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Model 9110T NOx Analyzer Troubleshooting & Service
Teledyne Analytical Instruments 266
12.1.2. FAULT DIAGNOSIS WITH TEST FUNCTIONS
In addition to being useful as predictive diagnostic tools, the test functions viewable from the analyzers
front panel can be used to isolate and identify many operational problems when combined with a
thorough understanding of the analyzer’s principles of operation (see Section 13).
The acceptable ranges for these test functions are listed in the “Nominal Range” column of the analyzer
Final Test and Validation Data Sheet (P/N 04490) shipped with the instrument. Values outside these
acceptable ranges indicate a failure of one or more of the analyzer’s subsystems. Functions whose
values are still within acceptable ranges but have significantly changed from the measurement recorded
on the factory data sheet may also indicate a failure.
A worksheet has been provided in Appendix C to assist in recording the value of these test functions.
Note A value of “XXXX” displayed for any of these TEST functions indicates an
OUT OF RANGE reading.
Note Sample Pressure measurements are represented in terms of ABSOLUTE
pressure because this is the least ambiguous method reporting gas
pressure.
Absolute atmospheric pressure is about 29.92 in-Hg-A at sea level. It
decreases about 1 in-Hg per 1000 ft gain in altitude. A variety of factors
such as air conditioning systems, passing storms, and air temperature,
can also cause changes in the absolute atmospheric pressure.
Table 12-2: Test Functions - Indicated Failures
TEST FUNCTION INDICATED FAILURE(S)
NOX STB
Unstable concentrations; leaks
SAMP FlW
Leaks; clogged critical flow orifice
OZONE FL
Leaks; clogged critical flow orifice
PMT
Calibration off; HVPS problem; no flow (leaks)
NORM PMT
Auto Zero too high
AZERO
Leaks; malfunctioning NO, NO
x
or Auto Zero valve; O
3
air filter cartridge exhausted
HVPS
Calibration off; preamp board circuit problems
RCELL TEMP
Malfunctioning heater; relay board communication (I
2
C bus); relay burnt out
BOX TEMP
Environment out of temperature operating range; broken thermistor
PMT TEMP
TEC cooling circuit broken; relay board communication (I
2
C bus); 12 V power supply
IZS TEMP (option)
Malfunctioning heater; relay board communication (I
2
C bus); relay burnt out
MOLY TEMP
Malfunctioning heater; disconnected or broken thermocouple; relay board communication
(I
2
C bus); relay burnt out; incorrect AC voltage configuration
RCEL (pressure)
Leak; malfunctioning valve; malfunctioning pump; clogged flow orifices
SAMP (pressure)
Leak; malfunctioning valve; malfunctioning pump; clogged flow orifices; sample inlet
overpressure
NOX SLOPE HVPS out of range; low-level (hardware) calibration needs adjustment; span gas