Teledyne 9700 instruction manual Theory of Operation, Oxygen Analyzer

Page 19

 

 

Flue Gas Analysis System

Theory of Operation 2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Theory of Operation

2.1Oxygen Analyzer

The cathode of the oxygen cell sensor is connected to electrical ground, while the anode is connected to input amplifier A1., a current-to- voltage transducer. The output voltage from A1 is equal to the input cur- rent multiplied by the resistance of the feedback resistor (R1, R2, or R3). The feedback resistance can be varied by RANGE switch SW1.

Field effect transistor (FET) Q1, connected across A1—2 and A1—3, is used to short circuit the oxygen cell when the RANGE switch is turned to OFF. The FET has the property that when the gate is at the same poten- tial as the source, it is turned ‘’on’’. The ‘’on’’ resistance is about 60 Ohms. When power is turned ‘’on”, the -15 VDC turns off the FET (or causes FET resistance to become greater than 10 Megohms so that it appears as an open circuit). Thus, when power is turned “on”, the FET is energized, opens the circuit, and allows cell current to flow through the feedback resistor instead of through the FET. The reason for this circuit arrangement is to insure that the oxygen cell is short circuited when power is turned ‘’off”. The liquid electrolyte in the cell will be depleted of resid- ual oxygen and, consequently, the cell will be ready to operate and mea- sure low concentrations of oxygen immediately after being placed into service. If the oxygen cell was not shorted when the analyzer was out of service, the electrolyte within the cell would become saturated with oxy- gen and, when the analyzer was placed in service, operational delay would occur while the cell burned up residual oxygen through the process of

TELEDYNE BROWN ENGINEERING

2-1

Analytical Instruments

Image 19
Contents Model Flue Gas Analysis System Important Notice WarrantyTable of Contents Maintenance & Troubleshooting Introduction Flue Gas Analysis SystemOverview Sample Conditioning General InformationSample Conditioning Oxygen Analyzer Section Standard FeaturesOxygen Analyzer Section General Information Optional Features General Information Combustible Gas Analyzer Section Combustible Gas Analyzer SectionGeneral Information Compound LEL Response Factor Operating Controls and Indicators Meter Trim Recessed Secondary ControlsAnalog Output Current MAX Load Output Impedance Oxygen Analyzer Theory of OperationTheory of Operation Combustible Analyzer Detector Flue Gas Analysis System Theory of Operation Electrical Connections InstallationPower Output Signal VoltageInterconnection Diagram Output Signal Current Alarm and/or Control CircuitryInstallation Meter Zeroing OperationStartup of Oxygen Analyzer PreliminaryInitial Calibration and Equilibration Flue Gas Analysis System Operational Calibration Routine Operational Calibration ProcedureStartup of Combustibles Analyzer Operation Sample System Startup Span GasSystem Startup Analyzer StartupOperation Oxygen Cell Replacement Flue Gas Analysis System Maintenance & TroubleshootingMaintenance Routine MaintenanceCell Warranty Combustible Sensor Spray NozzleWater Strainer Filter Condensate TrapPump TroubleshootingGeneral Oxygen Analyzer .2.2.1 Inability to Calibrate Inability to Calibrate Combustible Analyzer SectionNo Alarm With High Gas Level Lamp Failure Appendix SpecificationsOxygen Analysis Section Appendix ModelModel 9700 System Standard Unit Only Recommended Spare Parts ListReference Drawings Response of Combustible Sensor to Various Gases Appendix Model Supporting Equipment for Flue Gas Analysis Systems Figure A-1 Typical Dry Probe Maintenance General Maintenance for CC-2B Series PumpsRepair Appendix Model Flue Gas Analysis System Figure A-3 Pump Assembly Flue Gas Analysis System Figure A-4 Replacing Flex-I-Liner Replacing the Liner in the Flex-I-Liner PumpFlue Gas Analysis System