Teledyne 200AH 用户手册

 

Figure 9-9 and Figure 9-10 show the assembly of the NO

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. 

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. 

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.