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Teledyne API Model 200A NO
X
Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
9.2.7 Unstable Zero
Common causes are:
1.
Leak in pneumatic system. Perform leak check, see Section 8.9.
2.
Miscalibration. See Table 7-7-1.
3.
Light leak - check the sensor module with strong light.
4.
If equipped with IZS, zero air scrubber exhausted - replace charcoal and Purafil.
5.
Sample lines or sample filter dirty - clean or replace.
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 PMT - TEST function. With NO span gas in the instrument, the value should
be 2x the expected span concentration in step 1. above for range settings up to 2000 ppb. If
over 2000 ppb, the value should be 0.2x the expected span concentration.
3.
Check ET and OT for a response to 2000 mV on the PMT - TEST function.
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.
9-31
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