GE CGA 351, User Manual

Page: 86 / 133

December 2004
5-8 Service and Maintenance
Checking for Plumbing
Leaks
A plumbing leak permits cross-contamination of the reference air and
the sample gas. Use the following steps to remedy the problem:
1.
Make sure that the calibration gas port in the sample system has
not been left open. This would admit atmospheric air into the
sample system and force a 20.93% reading.
2.
Open the sensor enclosure cover and check all plumbing
connections for leaks. Make sure that the oxygen sensor nut and
the inlet connections are properly sealed.
When the reference air is contaminated by the same gases that are
being measured, the oxygen sensor generates a 0.00 mV analog
output signal and a 20.93% oxygen reading. Opening the cover
permits uncontaminated reference air to enter the unit. If opening the
cover and fixing any plumbing leaks does not cause the 20.93%
reading to drop, proceed to the next section.
3.
If the oxygen reading drops in Step 2 above, tighten all fittings by
1/8 turn and close the sensor enclosure cover. If the oxygen
reading gradually returns to 20.93%, try tightening the fittings an
additional 1/8 turn. If the problem persists, contact the factory for
assistance.
Caution!
Do not tighten fittings more than 1/8 turn at a time.
Checking the Digital
Display
If the shorted wiring and plumbing leak checks have not corrected the
problem, complete the following steps:
1.
Disconnect the oxygen sensor (
O2
) leads from terminal block
TB2
.
2.
Connect the positive lead of a digital voltmeter to the wire
(white - #1) removed from pin
+
and connect the negative
voltmeter lead to the wire (white - #2) removed from pin
-
.
IMPORTANT:
The oxygen sensor leads must be removed from the
terminal block for this test. If the leads are not
disconnected, a short on the digital display circuit
board could result in a false 0.00 mV reading.
3.
A voltage reading of 0.00 mV should be obtained, to correspond
with the 20.93% oxygen reading. If any voltage other than 0.00
mV is measured, the digital display is defective. Contact the
factory for assistance.
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