TROUBLESHOOTING & REPAIR PROCEDURES
Model 300E Carbon Monoxide Analyzer
Instruction Manual
202
P/N 04288 Rev: A
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Contaminated Zero gas. This can cause either a positive or negative offset
and will indirectly affect the slope. If contaminated with CO it will cause a
positive offset, if contaminated with excess CO
2
or H
2
O a negative offset.
11.3.2.
Non-Repeatable Zero and Span
As stated earlier, leaks both in the M300E 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 9.5. Don’t
forget to consider pneumatic components in the gas delivery system outside
the M300E. Such as:
q
A change in Zero Air source such as ambient air leaking into zero air line,
or;
q
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, do a flow check (see Section 9.4.1)
to make sure adequate 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 (See Section 3.1.2 and 5.5)
11.3.3.
Inability to Span – No SPAN Key
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 9.5.