Teledyne 9110EH - Nitrogen Oxides Analyzer - Manual (Page 234)

Troubleshooting & Repair Model 9110EH Instruction Manual
The semi-permeable PTFE membrane of the permeation tube is severely affected by
humidity. Variations in humidity between day and night are usually enough to yield very
variable output results. If the instrument is installed in an air-conditioned shelter, the air is
usually dry enough to produce good results. If the instrument is installed in an environment
with variable or high humidity, variations in the permeation tube output will be significant.
In this case, a dryer for the supply air is recommended (dew point should be –20° C or
less).
The IZS option is heated with a proportional heater circuit and the temperature is
maintained at 50° C ±1° . Check the front panel display or the IZS_TEMP signal voltage
using the SIGNAL I/O function under the DIAG Menu (Section 11.1.3). At 50° C, the
temperature signal from the IZS thermistor should be around 2500 mV.
11.5.19. Box Temperature
The box temperature sensor (thermistor) is mounted on the motherboard below the bottom
edge of the CPU board when looking at it from the front. It cannot be disconnected to check
its resistance. Box temperature will vary with, but will usually read about 5° C higher than,
ambient (room) temperature because of the internal heating zones from the NO
2
converter,
reaction cell and other devices.
• To check the box temperature functionality, we recommend to check the
BOX_TEMP signal voltage using the SIGNAL I/O function under the DIAG Menu
(Section 11.1.3). At about 30° C, the signal should be around 1500 mV.
• We recommend to use a certified or calibrated external thermometer / temperature
sensor to verify the accuracy of the box temperature by placing it inside the chassis,
next to the thermistor labeled XT1 (above connector J108) on the motherboard.
11.5.20. PMT Temperature
PMT temperature should be low and constant. It is more important that this temperature is
maintained constant than it is to maintain it low. The PMT cooler uses a Peltier, thermo-
electric cooler element supplied with 12 V DC power from the switching power supply PS2.
The temperature is controlled by a proportional temperature controller located on the
preamplifier board. Voltages applied to the cooler element vary from 0.1 to 12 VDC. The
temperature set point (hard-wired into the preamplifier board) will vary by ±1°C due to
component tolerances. The actual temperature will be maintained to within 0.1° C around
that set point. On power-up of the analyzer, the front panel enables the user to watch that
temperature drop from about ambient temperature down to its set point of 6-8° C. If the
temperature fails to adjust after 30 minutes, there is a problem in the cooler circuit. If the
control circuit on the preamplifier board is faulty, a temperature of –1° C is reported.
11.6. Repair Procedures
This section contains some procedures that may need to be performed when a major
component of the analyzer requires repair or replacement. Note that maintenance
procedures (e.g., replacement of regularly changed expendables) are discussed in
Chapter 9 (Maintenance) are not listed here. Also note that Teledyne-API customer service
may have a more detailed service note for some of the below procedures. Contact customer
service.
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