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Model 9110T NOx Analyzer Troubleshooting & Service
Teledyne Analytical Instruments 300
12.7.12. PHOTOMULTIPLIER TUBE (PMT) SENSOR MODULE
The PMT detects the light emitted by the reaction of NO with ozone. It has a gain of about 500000 to
1000000. It is not possible to test the detector outside of the instrument in the field. The basic method to
diagnose a PMT fault is to eliminate the other components using ETEST, OTEST and specific tests for
other sub-assemblies.
12.7.12.1. Optic Test
The optic test function tests the response of the PMT sensor by turning on an LED located in the cooling
block of the PMT (see Figure 13-20). The analyzer uses the light emitted from the LED to test its photo-
electronic subsystem, including the PMT and the current to voltage converter on the pre-amplifier board.
To ensure that the analyzer measures only the light coming from the LED, the analyzer should be
supplied with zero air.
The optic test should produce a PMT signal of about 2000±1000 mV.
To activate the optics test, press:
Note
This is a coarse test for functionality and not an accurate calibration tool.
The resulting PMT signal can vary significantly over time and also
changes with low-level calibration.