Reference Manual
00809-0100-4882, Rev AB
May 2019
Rosemount 5081FG
Section 5
Troubleshooting
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 5-1
Probe Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 5-1
Fault Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 5-3
Identifying And Correcting Fault Indications . . . . . . . . . . page 5-4
Calibration Passes, But Still Reads Incorrectly . . . . . . . . page 5-8
GENERAL
This troubleshooting section describes how to identify and isolate faults that
may develop in the Two-Wire In-Situ Oxygen Analyzer.
PROBE LIFE
The zirconium oxide technology for measuring oxygen is very stable and
should provide accurate service for several years.
Life of the probe is negatively impacted by:
• Continued operation at elevated temperatures above 1300°C (2372°F).
• Operation in processes that contain high levels of sulfur, SO
2
, or other
acidic compounds.
Operating conditions with simultaneously high levels of SO
2
and low levels of
O
2
are particularly damaging.
The health and accuracy of a given cell is closely related to the resistance, or
impedance, of the cell. Figure 5-1 illustrates that the amount of output from a
cell for a given O
2
value (represented as slope) will remain very stable to the
point where cell impedance increases to approximately 100 ohms.
Frequently conduct calibration checks to look for the following conditions:
• Continued degradation of cell slope.
• Sluggish response. (Note how long it takes the cell to respond to the
application of calibration check gases.) See Figure 5-2.
The slope will be valid only for the process temperature at which the
calibration check gases are flowed, so no adjustments to the electronics are
made as a result of a calibration check.
Note that cells exposed to temperatures above 1300°C (2372°F) may lose the
ability to measure accurately and respond quickly when returned to the lowest
end of the operating temperature range [550°C (1022°F)].
Summary of Contents for Rosemount 5081FG
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