Emerson Rosemount OCX 8800 Reference Manual page 113

Table 7-3: Descriptions of PlantWeb Alerts
Alerts Alarms
Sensor Degraded Transducer block:
O Cell Impe-
2
dance High
Reference Manual
(continued)
What does the
AMS tab alert indicate?
Sensor Alerts This alert is active
when the oxygen
sensor impedance
indicates that the
cell is beyond its
useful life.
Foundation Fieldbus
Recommended
action Description
also cause this
alarm. Refer
to Section 8.2
for details.
Replace the oxy- Oxygen cells de-
gen cell. grade over time
due to aging and
corrosion. An in-
creasing cell re-
sistance is a good
indicator of re-
duced cell per-
formance. As the
cell impedance in-
creases, the cell
output falls off,
and response
time increases.
Calibrating the in-
strument com-
pensates for the
increased cell re-
sistance up to sev-
eral hundred
ohms, beyond
which the cell is
no longer func-
tional. Diagnosis
must be done at
the analyzer. Re-
fer to Section 8.2
for details.
103