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Teledyne API Model 200A NO
X
Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
9.2.10 Non-Linear Response
Common causes are:
1.
Leak in pneumatic system, see Section 8.9.
2.
High zero background - the PMT TEST function should be near 50 mV with zero gas.
Readings above 100 mV indicate a light leak, contaminated reaction cell, bad zero gas, or
wet air coming into the ozone generator. If the reading is not less than 150 mV, the
instrument will not zero or span properly. Check Section 9.2.9.
3.
Calibration device in error - re-check flowrates and concentrations. Especially at low
concentrations. If you are using a Mass Flow calibrator and the flow is < 10% of the full
scale flow on either flowmeter you may need to purchase lower concentration standards.
4.
The standard gasses may be mis-labeled as to type or concentration. Labeled
concentrations may be outside the certified tolerance.
5.
Contamination in sample delivery system:
A.
Dirt in sample lines or reaction cell
B.
Contaminated cal gas source (NO
2
in NO cal gas is common)
C.
Dilution air contains sample or span gas
6.
Ozone concentration too low:
A.
Wet air in generator - need to disassemble, clean, dry
B.
Electrical short circuit
C.
Transformer partial failure
7.
Sample inlet vent line too short - should be at least 15".
8.
Sample exhaust not properly vented, creating a backpressure at the sample inlet port of
the instrument. See Table 2-2-3 for venting recommendations.
9-33
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