Teledyne API Model 200AU NOX Analyzer Instruction Manual, 02293, Rev. F
9-29
6. Broken PMT temperature control circuit or broken PMT cooler power supply. Check
PMT TEMP - TEST function.
7. Mis-calibration. Check NO/NOx SLOPES in TEST function.
8. Reaction cell pressure too high – leak on vacuum side or bad sample pump. Check RCEL
- TEST function.
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.