Pneumatic Sensor Board - Teledyne T200 Operation Manual

Principles of Operation
13.5.2.1. TEC CONTROL BOARD

13.6. PNEUMATIC SENSOR BOARD

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Teledyne API – T200 NO/NO2/NOx Analyzer Operation Manual
TEC PCA sets
appropriate
drive voltage for
cooler
Cooling Fan
Figure 13-21: PMT Cooling System Block Diagram
The target temperature at which the TEC system keeps the PMT is approximately 8.0ºC.
Arriving at this temperature may take up to 30 minutes after the instrument is turned on.
The actual temperature of the PMT can be viewed via the front panel as the test function
PMT TEMP (see Section 4.1.1).
The TEC control PCA is located on the sensor housing assembly, under the slanted
shroud, next to the cooling fins and directly above the cooling fan. Using the amplified
PMT temperature signal from the PMT preamplifier board (see Section 10.4.5), it sets
the drive voltage for the thermoelectric cooler. The warmer the PMT gets, the more
current is passed through the TEC causing it to pump more heat to the heat sink.

A red LED located on the top edge of this circuit board indicates that the control
circuit is receiving power.

Four test points are also located at the top of this assembly.

For the definitions and acceptable signal levels of these test points see 12.7.14.
The flow and pressure sensors of the T200 are located on a printed circuit assembly just
behind the PMT sensor. Refer to Section 12.7.6.1 for a figure and on how to test this
assembly. The signals of this board are supplied to the motherboard for further signal
processing. All sensors are linearized in the firmware and can be span calibrated from
the front panel.
Preamp PCA sends
buffered and
amplified thermistor
signal to TEC PCA
TEC
Control
PCA
Thermo-Electric Cooler
PMT Temperature Sensor
PMT
Cold Block
PMT
Preamp
PCA
Thermistor
outputs temp of
cold block to
preamp PCA
Heat form PMT is absorbed
by the cold block and
transferred to the heat sink
via the TEC then bled off
into the cool air stream.
06858E DCN7057