown in the circuit-door
schematic diagram, DWG 632363, and is described briefly in the following sections. For
detailed circuit analysis refer to Section Six.
Schematic diagrams and other engineering
drawings are placed at the back of this manual.
a.
Detector/Magnet Assembly
A cross-sectional view of the optical
bench and detector assemblies is shown
in Figure 4-3B (page 4-4). Source lamp
DS1 powered by a supply section within
the case circuit board assembly, see Section 4-3c (page 4-7), directs a light beam
onto the mirror attached to the test body.
The mirror reflects the beam onto dual
photocell BTI, BT2. The difference between the signals developed by the two
halves of the photocell constitutes the error signal supplied to the input of amplifier
4-6
Theory
b.
Control Board and Associated Circuitry
The Control Board contains signalconditioning and control circuitry. The
board is mounted on the inside of the
analyzer door, as shown in (Figure 1-2,
page 1-4).
The Control Board contains the following:
Input Amplifier AR1
This amplifier receives the error signal
from the dual photocell of the detector assembly and, in turn, drives amplifier AR2.
Amplifier AR2 and Associated Zero
and Span Circuitry
Amplifier AR2 supplies the restoring current to the titanium wire loop of the test
body within the detector assembly. Frontpanel ZERO Control R10 applies an adjustable zero-biasing signal to the input of
AR2, to permit establishing a downscale
calibration point on the meter scale or recorder chart. With downscale standard
gas flowing through the analyzer, the
ZERO control is adjusted for the appropriate reading.
If the analyzer is to incorporate a zerosuppressed range option, the required
Rosemount Analytical Inc.
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Instruction Manual
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April 2002
Model 755
zero offset is obtained by insertion of the
zero suppression resistor module into receptacle J6. This module may be inserted
either during factory assembly or in subsequent field installation of a range conversion kit.
Front-panel SPAN Control R4 provides
continuously variable adjustment of
closed-loop gain for AR2, to permit establishing an upscale calibration point on the
meter scale or recorder chart. With upscale standard gas flowing through the
analyzer. the SPAN control is adjusted for
the appropriate reading.
Amplifier AR3 and Associated Range
Circuitry
During factory assembly, or in subsequent
field installation of a range conversion kit,
the analyzer is provided with the desired
range option by inserting the appropriate
range resistor module into receptacle J3.
In subsequent operation, the desired operating range is selected with front-panel
% RANGE switch SW1, which determines
the feedback resistance for AR3.
Output Stage
Amplifier AR4 and Transistor Ql. The signal from range amplifier QR3 is routed
through phase lead adjust R20 to an output stage consisting of AR4 and Ql.
Potentiometer R20 provides a continuously variable adjustment of 5 to 25 seconds for the electronic response time
(90% of fullscale), and is factory-set for 20
seconds.
The output from Ql is routed to the following:
1. Output resistor network, Item 5.
2. Current output receptacle Jl. This
connector accepts any of the three
optional plug-in current-output boards.
3. Alarm output receptacle J2. This connector accepts the optional dualalarm amplifier board.
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Output Resistor Network
The output signal from Ql is routed to
ground via a voltage divider. A selector
plug associated with the voltage divider
provides a selectable output of 0 to 10
mV, 0 to 100 mV, 0 to 1 V, or 9 to 5 VDC
to drive a voltage recorder. Potentiometer
R38 permits adjusting the meter to agree
with the recorder.
c.
Case Board Assembly
The case circuit board contains powersupply and temperature-control circuitry.
The board is mounted within the analyzer
case, near the top, as shown in (Figure
1-2, page 1-4).
As shown in DWG 632363, the various
circuits operate on main power transformer T1. During instrument assembly,
the two primary windings of T1 are factory-connected for operation on either 120
VAC or 240 VAC, as noted on the namerating plate.
The Case Board contains the following:
Source Lamp Power Supply Section
This circuit provides a regulated output of
2.30 VDC to operate incandescent source
lamp DS1 within the optical bench assembly. One secondary of main power
transformer T1 drives a fullwave rectifier
consisting of CR7 and CR8. The output of
DS1 is held constant by a voltage regulator circuit utilizing AR7, Q4, and Q5.
The ±15 V Power Supply Section
This section provides DC voltage required
for various amplifiers and other circuits.
Fullwave rectifier bridge CR5 provides
both positive and negative outputs. Each
is routed through an associated seriestype integrated-circuit, voltage-regulator,
providing regulated outputs of +15V and 15V.
Theory
4-7
Instruction Manual
748183-K
April 2002
Model 755
range and zero-suppression resistor
modules.
Detector Temperature Control Section
This section maintains the detector at a
controlled temperature of 150°F (66°C).
Temperature is sensed by RT1, a resistance element permanently attached to
the detector assembly.
The signal from the sensor is applied to
amplifier AR6, which drives transistors Q2
and Q3, thus controlling application of DC
power from full-wave rectifier bridge CR6
to two heaters within the Detector/Magnet
Assembly: HRI, mounted on the top of the
magnet; and HR2, permanently mounted
on the rear of the detector assembly.
Case Temperature Control Section
This section maintains the interior of the
analyzer case at a controlled temperature
of 140°F (60°C).
Temperature is sensed by a thermistor on
the Control Board assembly (i.e., case
door circuit board), adjacent to critical
electronic components including the
4-8
Theory
The circuit provides an on-off control of
heater element HR3 via TRIAC element
Q7. Heater HR3 is a part of the heater/fan
assembly.
d.
Isolated Current Output Board (Optional)
An isolated current output is obtainable
the optional Current Output Board. The
board mounts onto the Control Board, see
(Figure 1-2, page 1-4).
e.
Alarm Option
The alarm option provides two sets of relay contacts for actuation of customersupplied alarm and/or process-control devices. The alarm has two single-pole,
double-throw relays, one each for the
ALARM 1 and ALARM 2 contacts. Alarm
output connections are on the terminal
board shown in (Figure 1-2, page 1-4).
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Instruction Manual
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April 2002
Model 755
SECTION 5
CIRCUIT ANALYSIS
The electronic circuitry of the Model 755 Oxygen
Analyzer consists of the following:
• Case heater circuit
• Detector heater circuit
• ±15 VAC power supply
• Voltage regulating circuit for a
stable light source
• Detector circuit with a first-stage
amplifier to provide a feedback
current for mechanical feedback
to the detector and a scaling
amplifier circuit to give an output
change of 0 to +7.5 V for a 0 to
100% change of the operating
span.
5-1 POWER SUPPLY ±15 VDC
The components of the ±VDC power supply
circuit are located in the lower the left-hand
corner of the case circuit board. 19 VAC
should be measured with respect to ground at
CR5 (WO4). A +15 VDC should be measured
at C27 (+) lead and -15 VDC at the C28 (-)
lead. If the specified voltage measurements
are obtained, the power supply is working correctly, see DWG 617186.
5-2 CASE HEATER CONTROL CIRCUIT
The case heater control circuit utilizes four
voltage-comparators (LM339 quad comparator). An understanding of how one of these
comparators functions is necessary before
any circuit analysis can be attempted.
In Figure 5-1 (page 5-2), comparators 1 and 2
are depicted having a comparator within an
overall comparator symbol. Also within this
symbol, the base of an NPN transistor is connected to the output of the comparator. A -15
VDC is supplied to the emitter. The collector is
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illustrated as the overall output for the comparator package.
When the non-inverting terminal of comparator 2 is more positive than the inverting terminal, the transistor does not conduct and the
collector of the transistor or comparator output
is at whatever potential is the present on the
collector.
When the non-inverting terminal of comparator 2 is less positive (more negative) than the
inverting terminal, the transistor conducts and
the output of the comparator is -5V. This value
is the output of the OR circuit.
Comparator 2 is biased at 0 volts on the inverting terminal. Comparator 1 is biased at
about 159 mV on the non-inverting terminal.
There is a slight amount of positive feedback
or hysteresis built into each comparator circuit
for stability or positive action. This is achieved
by the 20 M resistances, R70 and R73.
An approximate 8 V peak-to-peak AC signal is
applied to comparators 1 and 2. As the signal
starts going positive, comparator 2 transistor
ceases conducting and comparator 1 transistor is off. When the signal exceeds the +159
mV on the non-inverting terminal, it turns on
comparator 1 and the output is -15 V. Comparator 1 stays on until the signal drops below
+159 mV, at which time the output will be the
value on the OR bus. As the AC signal goes
negative with respect to ground, the transistor
of comparator 2 conducts and the output is
again -15 V. The output remains at -15 VDC
until the incoming signal crosses zero value
and the positive signal causes the comparator
2 transistor to cease to conduct.
Summing the effects of the two comparators
in the OR circuit results in no output from the
comparators for about 4° of the sinewave, 2°
after the signal goes positive (0 to 2°) and 2°
before the positive signal reaches 180° (178°
to 180°).
Circuit Analysis
5-1
Instruction Manual
748183-K
April 2002
Model 755
During the period that neither comparator is
conducting, the value on the OR bus is the
potential from the temperature-sensing bridge
plus the effect of the ramp generator, probably
-188 ±0.03 V.
Capacitor C36 is added to the input circuit to
delay the incoming AC signal so that the
pulses will occur at or just after the line frequency crossover point.
Circuits for a ramp generator and a temperature-sensing bridge are part of the case
heater control circuit of Figure 5-2 (page 5-3)
and Figure 5-3 (page 5-3).
The on-off effect of the comparators to the OR
circuit results in application of a positive-going
pulse (from -15 V to -1.89 V) to the temperature bridge at the rate of 120 pulses per second.
100µ
-1.7V
-15V
159mV
COMP 1
COMP 2
360°
0°
180°
0°
180°
ON
OFF
ON
OFF
ON
OFF
+15V
+15V
R69
2M
U1-A
-
+1
R71
21.5K
OUTPUT
-15V
R70
20M
+15V
U1-B
-2
+
R68
3.3K
-15V
R73
INPUT
R72
4.75K
C36
0.18uF
20M
CASE BOARD
-1.88 VDC
Source
Figure 5-1. Two-Comparator OR Circuit
5-2
Circuit Analysis
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Instruction Manual
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April 2002
Model 755
+15V
+15V
T1
120 V
RMS
19 VAC
R72
4.75K
R71
21.5K
-
C37
1.0uF
20M
-
R75
CR11
Q6
T2
U1-B
R68
+
R76
37.4K
C40
2200uF
R73
CR10
.18uF
10K
R79
10K
210K
3.3K
C36
R77
U1-C
+
R70
CR9
R67
10K
R74
590K
+
19 VAC
249K
U1-A
TO POWER
SUPPLY
12
R78
-
R69
2M
R80
10K
20M
R81
56.2
R85
-15V
R82
9.07K
C39
.01uF
CASE BOARD
R83 11.0K
63.4K
20M
.18uF
-
R84
169K
RT1
C38
R86
R87
10K
U1-D
+
-15V
Figure 5-2. Case Heater Control Circuit
OFF
OFF
+2.3V
OFF
-15V
-2.3V
R78
6 Hz
249K
+15V
+15V
R74
INPUT FROM
MULTIVIBRATOR
-
+3
590K
-15V
R75
C37
1.0uF
RT1
R83
63.4K
R84
169K
R77
10K
R79
10K
Q6
T2
210K
-15V to 1.88V ±0.3V
R82
9.09K
U1-C
R76
37.4K
TO
COMPARATOR
C40
2200uF
R80
10K
-15V
CASE BOARD
R81
56.2
C38
.18uF
R87
10K
-15V
Figure 5-3. Ramp Generator
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Circuit Analysis
5-3
Instruction Manual
748183-K
April 2002
On initial application of power to comparator
of Figure 5-2 (page 5-3), no potential exists on
the inverting terminal because no charge exists on capacitor, C37. If the transistor of
comparator 3 does not conduct, +15 V is at
the output terminal. With +15 V at the output,
the potential on the non-inverting terminals
will be about ±2.3V because of the resistance
divider R75, R76. Capacitor C37 will now start
to charge positively through R78. When the
positive potential across C37 and at the inverting terminal of comparator 3 exceeds the
potential on the non-inverting terminals, the
transistor conducts. The output is -15 V. A full
30 V drop appears across R77. The potential
on the non-inverting terminal will now be
about -2.3 V. Now C37 will discharge through
R78 until its potential exceeds that on the
non-inverting terminal. At that time. comparator 3 will switch polarity and start charging
C37 again. The result is that the potential
across C37 will vary almost linearly with time
and form a ramp signal of about 6 Hz.
As the potential across C37 increases and
decreases linearly, it affects the potential at
the top of the bridge circuit between R82 and
R83 through R74. Because of the ramp action
charging and discharging C37, the potential
between R82 and R83 varies approximately
from -1.85 V to -1.92 VDC.
The temperature-sensing device, RT1, in the
bridge circuit is a thermistor. The bridge is designed to control the temperature in the case
at 135°F (57°C). When the temperature is
135°F (57°C), the resistance of the thermistor
RT1 will be at its lowest and the potential at
the junction of RT1 and R84 should be the
same as the junction of R82 and R83. Comparator 4 in Figure 5-4 (page 5-6) does not
allow pulses from the OR circuit (comparators
1 and 2), to operate Q6 or TRIAC Q7 in the
case heater, see Figure 5-5 (page 5-7).
Theoretically at 135°F (57°C) the potential at
the junction of RT1 and R84 is -1.85 VDC.
This is equivalent to a resistance of 21.2 K. By
substituting a decade box for the thermistor
and placing 20.2 K into the bridge, the heater
should be off. With 22.7 K, the heater should
be full on.
5-4
Circuit Analysis
Model 755
Since the potential at the junction of R82 and
R83 can vary between 1.85 V and 1.92 V according to the 6 Hz ramp, and the potential at
the junction of RT1 and R84 may vary around
or within these limits, depending on temperature, the error signal to comparator 4 may
vary from 0 mV to some absolute value. The
polarity of the error signal will depend on the
deviation from the desired temperature and
the ramp value at the function of R82 and
R83.
The input from the OR circuit comparator,
Figure 5-1 (page 5-2), is either -15 VDC or the
ramp effect on the bridge. When -15V, the
junction of R82 and R83 is also this value.
The error signal into comparator 4 is negatively large to the inverting terminal. Comparator 4 output transistor does not conduct.
The base of Q6 is positive. Therefore Q6 does
not conduct and a charge builds up on capacitor C38.
The input from the OR comparators 1 and 2
form multi-vibrator circuit, pulses 120 times a
second. For about 100 microseconds the
junction of R82 and R83 is some value between -1.85 V and -1.92 V, depending on the
ramp generator. For this brief period of time
(one pulse), comparator 4 compares the potential of junction R82, R83 with junction RT1,
R84 of the bridge circuit. If the temperature at
RT1 is low, the potential at the non-inverting
terminal of comparator 4 is more negative and
the output is -15 V.
The base of Q6 is zero. because of the voltage drops across R79 and R80, therefore Q6
conducts. Energy stored in C38, flows through
Q6 as current and capacitor C38 discharges
to zero potential. No current flows through the
primary winding of transformer T2. At the end
of the 100 microsecond pulse, the NPN transistor in the output of comparator 4 ceases to
conduct. so the signal on the base of Q6 is
+15 V. Q6 ceases to conduct. C38 starts to
charge. driving electrons (current) through the
primary of T2. This induces a pulse into the
secondary of T2 and to the gate of TRIAC Q7,
turning it on. At the beginning of the next 100
microsecond pulse, comparator 4 output is
again -15 V, with zero volts on the base of Q6.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
Q6 again conducts, discharging C38. At the
end of the 100 microsecond pulse, Q6 ceases
to conduct and C38 charges and a pulse appears at the gate of TRIAC Q7, turning it on
again. The charging time for C38 is about
one-half a time constant (C38, R87), and ten
time constants (R81, C38) are available for
discharging C38.
The above action is repeated as long as the
temperature is low, causing an error between
R82, R83 junction, and RT1, R84 junction. As
the temperature approaches the desired case
temperature of 135°F (57°C), differences between these two junctions will exist for only
part of each ramp and the number of pulses
operating Q7 will be proportional to the
amount of error sensed by the 6 Hz ramp.
DWG 617186), is to delay the timing pulse,
relative to line frequency, so that a pulse arrives at the gate of TRIAC Q7 as the line potential just passes the zero-volt crossover
point (0 and 180 degrees of line phase).
Varistor RVI is a temperature-sensitive resistance device. When case temperature is low,
such as ambient, the value of RVI is low. Applying power at that temperature might cause
a current surge to damage TRIAC Q7. RVI
with its low initial value of resistance acts as a
bypass, and most of the current is shunted
through it. As the temperature increases and
approaches the desired case temperature, the
resistance of RVI increases to a large value.
This limits the current through it and gives fine
control of the heater to TRIAC Q7 and the
temperature-sensing circuit.
The pulses arrive at Q7 just as the supply AC
line voltage is passing the zero-volt crossover
point. The purpose of C36 (grid location F-7,
Rosemount Analytical Inc.
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Circuit Analysis
5-5
Instruction Manual
748183-K
April 2002
Model 755
If the temperature goes down, RT1 increases
in resistance and causes the junction of RT1
and R59 to go positive in voltage value. Since
R55 and R56 are of equal resistance, their
junction is at zero volts. Therefore terminal 3
of AR6 is more positive than terminal 2 and
the base of Q2 is positive. Q2 conducts, allowing alternating current to flow through
heaters 1 and 2. The voltage drop across the
heaters. when completely cold, would be
around 20 VAC and, when controlling, would
be AC of very low amplitude.
5-3 DETECTOR HEATER CONTROL CIRCUIT
Figure 6-5 below, is a simplified heater control
circuit drawing for the detector. Heaters 1 and
2 are actually connected in parallel and have
a combined resistance of about 17 ohm.
The thermistor resistance (RT1) in the resistance bridge varies inversely with temperature. The bridge is designed to maintain the
temperature of the detector at 150°F (65.5°C).
The junction point between R55 and R56 is
maintained at a specific voltage since these
resistances maintain a definite ratio. The
thermistor resistance is 149 K at 150°F
(65.5°C) and increases rapidly as the temperature decreases. R59 in this bridge circuit
represents the set-point value for temperature. Suppose that, at temperature, resistance
of the bridge (R55, R56, R59, and RT1)
equals 149 K.
As the temperature increases the resistance
of RT1 decreases and the junction point between RT1 and R59 becomes less positive.
Terminal 3 of AR6 becomes less positive with
respect to Terminal 2. The output of AR
causes Q2 and Q3 to conduct less. When
terminal 3 equals Terminal 2, or is less than
terminal 2, the output of AR6 is zero or less.
Q2 and Q3 do not conduct and the heater
would not be supplying heat energy to the
detector.
HR1 +2
F1
CR6
WO4
120 V
RMS
25VAC
R60
100
R58
5M
+15V
2
R55
700K
R59
700K
R56
149K
RT1
AR6
6
Q3
R62
1K
Q2
3 +
CR12
-15V
C31
01uF
R88
5M
R61
2.0
Figure 5-4. Detector Heater Control Circuit
5-6
Circuit Analysis
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
main current path, and goes through Q5,
which acts as a variable feedback resistance,
goes to the positive output potential of U7.
5-4 DETECTOR LIGHT SOURCE CONTROL
CIRCUIT
The detector light source control circuit maintains the light output from the bulb (DS1) as
uniform as possible, regardless of voltage
fluctuations or aging of the bulb, Figure 5-5
below.
As DS1 ages, its light emission decreases
and its resistance increases. The current
through DS1 tends to decrease, causing a
decrease in the voltage drop across DS1 and
the input potential to terminal 2 of U7. Now
the output U7 will increase, causing Q4 to
conduct more current through R66. As the
potential across R66 increases, Q5 will conduct more current, causing a further increase
in current flow through DS1. The net result is
that the voltage across DS1 will remain uniform and the operation of Q4 and Q5 will adjust the gain of U7 to maintain the light
emission from DS1 uniform for a long period
of time.
The power source for the light bulb is a center-tapped secondary of transformer T1. This
AC voltage is rectified by CR7 and CR8, and
filtered (C32), presenting an approximate +8.5
V bus to the current-limiting Darlington configuration of Q4.Q4 controls the basic amount
of current through DS1.
Amplifier U7 has a fixed value, approximately
+2.2 VDC on Terminal 3. The output of U7 is
positive, causing Q4 to conduct. As Q4 conducts, electrons flow from the center-tap of T1
to ground and from ground through DS1 for
an input voltage to terminal 2 of U7, through
R66 to develop a bias on the base of Q5,
through Q4 to the +8.5 V bus, and back to the
secondary. As Q5 conducts, some of the current going through DS1 is shunted from the
CR7
T1
α+8.5V BUS
R63
7.5K
6.1 VAC
Q4
+15V
6.1 VAC
120 V
RMS
Voltage fluctuations in the 120 VAC supply
could cause some variation in the amount of
current flowing through the bulb DS1, however the voltage drop across DS1 would
cause U7 to adjust Q4 and the voltage drop
across R66 to adjust Q5. The net result would
still be uniform current flow through DSI and
uniform light emission.
CR8
C31
2000u
F
VR3
9.0V
+
R64
14K
2
C34
.01uF
U7
3 +
a2.2V
R65
4530
C35
.01uF
Q5
R66
1.0
CASE BOARD
DS1
Figure 5-5. Detector Light Source Control Circuit
Rosemount Analytical Inc.
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Circuit Analysis
5-7
Instruction Manual
748183-K
April 2002
Model 755
platinum wires form a fulcrum around which
the test body pivots.
1-1 DETECTOR WITH FIRST STAGE AMPLIFIER
The detector assembly consists of a test body
suspended on a platinum wire and located in
a non-uniform magnetic field, Figure 5-6 below.
The detector operates in the following fashion.
If the sample gas contains oxygen, it collects
in the non-uniform magnetic field around the
test body. Oxygen, because of its paramagnetic qualities, gathers along the magnetic
lines of flux and forces the dumbbell of the
test body to be forced out of the magnetic
field.
The test body is constructed of two hollow
glass spheres forming a dumbbell shape.
They are filled and sealed with pure, dry nitrogen. Around the test body, a titanium wire is
chemically etched in order to form a feedback
loop that can create a counteracting magnetic
force to the test body displacement caused by
oxygen concentration in the test assembly
magnetic field.
A light source is focused on the test body mirror. As the test body moves out of the magnetic field. the mirror distributes light unevenly
on two photocells (BT1 and BT2). The photocells create a current proportional to light. This
current is converted to a plus-or-minus (±)
voltage by U1 and U2, located on the connector board in the detector housing. This
voltage is then presented to comparator U1.
The output of U1 goes to U2. The output of
U2 causes current to flow through the feedback loop attached to the dumbbell.
Attached to the center arm of the test body
dumbbell is a diamond-shaped mirror. Attached to the mirror are two separate platinum
wires in tension with the supports for the test
body. The supports are isolated from ground
and are electrically connected to the feedback
loop and the electronics for that loop. The
C10
.68uF
CONTROL BOARD
+
+15V
R16
56
U3
0 to 7.5V
R3
+15V
CR1
C6
3.3uF
-15V
R19
10
FRONT PANEL
SPAN
R18
29.9K
C42
R1
12.4K
R4
50K
0.01uF
+
R15
4.02K
C10
.68uF
CR2
PHOTOCELL
BOARD
-
BT2
CONNECTOR
BOARD
R1
1K
+
R2
1K
U2
R9
110K
R7
118K
R6
2M
+
BT1
+
-
R4
1K
R92
20K
-15V
R12
R11
.0022uF
-
C11
.1uF
R29
1M
SW1
FRONT
PANEL
%RANGE
PHASE
LEAD
ADJUST
R26
1070
U2
+
C41
1000pf
U1
+15V
CW
R3
1K
DS1
30.1K
C1
R5
1.78K
U1
CW
R91
C2
.47uF
R20
20K
R13
+15V
C3
R8
.47uF 1.69K
R14
R44
232K
R10
20K
-15V
FRONT
PANEL
ZERO
R17
FEEDBACK
LOOP
5-8
Circuit Analysis
Figure 5-6. Detector with First Stage Amplifier
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
This feedback current creates an electromagnetic field that attracts the dumbbell and
mirror into the test assembly magnetic field
until the mirror reflects light almost uniformly
on each photocell. A current proportional to
the oxygen concentration in the magnetic field
of the test assembly has to be flowing through
the feedback loop in order to maintain balance
and provide a reading of the oxygen content
of a sample.
Resistances R5, R17 and the resistance of
the wire in the feedback loop determine the
gain of amplifier U2. The mirror on the dumbbell is positioned by the amount of current in
the feedback loop. The mirror reflects light
from the source (DSI) to the photocells (BTI,
BT2). This repositioning of the mirror is a form
of mechanical feedback to the input of the
amplifier U1. The net result is that the output
of U1 could vary from 0 to -70 mV, or 0 to -7.0
V, depending on the range of the instrument.
R8, C3 and R6, and C2 form damping circuits
for the input amplifier UI and to smooth out
noise that might be introduced by the measurement source.
R8, C3 and R6, and C2 form damping circuits
for the input amplifier U1 and smooth out
noise that might be introduced by the measurement source.
Diode CR2 is a low-leakage device. Its purpose in the circuit is to ensure that the dumbbell and mirror are positioned correctly with
respect to the photocells on initial application
of power.
If the dumbbell was out of position on start-up,
the mirror might reflect light from the source
onto one of the photocells. If the photocell
output was positive, the current in the feedback loop would be in the wrong direction and
its electromagnetic field would cause the
dumbbell to be further repelled from the permanent magnetic field. The result would be
error, not balance.
cathode of CR2 will be initially at -15 VDC.
The anode of CR2 will be some value more
positive than -15 VDC. CR2 will conduct. The
input terminal of U1 will be negative and the
current through the feedback loop around U2
will cause the dumbbell and mirror to be positioned correctly in the test body.
As the charge on C6 increases, the cathode
of CR2 becomes more positive. When it exceeds that on the anode, CR2 ceases to conduct and isolates the +15 VDC and -15 VDC
power supply from the input circuit.
If the measurement span is zero-based (0% to
10% for example), a simple voltage from frontpanel ZERO potentiometer R10 may be
added to the input of U2 to counteract any
electrical offsets that may occur because of
any imbalance in the detector and the photocells BTl and BT2. If the span is elevated
(11% to 21% for example) or, in other words,
the zero is suppressed, a zero suppression
module is added to the circuitry around potentiometer R10. The modified potential from R10
is added to the input value to U2 to accomplish a balance at the lower limit of the particular measurement range.
Amplifier U3 receives the output of Ul (0 to -70
mV to 0 to -1.0 V) and amplifies this value.
The output of U3 is always 0 to +7.5 V. This is
accomplished by RANGE Switch SW1, which
selects some portion of the output and supplies this value as feedback to the input of U3.
Adjustment of the input resistance R4 gives
span trim adjustment once the range has
been selected by Range Switch SW1.
The output of U3 is picked off between R20
and R26 and brought into the final amplifier.
The wiper of potentiometer R20 picks off a
potential that helps give a little phase lead to
the measurement circuit.
On application of AC power, capacitor C6 has
no charge. The current will have to flow
through R18. Initially the full 30-V drop (the
difference between the +15 VDC and -15
VDC power) will appear across R18. The
Rosemount Analytical Inc.
A Division of Emerson Process Management
Circuit Analysis
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Instruction Manual
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April 2002
5-6 FINAL OUTPUT AMPLIFIER
The output of U3, in terms of 0 to +7.5 VDC
for a zero to 100% change in measurement
span, goes to the resistance divider circuit:
R20 and R26, see Figure 5-7 (page 5-11).
The potential at the junction of R20, R26, and
R29 for 100% of span would be about +0.465
V. This value is applied to the non-inverting
terminal of U4. The output of U4 causes Q1 to
conduct. The voltage at the emitter of Q1 and
its junction with R32 should vary from 0 to +5
VDC for a change of zero to 100% in measurement span. When the voltage at the emitter is +5 volts, the junction between R30 and
R32 is ±0.465 V. This value is fed back
through R31 to the inverting terminal of U4.
This feedback value balances the input.
As the input measurement varies, the 0 to
+7.5 V output of U3 varies proportionately.
The junction of R20 and R26 changes between 0 and +0.465 V, causing the output at
the emitter to vary from 0 to +5 V. This causes
the junction between R30 and R32 to move
between 0 and +0.465 V, to balance U4.
The wiper of R20 picks off a higher voltage
value than that at the junction of R20 and
R26. Under stable conditions, the difference
between these two values appears across the
capacitor C11, and the input to U4 is the value
at the junction of R20 and R26. If the meas-
5-10
Circuit Analysis
Model 755
urement increases, the wiper of R20 immediately picks off a higher value, which is transferred through C11 to U4, causing the output
of Q1 to give a quicker indication of a change
at the meter or recorder. Capacitor C11 will
charge up to the new difference between the
potential at the wiper of R20 and the junction
R20, R26. The amount of phase lead will depend on the R29, C11 time constant and the
potential difference during a change.
The +6.2 V zener diode (CR3), the +15VDC
supply, and the 1.0K (R40) combine to limit
the output supplied by U4 to the base of Ql to
-0.6 V and +6.2 VDC.
Since the output of the final amplifier is 0 to
+5 VDC, R38 is used as a trim potentiometer
to set the correct amount of current (1 mA)
through the output meter for fullscale deflection.
Jumper J7 is used to select the output range
value for a voltage input recorder. If a current
converter board or an alarm board is used,
the output voltage value is supplied to each
board as an input signal.
The 6.2 VDC determined by zener diode CR3
is also the reference supply for the alarm point
adjustments on the alarm board.
Rosemount Analytical Inc.
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April 2002
Model 755
COM
0 to +7.5V
VOLTAGE
OUTPUT
MV+
C11
PHASE
R20
LEAD
20K
ADJUST
1.0uF
R29
R28
R41
U4
+
1M
C12
.47uF
TO ALARM
0 - +5V
CR4
C17
R42
150K
1M
R26
1070
Q1
22K
R33
500
R32
453K
.0022uF
∝68
2.0M
R30
13.7K
+15V
R39
4.75K
5V
-15V
R31
TO CURRENT
OUTPUT BOARD
R34
3.83K
R38
500
1V
METER
CONTROL BOARD
R40
1K
R35
909
6.2V
100mV
CR3
R36
90.9
10mV
J7
Recorder Output (J7)
(Jumper Selectable)
R37
10
Figure 5-7. Final Output Amplifier
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Circuit Analysis
5-11
Instruction Manual
748183-K
April 2002
Model 755
into the output of the zero suppression module. This configuration is obtained through use
of the proper range resistor module designed
for zero suppression. In a standard range resistor module for zero-based ranges, R10 is
located between a +15 V, -15 VAC supply.
5-7 ZERO SUPPRESSION MODULE FOR ZERO
ADJUSTMENT
The zero suppression module plugs into J6
and supplies an adjustable negative voltage to
front-panel ZERO potentiometer R10. This
voltage is adjustable from about -10 VDC to 0
VDC. The adjustment allows elevation of the
measurement span and/or compensation for
altitude change, see Figure 5-8 below.
The voltage drop across R10, between the
wiper and the output of AR5, is divided by the
resistance divider made up of R25 and R44 in
parallel and the number of range resistances
in series selected by front panel RANGE
Switch SW1. This divided, or selected, voltage
is applied to the input of amplifier U2 (Figure
5-6, page 5-8) to provide the amount of zero
suppression that corresponds to the lower
range-limit of the zero-suppressed range.
The +10 VDC is a reference value from the
regulator U1 (designated PM REF). Potentiometer R45 allows adjustment of the input to
amplifier AR5. The output can vary from approximately -10 V to -4 VDC. Front-panel
ZERO potentiometer R10 is now connected
+15V
U1
PM REF
ZERO SUPPRESSION MODULE
R48
20K
R24
R46
R45
5K
CW
-
100K
+AR5
R49
10K
R50
56
C18
.033uF
R51
39
R23
SW1
FRONT
PANEL
%RANGE
R22
R21
+15V
R52
10
CW
R44
232K
C19
.047uF
R10
20K
-15V
FRONT
PANEL
ZERO
CONTROL BOARD
Figure 5-8. Zero-Suppression Module
5-12
Circuit Analysis
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 6
MAINTENANCE AND SERVICE
The information provided in this section will aid in
isolation of a malfunction to a particular assembly or
circuit board. A few detailed checks are included to
aid location of the defective assembly. It is recommended that those familiar with circuit in analysis
refer to the circuit theory presented in Section 5.
DANGER
ELECTRICAL SHOCK HAZARD
Do not operate without doors and covers secure.
Servicing requires access to live parts which can
cause death or serious injury. Refer servicing to
qualified personnel.
For safety and proper performance this instrument must be connected to a properly grounded
three-wire source of power.
If explosive gases are introduced into this analyzer,
the sample containment system must be carefully
leak-checked upon installation and before initial
start-up, during routine maintenance and any time
the integrity of the sample containment system is
broken, to ensure the system is in leak-proof condition. Leak-check instructions are provided in Section 2-7, page 2-14.
Tampering or unauthorized substitution of components may adversely affect safety of this product.
Use only factory documented components for repair.
6-1 INITIAL CHECKOUT WITH STANDARD
GASES
If instrument readings do not meet specifications, the first step in troubleshooting is to
isolate the analyzer from the sample stream
and the sample-handling system.
Admit downscale and upscale standard gases
to the analyzer; observe readout on meter,
and on recorder if used:
Meter reads correctly with standard gases
but not with sample gas, the sample and the
Rosemount Analytical Inc.
A Division of Emerson Process Management
sample-handling system are suspect. Check
these areas.
Meter reads correctly with standard gases
but the alarm or output devices do not,
these devices must be checked individually.
Meter reads offscale or erratic with standard gases, as well as with sample gas, the
trouble is probably in the detector or the electronic circuitry.
Offscale - Indication. If meter drives offscale
in either direction, turn off power; tap detector
compartment with fingers; wait 30 seconds;
then again apply power. If the suspension
within the detector assembly is hung up, this
procedure may correct the condition. If not,
proceed with tests of detector and electronics.
Erratic - If downscale and upscale standard
gases give noisy or drifting readings, the trouble is probably in the detector or the temperature-control circuits. Proceed with test of
detector and electronics. In general, before
concluding that the detector is defective and
must be replaced, it is desirable to verify correct operation of all circuits that could cause
erratic readings.
Troubleshooting Zero - Suppressed Range
Instruments
In troubleshooting an analyzer that has zerosuppressed ranges only, the use of a zerobased range change kit is recommended. In
the initial troubleshooting, the zero-based
range resistor module is installed temporarily,
to provide a temporary zero-based range.
Analyzer readout may then be checked with
100% nitrogen as the downscale standard gas
and air (20.93% O2) as the upscale standard
gas. Such testing will also eliminate the effects of variations in barometric pressure and
sample pressure. These effects are sometimes difficult to diagnose on zero-suppressed
ranges.
Maintenance and Service
6-1
Instruction Manual
748183-K
April 2002
Model 755
points within the detector circuit are as shown
in Figure 6-2 (page 6-3).
6-2 CHECKOUT AT TEST POINTS ON CASE
CIRCUIT BOARD
Initial checks are made at test points A, B, C
and D on the Case Board. There are two sets
of these test points for accessibility. See Figure 6-1, page 6-2. Test points A, B, C, and D
permit connection to the photocells and the
suspension of loop. Locations of the test
With zero gas flowing, connect a voltmeter
across B and A; measure voltage and note
polarity, then. measure voltage from C or D to
ground and note polarity. Check results
against table, Voltage Test Measurements.
Voltage Test Measurements
B TO A
+
+
C OR D
TO GROUND
+
+
-
DIAGNOSIS
CORRECTIVE ACTION
Normal
U1 or U2 defective
U1 or U2 defective
Detector defective
NA
Replace Case Board
Replace Case Board
Check detector per Section 6-3 page 6-4
If polarities are correct, set front-panel SPAN
potentiometer R4 at maximum. The output at
pin 6 of U3 should be 7.5 VDC. Pins 2 and 3
of U4 should both be at 0.465 VDC, resulting
in 5 VDC at the output of Q1 .
P12
Checkout of the case circuit board is now
complete.
CURRENT TO VOLTAGE OP AMPS
ON CONNECTOR BOARD
4
PHOTOCELLS
5
B
D
SUSPENSION
LOOP
A
C
6
Figure 6-1. Voltage Test Points
6-2
Maintenance and Service
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
P8
D C B
D C B
A
HOT
A
B
C
D
A
TB2
Case Board
MA MV
+ - + COM
A
B
C
D
TB1
N
GN E
U
T
H
O
T
Alarm Option removed for clarity.
Figure 6-2. Locations of Case Board Test Points A, B, C and D
Rosemount Analytical Inc.
A Division of Emerson Process Management
Maintenance and Service
6-3
Instruction Manual
748183-K
April 2002
Model 755
6-3 DETECTOR COMPONENT CHECKOUT
a.
d.
If the suspension has been damaged, the
cause may be improper operating conditions.
Detector
Before concluding that the detector is
defective and must be replaced, verify
that all components and circuits that could
cause erratic readings are operating
properly.
Maximum permissible operating pressure
for the detector is 10 psig (69 kPa gauge
pressure). To ensure against overpressurization, a pressure relief valve
may be inserted into the sample inlet line.
In addition, a check valve should be inserted into the vent line, if connected to a
manifold associated with a flare or other
outlet that is not at atmospheric pressure.
If the detector is over-pressurized, the
suspension could break.
To isolate the detector as a source of a
problem, the source lamp, photocells, and
suspension should be checked for proper
operation.
b.
Source Lamp
To verify that the source lamp in operating
properly:
To verify correct operation:
1. Verify that lamp is lit.
1. Turn electrical power to analyzer
OFF.
2. Voltage at U7 pin 2 should be 2.2
±0.2 VDC.
2. Remove optical bench assembly (see
Section 6-4b steps 1 through 4, page
6-7)
If lamp is not operating properly, replace
per instructions in Section 6-4b, page 6-7.
c.
Suspension
3. With 100% nitrogen flowing through
the analyzer, note the position of the
suspension.
Photocell
To verify that photocell is operating properly, perform the following steps:
4. Admit air and note response of suspension. It should rotate clockwise
(as viewed from the top) and to the
right (as viewed through the window).
1. Keeping power source ON, disconnect the leads of the photocell from
connector J12. See Figure 6-3 (page
6-5) and Figure 6-4 (page 6-7).
2. Note the current measurement between the gray and orange wires
(between 300 to 450 mA).
3. Measure between the orange and red
wires. The reading should be approximately the same as step 2.
If photocell readings not correct, replace
photocell per Section 6-4c, page 6-9.
Failure to rotate indicates that the suspension has been damaged and that the
detector assembly must be replaced. See
Section 6-4a, page 6-4.
6-4 DETECTOR COMPONENT REPLACEMENT
a.
Detector Replacement and Calibration
Replacement
Prior to removal of the detector, remove
power from instrument and stop flow of
sample gas.
1. Remove the four screws securing the
detector cover plate.
6-4
Maintenance and Service
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
2. Disconnect cable from J12 on the
detector assembly.
4. Remove the two screws at the bottom
of the detector assembly, slide detector out.
NOTE
5. Install replacement detector assembly
and connect cable to J12.
Note how the rubber sample lines are
looped into a "long coil". When reinstalling the sample lines they must be
configured in the same way. This precaution isolates the detector from the
effects of mechanical vibration. Otherwise vibration waves could travel
upward along the tubing walls, resulting in noisy readout.
6. Seat the detector assembly firmly
against the magnet pole pieces and
tighten attaching screws.
7. Reconnect rubber sample lines to
metal inlet and outlet tubes on detector assembly.
3. Refer to Figure 6-3 below. Using
needle-nose pliers, squeeze the hose
clamps to disconnect the rubber sample lines from the metal inlet and outlet tubes of the detector assembly.
8. Apply power to instrument and allow
to warm up approximately one hour.
A. Detector/Magnet Assembly - Exploded View
B. Optical Bench - Exploded View
Connector
J12
Sample Pre-Heating
Coil
Photocell
Lock Screws (2)
Connector
Board
Sample Inlet
Tube
Sample Outlet Tube
Lamp Retaining
Set Screw
Detector Assembly
Dual
Photocell
Magnet
Assembly
Optical Bench Assembly
Lamp Viewing
Hole
Source Lamp
Assembly
Mounting Screws (2)
Figure 6-3. Detector/Magnet Assembly
Rosemount Analytical Inc.
A Division of Emerson Process Management
Maintenance and Service
6-5
Instruction Manual
748183-K
April 2002
Model 755
Calibration
NOTE
The following adjustments are on the Control Board, refer to Figure 1-1 (page 1-2)
and Figure 3-1 (page 3-2).
1. Connect a digital voltmeter (4-digit resolution) from slider (S) of front-panel ZERO
potentiometer (R10) to chassis ground.
Adjust ZERO potentiometer for zero volts.
2. Connect the voltmeter from wiper of front
panel RANGE switch (SW1) to chassis
ground. Adjust Zero Suppression Adjustment (R45) for voltmeter reading of as
near zero as possible.
3. Connect the voltmeter from slider (S) of
front panel SPAN potentiometer (R4 to
chassis ground. With a steady flow of 50
to 500 cc/min. of nitrogen zero gas passing through the instrument, adjust Coarse
Zero Potentiometer (R92) for zero volts.
4. If instrument has zero-suppressed
ranges, proceed to Step 5. If instrument
has zero-based ranges, skip Step 5 and
proceed directly to Step 6.
6-6
Maintenance and Service
5. If instrument has zero-suppressed
ranges, the zero offset required for the
desired zero-suppressed range must now
be established. Supply a steady flow of
downscale standard gas appropriate to
the desired range, refer to Section 3-2
(page 3-1). Set Zero-Suppression Adjustment (R45) so that the reading on the
front-panel meter is appropriate to the
downscale standard gas. The required
reading may be the actual oxygen content
of the downscale standard gas, or may be
an adjusted value, depending on the relative magnetic susceptibilities involved,
and the range and span used, refer to
Section 3-3b (page 3-7).
6. With all internal adjustments now properly
set, the instrument may be calibrated in
the normal manner by adjustment of the
front-panel ZERO and SPAN controls.
NOTE
If subsequently the analyzer ranges are
changed through installation of a different
range resistor module, the calibration procedure must be repeated.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
b.
sembly to the magnet assembly.
Carefully remove optical bench and
detector assembly.
Source Lamp Replacement and Adjustment
Replacement
5. Remove the two lock screws (2-56 X
5/16 pan head) holding the photocell
in the optical bench. Carefully remove photocell.
1. Remove the four screws securing the
detector assembly cover plate.
2. Refer to Figure 6-4 below. Carefully
remove the small rubber hose connected from the Detector/Magnet Assembly to the detector.
6. Loosen lamp retaining set screw, remove lamp.
7. Note location of lamp wires in connector J12. Disconnect leads of lamp
assembly from connector J12 (see
Figure 6-4B) using method shown in
Figure 6-4C.
3. If retaining set screw for lamp is accessible, proceed to step 6. If the set
screw is not accessible continue to
step 4.
4. Remove the two screws holding the
optical bench assembly/detector as-
A. Connections to Source Lamp and Photocell
10
BRN
YEL
B. Connections to Suspension and Heater Circuits
RED
BLU
18
J12
WHT
WHT
BLK
BLK
1
ORN
Dual
Photocell
10
18
J12
GRY
HR2
Suspension
Heater
Suspension
Terminals
1
When dual photocell is
installed, the gap between
the two photocells should
be in position indicated by
this line.
Sense
PUR
GRN
RT1
Hole for Source Lamp
Old Style Lamp
Optical Bench
C. Removal and Insertion of Pin/Leads in Connector J12
Keeper
Upper Slot
Side View
of Connector
Connector Pin Removed
Connector Pin/
Leads in Place
Lower Slot
Improvised Pin Removal Tool, Such as a Paper Clip
Figure 6-4. Detector/Magnet Assembly Wiring
Rosemount Analytical Inc.
A Division of Emerson Process Management
Maintenance and Service
6-7
Instruction Manual
748183-K
April 2002
Model 755
8.
Depending on date of manufacture of
the analyzer, the original lamp assembly may be either of two types:
10. If the lamp assembly removed from
the instrument has two wires, proceed
to step 13.
a. Old style lamp assembly with
four color coded leads: Red,
blue, brown and yellow.
11. If the lamp assembly removed from
the instrument has four wires, the
Connector Board requires modification per steps 10 through 12. Continue to step 10.
Red
Blue
Brown
Yellow
12. Refer to Figure 6-3, page 6-5. Remove the two screws holding the
Connector Board to the magnet assembly. Carefully remove Connector
Board.
b. New style lamp assembly with
two leads color coded either both
red or both black.
Two Red or
Two Black Leads
The replacement lamp assembly is
the new style with two leads. On
J12, insert one lead into the position
formerly used for the brown lead to
the old style lamp and the other lead
into the position for the blue lead of
the old lamp. See Figure 6-4A, page
6-7.
9. Insert the lamp into the assembly.
After reassembly and application of
power, the lamp will have to be rotated to place the lamp filaments in
proper orientation.
13. Place Connector Board on a clean
working surface, with solder side (no
components) up.
14. Per Figure 6-5 below, add straps or
solder bridges at the two points
shown.
NOTE
If the Connector Board cannot be satisfactorily modified, a modified 633689
Connector Board may be ordered from
the factory. See Section 7.
15. Reassemble detector, etc., in reverse order of disassembly.
Add Straps or Solder Bridges
F3
HR1
Solder Side of Board
(Backside)
Figure 6-5. Modification of 633689 Connector Board for Compatibility with Replacement Lamp
6-8
Maintenance and Service
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
Alignment
Adjustment
The lamp has a red line on the base
housing. It is to be lined up with the setscrew that secures the lamp, see Figure
6-6 below. The base of the lamp should
extend from the hole approximately 1/4
inch, then tighten the set-screw.
1/4"
Set Screw
NOTE
The following adjustments are on the
Control Board, refer to Figure 1-2
(page 1-4) and Figure 3-1 (page 3-2).
With zero gas flowing:
1. Place a digital voltmeter on the wiper
of the zero potentiometer (R10) and
TP7 (ground), and adjust for 0 VDC.
2. Place the voltmeter from the left of
R91 and TP7, and adjust R92 for 0
VDC, see Figure 6-7 below.
Red Mark for
Alignment
c.
3. Place the voltmeter on TP8 and TP7,
then move the photocell to obtain a
direct-volt voltage as close to 0 mV as
possible but no more than ±750mV.
Figure 6-6. Lamp Alignment
4. Apply power to instrument and allow
to warm up for about one hour.
The photocell will need realigning per
Section 6-4c below.
5. Perform the Calibration procedure in
Section 6-4a (page 6-4).
Photocell Replacement and Adjustment
With all internal adjustments now properly
set, the instrument may be calibrated in
the normal manner by adjustment of the
front-panel ZERO and SPAN Controls.
In removing photocells for examination,
testing, or replacement, use the following
procedure. The range resistor module,
and zero suppression module. if used,
must be installed.
TP17
Replacement
To remove the photocell from the optical
bench, perform steps 1 thorough 5 of
Section 6-4b above.
Install replacement photocell by reversing
the procedure.
R91
TP9
Voltmeter
Lead
R92
TP15
TP16
Figure 6-7. Photocell Adjustment Voltmeter Lead
Location
Rosemount Analytical Inc.
A Division of Emerson Process Management
Maintenance and Service
6-9
Instruction Manual
748183-K
April 2002
Model 755
6-5 HEATING CIRCUITS
To ensure against damage from overheating
in event of malfunction, the heating circuits
receive power via thermal fuses F2 and F3. If
temperature of a heated area exceeds the
permissible maximum, the associated fuse
melts, opening the circuit. Each thermal fuse
should be plugged in, not soldered, as the
fuse element might melt and open the circuit.
a.
OVERHEATING
Do not operate for long periods of time
with decade box set for 22.2K ohms, as
overheating of equipment may result.
Set the decade box for 20.2K ohms to
simulate RT1 resistance at controlling
temperature. The voltmeter should now
show pulses of 1 VAC.
Case Heater Control Circuit
The case heater control circuit receives
power via thermal fuse F2 (setpoint
76°C). This fuse, accessible on the case
circuit board, may be checked for continuity.
Case heater element HR3, mounted on
the heater/fan assembly, has a normal resistance of 20 ohms.
To verify heater operation, place a hand
beside the right hand side of the detector
housing. Heated air should be felt; if not,
check the case heating circuit.
Temperature sensor RT1 has a cold resistance of 22.7K ohms and a normal operating resistance of 20.2K ohms,
indicating normal operating temperature
of 140°F (60°C). Until thyristor RV1
reaches operating temperature. it bypasses most of the current that would
otherwise flow through TRIAC Q7.
As a further check, disconnect plug P8 on
the Control Board assembly, thus disconnecting temperature sensor, RT1. Substitute a decade resistor box to simulate
the resistance of RT1. Also connect an
AC voltmeter from the hot side of the line
to the neutral side of F2.
6-10
CAUTION
Maintenance and Service
Set the decade box for 22.2K ohms to
simulate RT1 resistance at ambient temperature; the voltmeter should now show
pulses of 120 VAC.
b.
Detector/Magnet Heating Circuit
Heater HR1 is attached to the magnet:
heater HR2 is attached to the rear of the
detector. Combined resistance of these
two parallel-connected heaters, as measured at pins 15 and 16 of detector connector J12, should be approximately 17
ohms. If not, remove pin/leads 14 and 15
from the connector, to measure resistance of HR2 alone. This resistance
should be approximately 89 ohms. If resistance was correct, and yet the combined resistance was incorrect, heater
HR1 may be open. To reach the leads of
HR1. remove the printed circuit board on
the heater assembly. Resistance of HR1
should be approximately 21 ohms.
To check operation of the heater circuit,
connect a voltmeter across R61 on the
case circuit board . Normally the voltage
will be 4 VDC when cold, and will drop to
approximately 0.4 VDC at control temperature. Temperature sensor RT1 is
mounted in the detector with leads accessible at pins 10 and 11 of detector connector J12. The sensor resistance, as
measured at these pins, should be 1M
ohms at 25°C and approximately 149K
ohms at operating temperature of 65°C.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 7
REPLACEMENT PARTS
The following parts are recommended for routine maintenance and troubleshooting of the
Model 755 Oxygen Analyzer. If the troubleshooting procedures do not resolve the problem, contact Rosemount Analytical Customer
Service Center.
WARNING
7-1 CIRCUIT BOARD REPLACEMENT POLICY
In most situations involving a malfunction of a
circuit board, it is more practical to replace the
board than to attempt isolation and replacement of the individual component. The cost of
test and replacement will exceed the cost of a
rebuilt assembly. As standard policy, rebuilt
boards are available on an exchange basis.
PARTS INTEGRITY
Tampering or unauthorized substitution of
components may adversely affect safety of
this product. Use only factory-documented
components for repair.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Because of the exchange policy covering circuit boards the following list does not include
individual electronic components. If circumstances necessitate replacement of an individual component, which can be identified by
inspection or from the schematic diagrams,
obtain the replacement component from a local source of supply.
Replacement Parts
7-1
Instruction Manual
748183-K
April 2002
Model 755
7-2 MATRIX – MODEL 755 GENERAL PURPOSE ENCLOSURE
755G
MODEL 755 OXYGEN ANALYZER - ANALOG METER
Code
1
2
3
4
5
9
Ranges
0-1, 2.5, 5 and 10% fullscale
0-5, 10, 25 and 50% fullscale
0-10, 25, 50 and 100% fullscale
0-1, 2.5, 5 and 25% fullscale
0-1, 5, 10 and 25% fullscale
Special
Code
1
2
3
4
9
Corrosion Resistance
Standard Detector
Detector with rhodium plated current loop
Detector with stainless steel tubing(3)
Detector with rhodium plated current loop and stainless steel tubing.
Special
Code
01
02
99
Output
Voltage: 0-10 mV, 0-100 mV, 0-1V or 0-5VDC
Current: 0, 4-20 mA, Isolated
Special
Code
00
01
99
Alarm Relays
None
Dual
Special
Code
01
02
03
04
99
Case
General Purpose (NEMA-3R)
General Purpose with ISA Type Z Purge
General Purpose with Tropicalization
General Purpose Purge with Tropicalization
Special
Code
01
02
99
Operation
115V, 50/60 Hz
230V, 50/60 Hz
Special
Code
00 Features as selected above
99 Special
755G
7-2
4
2
Replacement Parts
01
00
01
01
00
Example
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
7-3 MATRIX – MODEL 755 EXPLOSION PROOF ENCLOSURE
755EX
MODEL 755 OXYGEN ANALYZER EXPLOSION-PROOF VERSION - ANALOG METER
Code Ranges
1
2
3
4
5
9
0-1, 2.5, 5, and 10% fullscale
0-5, 10, 25, and 50% fullscale
0-10, 25, 50, and 100% fullscale
0-1, 2.5, 5, and 25% fullscale
0-1, 5, 10, and 25% fullscale
Special
Code
1
2
3
4
9
Corrosion Resistance
Standard
Detector with rhodium plated current loop
Detector with stainless steel tubing
Detector with rhodium plated current loop and stainless steel tubing.
Special
Code
01
02
99
Output
Voltage: 0-10 mV, 0-100 mV, 0-1 V or 0-5 VDC
Current: 0, 4-20 mA, Isolated
Special
Code
00
01
99
Alarm Relays
None
Dual
Special
Code
01
02
99
Case
Class I, Groups B, C, D, Division 1
Class I, Groups B, C, D, Division 1 w/ Tropicalization
Special
Code
01
02
99
Operation
115V, 50/60 Hz
230V, 50/60 Hz
Special
Code
00
Features as selected above
99
Special
755EX
1
Rosemount Analytical Inc.
3
01
00
01
01
00
A Division of Emerson Process Management
Example
Replacement Parts
7-3
Instruction Manual
748183-K
April 2002
Model 755
7-4 REPLACEMENT PARTS
To minimize downtime, stocking of the following spare parts is recommended.
656143
622421
656190
656189
616418
622356
631773
623875
861273
860706
861652
861653
621023
860371
861649
Detector, 0-5% or greater range increments
Optical bench, for detector 632358
Detector/Optical bench assembly, corrosion resistant, 0 to 1 % or greater range increment
Detector/Optical bench assembly, non-corrosive applications, 0 to 1 % or greater range increments
Source lamp kit
Photocell assembly
Case circuit board assembly
Control board assembly
Fan (120 V)
Fan (240 V)
Heater (120 V)
Heater (240 V)
Current output board, 0 to 20 mA, 4 to 20 Ma
Alarm relay
Thermal fuse (F2-F3)
1*
1*
1*
1*
1
1
1
1
1
1
1
1
1*
1*
1
*If used
7-4
Replacement Parts
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 8
RETURN OF MATERIAL
8-1 RETURN OF MATERIAL
If factory repair of defective equipment is
required, proceed as follows:
1. Secure a return authorization from a
Rosemount Analytical Inc. Sales Office or
Representative before returning the
equipment. Equipment must be returned
with complete identification in accordance
with Rosemount instructions or it will not
be accepted.
Rosemount CSC will provide the shipping
address for your instrument.
In no event will Rosemount be
responsible for equipment returned
without proper authorization and
identification.
2. Carefully pack the defective unit in a
sturdy box with sufficient shock absorbing
material to ensure no additional damage
occurs during shipping.
3. In a cover letter, describe completely:
•
The symptoms that determined the
equipment is faulty.
• The environment in which the
equipment was operating (housing,
weather, vibration, dust, etc.).
• Site from where the equipment was
removed.
• Whether warranty or non-warranty
service is expected.
• Complete shipping instructions for the
return of the equipment.
4. Enclose a cover letter and purchase order
and ship the defective equipment
according to instructions provided in the
Rosemount Return Authorization, prepaid,
to the address provided by Rosemount
CSC.
Rosemount Analytical Inc.
Process Analytical Division
Customer Service Center
1-800-433-6076
Rosemount Analytical Inc.
A Division of Emerson Process Management
If warranty service is expected, the defective
unit will be carefully inspected and tested at
the factory. If the failure was due to the
conditions listed in the standard Rosemount
warranty, the defective unit will be repaired or
replaced at Rosemount’s option, and an
operating unit will be returned to the customer
in accordance with the shipping instructions
furnished in the cover letter.
For equipment no longer under warranty, the
equipment will be repaired at the factory and
returned as directed by the purchase order
and shipping instructions.
8-2 CUSTOMER SERVICE
For order administration, replacement Parts,
application assistance, on-site or factory
repair, service or maintenance contract
information, contact:
Rosemount Analytical Inc.
Process Analytical Division
Customer Service Center
1-800-433-6076
8-3 TRAINING
A comprehensive Factory Training Program of
operator and service classes is available. For
a copy of the Current Operator and Service
Training Schedule contact the Technical
Services Department at:
Rosemount Analytical Inc.
Customer Service Center
1-800-433-6076
Return of Material
8-1
Instruction Manual
748183-K
April 2002
8-2
Return of Material
Model 755
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
SECTION 9
INDEX
A
alarm, 1-3, 2-6, 4-8
manual reset, 2-6
output, 2-2, 2-6
output connections, 2-6
relay assembly, 1-3
Alarm 1 Relay, 2-6
Alarm 2 Relay, 2-6
Alarm Relay Assembly, 2-6, 2-8
Alarm Relay Characteristics, 2-6
Alarm Reset, 2-6
Alarm Setpoint Adjustment, 2-8
analyzer
power source, 2-2
warm-up, 3-1
analyzer exhaust port, 3-8
atmosphere, 3-8
barometric pressure changes, 3-8
D
B
background gas, 3-5
Bypass Flow, 2-13
C
cable conduit openings, 2-1
unused, 2-1
calibration, 3-1
ALARM 1, HIGH, 2-8
ALARM 2, LOW, 2-8
Detector/Magnet Assembly, 6-6
downscale calibration point, 2-10
gas cylinders, 2-10
gases, 2-10
preferred method, 3-1
pressure, 3-1
recorder readout, 3-4
upscale, 2-10
upscale calibration point, 2-10
Case Board, 1-1, 4-7
±15V power supply circuit, 4-7
case temperature control circuit, 4-8
detector temperature control circuit, 4-8
source lamp power supply circut, 4-7
Rosemount Analytical Inc.
test points, 6-2
case heater
control circuit, 5-1
control circuits - service, 6-10
verify operation, 6-10
circuit breaker, external, 2-2
computation of background corrections, 3-5
condensation, 2-11, 3-1
Control Board, 1-1, 1-3, 2-4, 4-6
amplifier AR2, 4-6
amplifier AR3 circuitry, 4-7
circuitry, 4-6
input amplifier AR1, 4-6
output resistor network, 4-7
output stage, 4-7
Span circuitry, 4-6
Zero circuitry, 4-6
corrosive applications, 2-11, 2-14
Current Output Board, 1-3, 4-8
A Division of Emerson Process Management
damping effect, 2-13
Detector/Magnet Assembly, 4-3
calibration, 6-6
detector assembly, 4-3
heater circuit check, 6-10
magnet assembly, 4-3
optical bench assembly, 4-3
E
Electronic Response Time, 4-6, 4-7
vibration effects, 4-6
Elements of Detector Temperature Control Circuit, 46
Erratic readings, 6-1
F
Fail-Safe Applications, 2-8
field-selectable voltage output, 1-1
flammable sample, 2-14, 3-1
fuse, external, 2-2
Index
9-1
Instruction Manual
748183-K
April 2002
Model 755
P
I
Installation
vibration effects, 4-6
Instrument Design
vibration effects, 4-6
instrument location
ANSI/NFPA requirements, 2-1
instrument location GP
outdoors, 2-1
instrument mounting EXP
surface, 2-1
wall, 2-1
instrument mounting GP
ambient temperature range, 2-1
NEMA 3R, 2-1
shock, 2-1
stanchion, 2-1
surface, 2-1
vibration, 2-1
instrument response time, 3-8
adjustment, 3-8
isolated current output, 1-1, 1-3, 2-2, 2-3, 4-8
L
lamp alignment, 6-9
Leakage, 2-14, 3-1
M
Maximum permissible operating pressure for the
detector, 6-4
maximum precision, 3-1
meter drives off-scale, 3-1
Meter reads correctly with standard gases but
not with sample gas, 6-1
Meter reads correctly with standard gases but
the alarm or output devices do not, 6-1
Meter reads offscale or erratic with standard
gases, as well as with sample gas, 6-1
minimum permissible operating pressure, 2-13
O
Offscale - Indication, 6-1
on-scale gas, 1, 3-5
Operating limits for sample flow rate, 2-13
Operating pressure limits, 2-11
output device, 2-2
cable routing, 2-2
Oxygen Equivalents of Gas Mixtures, 3-6
9-2
Index
percentage oxygen equivalent, 3-5
photocell adjustment, 6-9
photocell replacement, 6-9
POE (percentage oxygen equivalent), 3-6
positive sample pressure, 2-13
Potentiometric Output, 2-2
power cable
connection, 2-2
routing, 2-2
size, 2-2
type, 2-2
power failure, 2-6, 2-8
power source, 2-6, 5-7
Pressure at Sample Inlet, 2-13
R
radio frequency interference, 2-6
range resistor module, 6-9
ranges
overall, 1-1
special, 1-3
switch selectable, 1-1
three sub-ranges, 1-1
zero based, 1-1
zero suppressed, 1-1
recorder, 1-5
cable routing, 2-2
calibration readout, 3-4
RESET terminals, 2-6
Return Authorization, 8-1
S
sample
entry temperature, 2-11
Sample Exhaust, 2-13
Sample Exhaust Arrangements for Zero-Based
Ranges, 2-13
sample handling, 2-11
flow measurement, 2-11
gas selection, 2-11
particulate filter, 2-11
pressurizing the sample, 2-11
sample temperature at the analyzer inlet, 2-11
sample transport time, 2-14
Setpoint adjustment of ALARM 1, HIGH, 2-8
Setpoint adjustment of ALARM 2, LOW, 2-9
standard gas supply, 2-10
Rosemount Analytical Inc.
A Division of Emerson Process Management
Instruction Manual
748183-K
April 2002
Model 755
upscale calibration point, 4-7
upscale standard gas, 2-10, 2-11, 1, 3-4
T
time lag, 2-13
Too rapid a flow, 2-13
Troubleshooting Zero - Suppressed Range
Instruments, 6-1
Type Z Air Purge, 2-15
conduit connections, 2-15
flow rate, 2-15
installation options, 2-15
supply pressure, 2-15
U
V
voltage output, field-selectable, 1-1
Z
zero based range
normal zero gas, 2-11
zero suppression module, 6-9
zero-based range, 1-1
zero-suppressed range, 1-3, 2-11, 4-6, 5-12
normal gas (blend), 2-11
upscale calibration, 3-4, 4-7
Rosemount Analytical Inc.
A Division of Emerson Process Management
Index
9-3
Instruction Manual
748183-K
April 2002
9-2
Index
Model 755
Rosemount Analytical Inc.
A Division of Emerson Process Management
WARRANTY
Goods and part(s) (excluding consumables) manufactured by Seller are warranted to be free from
defects in workmanship and material under normal use and service for a period of twelve (12)
months from the date of shipment by Seller. Consumables, glass electrodes, membranes, liquid
junctions, electrolyte, o-rings, etc., are warranted to be free from defects in workmanship and
material under normal use and service for a period of ninety (90) days from date of shipment by
Seller. Goods, part(s) and consumables proven by Seller to be defective in workmanship and/or
material shall be replaced or repaired, free of charge, F.O.B. Seller's factory provided that the
goods, part(s) or consumables are returned to Seller's designated factory, transportation charges
prepaid, within the twelve (12) month period of warranty in the case of goods and part(s), and in
the case of consumables, within the ninety (90) day period of warranty. This warranty shall be in
effect for replacement or repaired goods, part(s) and the remaining portion of the ninety (90) day
warranty in the case of consumables. A defect in goods, part(s) and consumables of the
commercial unit shall not operate to condemn such commercial unit when such goods, part(s)
and consumables are capable of being renewed, repaired or replaced.
The Seller shall not be liable to the Buyer, or to any other person, for the loss or damage directly
or indirectly, arising from the use of the equipment or goods, from breach of any warranty, or from
any other cause. All other warranties, expressed or implied are hereby excluded.
IN CONSIDERATION OF THE HEREIN STATED PURCHASE PRICE OF THE GOODS,
SELLER GRANTS ONLY THE ABOVE STATED EXPRESS WARRANTY. NO OTHER
WARRANTIES ARE GRANTED INCLUDING, BUT NOT LIMITED TO, EXPRESS AND IMPLIED
WARRANTIES OR MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
Limitations of Remedy. SELLER SHALL NOT BE LIABLE FOR DAMAGES CAUSED BY
DELAY IN PERFORMANCE. THE SOLE AND EXCLUSIVE REMEDY FOR BREACH OF
WARRANTY SHALL BE LIMITED TO REPAIR OR REPLACEMENT UNDER THE STANDARD
WARRANTY CLAUSE. IN NO CASE, REGARDLESS OF THE FORM OF THE CAUSE OF
ACTION, SHALL SELLER'S LIABILITY EXCEED THE PRICE TO BUYER OF THE SPECIFIC
GOODS MANUFACTURED BY SELLER GIVING RISE TO THE CAUSE OF ACTION. BUYER
AGREES THAT IN NO EVENT SHALL SELLER'S LIABILITY EXTEND TO INCLUDE
INCIDENTAL OR CONSEQUENTIAL DAMAGES. CONSEQUENTIAL DAMAGES SHALL
INCLUDE, BUT ARE NOT LIMITED TO, LOSS OF ANTICIPATED PROFITS, LOSS OF USE,
LOSS OF REVENUE, COST OF CAPITAL AND DAMAGE OR LOSS OF OTHER PROPERTY
OR EQUIPMENT. IN NO EVENT SHALL SELLER BE OBLIGATED TO INDEMNIFY BUYER IN
ANY MANNER NOR SHALL SELLER BE LIABLE FOR PROPERTY DAMAGE AND/OR THIRD
PARTY CLAIMS COVERED BY UMBRELLA INSURANCE AND/OR INDEMNITY COVERAGE
PROVIDED TO BUYER, ITS ASSIGNS, AND EACH SUCCESSOR INTEREST TO THE GOODS
PROVIDED HEREUNDER.
Force Majeure. Seller shall not be liable for failure to perform due to labor strikes or acts beyond
Seller's direct control.
Instruction Manual
748183-K
April 2002
Model 755
Emerson Process Management
Rosemount Analytical Inc.
Process Analytic Division
1201 N. Main St.
Orrville, OH 44667-0901
T (330) 682-9010
F (330) 684-4434
E gas.csc@emersonprocess.com
Fisher-Rosemount GmbH & Co.
Industriestrasse 1
63594 Hasselroth
Germany
T 49-6055-884 0
F 49-6055-884209
ASIA - PACIFIC
Fisher-Rosemount
Singapore Private Ltd.
1 Pandan Crescent
Singapore 128461
Republic of Singapore
T 65-777-8211
F 65-777-0947
EUROPE, MIDDLE EAST, AFRICA
Fisher-Rosemount Ltd.
Heath Place
Bognor Regis
West Sussex PO22 9SH
England
T 44-1243-863121
F 44-1243-845354
http://www.processanalytic.com
© Rosemount Analytical Inc. 2001
LATIN AMERICA
Fisher - Rosemount
Av. das Americas
3333 sala 1004
Rio de Janeiro, RJ
Brazil 22631-003
T 55-21-2431-1882