Teledyne T100 Manuale Utente

13.5.4.2. TEC CONTROL BOARD 

The TEC control printed circuit assembly is located ion 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 (refer to 
Section 13.5.5), 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 refer to Section 12.1.2. 

The PMT preamplifier board amplifies the PMT signal into a useable analog voltage that 
can be processed by the motherboard into a digital signal to be used by the CPU to 
calculate the SO

2

 concentration of the gas in the sample chamber.  

The output signal of the PMT is controlled by two different adjustments. First, the 
voltage across the electron multiplier array of the PMT is adjusted with a set of two 
hexadecimal switches. Adjusting this voltage directly affects the HVPS voltage and, 
hence, the signal from the PMT. Secondly, the gain of the amplified signal can further 
be adjusted through a potentiometer. These adjustments should only be performed when 
encountering problems with the software calibration that cannot be rectified otherwise. 
Refer to Section 12.7.2.8 for this hardware calibration. 

06807C DCN6650