Teledyne GFC-7000T - Trace CO2 Analyzer - manual - Manual (Page 240)

Troubleshooting Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 222
Table 10-2: Test Functions - Indicated Failures
TEST
FUNCTIONS
INDICATED FAILURE(S)
TIME
Time of day clock is too fast or slow: To adjust See Section 6.6.
Battery in clock chip on CPU board may be dead.
RANGE
Incorrectly configured measurement range(s) could cause response problems with a Data logger or chart
recorder attached to one of the analog output.
If the Range selected is too small, the recording device will over range.
If the Range is too big, the device will show minimal or no apparent change in readings.
STABIL
Indicates noise level of instrument or CO
2
concentration of sample gas (See Section 10.4.2 for causes).
CO2 MEAS
&
CO2 REF
If the value displayed is too high the IR Source has become brighter. Adjust the variable gain
potentiometer on the sync/demod board
If the value displayed is too low or constantly changing and the CO
2
REF is OK:
o
Failed multiplexer on the mother board
o
Failed sync/demod board
o
Loose connector or wiring on sync/demod board
Flow of purge gas to the GFC wheel housing may have stopped
If the value displayed is too low or constantly changing and the CO
2
REF is BAD:
o
GFC wheel stopped or rotation is too slow
o Failed sync/demod board IR source
o
Failed IR source
o
Failed relay board
o
Failed I 2 C bus
o
Failed IR photo-detector
MR RATIO
When the analyzer is sampling zero air and the ratio is too low:
o
The reference cell of the GFC wheel is contaminated or leaking.
o
The alignment between the GFC wheel and the segment sensor, the M/R sensor or both is
incorrect.
o
Failed sync/demod board
o
Flow of purge gas to the GFC wheel housing may have stopped
When the analyzer is sampling zero air and the ratio is too high:
o Zero air is contaminated
o
Failed IR photo-detector
PRES
See Table 11-1 for SAMPLE PRES WARN
SAMPLE FL
Check for gas flow problems. see Section 11.1.6
SAMPLE
TEMP
SAMPLE TEMP should be close to BENCH TEMP. Temperatures outside of the specified range or
oscillating temperatures are cause for concern
BENCH TEMP
Bench temp control improves instrument noise, stability and drift. Temperatures outside of the specified
range or oscillating temperatures are cause for concern. See Table 11-1 for BENCH TEMP WARNING
WHEEL TEMP
Wheel temp control improves instrument noise, stability and drift. Outside of set point or oscillating
temperatures are cause for concern. See Table 11-1 for WHEEL TEMP WARNING
BOX TEMP
If the box temperature is out of range, check fan in the power supply module. Areas to the side and rear
of instrument should allow adequate ventilation. See Table 11-1 for BOX TEMP WARNING.
PHT DRIVE
If this drive voltage is out of range it may indicate one of several problems:
- A poor mechanical connection between the various components in inside the detector housing
- An electronic failure of the IR Photo-Detector’s built-in cooling circuitry, or;
- A temperature problem inside the analyzer chassis. In this case other temperature warnings would also
be active such as BENCH TEMP WARNING or BOX TEMP WARNING.