Specifications

PCA
®
3
91
6.3 Sensor Replacement
All sensors are replaced in a similar manner. Do the following to replace
either the O
2
, CO
Low
, CO
High
, NO, NO
2
, or SO
2
sensor. Refer to Section 8.1
Replacement Parts for list of sensors and part numbers.
1. Turn OFF the analyzer.
2. Remove the battery cover.
3. Remove the sensor retainer.
4. Remove the tubing from the gas cup of sensor being replaced.
5. Unplug the sensor along with its printed circuit board from the
analyzer’s main board.
6. Remove the sensor’s gas cup by twisting its bayonet fi tting coun-
terclockwise, and then pulling the cup straight up.
7. Carefully remove the old sensor from the B-Smart
®
sensor PCB,
keeping in mind that there is an adhesive foam disk in between
the PCB and sensor.
IMPORTANT: When replacing the O
2
sensor, be sure that
the “+” sensor pin plugs into the PCB socket that is also
marked “O
2
+”.
When replacing an NO sensor, also replace the bias battery.
8. Remove the
replacement sensor
from its plastic
canister. Note that
the CO
Low
, CO
High
,
SO
2
, and NO
2
sensors have a short-
ing-spring installed
between two of their
pins. Remove and
discard this spring
before installing the
sensor.
Gas Cup
Sensor Retainer
Sensor
Twist gas cap
bayonet fitting
counterclockwise
to release
Sensor electrical
connector mates with
pins on analyzer’s main
board
Printed
Circuit Board
Adhesive
foam
disk
Be sure to remove any
shorting spring from the
new sensor pins before
installing! There is no
shorting spring on the
O2 or NO sensors.
Figure 6-6. Sensor Assembly
CAUTION: