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Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
9-30
9.2.7 Unstable Zero
Common causes are:
1. Leak in pneumatic system. Perform leak check, see Section 8.7.
2. Miscalibration. See Table 7-1.
3. Light leak - check the sensor module with strong light.
4. Sample lines or sample filter dirty - clean or replace.
5. PMT temp control unstable
9.2.8 Inability to Span
If the SPAN button is not illuminated when attempting to span, that means the reading is outside
of the software gain ranges allowed. In an analog instrument it would be the equivalent to the
span pot hitting the rotation stop.
Here are some things to check:
1. Check the expected span concentration values in CAL-CONC-NOX and CAL-CONC-
NO, and compare them to the values of the calibration span gas being input. They should be
nearly equal.
2. Check the NORM_PMT - TEST function. With NO span gas in the instrument, the value
should be 2x the expected span concentration.
3. Check ET and OT to verify instrument detector and signal processing is working
correctly.
4. If the above do not check out, perform the Factory Calibration Procedure Section 9.1.6.
5. If the PMT voltage is near zero with span gas, check fuse and power to ozone generator.