Instruction Manual
748441-D
April 2002
5-22 Maintenance and Service
Rosemount Analytical Inc. A Division of Emerson Process Management
Model CAT100
TP1
TP2
•
About 450,000 hours for a sensor with
a response time of about 6 s
The sensors have the following life time at
about 21% oxygen and 20
°
C:
•
About 42,857 hours (5 years) for a
sensor with a response time of about
12 s
•
About 21,428 hours (2.5 years) for a
sensor with a response time of about
6 s
The values stated above are presented as
guidelines only. Actual values will depend
on measured concentrations and opera-
tion temperature. The result of higher
temperatures, for example 40
°
C, could
be half the life time.
NOTE
The electrochemical O
2
cell requires a
minimum internal consumption of
oxygen. Sample gases with an oxygen
concentration of less than 0.1 % could
result in a reversible detuning of sensi-
tivity and the output will become un-
stable. The recommended practice is
to purge the cell with conditioned am-
bient air between periods of measure-
ment. If the oxygen concentration is
below 0.1 % for several hours or days,
the cell must be regenerated for about
one day with ambient air. Temporary
flushing with nitrogen (N
2
) for less than
one hour (analyzer zeroing) will have
no effect on the sensitivity or stability.
k.
Check of the Sensor
Exchange the sensor if the voltage is less
than 70% of the initial output voltage.
The check requires a digital voltmeter
(DVM) with a range of 2 V DC.
1. Remove the analyzer from the enclo-
sure (see Section 5-2a, page 5-3)
2. Remove the analyzer cover (see
Section 5-4b, page 5-16)
3. Switch on the analyzer.
4. Admit ambient air to the analyzer of
about 21% O
2
.
5. Connect the DVM to the following
measuring points:
a.
TP1 (signal) and TP2 (gnd) of
the OXS PCB, mounted directly
at the connection block (see
Figure 5-14, page 5-22).
b.
The voltage should be in the
range of 700 mV to 1000 mV
DC. If the voltage value is lower
that 700 mV at gas flow with am-
bient air, the sensor is consumed
and must be replaced.
Figure 5-14. OXS PCB Measuring Points
