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Instruction Manual
IB-106-5081, Rev. 1.0
May 2005
6-6 Troubleshooting Rosemount Analytical Inc. A Division of Emerson Process Management
Model 5081FG
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26020028
Figure 6-9. Fault 5, O
2
Cell Open
e. Fault 5, O
2
Cell Open
The O
2
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 6-4 and check the O
2
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%
O
2
). Measure the cell output from the
O
2
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 O
2
cell is open, replace the oxy-
gen probe per paragraph 5-2.
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26020029
Figure 6-10. Fault 6, Cell Impedance Too High
f. Fault 6, Cell Impedance Too High
The O
2
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 O
2
cell has become too old, re-
place the oxygen probe per paragraph
5-2.