Inability To Zero; Non-Linear Response - Teledyne 6400A Instruction Manual

Sulfur dioxide analyzer
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TAI Model 6400A SO

9.2.9 Inability to Zero

If the ZERO button is not illuminated when attempting to zero, that means the reading is
outside of the software gain ranges allowed. In an analog instrument it would be the equivalent
to the zero pot hitting the maximum.
Here are some things to check:
Select the PMT - TEST function. With zero gas going into the instrument, the value should be less than
250 mV, typically 80 - 160 mV. If you are getting a high reading, the probable reasons are:
A. Leak that admits gas containing SO
B. Contaminated reaction cell. Remove and clean cell.
C. Light leak.
D. Zero gas that isn't really zero. Make sure you're not trying to zero the machine with
ambient air or span gas.
E. Bad UV filter.

9.2.10 Non-Linear Response

Common causes are:
1. Leak in pneumatic system.
2. Calibration device in error - re-check flowrate and concentrations, especially at low
concentrations.
3. Contamination in sample delivery system:
A. Dirt in sample lines or reaction cell.
B. Dilution air contains sample or span gas.
C. Dirty particulate filter.
4. Sample inlet vent line too short - should be at least 15".
5. Back pressure on sample inlet.
Analyzer Operator Manual, 02164, Rev. G
2
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9-28

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