Teledyne 6200E - Sulfides Analyzer - Manual (Page 222)

Theory Of Operation Model 6200E Instruction Manual
222 M6200E Rev: A1
10.4.4. Photo Multiplier Tube (PMT)
The M6200E uses a photo multiplier tube (PMT) to detect the amount of fluorescence created by
the H
2
S and O
3
reaction in the sample chamber.
PMT Input
Signal
Connector
Optical Test
LED
PMT
High Voltage
Power Supply
Insulator
Cold Block
PMT Temperature
Sensor
Heat Sink
PMT Output
Signal
Connector
TEC located
between Cold Block
and Heat Sink
Light from Reaction
Chamber shines
through hole in side
of Cold Block
Figure 10-13: PMT 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 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.