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Troubleshooting and Service Teledyne API T801 NDIR CO2 Analyzer Operation Manual
190
upstream of the flow sensor. First, check the sample filter and make sure it is not
plugged and then systematically check all the other components upstream of the
orifice to ensure that they are not obstructed.
If the sample pressure is reading normal but the sample flow is reading low, then
it is likely that the pump diaphragm is worn or there is an obstruction downstream
of the flow sensor.
11.3.2.5. ACTUAL FLOW DOES NOT MATCH DISPLAYED FLOW
If the actual flow measured does not match the displayed flow, but is within the
limits of 110-130 cm
3
/min, adjust the calibration of the flow measurement as
described in Section 10.3.4.
11.3.2.6. SAMPLE PUMP
The sam
ple pump should start immediately after the front panel power switch is
turned ON. With the SAMPLE inlet plugged the test function PRES should read
about 10”-Hg for a pump in good condition. Readings above 10” Hg indicate that
the pump needs rebuilding. If the test function SAMP FL is greater than 10
cm
3
/min there is a leak in the pneumatic lines.
11.4. CALIBRATION PROBLEMS
11.4.1. MISCALIBRATED
There are several symptoms that can be caused by the analyzer being
miscalibrated. Miscalibration is indicated by out-of-range Slopes and Offsets as
displayed through the test functions and is frequently caused by the following:
Bad span gas: This can cause a large error in the slope and a small error in
the offset. Delivered from the factory, the T801’s slope is within ±15% of
nominal. Bad span gas will cause the analyzer to be calibrated to the wrong
value. If in doubt have the span gas checked by and independent lab.
Contaminated zero gas: Excess H2O can cause a positive or negative offset
and will indirectly affect the slope.
Dilution calibrator not set up correctly or is malfunctioning: This will also
cause the slope, but not the zero, to be incorrect. Again the analyzer is being
calibrated to the wrong value.
Too many analyzers on the manifold: This can cause either a slope or offset
error because ambient gas with its pollutants will dilute the zero or span gas.
11.4.2. NON-REPEATABLE ZERO AND SPAN
As stated earlier, leaks both in the T801 and in the external system are a common
source of unstable and non-repeatable readings.
07274B DCN6418