Teledyne 9110T - Nitrogen Oxides Analyzer - Manual (Page 352)

Model 9110T NOx Analyzer Principles of Operation
Teledyne Analytical Instruments 352
PMT Housing End Plate
This is the entry to the PMT Exchange
PMT Preamp PCA
High voltage Power Supply
(HVPS)
PMT
PMT Cold Block
Connector to PMT
Pre Amp PCA
12V Power
Connector
Cooling Fan
Housing
TEC Driver PCA
PMT Heat Exchange Fins
Light from Reaction
Chamber shines
through hole in side
of Cold Block
Insulation Gasket
PMT Power Supply
& Aux. Signal
Connector
PMT Output
Connector
Thermo-Electric Cooler
(TEC)
PMT Temperature
Sensor
O-Test LED
Figure 13-20: 9110T Sensor Module Assembly
13.5. PHOTO MULTIPLIER TUBE (PMT)
The 9110T uses a photo multiplier tube (PMT) to detect the amount of chemiluminescence created in the
Reaction Cell.
A typical PMT is a vacuum tube containing a variety of specially designed electrodes. Photons from the
reaction are filtered by an optical high-pass filter, enter the PMT and strike a negatively charged photo
cathode causing it to emit electrons. A high voltage potential across these focusing electrodes directs the
electrons toward an array of high voltage dynodes.
The dynodes in this electron multiplier array are designed so that each stage multiplies the number of
emitted electrons by emitting multiple, new electrons. The greatly increased number of electrons
emitted from one end of electron multiplier are collected by a positively charged anode at the other end,
which creates a useable current signal. This current signal is amplified by the preamplifier board and
then reported to the motherboard.