116 Maintenance and Service 083730300A DCN8101
Table 5-5. Dashboard Functions - Indicated Failures
TEST
FUNCTIONS
(AS DISPLAYED)
INDICATED FAILURE(S)
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.
Indicates noise level of instrument or CO concentration of sample gas (see Section 5.7.13 for causes).
CO MEAS
&
CO REF
If the value displayed is too high the IR Source has become brighter. Adjust the variable gain potentiometer on
the sync/demod board (see Section 5.7.14.7).
If the value displayed is too low or constantly changing and the CO REF is OK:
• Failed multiplexer on the motherboard
• Failed sync/demod board
• Loose connector or wiring on sync/demod board
• If the value displayed is too low or constantly changing and the CO REF is bad:
• GFC Wheel stopped or rotation is too slow
• Failed sync/demod board IR source
• Failed IR source
• Failed relay board
• Failed I
2
C bus
• Failed IR photo-detector
MR Ratio
When the analyzer is sampling zero air and the ratio is too low:
• The reference cell of the GFC Wheel is contaminated or leaking.
• The alignment between the GFC Wheel and the segment sensor, the M/R sensor or both is incorrect.
• Failed sync/demod board
When the analyzer is sampling zero air and the ratio is too high:
• Zero air is contaminated
• Failed IR photo-detector
See Table 5-4 for SAMPLE PRES WARN.
Check for gas flow problems (see Section 5.7.9).
SAMP TEMP
SAMPLE TEMP should be close to BENCH TEMP. Temperatures outside of the specified range or oscillating
temperatures are cause for concern.
TEMP
Bench temp control improves instrument noise, stability and drift. Temperatures outside of the specified range
or oscillating temperatures are cause for concern. Table 5-4 for BENCH TEMP WARNING.
WHEEL
Wheel temp control improves instrument noise, stability and drift. Outside of set point or oscillating
temperatures are causes for concern. See Table 5-4 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 5-4 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 photodetector, its associated mounting hardware and the
absorption cell 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.
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