Panametrics CGA 351, User Manual, Page: 81 / 119

CGA 351 User’s Manual 75
Chapter 5.
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.