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M

ODEL

755

O

XYGEN

A

NALYZER

6-8

748183-H

Rosemount Analytical

December 1997

-

+

U1

R3
1K

R4
1K

-

+

U2

R17

+15V

-15V

R44

232K

R10
20K

CW

FRONT
PANEL
ZERO

DS1

FEEDBACK
LOOP

BT1

BT2

PHOTOCELL

BOARD

R9

110K

-

+

U2

R1
1K

R2
1K

CR2

R19
10

+15V

-15V

C6

3.3uF

+15V

R18
29.9K

CR1

+

CONNECTOR

BOARD

R91

30.1K

C10
.68uF

R16

56

+15V

-15V

R92
20K

CW

C1

.0022uF

R1

12.4K

R4

50K

FRONT PANEL

SPAN

-

+

U3

R3

R15

4.02K

C10

.68uF

SW1

FRONT
PANEL
%RANGE

C41
1000pf

C3

.47uF

R7

118K

-

+

U1

R8

1.69K

R6

2M

C42

0.01uF

R5

1.78K

C2

.47uF

CONTROL BOARD

R20

20K

R26

1070

PHASE
LEAD
ADJUST

R14

R13

R12

R11

R29
1M

C11
.1uF

0 to 7.5V

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.

F

IGURE

6-6. D

ETECTOR WITH

F

IRST

S

TAGE

A

MPLIFIER

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.

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Содержание 755

Страница 1: ...Rosemount Analytical MODEL 755 OXYGEN ANALYZER INSTRUCTION MANUAL 748183 H ...

Страница 2: ...ual Part Number 748183 H November 1997 Printed in U S A Rosemount Analytical Inc 4125 East La Palma Avenue Anaheim California 92807 1802 Viton are registered trademarks of E I duPont de Nemours and Co Inc Paliney No 7 is a trademark of J M Ney Co SNOOP is a registered trademark of NUPRO Co ...

Страница 3: ...SICAL EXPLOSION PROOF ENCLOSURE P 5 CUSTOMER SERVICE TECHNICAL ASSISTANCE AND FIELD SERVICE P 6 RETURNING PARTS TO THE FACTORY P 6 TRAINING P 6 DOCUMENTATION P 6 COMPLIANCES P 7 SECTION 1 INTRODUCTION 1 1 RANGE OPTIONS 1 1 1 1 1 Standard Zero Based Range Options 1 1 1 1 2 Standard Zero Suppressed Range Options 1 3 1 1 3 Special Range Options 1 3 1 2 ISOLATED CURRENT OUTPUT OPTIONS 1 5 1 3 ALARM OP...

Страница 4: ... HANDLING 2 12 2 6 1 Sample Temperature Requirements 2 12 2 6 2 Sample Pressure Requirements General 2 13 2 6 3 Normal Operation at Positive Gauge Pressures 2 13 2 6 4 Operation at Negative Gauge Pressures 2 14 2 6 5 Sample Flow Rate 2 14 2 6 6 Corrosive Gases 2 15 2 7 LEAK TEST 2 15 2 8 PURGE KIT OPTIONAL 2 15 SECTION 3 STARTUP 3 1 STARTUP PROCEDURE 3 1 3 2 CALIBRATION 3 1 3 2 1 Calibration with ...

Страница 5: ...ressure Effects 5 5 5 2 2 Temperature Effects 5 6 5 2 3 Interferents 5 6 5 2 4 Vibration Effects 5 6 5 3 ELECTRONIC CIRCUITRY 5 7 5 3 1 Detector Magnet Assembly 5 7 5 3 2 Control Board and Associated Circuitry 5 7 5 3 3 Case Board Assembly 5 8 5 3 4 Isolated Current Output Board Optional 5 9 5 3 5 Alarm Option 5 9 SECTION 6 CIRCUIT ANALYSIS 6 1 POWER SUPPLY 15VDC 6 1 6 2 CASE HEATER CONTROL CIRCUI...

Страница 6: ...pension 7 5 7 4 DETECTOR COMPONENT REPLACEMENT 7 5 7 4 1 Detector Replacement and Calibration 7 5 7 4 2 Source Lamp Replacement and Adjustment 7 8 7 4 3 Photocell Replacement and Alignment 7 10 7 5 HEATING CIRCUITS 7 11 7 5 1 Case Heater Control Circuit 7 11 7 5 2 Detector Magnet Heating Circuit 7 11 SECTION 8 REPLACEMENT PARTS 8 1 CIRCUIT BOARD REPLACEMENT POLICY 8 1 8 2 REPLACEMENT PARTS 8 1 GEN...

Страница 7: ...etic Field 5 3 5 3 Detector Magnet Assembly 5 4 6 1 Two Comparator OR Circuit 6 2 6 2 Case Heater Control Circuit 6 3 6 3 Ramp Generator 6 3 6 4 Detector Heater Control Circuit 6 6 6 5 Detector Light Source Control Circuit 6 7 6 6 Detector with First Stage Amplifier 6 8 6 7 Final Output Amplifier 6 11 6 8 Zero Suppression Module 6 12 7 1 Locations of Case Board Test Points A B C and D 7 3 7 2 Volt...

Страница 8: ...617186 Schematic Diagram Case Board 620434 Schematic Diagram Isolated Current Output Board 624549 Pictorial Wiring Diagram Model 755 632349 Installation Drawing Model 755 General Purpose 638277 Schematic Diagram Alarm 643127 Installation Drawing Model 755 Explosion Proof 652188 Schematic Diagram Control Board ...

Страница 9: ... 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 prope...

Страница 10: ...d in place Installation must be made in accordance with applicable parts of the NEC especially Articles 501 4 a and 501 5 a 1 If explosive gases are introduced into this analyzer the sample containment system must be carefully leak checked upon installation and before initial start up during routine maintenance and any time the integrity of the sample containment system is broken to ensure the sys...

Страница 11: ...rmance 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 whe...

Страница 12: ...ard 115 VAC 10 VAC 50 60 Hz Optional 230 VAC 10 VAC 50 60 Hz POWER CONSUMPTION Maximum 300 watts OUTPUTS Standard Field selectable voltage output of 0 to 10mV 0 to 100mV 0 to 1V or 0 to 5VDC Optional Isolated current output of 0 to 20mA or 4 to 20mA with Current Output Board ALARM OPTION High Low Alarm Contact Ratings 5 amperes 240V AC resistive 3 amperes 120 VAC inductive 1 amperes 24V DC resisti...

Страница 13: ...CAL EXPLOSION PROOF ENCLOSURE MOUNTING Surface or wall ENCLOSURE CLASSIFICATION Class I Groups B C and D Division 1 hazardous locations ANSI NFPA 70 REFER TO INSTALLATION DRAWING 643127 IN THE REAR OF THIS MANUAL 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 Anal...

Страница 14: ...authorized returns will be returned to the sender freight collect When returning any product or component that has been exposed to a toxic corrosive 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 Ros...

Страница 15: ...f installed in accordance with the requirements of the National Electrical Code NEC of the United States in non hazardous areas and operated and maintained in the recommended manner MODEL 755 OXYGEN ANALYZER EXPLOSION PROOF ENCLOSURE The Model 755 Oxygen Analyzer explosion proof enclosure catalog number 632440 is approved by Factory Mutual FM for installation in Class I Groups B C and D Division 1...

Страница 16: ...MODEL 755 OXYGEN ANALYZER Rosemount Analytical 748183 H November 1997 P 8 NOTES ...

Страница 17: ...cept 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 rang...

Страница 18: ...r ZERO Control RANGE Switch SPAN Adjust Controls have slotted shafts for screwdriver adjustment from outside the enclosure Meter Rosemount Analytical M o d e l 7 5 5 O xy g e n An a l y ze r Meter ZERO Adjust SPAN Adjust RANGE Switch A GENERAL PURPOSE ENCLOSURE B EXPLOSION PROOF ENCLOSURE FIGURE 1 1 MODEL 755 FRONT VIEW ...

Страница 19: ...er 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 CONTROL FUNCTION METER 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 operat...

Страница 20: ...R R 8 U I G U U 1 2 I G C C C U U I G C3 U J Alarm Relay Assembly Alarm Option Case Board Transformer Power T1 Behind TB1 AC Power TB1 Detector Magnet Assembly Detector Magnet Assembly Shock Mount Fuse AC Power Recorder Output TB2 Case Heater Assembly Fuse Case Heater Current Output Board Option Control Board Door General Purpose enclosure shown Components mounted in same locations in Explosion Pr...

Страница 21: ... 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 customer supplied alarm and or control devices 1...

Страница 22: ...MODEL 755 OXYGEN ANALYZER 1 6 748183 H Rosemount Analytical November 1997 NOTES ...

Страница 23: ...ounted outdoors Permissible ambient temperature range is 20 F to 120 F 7 C to 49 C The analyzer is designed for either surface or stanchion optional kit mounting Avoid mounting outside in direct sunlight or inside in a closed building where ambient temperature may exceed the allowable maximum EXPLOSION PROOF ENCLOSURE The analyzer can be either surface or wall mounted and meets ANSI NFPA 70 Class ...

Страница 24: ... 4 1 LINE 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 extern...

Страница 25: ... tubing This precaution ensures against possible transmission of mechanical vibration through the cable to the detector which could cause noisy readout FIGURE 2 1 ELECTRICAL INTERCONNECTION N E U T H O T TB1 N E U T H O T TB1 Jumpers 120 VAC CONFIGURATION 240 VAC CONFIGURATION Jumper GND GND NO COM NC RESET NO 2 GND N E U T H O T TB1 NO COM NC RESET NO 1 HOT TB2 MA MV COM Power Connections see bel...

Страница 26: ... 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 interm...

Страница 27: ...rent actuated device making sure that polarity is correct If two or more current actuated devices are to be used they must be connected in series see Figure 2 4 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 zero an...

Страница 28: ...ls 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 po...

Страница 29: ...rm 1 and Alarm 2 relays are as follows ALARM 1 RELAY 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 ALARM 2 RELAY Relay The Alarm 2 relay coil is de energized when the me...

Страница 30: ...L SAFE APPLICATIONS 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 for fail safe applications the User understand what circuit conditions are desired in event of power failure and...

Страница 31: ... 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 FIGURE 2 7 ALARM RELAY OPTION SCHEMATIC DIAGRAM 6 Calibration of ALARM 2 LOW a ...

Страница 32: ...ntrol 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 Calibration gas cylinders are under pressure Mishandling of gas cylinders could resu...

Страница 33: ...3 O2 0 to 50 Nitrogen 0 45 O2 balance N2 0 to 100 Nitrogen 100 O2 B ZERO SUPPRESSED RANGES RANGE O2 RECOMMENDED DOWNSCALE STANDARD GAS RECOMMENDED UPSCALE STANDARD GAS 90 to 100 91 0 5 O2 balance N2 High purity O2 80 to 100 82 1 O2 balance N2 100 O2 60 to 100 62 1 O2 balance N2 100 O2 50 to 100 52 1 O2 balance N2 100 O2 Note Each standard gas used should have a composition within the specified lim...

Страница 34: ... 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 a...

Страница 35: ... Hg absolute 88 1 kPa absolute pressure 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 p...

Страница 36: ...uge 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...

Страница 37: ...rable as most of these gases are practically inert when totally dry For corrosive applications consult the factory 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 Failu...

Страница 38: ...ay be flammable If used for analysis of such gases the instrument must be protected by a continuous dilution purge system in accordance with Standard ANSI NFPA 496 1086 Chapter 8 or IEC Publication 79 2 1983 Section Three If explosive gases are introduced into this analyzer the sample containment system must be carefully leak checked upon installation and before initial start up during routine mai...

Страница 39: ...ass 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 FIGURE 2 9 INSTALLATION OF PURGE KIT 645835 Purge Outlet Fitting 190697 Purge Inlet Fitting Flow Indicator Purge Supply Analyzer Door Affix...

Страница 40: ...MODEL 755 OXYGEN ANALYZER 2 18 748183 H Rosemount Analytical November 1997 NOTES ...

Страница 41: ...l 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 ...

Страница 42: ...ever 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 pressu...

Страница 43: ...he detector within the magnetic field It is adjusted during factory checkout and does not require readjustment except after replacement of detector 10 CURRENT OUTPUT ZERO ADJUSTMENT R1 Used to set zero level current output i e 4 mA for 4 to 20 mA board 0 mA for 0 to 20 mA board or 10 mA for 10 to 50 mA board 11 CURRENT OUTPUT SPAN ADJUSTMENT R2 Used to set fullscale current output at 20 mA for 4 t...

Страница 44: ...ale 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 analyz...

Страница 45: ...e 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 stan...

Страница 46: ...ns 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 bac...

Страница 47: ...ble 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 O2 GAS EQUIV AS Acetylene C2H2 0 612 Allene C3H4 0 744 Ammonia NH3 0 479 Argon A 0 569 Bromine Br2 1 83 1 2 Butadiene C4H6 1 047 1 3 Butadiene C4H6 1 944 n Butane C4H10 1 481 iso Butane C4H10 1 485 Butene 1 C4H8 1 205 cis Butene 2 C4H8 1 252 iso Butene C4H8 1 201 trans but...

Страница 48: ...sceptibility 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 ...

Страница 49: ...he 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 provid...

Страница 50: ...MODEL 755 OXYGEN ANALYZER 3 10 748183 H Rosemount Analytical November 1997 NOTES ...

Страница 51: ...mpromise 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 standardi...

Страница 52: ...l 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 t...

Страница 53: ...ound lengthwise around the dumbbell In effect each sphere is wound with a one turn circular loop The current required to restore the test body to null position is directly proportional to the original displacement torque and is a linear function of the volume magnetic susceptibility of the sample gas The restoring current is automatically maintained at the correct level by an electro optical feedb...

Страница 54: ...l Alloy Suspension Ribbon Balancing Weight Balancing Weight Nitrogen Filled Hollow Glass Test Body Mirror Titanium Wire Conductor TEST BODY DETAIL Electromagnetic Axis Electromagnetic Axis Restoring Current Restoring Current Displacement Torque Restoring Torque CONTROL ASSEMBLY DETECTOR MAGNET ASSEMBLY Test Body Shaded Pole Pieces 4 Source Lamp DS1 Restoring Current Span Zero Dual Photocell BT1 BT...

Страница 55: ...magnetic susceptibility of this sphere and that of the surrounding gas Magnitude of the force is expressed by the following simplified equation Fk c k ko Where c A function of the magnetic field strength and gradient k Magnetic susceptibility of the surrounding gas ko Magnetic susceptibility of the sphere The forces exerted on two spheres of the test body are thus a measure of the magnetic suscept...

Страница 56: ...he same temperature as the detector assembly FIGURE 5 3 DETECTOR MAGNET ASSEMBLY Detector Assembly Mounting Screws 2 Optical Bench Assembly Magnet Assembly Sample Outlet Tube Sample Inlet Tube Sample Pre Heating Coil Connector J12 Dual Photocell Connector J12 Lamp Retaining Set Screw Photocell Lock Screws 2 Source Lamp Assembly Lamp Viewing Hole Dual Photocell Integral Temperature Sensor RT1 Integ...

Страница 57: ...e Section 5 2 2 interfering sample components Section 5 2 3 and vibration Section 5 2 4 5 2 1 PRESSURE EFFECTS Although normally calibrated for readout in percent oxygen the Model 755 actually responds to oxygen partial pressure The partial pressure of the oxygen component in a gas mixture is proportional to the total pressure of the mixture Thus readout is affected by pressure variations For inst...

Страница 58: ...e 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 INTERFERENTS Instrument response to most non oxygen sample components is comparatively slight but is not in all cases negligible During initial installation of an instrument in a given application effects of the background gas should be calculated to determine if correction is...

Страница 59: ...oop on the test body refer to Section 5 1 ELEMENTS OF DETECTOR TEMPERATURE CONTROL CIRCUIT 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 ...

Страница 60: ...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...

Страница 61: ...drives transistors Q2 and Q3 thus controlling application of DC power from full wave rectifier bridge CR6 to two heaters within the detector magnet assembly HRI mounted on the top of the magnet and HR2 permanently mounted on the rear of the detector assembly CASE TEMPERATURE CONTROL SECTION This section maintains the interior of the analyzer case at a controlled temperature of 140 F 60 C Temperatu...

Страница 62: ...MODEL 755 OXYGEN ANALYZER 5 10 748183 H Rosemount Analytical December 1997 NOTES ...

Страница 63: ...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 ...

Страница 64: ...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 ...

Страница 65: ...76 37 4K C40 2200uF C37 1 0uF C39 01uF R83 63 4K R84 169K R82 9 07K RT1 15V R78 249K Q6 R80 10K R79 10K R81 56 2 C38 18uF R87 10K R77 10K CR11 T2 15V CASE BOARD 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...

Страница 66: ...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 su...

Страница 67: ...e 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 l...

Страница 68: ...etween 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 FIGURE 6 4 DETECTOR HEATER CONTROL CIRCUIT 6 4 DETECTOR ...

Страница 69: ...d the operation of Q4 and Q5 will adjust the gain of U7 to maintain the light emission from DS1 uniform for a long period of time 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...

Страница 70: ...long 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 l...

Страница 71: ...application of AC power capacitor C6 has no charge The current will have to flow through R18 Initially the full 30 V drop the difference between the 15 VDC and 15 VDC power will appear across R18 The 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...

Страница 72: ...ses 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...

Страница 73: ...ation 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 resist...

Страница 74: ...December 1997 FRONT PANEL ZERO AR5 15V 15V R44 232K R10 20K CW U1 PM REF 15V R46 100K SW1 FRONT PANEL RANGE C18 033uF R50 56 R24 R23 R22 R21 R48 20K R49 10K R51 39 R52 10 C19 047uF R45 5K CW CONTROL BOARD ZERO SUPPRESSION MODULE FIGURE 6 8 ZERO SUPPRESSION MODULE ...

Страница 75: ...proper performance this instrument must be connected to a properly grounded three wire source of power If explosive gases are introduced into this analyzer the sample containment system must be carefully leak checked upon installation and before initial start up during routine maintenance and any time the integrity of the sample containment system is broken to ensure the system is in leak proof co...

Страница 76: ...g that the detector is defective and must be replaced it is desirable to verify correct operation of all circuits that could cause erratic readings TROUBLESHOOTING ZERO SUPPRESSED RANGE INSTRUMENTS In troubleshooting an analyzer that has zero suppressed ranges only the use of a zero based range change kit is recommended In the initial troubleshooting the zero based range resistor module is install...

Страница 77: ...ck 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 FIGURE 7 1 LOCATIONS OF CASE BOARD TEST POINTS A B C AND D HOT GN N E U T H O T TB1 MA MV TB2 COM P8 A B C D D C B A...

Страница 78: ...hould be checked for proper operation 7 3 2 SOURCE 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 PHOTOCELL To verify that photocell is operating properly perform the following steps 1 Keeping power source ON disconnect the leads of the ...

Страница 79: ...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 DETECTOR REPLACEMENT AND CALIBRATION REPLACEMENT Prior to removal of the detector remove power from inst...

Страница 80: ...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 FIGURE 7 3 DETECTOR MAGNET ASSEMBLY CALIBRATION 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 chassi...

Страница 81: ... 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 r...

Страница 82: ...n 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 8 New style lamp assembly with two leads color coded either both red or both black The replacement lamp assembly is the new style with two leads On J12 insert one lead into the position formerly use...

Страница 83: ...IGURE 7 5 MODIFICATION OF 633689 CONNECTOR BOARD FOR COMPATIBILITY WITH REPLACEMENT LAMP 15 Reassemble detector etc in reverse order of disassembly ALIGNMENT 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 FIGURE 7 6 LAMP ALIGNM...

Страница 84: ... 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 ...

Страница 85: ...rmal 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 lin...

Страница 86: ...sistance 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 measur...

Страница 87: ...dividual 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 fro...

Страница 88: ... Photocell assembly 1 631773 Case circuit board assembly 1 623875 Control board assembly 1 632449 Fan 120 V 1 632441 Fan 240 V 1 861652 Heater 120 V 1 861653 Heater 240 V 1 620433 Current output board 0 to 20 mA 4 to 20 Ma 1 860371 Alarm relay 1 861649 Thermal fuse F2 F3 1 If used ...

Страница 89: ... 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 ...

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Страница 91: ... or from any other cause All other warranties expressed or implied are hereby excluded IN CONSIDERATION OF THE HEREIN STATED PURCHASE PRICE OF THE GOODS SELLER GRANTS ONLY THE ABOVE STATED EXPRESS WARRANTY NO OTHER WARRANTIES ARE GRANTED INCLUDING BUT NOT LIMITED TO EXPRESS AND IMPLIED WARRANTIES OR MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE Limitations of Remedy SELLER SHALL NOT BE LIAB...

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Страница 93: ...r 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 returning any product or component that has been exposed to a toxic corrosive or other hazardous materi...

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