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Model 9110T NOx Analyzer Troubleshooting & Service
Teledyne Analytical Instruments 281
The converter efficiency parameter has been set to a value not equal to 1.000 even though the
conversion efficiency is 1.0.
The actual conversion efficiency needs to match the parameter set in the CAL menu.
See Section 9.1.4 for more information on this feature.
An instrument calibration with the IZS option (and expected concentrations set to the same amount) will
always yield identical slopes for NO and NO
X
, as the instrument measures only NO
X
and assumes NO to
be the same (with NO
2
being zero).
12.6. OTHER PERFORMANCE PROBLEMS
Dynamic problems (i.e. problems that only manifest themselves when the analyzer is monitoring sample
gas) can be the most difficult and time consuming to isolate and resolve. The following section provides
an itemized list of the most common dynamic problems with recommended troubleshooting checks and
corrective actions.
12.6.1. EXCESSIVE NOISE
Excessive noise levels under normal operation usually indicate leaks in the sample supply or the analyzer
itself. Ensure that the sample or span gas supply is leak-free and carry out a detailed leak check as
described earlier in this chapter.
Another possibility of excessive signal noise may be the preamplifier board, the high voltage power
supply and/or the PMT detector itself.
Contact the factory on troubleshooting these components.
12.6.2. SLOW RESPONSE
If the analyzer starts responding too slow to any changes in sample, zero or span gas, check for the
following:
Dirty or plugged sample filter or sample lines.
Sample inlet line is too long.
Leaking NO/NO
X
valve. Carry out a leak check.
Dirty or plugged critical flow orifices. Check flows, pressures and, if necessary, change orifices
(Section 11.3.10).
Wrong materials in contact with sample - use glass, stainless steel or Teflon materials only. Porous
materials, in particular, will cause memory effects and slow changes in response.
Dirty reaction cell. Clean the reaction cell.
Insufficient time allowed for purging of lines upstream of the analyzer. Wait until stability is low.
Insufficient time allowed for NO or NO
2
calibration gas source to become stable. Wait until stability
is low.
NO
2
converter temperature is too low. Check for proper temperature.