Det-Tronics TXL Series Gas Transmitter - Manual (Page 17)

SENSOR CELL REPLACEMENT
The electrochemical sensor is not field repairable. If
calibration can no longer be properly performed, the
sensor must be replaced.
NOTE
Handle the sensor cell carefully. To avoid possible
damage, observe the normally accepted proce-
dures for handling electrostatic sensitive devices.
See form 75-1005 for additional information.
Follow the procedure below to replace the sensor cell.
1. Remove power to the detector prior to replacing the
sensor cell.
2. Remove the knurled cover from the sensor base.
(There is no need to remove the sensor housing from
the junction box for this operation.)
NOTE
Compare part numbers to be sure that the correct
replacement cell is being used.
3. Remove the old sensor cell. The sensor cell contains
a small amount of lead – dispose of properly. Check
for corrosion or contamination on the terminals of the
sensor base, and clean if necessary.
4. Remove the shorting spring from the bottom of the
new sensor (see Figure 5).
5. Determine proper orientation for the new cell, then
carefully plug it in.
6. Replace the knurled cap. Do not over-tighten; it
should be finger tight only.
7. Apply power and allow the sensor to stabilize for a
minimum of 1 hour (24 hrs. recommended).
8. Calibrate the new sensor.
An adequate supply of spare electrochemical cell
assemblies should be kept on hand for field replace-
ment. For maximum protection against contamination
and deterioration, they should not be removed from the
original protective packaging until the time of installa-
tion. To ensure maximum storage life, electrochemical
cells should be stored in the unopened package, at a
temperature between 32°F and 68°F (0 to 20°C) and a
relative humidity between 15 and 90 percent.
HYDROPHOBIC FILTER REPLACEMENT
The hydrophobic filter on the front of some of the elec-
trochemical sensor housings protects the sensor cell
from contaminants in the environment, and also
enables the operation of the cell in "wet" environments
without plugging its screen. The operator should fre-
quently inspect the hydrophobic filter for cleanliness.
A dirty filter can significantly reduce the amount of
gas that is able to reach the sensor cell, thereby
impairing the ability of the system to respond to a
hazardous condition. If the filter becomes dirty or if it
is damaged, it must be replaced. To replace the
hydrophobic filter, simply unscrew the knurled cover,
carefully extract the internal rubber O-ring, and extract
the hydrophobic filter. Replace it with a new filter and
reinstall the O-ring. Do not over-tighten the knurled
cover after replacement.
NOTE
A dirty hydrophobic filter can adversely affect the
response of the sensor by blocking the flow of gas
to the sensor cell. If the detector cannot be cali-
brated or responds slowly to the calibration gas,
check the condition of the hydrophobic filter before
replacing the sensor cell.
15 95-8541 1.1
REMOVE SHORTING SPRING
FROM THE BOTTOM OF
THE NEW SENSOR
A2132
Figure 5—Shorting Spring on Replacement Sensor