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Teledyne API Model 200A NO
X
Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
9.3.8.4 PMT Cooler
The PMT cooler uses a Peltier cooler supplied with DC current from the switching power supply
in the Power Supply Module. An overall view is shown in Table 9-9-20. The temperature is
controlled by a proportional temperature controller located on the Pream
p board. Voltages
applied to the cooler element vary from 0.1 to 12 VDC. The input voltage from the supply is
15 VDC. The actual 7
C setpoint will vary ± 1 C due to component tolerances. The
temperature will be maintained within 0.1
C about the setpoint. The maximum temperature the
control circuit is able to report is 15
C. The M200A reports this temperature when the unit
initially powered on. If the temperature fails to drop after 30 minutes, there is a problem in the
cooler circuit. If the control circuit on the Preamp card is faulty a temperature of -1
C is
reported.
9.3.8.5 High Voltage P.S.
The HVPS is located in the interior of the Sensor Module, and is plugged into the PMT tube. It
requires 2 voltage inputs. The first is +15 which powers the supply. The second is the
programming voltage which is generated on the Preamp Board. This power supply is unlike a
traditional PMT HVPS. It is like having 10 independent power supplies, one to each pin of the
PMT. The test procedure below allows you to test each supply.
Adjustment of the HVPS is covered in the Factory Calibration Procedure in Section 9.1.6. To
troubleshoot the HVPS:
1.
Turn off the instrument.
2.
Remove the cover and disconnect the 2 connectors at the front of the NO
x
Sensor
Module.
3.
Remove the end cap from the sensor.
4.
Remove the HVPS/PMT assembly from the cold block inside the sensor. Un-plug the
PMT tube.
5.
Re-connect the 7 pin connector to the Sensor end cap, and power-up the instrument.
6.
Use Table 9-9-23 to check the voltages at each pin of the supply, and the overall voltage.
7.
Turn off the instrument power, and re-connect the PMT tube, then re-assemble the
sensor.
If any faults are found in the test, you must obtain a new HVPS as there are no user servicable
parts inside the supply.
9-64
PRINTED DOCUMENTS ARE UNCONTROLLED