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Theory of Operation Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 248
BENCH TEMPERATURE SENSOR
This thermistor is attached to the sample chamber housing. It reports the current temperature of the chamber
housing to the CPU as part of the bench heater control loop.
WHEEL TEMPERATURE SENSOR
This thermistor is attached to the heatsink on the GFC Wheel motor assembly. It reports the current temperature
of the wheel/motor assembly to the CPU as part of the Wheel Heater control loop.
BOX TEMPERATURE SENSOR
A thermistor is attached to the motherboard. It measures the analyzer’s internal temperature. This information is
stored by the CPU and can be viewed by the user for troubleshooting purposes via the front panel display (see
Section 13.1.2).
11.5.6.4. Analog Outputs
The analyzer comes equipped with four analog outputs: A1, A2, A3 and A4. The type of data and electronic
performance of these outputs are configurable by the user (see Section 7.4).
OUTPUT LOOP-BACK
All four analog outputs are connected back to the A/D converter through a loop-back circuit. This permits the
voltage outputs to be calibrated by the CPU without need for any additional tools or fixtures.
11.5.6.5. Internal Digital I/O
This channel is used to communicate digital status and control signals about the operation of key components of
the Optical Bench. The CPU sends signals to the sync/demod board that initiate the ELECTRICAL TEST and
DARK CALIBRATION procedures.
11.5.6.6. External Digital I/O
This External Digital I/O performs two functions.
STATUS OUTPUTS
Logic-Level voltages are output through an optically isolated 8-pin connector located on the rear panel of the
analyzer. These outputs convey good/bad and on/off information about certain analyzer conditions. They can
be used to interface with certain types of programmable devices (See Section 3.3.3).
CONTROL INPUTS
By applying +5VDC power supplied from an external source such as a PLC or Data logger (See Section 3.3.4),
Zero and Span calibrations can be initiated by contact closures on the rear panel.