Teledyne 9110TH - Nitrogen Oxides Analyzer - Manual (Page 241)

Troubleshooting & Repair Model 9110TH NOx Analyzer
Teledyne Analytical Instruments 221
 Check for disconnected cables to the sensor module.
 Carry out an electrical test with the ELECTRICAL TEST procedure in the
diagnostics menu, see Section 4.13.7.3. If this test produces a concentration
reading, the analyzer’s electronic signal path is correct.
 Carry out an optical test using the OPTIC TEST procedure in the
diagnostics menu, see Section 4.13.7.2. If this test results in a concentration
signal, then the PMT sensor and the electronic signal path are operating
properly. If the 9110TH/M passes both ETEST and OTEST, the instrument
is capable of detecting light and processing the signal to produce a reading.
Therefore, the problem must be in the pneumatics or the ozone generator.
 If NO
2
signal is zero while NO signal is correct, check the NO/NO
X
valve
and the NO
2
converter for proper operation.
7.3.3. UNSTABLE ZERO AND SPAN
Leaks in the 9110TH/M or in the external gas supply and vacuum systems are the most
common source of unstable and non-repeatable concentration readings.
 Check for leaks in the pneumatic systems as described in Section 7.5.
Consider pneumatic components in the gas delivery system outside the
9110TH/M 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.
 Once the instrument passes a leak check, do a flow check (this Section) to
make sure that the instrument is supplied with adequate sample and ozone
air.
 Confirm the sample pressure, sample temperature, and sample flow readings
are correct and steady.
 Verify that the sample filter element is clean and does not need to be
replaced.
7.3.4. INABILITY TO SPAN - NO SPAN BUTTON
In general, the 9110TH/M will not display certain keyboard choices 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 key 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.