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Model 9110T NOx Analyzer Troubleshooting & Service
Teledyne Analytical Instruments 278
1. Check for leaks in the pneumatic systems as described in Section 11.3.12.
2. Consider pneumatic components in the gas delivery system outside the
9110T such as a change in zero air source (ambient air leaking into zero air
line or a worn-out zero air scrubber) or a change in the span gas
concentration due to zero air or ambient air leaking into the span gas line.
3. Once the instrument passes a leak check, do a flow check (this chapter) to
ensure that the instrument is supplied with adequate sample and ozone air.
4. Confirm the sample pressure, sample temperature, and sample flow readings
are correct and steady.
5. Verify that the sample filter element is clean and does not need to be
replaced.
12.5.4. INABILITY TO SPAN - NO SPAN BUTTON (CALS)
In general, the 9110T will not display certain buttons whenever the actual value of a parameter is outside
of the expected range for that parameter. If the calibration menu does not show a SPAN button when
carrying out a span calibration, the actual concentration must be outside of the range of the expected
span gas concentration, which can have several reasons.
1. Verify that the expected concentration is set properly to the actual span gas
concentration in the CONC sub-menu.
2. Confirm that the NO
x
span gas source is accurate.
This can be done by comparing the source with another calibrated analyzer, or
by having the NO
x
source verified by an independent traceable photometer.
3. Check for leaks in the pneumatic systems as described in Section 11.3.12.
Leaks can dilute the span gas and, hence, the concentration that the analyzer
measures may fall short of the expected concentration defined in the CONC
sub-menu.
4. If the low-level, hardware calibration has drifted (changed PMT response) or
was accidentally altered by the user, a low-level calibration may be
necessary to get the analyzer back into its proper range of expected values.
One possible indicator of this scenario is a slope or offset value that is outside
of its allowed range (0.7-1.3 for slope, -20 to 150 for offsets). See Section
12.8.4 on how to carry out a low-level hardware calibration.
12.5.5. INABILITY TO ZERO - NO ZERO BUTTON (CALZ)
In general, the 9110T will not display certain buttons whenever the actual value of a parameter is outside
of the expected range for that parameter. If the calibration menu does not show a ZERO button when
carrying out a zero calibration, the actual gas concentration must be significantly different from the
actual zero point (as per last calibration), which may be for any of several reasons.
1. Confirm that there is a good source of zero air. If the IZS option is installed,
compare the zero reading from the IZS zero air source to a zero air source