Emerson 5081FG instruction manual Fault 5, O2 Cell Open Fault 6, Cell Impedance Too High

Instruction Manual

IB-106-5081, Rev. 1.0 May 2005

Model 5081FG

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26020028	26020029
Figure 6-9. Fault 5, O2 Cell Open	Figure 6-10. Fault 6, Cell Impedance Too High
e. Fault 5, O2 Cell Open	f. Fault 6, Cell Impedance Too High

The O2 cell connection is open. The fault displays as shown in Figure 6-9.

1.Allow adequate time for the oxygen probe to reach operating temperatures. Probe temperatures below approxi- mately 500°C (932°F) may result in this fault.

2.Refer to Figure 6-4and check the O2 cell wiring connections at terminals 7 and 8. Ensure the wires are properly connected.

NOTE

Check the cell output voltage at the probe terminals -- not at the electronics.

3.Apply low calibration check gas (0.4% O2). Measure the cell output from the O2 cell wires at the probe terminal block. The cell output should be 100 ±20 mV. If no voltage can be meas- ured, the cell is open.

4.If the O2 cell is open, replace the oxy- gen probe per paragraph 5-2.

The O2 cell impedance has exceeded 100 ohms. The fault displays as shown in Figure 6-10.

1.This fault is usually indicated in con- junction with Fault 5, Cell Open. Cor- recting Fault 5 should correct Fault 6.

2.If Fault 6 appears independently, the cell has degraded beyond specification.

3.If the O2 cell has become too old, re- place the oxygen probe per paragraph 5-2.

6-6 Troubleshooting Rosemount Analytical Inc. A Division of Emerson Process Management