Teledyne 3160 manual Operational Theory

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2 Operational Theory

Electronics in the analyzer are grouped according to function:

1.Analog in

2.Analog out

3.Digital circuit

4.Power supply

Analog signal processing is accomplished in two plug-in circuit cards operating under control of the microcomputer. All analog signals are converted to digital early in the processing cycle to minimize analog processing and assure maximum system accuracy, since digital processing is much more accurate than analog and immune to many parameters such as drift and aging.

The initial processing and digitization of the signal from the Micro-Fuel Cell takes place on two circuit boards: the six-decade programmable printed circuit board (PCB), and the analog input board.

The first step in the chain takes place on the six-decade programmable PCB, which is mounted directly on top of the cell block. The output of the sensor is a current that is linearly proportional to the oxygen concentration. At low concentra- tions, the current from the sensor is low, which makes the close physical proximity of the pre-amp circuitry to the Micro-Fuel Cell necessary.

The sensor current is routed into a low-offset, low-bias current operational amplifier configured as a current-to-voltage converter. The signal is sent through two amplifiers to the analog input board. The pre-amp board provides sensor zeroing and a connection to the thermistor in the sensor cell block.

The analog input PCB, which plugs into a DIN connector on the digital PCB, performs three functions:

Temperature compensation in the sensor signal

Sensor offset correction

Digitization

A thermistor inside the sensor block registers resistance and thus the temperature of the sensor. Accordingly, an analog-to-digital converter configured as a digitally- programmed attenuator (DPA) is used to reduce or increase the gain of the sensor signal, so that the signal coming out of the DPA is independent of temperature.

If the software determines that the sensor needs offsetting, the sensor current is back-calculated and an analog-to-digital converter on the analog board is driven by the software to produce a voltage that is used to force a current into the current-to-voltage converter located on the pre-amp board. The current injected is equal and opposite in polarity to the portion of the sensor current that needs offsetting.

Digitization is provided by a 12-bit analog-to-digital converter, which digitizes the oxygen and temperature signals.

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TELEDYNE ANALYTICAL INSTRUMENTS

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Contents Model Copyright 1999 Teledyne Analytical Instruments Iii Table of Contents Maintenance & Troubleshooting AppendixTeledyne Analytical Instruments Features Fixed FeaturesVariable Features IntroductionIntroduction Options and Model Numbers Introduction Components3160DA Dual fuel cell Introduction Applications Operational Theory Principles of OperationMajor Components Operational Theory Micro-Fuel Cell Sensor Sample SystemOperational Theory Electronics and Signal Processing Model 3160 flow schematicOperational Theory Analog signal output offset Identifier Range Scale Voltage CurrentmADefaults Programmable Options Installation Unpacking the AnalyzerFront Panel Qty DescriptionRear Panel Analyzer front and rear panels Installation Gas Line Connections Span GasInstrument Air Compressed Air Fitting Sample GasSensor Installation Electrical Connections Voltage Selection 3160 Rear PanelFuse Changing Removing the Voltage CardFuse Replacement Installation Checklist 3 RS-232 Serial Digital PortOperations Front Panel ControlsSpinning Wheel Modes of OperationCell Output Factor Span Factor Operations Changing Passwords For Remote Monitoring and Control Uled Span in ProgressOperations Cold Start-Up Operations Calibration Zeroing Operations Operations Calibration Using Span Gas Operations Operations Operations Select Active Sensor Two Cells Only Setup Operations Operations O2 Range Set-Up AccptOperations Set-Up Alarms Cold StartOperations Operations Logger Set-Up Operations Operations Set-Up Clock Functions Accpt Teledyne Analytical Instruments Operations Operations System Statistics Ascii Data Bits 7 or Stop Bits 1 or Baud rateComm. Std. for 1200B Bell USA/CCITT Operations Operations Maintenance & Troubleshooting Routine MaintenanceSensor Maintenance Scrubber MaintenanceTroubleshooting Symptom Cause CorrectionMaintenance & Troubleshooting Symptom Cause Correction Maintenance & Troubleshooting Operating Temperature0-50C 32 -122 F SpecificationsAppendix Altitude 1,609 m Relative Humidy Up to 99% Teledyne Analytical InstrumentsAppendix Recommended Spare Parts List Drawing ListAppendix Material Safety Data Sheet Customer Service Extension Environmental HealthDate Prepared 2/12/96 Material or Component S. # QuantitySection IV Fire and Explosion Hazard Data Protective measures during cell replacement ExposureSection Viii Control Measures Product Name ManufacturerAddress PhoneSigns/symptoms of exposure Primary route of entryExposure limits Osha PEL Effects of overexposure IngestionProtective measures Disposal