Teledyne 100E, Instruction Manual, Page: 185 / 258

Model 100E Instruction Manual Theory Of Operation
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To
Motherboard
PMT Preamp PCA
Low Pass
Noise
Filter
E Test Control
From CPU
MUX
Amp to
Voltage
Converter/
Amplifier
D-A
Converter
PMT Coarse
Gain Set
(Rotary
Switch)
PMT Fine
Gain Set
(Rotary
Switch)
PMT
Signal
Offset
E-Test
Generator
O-Test
Generator
O Test Control
From CPU
PMT Temp
Sensor
PMT
Temperature
Feedback
Circuit
TEC Control
PCA
PMT Output
PMT HVPS
Drive Voltage
PMT Temp Analog Signal
to Motherboard
PMT Output Signal
( PMT ) to Motherboard
O Test
LED
Figure 10-16: PMT Preamp Block Diagram
The PMT temperature control loop maintains the PMT temperature around 7° C and can
be viewed as test function
PMT TEMP on the front panel.
The electrical test ( ETEST ) circuit generates a constant, electronic signal intended to
simulate the output of the PMT (after conversion from current to voltage). By bypassing
the detector’s actual signal, it is possible to test most of the signal handling and
conditioning circuitry on the PMT preamplifier board. See section 6.7.6 for instructions on
performing this test.
The optical test ( OTEST ) feature causes an LED inside the PMT cold block to create a
light signal that can be measured with the PMT. If zero air is supplied to the analyzer, the
entire measurement capability of the sensor module can be tested including the PMT and
the current to voltage conversion circuit on the PMT preamplifier board.
10.4.7.
Pneumatic Sensor Board
The flow and pressure sensors of the M100E are located on a printed circuit assembly
just behind the PMT sensor. Refer to Section 11.5.15 on how to test this assembly. The