Teledyne T101 Operation Manual page 272

Principles Of Operation
Optical Test Control
From CPU
Optical Test LED
To
Motherboard
Electrical Test Control
From CPU
PMT Temp Analog Signal
to Motherboard
PMT Temp
Sensor
TEC Control
PCA
268
be adjusted through a potentiometer. These adjustments should only be performed when
encountering problems with the software calibration that cannot be rectified otherwise.
See Section 9.6.4 for this hardware calibration.
PMT Coarse
Gain Set
(Rotary
Switch)
PMT HVPS
Converter
Drive Voltage
Amp to
PMT Output
Voltage
Converter/
Amplifier
Electrical Test
Temperature
Feedback
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 4.6.5 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. See
Section 4.6.4 for instructions on performing this test.
PMT Preamp PCA
Optical Test
Generator
PMT Fine
Gain Set
(Rotary
Switch)
D-A
MUX
Generator
PMT
Circuit
PMT Output Signal
(PMT) to Motherboard
Teledyne ML - T101 Operation Manual
Low Pass
Noise
Filter
PMT
Signal
Offset