Emerson 3081FG - Manual (Page 59)

Instruction Manual
IB-106-3081 Rev. 1.5
September 2002
Rosemount Analytical Inc. A Division of Emerson Process Management Troubleshooting 6-1
Model 3081FG
SECTION 6
TROUBLESHOOTING
Install all protective equipment covers
and safety ground leads after trouble-
shooting. Failure to install covers and
ground leads could result in serious
injury or death.
6-1 GENERAL
This troubleshooting section describes how to
identify and isolate faults that may develop in
the Two-Wire In Situ Oxygen Analyzer.
6-2 PROBE LIFE
The zirconium oxide technology for measuring
oxygen is very stable and should provide accu-
rate service for several years.
Life of the probe is negatively impacted by:
• Continued operation at elevated tempera-
tures above 1300°C (2372°F).
• Operation in processes that contain high
levels of sulfur, SO
2
, or other acidic com-
pounds.
Operating conditions with simultaneously high
levels of SO
2
and low levels of O
2
are particu-
larly damaging.
The health and accuracy of a given cell is
closely related to the resistance, or impedance,
of the cell. Figure 6-1 illustrates that the amount
of output from a cell for a given O
2
value (repre-
sented as slope) will remain very stable to the
point where cell impedance increases to ap-
proximately 100 ohms.
Ω
SLOPE
(mV/Dec)
IMPEDANCE,
NORMAL
OPERATIONAL
CONDITIONS
48.0<S<51
mV/Dec
45.0<S<48
mV/Dec
S<45
mV/Dec
DETERIORATED PERFORMANCE,
SLOW RESPONSE,
HIGH MEASUREMENT ERROR
0
26020059
10
20
30
40
50
DETERIORATED PERFORMANCE,
SLOW RESPONSE,
HIGH MEASUREMENT ERROR.
CONDUCT FREQUENT CALIBRA-
TION CHECKS.
Figure 6-1. Slope vs. Impedance
6