Unstable Span - Teledyne 6400A Instruction Manual

Sulfur dioxide analyzer
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TAI Model 6400A SO

9.2.6 Unstable Span

Common causes are:
1. Leak in pneumatic system.
2. Unstable UV lamp output - replace lamp.
3. Sample lines or sample filter dirty - clean or replace.
4. Plugged sample inlet orifice - clean with methanol and sonic cleaner.
5. Defective HVPS - use optic test and electric test to isolate the HVPS. See also Section 9.3.10
HVPS test procedure.
6. Bad or defective PMT detector - check Optic test.
7. Reaction cell temperature not stable - observe warning messages, or RCELL TEMP in TEST
functions. Check diagnostic LED in Power Supply Module for normal cycling.
8. PMT temperature not stable - observe warning messages, or PMT TEMP in TEST functions.
9. Sample vent line too short, allowing room air to mix with span gas - line should be a
minimum of 15" long.
10. 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.
11. IZS permeation tube unstable.
A. IZS subsystem leaking - leak check
B. IZS zero air scrubber exhausted - replace charcoal
C. IZS oven temperature unstable - verify stable temperature
D. Permeation tube installed upside down or wrong side, see Figure 6-1 for correct
installation.
Analyzer Operator Manual, 02164, Rev. G
2
9-26

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