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Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
4-3
4.2 Operation Summary
4.2.1 Sensor Module, Reaction Cell, Detector
The sensor module (Figure 9-9) is where light from the chemilumenescent reaction is generated
and detected. It is the most complicated and critical sub-assembly in the entire analyzer. It
consists of the following assemblies and functions:
1. The reaction cell and flow control module
2. Reaction cell heater/thermistor
3. PMT and high voltage power supply
4. PMT cooler/cold block/heatsink/fan
5. Preamp assembly:
A. Preamp range control hardware
B. HVPS control
C. PMT cooler temp control
D. Electric test electronics
E. Optic test electronics
4.2.2 Pneumatic Sensor Board
The sensor board consists of 2 pressure sensors and a flow sensor. One pressure sensor measures
the pressure in the reaction cell. The reaction cell is maintained at about 0.1 atmospheric
pressure. The second pressure sensor measures the pressure just upstream of the reaction cell,
which is near ambient pressure. From these two pressures the sample flow rate can be computed
and is displayed as sample flow in the TEST menu. Finally, a solid state flow meter measures the
ozone flow using a resistive bridge. Likewise, it is displayed as a TEST function.
The M200AU displays all pressures in inches of mercury-absolute (in-Hg-A). Absolute pressure
is the reading referenced to a vacuum or zero absolute pressure. This method was chosen so that
ambiguities of pressure relative to ambient pressure can be avoided.