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Teledyne API Model 200A NO
X
Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
9.2.6 Unstable Span
Common causes are:
1.
Leak in pneumatic system.
2.
Light leak - check the sensor module with strong light.
3.
Instrument not fully warmed up.
4.
Sample lines or sample filter dirty - clean or replace.
5.
Plugged sample inlet orifice - clean with methanol and sonic cleaner.
6.
Defective HVPS - see HVPS test procedure.
7.
Bad or defective PMT detector - replace.
8.
Reaction cell temp not stable - observe warning messages, or RCELL TEMP in TEST
functions. Check diagnostic LED in Power Supply Module for normal cycling.
9.
Large variations in ambient temperature - observe warning messages, or BOX TEMP in
TEST functions.
10.
Large variations in line voltage. - Line voltage should remain within +-10% of nominal.
11.
Pump not maintaining steady vacuum - observe warning messages, or RCEL in TEST
functions.
12.
Sample vent line too short, allowing room air to mix with span gas. Line should be a
minimum of 15" long.
13.
Calibration gas source unstable - if equipped with IZS option, permeation tube could be
nearing exhaustion or IZS oven temperature is unstable, check warning messages, or observe
IZS TEMP in TEST function.
14.
IZS permeation tube unstable -
A.
IZS subsystem leaking - leak check
B.
IZS zero air scrubber exhausted - replace charcoal and Purafil
C.
Moly converter efficiency unstable - check converter efficiency or replace
D.
IZS oven temperature unstable - verify stable temperature
E.
Permeation tube installed upside down or wrong side, see Table 6-6-6 for correct
installation.
F.
Variations in humidity. The permeation tube changes output depending on the humidity
of the dilution air. Room air is drawn into the zero air scrubber. If the room air has high
humidity or if the humidity varies, the output of the permeation tube will be unstable.
9-30
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