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Troubleshooting and Service Teledyne API – Model T300/T300M CO Analyzer
274
4. 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.
12.3.2. NON-REPEATABLE ZERO AND SPAN
As stated earlier, leaks both in the T300/T300M and in the external system are a
common source of unstable and non-repeatable readings.
1. Check for leaks in the pneumatic systems as described in Section 11.3.3. Don’t
forget to consider pneumatic components in the gas delivery system outside the
T300/T300M such as:
A change in zero air source such as ambient air leaking into zero air line, or;
A change in the span gas concentration due to zero air or ambient air leaking
into the span gas line.
2. Once the instrument passes a leak check, perform a flow check (see Section 11.3.4)
to make
sure adeq
uate sample is being delivered to the sensor assembly.
3. A failing IR photo-detector may be at fault. Check the CO MEAS and CO REF test
functions via the front panel display to make sure the signal levels are in the normal
range (See Appendix A) and are quiet.
4. Confirm the sample pressure, wheel temperature, bench temperature, and sample
flow readings are correct and have steady readings.
5. Disconnect the exhaust line from the optical bench near the rear of the instrument
and plug this line into the SAMPLE inlet creating a pneumatic loop. The CO
concentration (either zero or span) now must be constant. If readings become quiet,
the problem is in the external pneumatics supplies for sample gas, span gas or zero
air.
6. If pressurized span gas is being used with a zero/span valve option, make sure that
the venting is adequate.
12.3.3. INABILITY TO SPAN – NO SPAN BUTTON (CALS)
1. Confirm that the carbon monoxide span gas source is accurate; this can be done by
switching between two span-gas tanks. If the CO concentration is different, there is
a problem with one of the tanks.
2. Check for leaks in the pneumatic systems as described in Section 11.3.3.
3.
Make
sure that the expected span gas concentration entered into the instrument
during calibration is the correct span gas concentration and not too different from
expected span value. This can be viewed via the CONC submenu of the Sample
Displays.
4. Check to make sure that there is no ambient air or zero air leaking into span gas
line.
12.3.4. INABILITY TO ZERO – NO ZERO BUTTON (CALZ)
1. Confirm that there is a good source of zero air. Dilute a tank of span gas with the
same amount of zero air from two different sources. If the CO Concentration of the
two measurements is different, there is a problem with one of the sources of zero
air.
2. Check for leaks in the pneumatic systems as described in 11.3.3.
3.
If the analyze
r has had zero/span valve options, the CO scrubber may need
maintenance.
4. Check to make sure that there is no ambient air leaking into zero air line.
06864B DCN6314