Teledyne 9110T instruction manual Pneumatic Sensor Board, TEC Control Board, Pmt, Preamp, Pca

Model 9110T NOx Analyzer Principles of Operation

	Preamp PCA sends
TEC PCA sets	buffered and
	amplified thermistor
appropriate
	signal to TEC PCA
drive voltage for
cooler
	TEC
	Control
	PCA

Thermo-Electric Cooler

PMT

Preamp

PCA

Heat Sink

Cooling Fan

PMT Temperature Sensor	Thermistor
	outputs temp of
	cold block to
	preamp PCA

PMT

Cold Block

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.

Figure 13-24: 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).

13.5.2.1. TEC Control Board

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.

13.6.PNEUMATIC SENSOR BOARD

The flow and pressure sensors of the 9110T 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.

Teledyne Analytical Instruments 356