7-7 Photocell Adjustment Voltmeter Lead Location........................................7-10
ONTENTS
C
TABLES
1-1 Front Panel Controls.................................................................................1-3
1-2 Range Options..........................................................................................1-3
2-1 Calibration Range for Various Operating Ranges.....................................2-11
3-1 Control Board - Adjustment Functions......................................................3-3
3-2 Calibration Range for Various Operating Ranges.....................................3-4
3-3 Oxygen Equivalents of Common Gases...................................................3-7
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DRAWINGS (LOCATED IN REAR OF MANUAL)
617186Schematic Diagram, Case Board
620434Schematic Diagram, Isolated Current Output Board
624549Pictorial Wiring Diagram, Model 755
632349Installation Drawing, Model 755 - General Purpose
638277Schematic Diagram, Alarm
643127Installation Drawing, Model 755 Explosion-Proof
652188Schematic Diagram, Control Board
vi
April 2000
748183-JRosemount Analytical
P
REFACE
I
NTENDED 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.
S
AFETY SUMMARY
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 Model 755
Oxygen Analyzer should be thoroughly familiar with and strictly follow the instructions
in this manual. Save these instructions.
DANGER is used to indicate the presence of a hazard which will cause severe
personal injury, death, or substantial property damage if the warning is ignored
WARNING is used to indicate the presence of a hazard which can cause severe
personal injury, death, or substantial property damage if the warning is ignored.
CAUTION is used to indicate the presence of a hazard which will or can cause minor
personal injury or property damage if the warning is ignored.
NOTE is used to indicate installation, operation, or maintenance information which is
important but not hazard-related.
WARNING: 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.
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WARNING: 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).
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 startup, 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.
Internal leakage of sample resulting from failure to observe these precautions
could result in an explosion causing death, personal injury, or property damage.
CAUTION: PARTS INTEGRITY
Tampering or unauthorized substitution of components may adversely affect
safety of this product. Use only factory documented components for repair.
WARNING: HIGH PRESSURE GAS CYLINDERS
This analyzer requires periodic calibration with known zero and standard gases.
See General Precautions for Handling and Storing High Pressure Cylinders, in
the rear of this manual.
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April 2000
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REFACE
P
SPECIFICATIONS - GENERAL
C
ATALOG NUMBER
191102 General Purpose for operation in non-hazardous locations
632440 Explosion-Proo f for opera ti on i n haz ar dous loc ati ons
S
TANDARD RANGE OPTIONS
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.
R
EPRODUCIBILITY
±0.01% Oxygen or ±1% of fullscale, whichever is greater
A
MBIENT TEMPERATURE LIMITS
Maximum: 49°C (120°F)
Minimum: -7°C (20°F)
Z
ERO AND SPAN DRIFT
±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.
(%
OXYGEN FULLSCALE
3
1
2
)
1
Performance specifications based on recorder output.
2
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.
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SPECIFICATIONS - SAMPLE
D
RYNESS
Sample dewpoint below 43°C (110°F), sample free of entrained liquids.
Class I, Groups B, C, and D, Division 1 hazardous locations (ANSI/NFPA 70)
R
EFER TO INSTALLATION DRAWING
643127
IN THE REAR OF THIS MANUAL
IN THE REAR OF THIS MANUAL
.
.
5
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.
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CUST OMER SERVICE, TECHNICAL ASSIST ANCE AND FIELD SERVIC E
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
R
ETURNING PARTS TO THE FACTORY
Before returning parts, contact the Customer Service Center and request a Returned
Materials Authorization (RMA) number. Please have the following information when
you call: Model Number, Serial Number, and Purchase Order Number or Sales Order
Number.
Prior authorization by the factory must be obtained before returned materials will be
accepted. Unauthorized returns will be returned to the sender, freight collect.
When returnin g any pro duct o r compon ent t hat has be en expo sed to a toxic, corrosi ve
or other hazardous material or used in such a hazardous environment, the user must
attach an appropriate Material Safety Data Sheet (M.S.D.S.) or a written certification
that the material has been decontaminated, disinfected and/or detoxified.
Return to:
Rosemount Analytical Inc.
4125 East La Palma Avenue
Anaheim, California 92807-1802
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 Depart men t at:
Rosemount Analytical Inc.
Phone: 1-714-986-7600
FAX: 1-714-577-8006
D
OCUMENTATION
The following Model 755 Oxygen Analyzer instruction materials are available.
Contact Customer Service or the local representative to order.
748183 Instruction Manual (this document)
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COMPLIANCES
REFACE
P
ODEL
M
755 O
XYGEN ANALYZER
ENERAL PURPOSE ENCLOSURE
- G
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 nonhazardous areas and operated and maintained in the recommended manner.
®
ODEL
M
755 O
XYGEN ANALYZER
XPLOSION-PROOF ENCLOSURE
- E
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
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NOTES
XYGEN ANALYZER
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I
NTRODUCTION
1
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 master boards designated the
Control Board and the Case Board, see Figure 1-2. 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 Figures 1-1.
1.1 RANGE OPTIONS
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: zero-based (Section 1.1.1) and zerosuppressed (Section 1.1.2). In addition, special range options incorporating
combinations of zero-based and zero-suppressed ranges are available on factory
special order, refer to Section 1.1.3. All range options utilize a front-panel meter with
left-hand zero. See Figure 1-1 and Table 1-1.
1.1.1 S
TANDARD 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.
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A. G
RANGE Switch
ENERAL PURPOSE ENCLOSURE
ZERO Adjust
Meter
Rosemount Analytical
Model 755
Oxygen Analyzer
SPAN Adjust
F
IGURE
B. E
1-1. M
XPLOSION-PROOF ENCLOSURE
ZERO Control
RANGE Switch
Controls have slotted shafts for screwdriver adjustment from outside the enclosure.
ODEL
755 - F
RONT VIEW
Rosemount Analytical
Model 755
Oxygen Anal yzer
Meter
SPAN Adjust
1-2
Rosemount AnalyticalApril 2000
748183-J
CONTROLFUNCTION
M
ETER
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.
NTRODUCTION
I
T
ABLE
%RANGE
SWITCH
Select percentage oxygen range for meter and recorder
ZERO A
DJUST
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.
SPAN A
DJUST
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.
1-1. F
RANGE
OPTION
RONT PANEL CONTROLS
SUB-RANGE ASUB-RANGE BSUB-RANGE C
OVERALL
RANGE
010 to 1%0 to 2.5%0 to 5%0 to 10%
020 to 5%0 to 10%0 to 25%0 to 50%
030 to 10%0 to 25%0 to 50%0 to 100%
040 to 1%0 to 2.5%0 to 5%0 to 25%
0690 to 100%80 to 100%60 to 100%50 to 100%
T
ABLE
1.1.2 S
1-2. R
TANDARD ZERO-SUPPRESSED RANGE OPTIONS
ANGE OPTIONS
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.
1.1.3 S
PECIAL RANGE OPTIONS
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.
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Control Board
Door
Current Output
Board (Option)
R
R
R
1
U
I
Alarm Relay
Assembly
(Alarm Option)
Fuse
AC Power
AC Power
TB1
Transformer, Power
T1
(Behind TB1)
NO. 1
RESET
NO. 2
RESET
COM
COM
NO
NC
NO
NC
N
GND
E
U
T
Case Board
TB1
H
O
Recorder Output
TB2
Case Heater
Assembly
HOT
MA
-
+
COM
TB2
Fuse
Case
Heater
Detector/Magnet
Assembly Shock
Mount
Detector/Magnet
Assembly
General Purpose enclosure shown. Components mounted in same locations in Explosion-Proof enclosure.
F
IGURE
1-4
1-2. M
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OCATION OF MAJOR COMPONENTS
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748183-J
1.2 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 f ield. The maximum load
resistance for this board is 850 ohms.
1.3 ALARM OPTION
If equipped with the alarm option:
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 full-scale. The
dead-band is adjustable from l% to 20% of full-scale.
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, customersupplied alarm and/or control devices.
1.4 CASE MOUNTING OPTIONS
General Purpose Enclosure, see drawing 632349.
Explosion Proof Enclosure, see drawing 643127.
NTRODUCTION
I
1.5 ELECTRICAL OPTIONS
The analyzer is supplied, as ordered, for operation on either 120 VAC, 50/60 Hz, or
240 VAC, 50/60 Hz.
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I
NSTALLATION
2
2.1 UNPACKING
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
2.2.1 L
2.3 VOLTAGE REQUIREMENTS
OCATION AND MOUNTING
Shock and mechanical motion can reduce instrument accuracy; therefore, mount the
instrument in an area that is as vibration free as possible
ENERAL PURPOSE ENCLOSURE
G
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.
XPLOSION-PROOF ENCLOSURE
E
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.
WARNING: ELECTRICAL SHOCK HAZARD
748183-J
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.
April 2000
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Note
Refer to Installation Drawing 632349 or 643127 at the rear of this manual for
recommended cable conduit openings.
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
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
2.4.1 L
2.4.2 R
INE POWER CONNECTIONS
Electrical power is supplied to the analyzer via a customer-supplied three-conductor
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.
ECORDER 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
2-2
Route recorder cable through a separate conduit, not with power cable or alarm
output cable.
April 2000
748183-JRosemount Analytical
NSTALLATION
I
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.
Optional Alarm Kit
Explosion-Proof
Enclosure
General Purpose
Enclosure
NO
Power Connections
(see below)
NC
RESET
NO. 2
COM
NC
RESET
TB1
N
H
E
O
U
T
T
Jumpers
TB1
N
GNDGND
120 VAC CONFIGU RATION240 VAC CONFIGU RATION
H
E
O
U
T
T
COM
-
Jumper
TB1
N
H
E
O
U
T
T
+
mV Recorder
-
+
mA Recorder
-
F
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LECTRICAL INTERCONNECTION
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OTENTIOMETRIC OUTPUT
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1. Insert RECORDER OUTPUT Selector Plug (Figure 2-2) in position appropriate
to the desired output: 10 mV, 100 mV, 1 V, or 5 V.
2. On TB2, Figure 2-1, 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.
R63
RECORDER OUTPUT
Selector Plug
R64
R73
R78
5V
1V
100mV
10mV
R68
R3
I G O
I G O
R4
R5
R6
U6
U3
U2
C4
C2
U4
C3 CR1 C1
R2 R1
U1
J1
R8
R9
CR2
1
2
3
4
C5
I
G
O
R67
R1
R2
Current Output Board
F
IGURE
2-4
2-2. C
ONTROL BOARD
April 2000
- A
DJUSTMENT LOCATIONS
748183-JRosemount Analytical
NSTALLATION
I
F
IGURE
755
Analyzer
Voltage Divider
(Customer Supplied)
Position of R ecorder Output
Selector Plug
10 mV 1K Ohm
100 mV 10K Ohm
1 V 100K Ohm
5 V 2K Ohm
2-3. P
SOLATED CURRENT OUTPUT (OPTION
I
OTENTIOMETRIC RECORDER WITH NON-STANDARD SPAN
Minimum Permissible
Resistance for R1 + R2
)
Potentiometric
Recorder
Input
Terminals
(Make sure polarity
is correct)
The isolated current output board (Figure 2-2) 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).
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, connect leads of shielded recorder cable to MA+ and " - "
terminals.
5. Connect free end of output cable to input terminals of recorder or other currentactuated device, making sure that polarity is correct. If two or more currentactuated devices are to be used, they must be connected in series, see Figure
2-4. Do not exceed the maximum load resistance (see Section 1.2).
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 ze ro and span.
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.
b. With analyzer meter at fullscale, adjust R2 for desired fullscale current
(typically 20 mA).
7. Cu rrent and voltage outputs may be utilized simultaneously, if desired.
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+
Recorder
-
+
Controller
-
+
Remote
Indicator
F
IGURE
2.4.3 O
+
mA
-
755
Analyzer
2-4. M
UTPUT CONNECTIONS
ODEL
O
UTPUT DEVICES
755 C
ONNECTED TO DRIVE CURRENT OUTPUT-ACTIVATED
NITIAL SETUP FOR DUAL ALARM OPTION
, I
If so ordered the analyzer is factory-equipped with alarm output. Alternatively the
alarm feature is obtainable by subsequent installation of the Alarm Kit.
LARM OUTPUT CONNECTIONS
A
The alarm output provides two sets of relay contacts for actuation of alarm or processcontrol functions. Leads from the customer-supplied external alarm system connect to
terminals on the Alarm Assembly, see Figure 2-1.
Note the following recommendations:
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.
LARM RELAY CHARACTERISTICS
A
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:
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:
LARM
A
1 R
ELAY
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.
LARM
A
2 R
ELAY
Relay The Alarm 2 relay coil is de-energized when the meter needle moves upscale
through the value that corresponds to the setpoint plus dead-band. This relay coil is
energized when needle moves downscale through the value that corresponds to
setpoint minus dead-band, see Figure 2-5B.
A. Typical ALARM 1 Setting
DEADBAND SET FOR
20% OF FULLSCALE
INPUT SIGNAL
Percent of Fullscale
40
30
20
When input signal move s 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.
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.
B. Typical ALARM 2 Setting
DEADBAND SET FOR
10% OF FULLSCALE
F
IGURE
2-5. T
LARM RESET
A
YPICAL ALARM SETTINGS
INPUT SIGNAL
Percent of Fullscale
50
45
When input signal move s 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.
ALARM 2 Setpoint
When input signal move s 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.
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 deenergized; when the meter reading returns within the acceptable range, the relay is
turned on.
If desired the ALARM 1 or ALARM 2 alarm function may be converted to manual reset.
The conversion consists of substituting an external push-button or other momentarycontact switch for the jumper that normally connects the RESET terminals on the
Alarm Relay Assembly, see Figure 2-1. If the corresponding relay is now deenergized, i.e., in alarm condition, the relay remains de-energized until the operator
momentarily closes the switch.
By appropriate connection to the double-throw 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 de-energized relay. It is
important that f or fail-safe 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.
LARM SETPOINT ADJUSTMENT
A
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 acc ordi ng 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) are turned fully counter-clockwise to set the dead-band at
minimum. Normally these potentiometers are factory-set for minimum dead-
2-8
April 2000
748183-JRosemount Analytical
NSTALLATION
I
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.
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).
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).
F
IGURE
J5
+15V
-15V
ALARM 1
ALARM 2
2. RELAYS SHOWN IN ENERGIZED POSITION.
1. CR1 AND CR2 ARE ANY 600 V, 1 AMP DIODE.
NOTES:
2-7. A
LARM RELAY OPTION SCHEMATIC DIAGRAM
CR1
1
14
2
4
CR2
14
6
K1
K2
13
13
1
5
128
1
5
128
9
NO
COM
NC
ALARM 1
RESET
NO
9
COM
NC
ALARM 2
RESET
748183-J
6. Calibration of ALARM 2, LOW.
a. Rotate setpoint adjustment, R68, fully counter-clockwise.
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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 lim it. Rotate R67
counter-clockwise, the minimum amount required to energize ALARM 2,
relay K2. Verif y that the alarm has been energized with the ohmmeter on the
relay contacts (Figure 2-7).
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 de-energize the relay. Rotating R64 above the setpoint
will energize the relay.
8. Setpoint adjustment of ALARM 2, LOW.
a. With span gas flowing, adjust the SPAN control to read desired alarm
setpoint on display or recorder.
b. Rotate setpoint adjustment, R68, clockwise to energize relay.
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.
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,
in the rear of this manual.
Analyzer calibration consists of establishing a downscale calibration point and an
upscale calibration point.
2-10
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.
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
April 2000
748183-JRosemount Analytical
NSTALLATION
I
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 and are explained in Sections 2.5.1 and 2.5.2.
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
RANGE
2
% O
0 to 1Nitrogen0.9% O2, balance N
0 to 2.5Nitrogen2.3% O2, balance N
0 to 5Nitrogen4.5% O2, balance N
0 to 10Nitrogen9% O2, balance N
RECOMMENDED DOWNSCALE
STANDARD GAS
RECOMMENDED UPSCALE
STANDARD GAS
2
2
2
2
0 to 25NitrogenAir (20.93% O2)
0 to 50Nitrogen0.45% O2, balance N
0 to 100Nitrogen100% O
2
2
B. ZERO SUPPRESSED RANGES
RANGE
2
% O
90 to 10091% 0.5% O2, balance N
80 to 10082% 1% O2, balance N
60 to 10062% 1% O2, balance N
50 to 10052% 1% O2, balance N
RECOMMENDED DOWNSCALE
STANDARD GAS
2
2
2
2
RECOMMENDED UPSCALE
STANDARD GAS
High-purity O
100% O
100% O
100% O
2
2
2
2
Note
Each standard gas used should have a composition within the specified limits, and should
have a certified analysis provided by the supplier.
T
ABLE
2.5.1 D
2-1. C
OWNSCALE STANDARD GAS
ALIBRATION RANGE FOR VARIOUS OPERATING RANGES
In the preferred calibration method described in Section 3.2.1, 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 3.2.2, uses an upscale
standard gas only and does not require a downscale standard gas.)
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2.5.2 U
PSCALE ST ANDARD GAS
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).
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.
• 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.
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.
F
IGURE
2-12
Sample In
Downscale
Standard
Gas
Upscale
Standard
Gas
2-8. C
Needle
Valves
Two Micron
Flowmeter
Filter
Model 755
Oxygen Analyzer
To Vent
(via back-pressure
regulator if required)
ONNECTION OF TYPICAL GAS SELECTOR PANEL TO MODEL
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2.6.1 S
AMPLE TEMPERATURE REQUIREMENTS
Sample temperature at the analyzer inlet should be in the range of 50°F to 150°F
(10°C to 66°C).
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.
2.6.2 S
AMPLE PRESSURE REQUIREMENTS
: G
ENERAL
Operating pressure limits are as follows: Maximum, 10 psig (69 kPa gauge pressure);
minimum, 660 mm Hg absolute (88.1 kPa absolute pressure).
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 required 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 2.6.3, Normal Operation at Positive Gauge
Pressures; or Section 2.6.4, Operation at Negative Gauge Pressure.
2.6.3 N
ORMAL OPERATION AT POSITIVE GAUGE PRESSURES
RESSURE AT SAMPLE INLET
P
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.
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AMPLE 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.
AMPLE EXHAUST ARRANGEMENTS FOR ZERO-BASED RANGES
S
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.
2.6.4 O
PERATION AT NEGATIVE GAUGE PRESSURES
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 d uring subsequent ope ration. In addition, any le akage
in the sample-handing system will result in decreased readout accuracy as compared
with operation at atmospheric pressure.
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.
2.6.5 S
AMPLE 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.
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NSTALLATION
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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 operatin g pressure remains constant.
YPASS FLOW
B
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 analyzer via a 100-foot (30.5 m) length of 1/4-inch (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.
2.6.6 C
ORROSIVE 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.
2.7 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.
748183-J
WARNING: 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 startup, during routine maintenance and any time the integrity of the sample
containment system is broken, to ensure the system is in leak-proof condition.
Internal leakage of sample resulting from failure to observe these precautions
could result in an explosion causing death, personal injury, or property damage.
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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 leak-free, use the flow stoppage test.
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 496-1986, Chapter Two. The kit, along with user-supplied 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.
WARNING: 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 startup, during routine maintenance and any time the integrity of the sample
containment system is broken, to ensure the system is in leak-proof condition.
Internal leakage of sample resulting from failure to observe these precautions
could result in an explosion causing death, personal injury, or property damage.
This kit is designed only for protection against the invasion of flammable gases into the
enclosure from the outside atmosphere. It does not cover protection from possible
abnormal release (leakage) of flammable gases intentionally introduced into the
enclosure.
Note: 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.
2-16
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748183-JRosemount Analytical
NSTALLATION
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Installation options are shown in Figure 2-9. 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.
A. Option with Flow Indicator B. Option with Pressure Indicator or Alarm
Affix W a r ni ng
Label
Analyzer
Door
190697 Purge
Inlet Fitting
Flow
Indicator
645835 Purge
Outlet Fitting
Purge Supply
Components in dashed line are supplied by customer.
F
IGURE
2-9. I
NSTALLATION OF PURGE KIT
Affix W a r ni ng
Label
Analyzer
Door
190697 Purge
Inlet Fitting
Purge
Supply
645835 Purge
Outlet Fitting
Pressure
Indicator or
Alarm
748183-J
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NOTES
XYGEN ANALYZER
2-18
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748183-JRosemount Analytical
S
TARTUP
3
Preparatory to start-up and calibration, a familiarization with Figures 1-1, 1-2 and 3-1, and
Tables 3-1 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.
3.1 START-UP PROCEDURE
WARNING: 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 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. Otherwise refer to Section 7, Service and Maintenance.
3.2 CALIBRATION
Calibration consists of establishing a downscale calibration point and an upscale
calibration point, see T able 3-3. Downscale calibration may be performed on the range
that will be used during sample analysis. For maximum precision however, it should be
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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 sam ple
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 u s ed 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 3.2.1. An alternative method using an upscale standard gas
only is described in Section 3.2.2.
15
R63
Meter
16
R64
17
R73
SPAN potentiometer
R33
7
R45
%RANGE switch
R92
14
R78
13
R68
12
10
11
R67
R1
R2
2
R38
R8
R9
CR2
1
1
2
3
4
C5
I
G
O
U5
I G O
I G O
R3
R4
R5
R6
U6
U3
U2
C4
C2
U4
C3 CR1 C1
R2 R1
U1
J1
Current Output Board
8
ZERO potentiometer
R20
5
9
F
IGURE
3-2
3-1. C
ONTROL BOARD
April 2000
3
R89
- A
DJUSTMENT LOCATIONS
4
R90
748183-JRosemount Analytical
ADJUSTMENTFUNCTION
1. RECORDER OUTPUT (S
ELECTOR PLUG
)
Provides selectable output of 10 mV 100 mV, 1 V, or 5 V for a voltage recorder.
ETER ADJUSTMENT
2. M
(R38)
Used to set meter to agree with recorder.
3. A
MPLIFIER
AR3 Z
ERO ADJUSTMENT
(R89)
Used for initial factory zeroing of am plif ier AR3. (With slider of front-panel SPAN
potentiometer R4 connected to ground, R89 is adjusted for zero.)
MPLIFIER AR4 ZERO ADJUSTMENT (R90)
4. A
Used for initial factory zeroing of amplifier AR4. (With R10 connected to ground,
R90 is adjusted for zero.)
ESPONSE TIME ADJUSTMENT
5. R
(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.
ERO SUPPRESSION ADJUSTMENT
8. Z
(R45)
Used to set appropriate zero offset for suppressed-zero ranges.
ETECTOR COARSE ZERO ADJUSTMENT
9. D
(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 aft er replacement of detector.
URRENT OUTPUT ZERO ADJUSTMENT
10. C
(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.
URRENT OUTPUT SPAN ADJUSTMENT
11. C
(R2)
Used to set fullscale current output at 20 m A 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 D
EADBAND 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 C
16. ALARM 1 S
17. ALARM 1 D
ALIBRATION ADJUSTMENT
ETPOINT ADJUSTMENT
EADBAND ADJUSTMENT
(R63)
(R64)
(R73)
Functions identical to the corresponding adj ustment for ALARM 2 circuit.
TARTUP
S
T
ABLE
748183-J
3-1. C
ONTROL BOARD
- A
DJUSTMENT FUNCTIONS
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A. ZERO BASED RANGES
RANGE
2
% O
0 to 1Nitrogen0.9% O2, balance N
0 to 2.5Nitrogen2.3% O2, balance N
0 to 5Nitrogen4.5% O2, balance N
0 to 10Nitrogen9% O2, balance N
RECOMMENDED DOWNSCALE
STANDARD GAS
RECOMMENDED UPSCALE
STANDARD GAS
2
2
2
2
0 to 25NitrogenAir (20.93% O2)
0 to 50Nitrogen0.45% O2, balance N
0 to 100Nitrogen100% O
2
2
B. ZERO SUPPRESSED RANGES
RANGE
2
% O
90 to 10091% 0.5% O2, balance N
80 to 10082% 1% O2, balance N
60 to 10062% 1% O2, balance N
50 to 10052% 1% O2, balance N
RECOMMENDED DOWNSCALE
STANDARD GAS
2
2
2
2
RECOMMENDED UPSCALE
STANDARD GAS
High-purity O
100% O
100% O
100% O
2
2
2
2
Note
Each standard gas used should have a composition within the specified
limits, and should have a certified analysis provided by the supplier.
T
ABLE
3.2.1 C
3-2. C
ALIBRATION WITH DOWNSCALE AND UPSCALE STANDARD GASES
ALIBRATION RANGE FOR VARIOUS OPERATING RANGES
Set downscale calibration point as follows:
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 3.3.2.) If proper reading is unobtainable by an
adjustment of the ZERO Control, refer to Section 7, Service and Maintenance.
d. If previous reading was obtained on a recorder, set Meter Adjustment R38,
see Figure 3-1, so that meter reading agrees with recorder setting.
2. Set upscale calibration point as follows:
3-4
a. Set % RANGE Switch in po sition appropriate to the selected upscale standard
April 2000
748183-JRosemount Analytical
TARTUP
S
gas.
b. Pass upscale standard gas through analyzer at same flow rate as was used
for downscale standard ga s. Allow gas to purge analyzer for minimum of three
minutes.
c. 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 3.2.2.) If proper reading is unobtainable by adjustment of
the SPAN Control, refer to Section 7, Service and Maintenance.
3.2.2 A
LTERNATIVE CALIBRATION PROCEDURE USING UPSCALE STANDARD GAS
NLY
O
The following calibration procedure, using an upscale standard gas only, is an
alternative to the calibration procedure described in Section 3.2.1, 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 mid-range.
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 most-sensitive range, obtain reading equal to the
oxygen content of the upscale standard gas by adjustment of the appropriate
control:
a. If the most-sensitive range is zero-suppressed, obtain the correct reading by
adjustment of internal Zero Suppression Potentiometer R45, see Figure 3-1.
748183-J
b. If the most-sensitive range is zero-based, or if a stable reading is unobtainable
by adjustment of R45, obtain correct reading by adjustment of ZERO control.
5. Set % RANGE Switch for least-sensitive 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 most-sensitive 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.
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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 90% to
100% oxygen. Verify that the recorder indicates the correct value.
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 3.3.2.
3-6
April 2000
748183-JRosemount Analytical
TARTUP
S
3.3.1 O
XYGEN EQUIVALENT VALUES OF
ASES
G
For computation of background
corrections, the analyzer response to
each component of the sample must be
known. Table 3-3 lists the percentage
oxygen equivalent values for many
common gases. The percentage oxygen
equivalent (POE) of a gas in the
instrument 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
3-4, if analyzer response to oxygen is
+100%, the response to xenon would be
-1.34%.
XYGEN EQUIVALENTS OF GAS
O
IXTURES
M
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% N
2.
From Table 3-4, 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% O
-0.512
Neon, Ne-0.205
Nitric Oxide, NO+44.2
Nitrogen, N
Nitrogen Dioxide, NO
n-Octane, C8H
Oxygen, O
n-Pentane, C5H
iso-Pentane, C5H
neo-Pentane, C5H
Propane, C3H
Propylene, C3H
2
2
18
2
12
12
12
8
6
-0.358
+28.7
-2.840
+100.0
-1.810
-1.853
-1.853
-1.135
-0.903
Water, H2O-0.381
Xenon, Xe-1.340
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T
ABLE
3-3. O
C
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XYGEN EQUIVALENT OF
OMMON GASES
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XYGEN ANALYZER
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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 3-4, 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% O
2
3.3.2 C
OMPUTING 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 the magnetic susceptibility of the background gas.
The quantities are defined as follows (see Table 3-3):
BGGst=Oxygen equivalent of background gas in standard gas
BGGs=Oxygen equivalent of background gas in sample
PO=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%.
3-8
Downscale standard gas is 100% N
Upscale standard gas is air: 21% O2, 79% N2.
Background gas in downscale and upscale standard gases is N2, oxygen
2.
equivalent = -0.358%.
With N2 downscale standard ga s flowing, ZERO control is adjusted so meter reads:
With air flowing SPAN control is adjusted so meter reads:
21 (100 - 0.265) - 100 (-0.265)
= 21.209 % O
2
100
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.)
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O
PERATION
4
4.1 ROUTINE OPERATION
After the calibration procedure of Section 3.2, 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) may be
desirable to obtain the optimum compromise between response speed and noise.
4.2 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 result 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:
748183-J
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% O
2
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EXAMPLE (S.I. Units)
Pst = 101 kPa
Pan = 98.2 kPa
Indicated % O2 = 40%
True % O2 = 101/98.2 x 40% = 41.1% O
2
4.3 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.
4-2
Rosemount AnalyticalApril 2000
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I
NSTRUMENT THEORY
5
5.1 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 f ield, analogous to the magnetization of a piece of
soft iron. Diamagnetic gases are analogous to non-magnetic substances.
With the Model 755, the volume magn etic susceptibility of the flowing gas sample is
sensed in the detector/magnet assembly. As shown in the functional diagram of Figure
5-1, 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 ies proportional to the volume magnetic
susceptibility of the gas surrounding the test body.
Measurement is accomplished by a null-balance 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.
748183-J
The restoring current is automatically maintained at the correct level by an electrooptical 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 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 5.3 and in greater detail in
Section Six.
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Displacement
Torque
Balancing
Weight
Electromagnetic
Axis
Restoring
Platinum/Nickel Alloy
Suspension Ribbon
TEST BODY DETAIL
Displacement
Torque
Restoring
Torque
Current
Mirror
Restoring
Torque
Titanium Wire Conductor
Restoring
Current
Electromagnetic
Axis
Balancing Weight
Nitrogen-Filled Hollow Glass
Test Body
F
IGURE
Magnet
Shaded Pole Pieces (4)
Dual Photocell
BT1, BT2
5-1. F
UNCTIONAL DIAGRAM OF MODEL
M
EASUREMENT SYSTEM
Test Body
Source Lamp
DS1
Restoring
Current
DETECTOR/MAGNET
ASSEMBLY
Zero
755 P
ARAMAGNETIC OXYGEN
CONTROL
ASSEMBLY
Span
% Oxygen
Readout
5-2
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NSTRUMENT THEORY
I
5.1.1 M
AGNETIC DISPLACEMENT FORCE
Because the magn etic forces on the spherical ends of the test body are the basis of
the oxygen measurem ent, 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 5-2, is subjected to a
force proportional to the difference between the ma gnetic 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 samp le, and therefore of its oxygen content.
F
IGURE
5-2. S
Shaded
Pole
Piece
Sphere
(Magnetic Susceptibility = k
F
k
Sample Gas
(Magnetic Susceptibility = k
As percentage of oxygen in sample gas increases,
displacement force (F
Note:
) increases.
k
)
o
)
PHERICAL BODY IN NON-UNIFORM MAGNETIC FIELD
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5.1.2 P
HYSICAL CONFIGURATION OF DETECTOR/MAGNET ASSEMBLY
As shown in the exploded view of Figure 5-3A, the detector/magnet assembly consists
of three major subasse mblies: 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.
Sample Pre-Heating Coil
Sample Inlet Tube
Sample Outlet Tube
Magnet Assembly
Integral Heater (HR2
➋
Dual Photocell
➊
Optical Bench Assembly
➊
Detector Assembly
➋
Detector Assembly
Optical Bench Assembly
Mounting Screws (2)
A. Exploded View of Detector/Magnet Assembly
Integral Temperature
➋
Sensor (RT1)
Photocell
➋
Diffusion Screen
➋
Mirror
Source Lamp
➊
Integral 5-Micron
Test Body
Lock Screws (2)
Lamp Retaining
Set Screw
Lamp Viewing Hole
Connector J12
Connector J12
Source Lamp
Assembly
Dual Photocell
B. Sectional Top View of Optical Bench
and Detector Assemblies
F
IGURE
5-4
5-3. D
Rosemount AnalyticalApril 2000
ETECTOR/MAGNET ASSEMBLY
C. Exploded View of Optical Bench
Assembly
748183-J
NSTRUMENT THEORY
I
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 5-3B, the incoming preheated sample passes
through an integral 5-micron diffusion screen. It protects the test body 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 5.3.3. This section controls application of electrical power to both
HR1 and HR2.
On the optical bench assembly, see Figure 5-3C, the source lamp and the photocell
plate are externally accessible, permitting convenient replacement.
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 in strument at the same pressure that will be
used during subsequent operati o n, and to mai n tai n this press ur e duri ng oper ati on .
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 temperaturecontrolled housing, see Section 2.6.3.
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CAUTION: PRESSURE LIMITS
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 2.6.4.
5.2.2 T
EMPERATURE EFFECTS
Magnetic susceptibilities and partial pressure s of gases vary with temperature. In the
Model 755, temperature-induced readout error is avoided by control of temperatures in
the following areas:
1. Interior of the analyzer is maintained at 140°F (60°C) by an electrically controlled
heater and associated fan.
2. 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 5-3A.
3. The detector is maintained at a controlled temperature of 150°F (66°C).
5.2.3 I
NTERFERENTS
Instrument response to most non-oxygen sample components is comparatively slight,
but is not in all cases negligible. Durin g 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.
5.2.4 V
IBRATION EFFECTS
5-6
NSTRUMENT DESIGN
I
To minimize vibration effects, the detector/magnet assembly is contained in a shockmounted compartment (Figure 1-2).
NSTALLATION
I
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.
Rosemount AnalyticalApril 2000
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NSTRUMENT THEORY
I
LECTRONIC RESPONSE TIME
E
If readout is noisy despite observance of the precautions mentioned, obtain slower
electronic response by counter-clockwise adjustment of R20, Figure 3-1.
5.3 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.
5.3.1 D
ETECTOR/MAGNET ASSEMBLY
A cross-sectional view of the optical bench and detector assemblies is shown in Figure
5-3B. Source lamp DS1 powered by a supply section within the case circuit board
assembly, see Section 5.3.3, 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 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 5.1.
LEMENTS OF DETECTOR TEMPERATURE CONTROL CIRCUIT
E
Detector temperature is sensed by thermistor RT1, an integral part of the detector
assembly, see Figure 5-3B. 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.
5.3.2 C
ONTROL BOARD AND ASSOCIATED CIRCUITRY
The control board contains signal-conditioning and control circuitry. The board is
mounted on the inside of the analyzer door, as shown in Figure 1-2.
748183-J
The control board contains the following:
NPUT AMPLIFIER
I
AR1
This amplifier receives the error signal from the dual photocell of the detector
assembly and, in turn, drives amplifier AR2.
MPLIFIER
A
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. Front-panel 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.
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If the analyzer is to incorporate a zero-suppressed range option, the required 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 closedloop gain for AR2, to permit establishing an upscale calibration point on the meter
scale or recorder chart. W ith upscale standard gas flowing through the analyzer. the
SPAN control is adjusted for the appropriate reading.
MPLIFIER
A
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.
UTPUT STAGE
O
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 plugin current-output boards.
3. Alarm output receptacle J2. This connector accepts the optional dual-alarm
amplifier board.
O
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.
5.3.3 C
The case circuit board contains power-supply and temperature-control circuitry. The
board is mounted within the analyzer case, near the top, as shown in Figure 1-2.
As shown in DW G 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 name-rating plate.
The case board contains the following:
5-8
UTPUT RESISTOR NETWORK
ASE BOARD ASSEMBLY
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NSTRUMENT THEORY
I
OURCE LAMP POWER SUPPLY SECTION
S
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.
±±±±15 V P
T
HE
OWER 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 series-type integrated-circuit, voltage-regulator,
providing regulated outputs of +15V and -15V.
ETECTOR TEMPERATURE CONTROL SECTION
D
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 f rom 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.
ASE TEMPERATURE CONTROL SECTION
C
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 range and zerosuppression resistor modules.
The circuit provides an on-off control of hea ter element HR3 via TRIAC element Q7.
Heater HR3 is a part of the heater/fan assembly.
5.3.4 I
SOLATED 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.
5.3.5 A
LARM OPTION
748183-J
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, doublethrow relays, one each for the ALARM 1 and ALARM 2 contacts. Alarm output
connections are on the terminal board shown in Figure 1-2.
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C
IRCUIT ANALYSIS
6
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.
6.1 POWER SUPPLY
The components of the ±VDC power supply circuit are located in the lower the lefthand 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.
6.2 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 6-1, 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 illustrated as the overall output for the comparator package.
When the noninverting 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 noninverting 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.
±±±±
15 VDC
748183-J
April 2000
Rosemount Analytical
6-1
M
ODEL
XYGEN ANALYZER
755 O
INPUT
R69
2M
R71
21.5K
4.75K
COMP 1
COMP 2
+15V
R72
-1.7V
-15V
159mV
3.3K
R68
0
°
ONONOFF
OFF
-
+
C36
0.18uF
100µ
180
°
+15V
U1-A
1
-15V
R70
20M
CASE BOARD
ON
360
0
°
°
180
°
OFF
OUTPUT
+15V
U1-B
-
2
+
-15V
R73
20M
-1.88 VDC
Source
F
IGURE
6-1. TWO-C
OMPARATOR
OR C
IRCUIT
Comparator 2 is biased at 0 volts on the inverting terminal. Comparator 1 is biased at
about 159 mV on the noninverting 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
noninverting 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 re sults 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°).
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
6-2
April 2000
748183-JRosemount Analytical
IRCUIT ANALYSIS
C
generator, probably -188 ±0.03 V.
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.
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 Figures 6-2 and 6-3.
+15V
F
IGURE
120 V
RMS
6-2. C
INPUT FROM
MULTIVIBRATOR
C39
.01uF
-
+
-
+
+15V
U1-A
R70
20M
U1-B
R73
20M
9.07K
RT1
T1
R72
4.75K
19 VAC
12
TO POWER
SUPPLY
19 VAC
CR9
R67
10K
C38
.18uF
CASE BOARD
-15V
CR10
R69
2 M
R71
21.5K
R68
3.3K
ASE HEATER CONTROL CIRCUIT
R74
590K
C37
1.0uF
+2.3V
-2.3V
R76
37.4K
-15V
OFFOFF
R82
9.09K
RT1
OFF
-15V to 1.88V ±0.3V
R83
63.4K
-15V
R84
169K
TO
COMPARATOR
R82
R78
R74
590K
C37
1.0uF
R85
R83
11.0K
63.4K
R84
169K
-15V
R78
249K
+15V
U1-C
-
3
+
-15V
R75
210K
C40
2200uF
-
+
R76
37.4K
R77
10K
R79
10K
R80
10K
249K
U1-C
210K
-
+
6 Hz
+15V
R75
R86
20M
U1-D
C40
2200uF
Q6
R81
56.2
R77
10K
R79
10K
R80
10K
C38
.18uF
CR11
Q6
R81
56.2
.18uF
R87
10K
T2
T2
C38
F
IGURE
748183-J
6-3. R
AMP GENERATOR
CASE BOARD
April 2000
R87
10K
-15V
Rosemount Analytical
6-3
M
ODEL
XYGEN ANALYZER
755 O
On initial application of power to comparator of Figure 6-2, 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 noninverting term inals 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 noninverting terminals, the transistor
conducts. The output is -15 V. A full 30 V drop appears across R77. The potential on
the noninverting terminal will now be about -2.3 V. Now C37 will discharge through
R78 until its potential exceeds that on the noninverting terminal. At that time.
comparator 3 will switch polarity and start charging C37 again. The result is that the
potential across C37 will vary alm ost lin early with tim e an d form a ramp signa l of ab out
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 6-4 does not allow pulses from the OR circuit
(comparators 1 and 2), to operate Q6 or TRIAC Q7 in the case heater, see Figure 6-5.
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.
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 6-1, 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.
6-4
The input from the OR comparators 1 and 2 form multivibrator 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
April 2000
748183-JRosemount Analytical
IRCUIT ANALYSIS
C
the noninverting 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 T RIAC
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. 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 opera ting Q7
will be proportional to the amount of error sensed by the 6 Hz ramp.
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, 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.
6.3 DETECTOR HEATER CONTROL CIRCUIT
Figure 6-4 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).
748183-J
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,
April 2000
Rosemount Analytical
6-5
M
ODEL
XYGEN ANALYZER
755 O
resistance of the bridge (R55, R56, R59, and RT1) equals 149 K.
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.
As the temperature increases the resistance of RT 1 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
CR6
WO4
120 V
RMS
F1
25 VAC
R60
100
F
IGURE
6-4. D
R55
700K
R56
149K
+15V
-15V
R59
700K
RT1
C31
.01uF
2
3
R88
5M
ETECTOR HEATER CONTROL CIRCUIT
R58
5M
-
AR6
+
R62
1K
6
CR12
6.4 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, see
Figure 6-5
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.
Q3
Q2
R61
2.0
6-6
Amplifier U7 has a f ixed 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-
April 2000
748183-JRosemount Analytical
IRCUIT ANALYSIS
C
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 main current path, and goes through Q5, which acts as a variable
feedback resistance, goes to the positive output potential of U7.
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 operat ion of Q4
and Q5 will adjust the gain of U7 to maintain the light emission from DS1 uniform for a
long period of time.
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 emissio n.
CR7
CR8
2000u
C31
VR3
9.0V
+
+15V
R63
7.5K
R64
14K
R65
4530
+8.5V BUS
α
2
3
2.2V
a
Q4
C34
-
U7
+
.01uF
C35
.01uF
Q5
R66
1.0
120 V
RMS
T1
6.1 VAC
6.1 VAC
CASE BOARD
F
IGURE
6-5. D
ETECTOR LIGHT SOURCE CONTROL CIRCUIT
6.5 DETECTOR WITH FIRST STAGE AMPLIFIER
The detector assembly consists of a test body suspended on a platinum wire and
located in a nonuniform magnetic field, Figure 6-6.
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.
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
DS1
748183-J
April 2000
Rosemount Analytical
6-7
ODEL
M
PHOTOCELL
BOARD
BT2
BT1
DS1
XYGEN ANALYZER
755 O
the feedback loop and the electronics for that loop. The platinum wires form a fulcrum
around which the test body pivots.
The detector operates in the following fashion. If the sample gas contains oxygen, it
collects in the nonuniform 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.
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.
C10
4.02K
-15V
-15V
R15
R92
20K
R10
20K
R3
.68uF
-
U3
+
C10
.68uF
SW1
FRONT
PANEL
%RANGE
FRONT
PANEL
ZERO
R16
56
0 to 7.5V
R14
R20
20K
R13
R12
R26
R11
1070
R1
1K
-
U2
+
+
U1
-
R3
1K
-15V
CONNECTOR
BOARD
R2
1K
R9
110K
R4
1K
CR1
C6
3.3uF
+15V
+
R19
10
+15V
R18
29.9K
CR2
C3
.47uF
R8
1.69K
R7
118K
C41
1000pf
CONTROL BOARD
C42
0.01uF
C2
R6
.47uF
2M
-
U1
+
FRONT PANEL
SPAN
R4
50K
R5
1.78K
R1
12.4K
R91
30.1K
C1
.0022uF
-
U2
+
R44
232K
+15V
CW
+15V
CW
PHASE
LEAD
ADJUST
C11
.1uF
R29
1M
FEEDBACK
LOOP
F
IGURE
6-8
R17
6-6. D
ETECTOR WITH FIRST STAGE AMPLIFIER
This feedback current creates an electro-magnetic 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.
April 2000
748183-JRosemount Analytical
IRCUIT ANALYSIS
C
Resistances R5, R17 and the resistance of the wire in the feedback loop determine the
gain of amplif ier 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 migh t be
introduced by the measure ment sour ce.
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.
On application of AC power, capac itor C6 has no charge . The current will ha ve to flo w
through R18. Initially the full 30-V drop (the difference between the +15 VDC and -15
VDC power) will appear across R18. The 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 front-panel 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 rang e.
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
748183-J
April 2000
Rosemount Analytical
6-9
M
ODEL
XYGEN ANALYZER
755 O
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.
6.6 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 6-
7. 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 noninverting 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 measurement 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.
6-10
April 2000
748183-JRosemount Analytical
+
0 to +7.5V
PHASE
LEAD
ADJUST
R20
20K
C11
1.0uF
R29
1M
R26
1070
CONTROL BOARD
R28
1M
C12
.47uF
-
U4
C17
.0022uF
68
∝
R31
2.0M
R41
22K
R40
1K
+15V
CR4
R42
150K
CR3
-15V
6.2V
R32
453K
R30
13.7K
Q1
5V
1V
100mV
10mV
R34
3.83K
R35
909
R36
90.9
R33
500
IRCUIT ANALYSIS
C
0 - +5V
R39
4.75K
R38
500
METER
COM
VOLTAGE
OUTPUT
MV+
TO ALARM
TO CURRENT
OUTPUT BOARD
F
IGURE
6-7. F
J7
Recorder Output (J7)
(Jumper Selectable)
INAL OUTPUT AMPLIFIER
R37
10
6.7 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 6-8.
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 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.
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 6-8) to provide the
amount of zero suppression that corresponds to the lower range-limit of the zerosuppressed range.
748183-J
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+15V
F
IGURE
U1
6-8. Z
ZERO SUPPRESSION MODULE
CW
R46
100K
R49
10K
R45
5K
-
AR5
+
R48
20K
R51
39
R52
10
ERO-SUPPRESSION MODULE
R50
56
C18
.033uF
C19
.047uF
SW1
FRONT
PANEL
%RANGE
CONTROL BOARD
R24
R23
R22
R21
R44
232K
+15V
CW
-15V
R10
20K
FRONT
PANEL
ZERO
6-12
April 2000
748183-JRosemount Analytical
S
ERVICE AND MAINTENANCE
7
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 recommende d that those fam iliar with circuit in a nalysis
refer to the circuit theory presented in Section Six of this manual.
WARNING: 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: 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 leak-proof condition. Leak-check instructions are provided in Section
2.7.
CAUTION: PARTS INTEGRITY
Tampering or unauthorized substitution of components may adversely
affect safety of this product. Use only factory documented components for
repair.
7.1 INITIAL CHECKOUT WITH STANDARD GASES
If instrument readings do not meet specifications, the first step in troubleshooting is to
isolate the analyzer f rom the sample stream and the sample-handling system.
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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 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.
ROUBLESHOOTING ZERO
T
UPPRESSED RANGE INSTRUMENTS
- S
In troubleshooting an analyzer that has zero-suppressed ranges only, the use of a
zero-based range change kit is recommended. In the initial troubleshooting, the zerobased range resistor module is installed temporarily, to provide a temporary zerobased 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 effe cts of variations in barometric p ressure and sample
pressure. These effects are sometimes difficult to diagnose on zero-suppressed
ranges.
7.2 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 7-1.
Test points A, B, C, and D permit connection to the photocells and the suspension of
loop. Locations of the test points within the detector circuit are as shown in Figure 7-2.
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.
7-2
Rosemount AnalyticalApril 2000
748183-J
OLTAGE TEST MEASUREMENTS
N
E
U
A
V
ERVICE AND MAINTENANCE
S
B TO A
C OR D TO
GROUND
DIAGNOSISCORRECTIVE ACTION
- +NormalNA
+ +U1 or U2 defectiveReplace case board
- -U1 or U2 defectiveReplace case board
+ -Detector defectiveCheck detector per Section 7.3
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 .
Checkout of the case circuit board is now complete.
P8
D C B A
HOT
B
C
D
F
IGURE
D C B A
Case Board
Alarm Option removed for clarity.
7-1. L
OCATIONS OF CASE BOARD TEST POINTS
MAMV
COM
+-+
TB2
H
O
T
T
A
B
C
D
A, B, C
AND
D
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P12
CURRENT TO VOLTAGE OP AMPS
ON CONNECTOR BOARD
4
F
IGURE
PHOTOCELLS
7-2. V
5
6
OLTAGE TEST POINTS
B
A
D
C
SUSPENSION
LOOP
7.3 DETECTOR COMPONENT CHECKOUT
7.3.1 D
7.3.2 S
ETECTOR
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.
To isolate the detector as a source of a problem, the source lamp, photocells, and
suspension should be checked for proper operation.
OURCE LAMP
To verify that the source lamp in operating properly:
1. Verify that lamp is lit.
2. Voltage at U7 pin 2 should be 2.2 ±0.2 VDC.
If lamp is not operating properly, replace per instructions in Section 7.4.2.
7.3.3 P
HOTOCELL
To verify that photocell is operating properly, perform the following steps:
1. Keeping power source ON, disconnect the leads of the photocell from connector
J12. See Figures 7-3, 7-4.
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 7.4.3.
7-4
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ERVICE AND MAINTENANCE
S
7.3.4 S
USPENSION
If the suspension has been damaged, the cause may be improper operating
conditions.
Maximum permissible operating pressure for the detector is 10 psig (69 kPa gauge
pressure). To ensure against over-pressurization, 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 verify correct operation:
1. Turn electrical power to analyzer OFF.
2. Remove optical bench assembly (see Section 7.4.2, steps 1 through 4.)
3. With 100% nitrogen flowing through the analyzer, note the position of the
suspension.
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).
Failure to rotate indicates that the suspension has been damaged and that the
detector assembly must be replaced. See Section 7.4.1.
7.4 DETECTOR COMPONENT REPLACEMENT
7.4.1 D
ETECTOR REPLACEMENT AND CALIBRATION
EPLACEMENT
R
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.
2. Disconnect cable from J12 on the detector assembly.
Note
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.
3. Refer to Figure 7-3. 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.
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4. Remove the two screws at the bottom of the detector assembly, slide detector out.
5. Install replacement detector assembly and connect cable to J12.
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.
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
Sample Pre-Heating
Coil
Photocell
Lock Screws (2)
Connector
Board
J12
Sample Inlet
Tube
Sample
Outlet Tube
F
IGURE
Mounting Screws (2)
7-3. D
ALIBRATION
C
Magnet
Detector Assembly
Optical Bench Assembly
Assembly
ETECTOR/MAGNET ASSEMBLY
Lamp Retaining
Set Screw
Lamp Viewing
Hole
Source Lamp
Assembly
Note
The following adjustments are on the control board, refer to Figures 1-1
and 3-1.
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.
Dual
Photocell
7-6
2. Connect the voltmeter from wiper of front panel RANGE switch (SW 1) 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.
Rosemount AnalyticalApril 2000
748183-J
ERVICE AND MAINTENANCE
p
p
p
S
4. If instrument has zero-suppressed ranges, proceed to Step 13. If instrument has
zero-based ranges, skip Step 13 and proceed directly to Step 14.
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. 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 suscept ibilities involved, and the range
and span used, refer to Section 3.3.2.
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 of Steps 9
through 14 must be repeated.
A. Connections to Source Lamp and Photocell B. Connections to Suspension and Heater Circuits
1018
BRN
YEL
Dual
Photocell
Sense
Old Style Lam
J12
RED
BLU
1
ORN
GRY
When dual photocell is
installed, the gap between
the two photocells should
be in position indicated by
this line.
10
J12
Optical Bench
18
1
WHT
WHT
BLK
BLK
PUR
GRN
Hole for Source Lamp
RT1
HR2
Suspension
Heater
Suspension
Terminals
C. Removal and Insertion of Pin/Leads in Connector J12
Upper Slot
Side View
of Connector
Lower Slot
Connector Pin/
Leads in Place
Im
rovised Pin Removal Tool, Such as a Paper Cli
Keeper
Connector Pin Removed
F
IGURE
748183-J
7-4. D
ETECTOR/MAGNET ASSEMBLY WIRING
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7.4.2 S
OURCE LAMP REPLACEMENT AND ADJUSTMENT
EPLACEMENT
R
1. Remove the four screws securing the detector assembly cover plate.
2. Refer to Figure 7-3. Carefully remove the small rubber hose connected from the
detector/magnet assembly to the detector.
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 assembly to
the magnet assembly. Carefully remove optical bench and detector assembly.
5. Remove the two lock screws (2-56 X 5/16 pan head) holding the photocell in the
optical bench. Carefully remove photocell.
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 7-4A) using method shown in Figure 7-4C.
8. Depending on date of manufacture of the analyzer, the original lamp assembly may
be either of two types:
7. Old style lamp assembly with four color coded leads: Red, blue, brown and
yellow.
Red
Blue
Brown
Yellow
8. 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 7-4A.
9. Insert the lamp into the assembly. After reassembly and application of power, the
lamp will have to be rotated to place the lam p filaments in proper orientation.
10. If the lamp assembly removed from the instrument has two wires, proceed to step
13.
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.
7-8
12. Refer to Figure 7-3. Remove the two screws holding the Connector Board to the
magnet assembly. Carefully remove Connector Board.
13. Place Connector Board on a clean working surface, with solder side (no
components) up.
Rosemount AnalyticalApril 2000
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ERVICE AND MAINTENANCE
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14. Per Figure 7-5, 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 8.
Add Straps or Solder Bridges
F3
HR1
Solder Side of Board (Backside)
F
IGURE
7-5. M
WITH
ODIFICATION OF
R
EPLACEMENT LAMP
633689 C
ONNECTOR BOARD FOR COMPATIBILITY
15. Reassemble detector, etc., in reverse order of disassembly.
LIGNMENT
A
The lamp has a red line on the base housing. It is to be lined up with the set-screw that
secures the lamp, see Figure 7-6. The base of the lamp should extend from the hole
approximately 1/4 inch, then tighten the set-screw.
1/4"
Set Screw
F
IGURE
748183-J
Red Mark for
Alignment
7-6. L
AMP ALIGNMENT
The photocell will need realigning per subsection 7.4.3.
April 2000
Rosemount Analytical
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7.4.3 P
HOTOCELL REPLACEMENT AND ALIGNMENT
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.
EPLACEMENT
R
To remove the photocell from the optical bench, perform steps 1 thourgh 5 of Section
7.4.2.
Install replacement photocell by reversing the procedure.
DJUSTMENT
A
Note
The following adjustments are on the control board, refer to Figures 1-2
and 3-1.
1. With zero gas flowing:
a. Place a digital voltmeter on the wiper of the zero potentiometer (R10) and TP7
(ground), and adjust for 0 VDC.
b. Place the voltmeter from the left of R91 and TP7, and adjust R92 for 0 VDC,
see Figure 7-7.
c. 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.
2. Apply power to instrument and allow to warm up for about one hour.
3. Perform the Calibration procedure in Section 7.4.1.
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.
TP17
R91
TP9
Voltmeter
Lead
R92
TP15
TP16
F
IGURE
7-10
7-7. P
Rosemount AnalyticalApril 2000
HOTOCELL ADJUSTMENT VOLTMETER LEAD LOCATION
748183-J
ERVICE AND MAINTENANCE
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7.5 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.
7.5.1 C
ASE 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.
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.
Set the decade box for 22.2K ohms to simulate RT1 resistance at ambient
temperature; the voltmeter should now show pulses of 120 VAC.
7.5.2 D
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.
748183-J
CAUTION: EQUIPMENT OVERHEATING
ETECTOR/MAGNET HEATING CIRCUIT
April 2000
Rosemount Analytical
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This resistance should be approximately 89 ohms. If resistance was correct, and yet
the combined resistance wa s 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.
7-12
Rosemount AnalyticalApril 2000
748183-J
R
EPLACEMENT PARTS
8
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 your local Rosemount Analytical service office. A list of
Rosemount Analytical Service Centers is located in the back of this manual.
WARNING: PARTS INTEGRITY
Tampering or unauthorized substitution of components may adversely affect
safety of this product. Use only factory-documented components for repair.
8.1 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.
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.
8.2 REPLACEMENT PARTS
To minimize downtime, stocking of the following spare parts is recommended.
656143Detector, 0-5% or greater range increments1*
622421Optical bench, for detector 6323581*
656190Detector/Optical bench assembly, corrosion resistant, 0 to 1
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. W hen electric
arc welding, precautions must be taken to prevent striking an arc against the cylinder.
4125 E
AST LA PALMA AVENUE
Rosemount Analytical Inc.
• A
J
ULY
, C
NAHEIM
ALIFORNIA
1997 • 748525-C • P
92807-1802 • 714-986-7600 • FAX 714-577-8006
RINTED IN
USA
(blank)
ARRANTY
W
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 W ARRANTIES 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 W ARRANTY 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.
Rosemount Analytical
4125 E
AST LA PALMA AVENUE
Rosemount Analytical Inc.
• A
F
EBRUARY 1997 • 7485189-C • PRINTED IN USA
NAHEIM
, C
ALIFORNIA
92807-1802 • 714-986-7600 • FAX 714-577-8006
(blank)
IELD SERVICE AND REPAIR FACILITIES
F
Field service and repair facilities are located worldwide.
U.S.A.
To obtain field service on-site or assistance with a service problem, contact (24 hours, 7
days a week):
National Response Center
1-800-654-7768
INTERNATIONAL
Contact your local Rosemount Sales and Service office for service support.
FACTORY
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
RETURNING PARTS TO THE FACTORY
Before returning parts, contact the Customer Service Center and request a Returned
Materials Authorization (RMA) number. Please have the following information when you call:
Model Number, Serial Number, and Purchase Order Number or Sales Order Number.
Prior authorization by the factory must be obtained before returned materials will be
accepted. Unauthorized returns will be returned to the sende r, f re ight collect.
When return ing any product or compon ent that has been expo sed to a toxic, co rrosive or
other hazardous material or used in such a hazardous environment, the user must attach an
appropriate Material Safety Data Sheet (M.S.D.S.) or a written certification that the material
has been decontaminated, disinfected and/or detoxified.
Return to:
Rosemount Analytical Inc.
4125 East La Palma Avenue
Anaheim, California 92807-1802
4125 E
AST LA PALMA AVENUE
Rosemount Analytical Inc.
• A
ULY 1997 • 748190-G • PRINTED IN USA
J
NAHEIM
, C
ALIFORNIA
92807-1802 • 714-986-7600 • FAX 714-577-8006
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