Teledyne 6200T - Sulfides Analyzer - Manual (Page 308)

Principles of Operation Model 6200T Total Sulfur Analyzer
308 Teledyne Analytical Instruments
13.5.3. Photo Multiplier Tube (PMT)
The 6200T uses a photo multiplier tube (PMT) to detect the amount of fluorescence
created by the SO
2
and O
3
reaction in the sample chamber.
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 13-17: PMT Housing Assembly
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 is
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.