6-12 | Thermox TM2000 Oxygen Analyzer
Remote Calibration Unit (RCU) problem
Problems with the RCU are usually as follows:
Vacuum check
Plumbing leaks
Solenoids not energizing
Vacuum Check
Perform a vacuum check as follows:
1. Connect a digital volt meter across the connections labeled 1 and 2 on
the sensor board. Observe polarity (pin 1 - positive, pin 2 - negative).
2. Connect the lowest calibration gas value that you will encounter dur-
ing daily operations to the sample gas inlet of the analyzer. Allow gas
to stabilize then measure the cell millivolt signal.
3. Connect the vacuum port side of the pressure gauge (for example, a
Magnehelic gauge) to the T-fitting.
4. Connect the sample gas outlet to the T-fitting.
5. Connect an aspirator to the T-fitting.
6. Connect the air supply to the aspirator.
7. Adjust sample gas and air supply flow valves until the flow rate is 150
ml/min and the pressure gauge is slightly greater that 25” H
2
O pres-
sure.
8. Measure the cell millivolt signal with the digital volt meter. If the cell
millivolt signal stays the same or increases, the analyzer has passed
the vacuum test. If the cell millivolt signal decreases, troubleshoot
to find the leak, then repeat Steps 1 through 7. Possible source of
leaks include: 1) the sample gas line, 2) compression fittings, and 3) a
cracked cell.
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