GE CGA 351, User Manual

Page: 88 / 133

December 2004
5-10 Service and Maintenance
Check for Plumbing Leaks
A plumbing leak permits contamination of the reference air by the
sample gas. The resulting reduction in the ratio of the oxygen partial
pressures reduces the mV output from the oxygen sensor and yields a
percent oxygen reading that is higher than expected. Use the
following steps to remedy the problem:
1.
Open the sensor enclosure cover to allow uncontaminated
reference air to enter the unit.
2.
If the oxygen reading drops in Step 1 above, tighten all fittings by
1/8 turn and close the sensor enclosure cover. If the oxygen
reading gradually increases, repeat Step 1. If the problem persists,
proceed to the next section.
Caution!
Do not tighten fittings more than 1/8 turn at a time.
Check the Oxygen Sensor
Temperature
If the oxygen sensor is below its normal operating temperature, the
mV output will be too low and the percent oxygen reading will be
higher than expected. Proceed as follows:
•
The easiest way to check the sensor temperature is to calibrate the
oxygen sensor as described in “Calibrating the Model CGA 351”
on page 4-31. The calibration procedure includes instructions for
adjusting the sensor furnace temperature, if necessary.
If the problem has not been resolved by the steps in this section,
contact the factory for assistance.
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