Teledyne Trace Oxygen Analyzer, 3000TA-XL-EU Effect of Pressure, Calibration Characteristics

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2 Operational Theory

Model 3000TA-XL-EU

 

 

 

 

 

 

 

 

 

(These reactions are specific to oxygen as long as no gaseous compo- nents capable of oxidizing lead—such as iodine, bromine, chlorine and fluorine—are present in the sample.)

In the absence of oxygen, no current is generated.

2.2.4 The Effect of Pressure

In order to state the amount of oxygen present in the sample in parts- per-million or a percentage of the gas mixture, it is necessary that the sample diffuse into the cell under constant pressure.

If the total pressure increases, the rate that oxygen reaches the cathode through the diffusing membrane will also increase. The electron transfer, and therefore the external current, will increase, even though the oxygen concen- tration of the sample has not changed. It is therefore important that the sample pressure at the fuel cell (usually vent pressure) remain relatively constant between calibrations.

2.2.5 Calibration Characteristics

Given that the total pressure of the sample gas on the surface of the Micro-Fuel Cell input is constant, a convenient characteristic of the cell is that the current produced in an external circuit is directly proportional to the rate at which oxygen molecules reach the cathode, and this rate is directly proportional to the concentration of oxygen in the gaseous mixture. In other words it has a linear characteristic curve, as shown in Figure 2-3. Measuring circuits do not have to compensate for nonlinearities.

In addition, since there is zero output in the absence of oxygen, the characteristic curve has close to an absolute zero (less than ± 0.2 ppm oxy- gen). Depending upon the application, zeroing may still be used to compen- sate for the combined zero offsets of the cell and the electronics.

2-4

Teledyne Analytical Instruments

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Contents Trace Oxygen Analyzer Teledyne Analytical InstrumentsModel 3000TA-XL-EU Copyright 1999 Teledyne Analytical InstrumentsIii Trace Oxygen Analyzer Specific Model InformationGround Protective Earth Teledyne Analytical InstrumentsOperational Theory Trace Oxygen Analyzer Table of Contents IntroductionInstallation OperationMaintenance AppendixVii Trace Oxygen Analyzer AppendixCombustible GAS Usage Warning ViiiTypical Applications Main Features of the AnalyzerOverview Trace Oxygen Analyzer IntroductionModel Designations Introduction Model 3000TA-XL-EUFront Panel Operator Interface Model 3000TA-XL Front PanelIntroduction Model 3000TA-XL-EU Rear Panel Equipment Interface Analog OutputsRS-232 Port Remote ProbeNetwork I/O Trace Oxygen Analyzer Operational Theory Operational Theory IntroductionMicro-Fuel Cell Sensor Principles of OperationOperational Theory Model 3000TA-XL-EU Anatomy of a Micro-Fuel CellElectrochemical Reactions + 2H 2O + 4e → 4OHCalibration Characteristics Effect of PressureCharacteristic Input/Output Curve for a Micro-Fuel Cell Sample SystemTOP Flow Diagram-Sample Under Pressure Standard Model Electronics and Signal Processing Electronic Component Location Inside the Model 3000TA-XLBlock Diagram of the Model 3000TA-XL Electronics Operational Theory Model 3000TA-XL-EU Trace Oxygen Analyzer Installation Unpacking the AnalyzerMounting the Analyzer Installation Model 3000TA-XL-EU Rear Panel ConnectionsGas Connections Rear Panel of the Model 3000TA-XLPrimaryInputPower 2.2 50-Pin Equipment Interface ConnectorElectrical Connections Equipment Interface Connector Pin Arrangement Pin FunctionPin Contact Remote Calibration Connections Range ID Relay Connections 2.3 RS-232 Port FET Series ResistanceCommand Description Parameter SettingInstalling the Micro-Fuel Cell Testing the SystemRemoving the Micro-Fuel Cell Trace Oxygen Analyzer Operation Auto Ranging onUsing the Data Entry and Function Buttons Operation Model 3000TA-XL-EUSystem Function Analyze SystemOperation Model 3000TA-XL-EU Setting up an Auto-Cal Password Protection Entering the Password Installing or Changing the Password System Self-Diagnostic Test LogoutVersion Screen Air Calibration Calibration of the AnalyzerSpan Gas Calibration Zero CalAuto Mode Zeroing Manual Mode ZeroingCell Failure Auto Mode Spanning Operation Model 3000TA-XL-EU Span CalManual Mode Spanning Switching of Sample Streams Span FailureAlarms Function Special Notes on Hydrogen Gas StreamAL-1 AL-2 Choose Alarm Range Function Setting the Analog Output Ranges Fixed Range AnalysisSignal Output Analyze FunctionRange Voltage Current mA MEDTrace Oxygen Analyzer Maintenance Routine MaintenanceCell Replacement Storing and Handling Replacement CellsMaintenance Model 3000TA-XL-EU When to Replace a Cell Removing the Micro-Fuel CellRemoving the Micro-Fuel Cell Warranty Fuse Replacement Removing Fuse Block from HousingSystem Self Diagnostic Test Maintenance Model 3000TA-XL-EUMajor Internal Components Cleaning Rear-Panel ScrewsTroubleshooting SolutionSpecifications Operating Temperature 5-35 C AppendixRecommended 2-Year Spare Parts List Drawing List 19-inch Relay Rack Panel Mount3000XL Series Analyzers Conversions Page Material Safety Data Sheet Section IV Fire and Explosion Hazard Data Protective measures during cell replacement ExposureSection Viii Control Measures Read completely before beginning the procedure
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