Teledyne 9110AH, Instruction Manual, Page: 174 / 181

TELEDYNE Model 9110AH NO
X
Analyzer Operator Manual, 01620, Rev. F
9-58
9.3.8 NO
x
Sensor Module
Figure 9-9 and Figure 9-10 show the assembly of the NO
x
sensor module.
9.3.8.1 PMT
The PMT detects the light emitted by the reaction of NO with ozone. It has a gain of about
500,000 to 1,000,000. Because of its high sensitivity to light, it is not possible to test the detector
outside of the instrument in the field. The best way to determine if the PMT is working is by
using Optic test. OT operation is described in Section 9.1.3.3.
The basic method to diagnose a PMT fault is to eliminate the other components using ET, OT
and specific tests for other sub-assemblies.
9.3.8.2 Reaction Cell Temperature
The reaction cell temperature is controlled by the CPU. It operates by reading a thermistor
amplifier on the Status/Temp board. The CPU controls the temperature by toggling a bit on the
V/F board. The V/F board TTL logic controls a solid state switch on the Switch Board in the
PSM. The switched 115 VAC comes out of the PSM to a connector near the underside of the
reaction cell. A warning message may be present during initial warm-up due to the temperature
being below the 50 C setpoint.
9.3.8.3 Preamp Board
The NO
x
Preamp Board is a multifunction board providing circuitry to support the following
functions.
1. Preamp, buffer amplifier, physical range control hardware for the PMT detector.
2. Precision voltage reference and voltage generation, and control for the PMT - HVPS inside
the sensor module.
3. Constant current generator and adjustment for the Optic Test LED.
4. Voltage generation and adjustment for Electric Test.
5. Thermistor amplifier, control signal generation for the PMT cooler.
The setup and adjustment of items 1-4 above is covered in the Factory Calibration procedure in
Section 9.1.6. Item 5 has no adjustable features.