Pmt Cooling System; Figure 6-19. Typical Thermo-Electric Cooler - Teledyne T200 User Manual

PMT C S
OOLING YSTEM
The performance of the analyzer's PMT is significantly affected by temperature. Variations
in PMT temperature are directly reflected in the signal output of the PMT. Also the signal
to noise ratio of the PMT output is radically influenced by temperature as well. The warmer
the PMT is, the noisier its signal becomes until the noise renders the concentration signal
useless.
To alleviate this problem, the instrument uses a special cooling system called a thermo-
electric cooler (TEC), which is a solid-state active heat pump that transfers heat from a heat
absorbing "cool" side to a heat releasing "hot" side via a series of DC powered
semiconductor junctions. The effectiveness of the pump at moving heat away from the cold
side is reliant on the amount of current flowing through the semiconductor junctions and
how well the heat from the hot side can be removed.

Figure 6-19. Typical Thermo-Electric Cooler

In this case, the current flow is controlled by the TEC Control PCA which adjusts the
amount of current applied to the TEC based on the temperature sensed by a thermistor
embedded in the PMT's cold block. The higher the temperature of the PMT, the more
current is pumped through the TEC. The "hot" side of the TEC is cooled by a constant flow
of ambient air that is directed across a set of heat sinks by a fan.
210 Teledyne API T200 NO/NO /NO Analyzer with NumaView™ Software 083730200A DCN7962
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