20 • 35-3010RK-01 Sample-Draw Detector
Calibration, Oxygen Detector
This section describes how to calibrate the oxygen detector in the sample-draw detector. It
includes procedures to set the zero reading, set the fresh air, and return to normal
operation.
NOTE:
This procedure describes calibration using a demand flow regulator, a zero air
calibration cylinder, and a 4-gas calibration cylinder to set the zero reading. A 4-
gas cylinder is used to set the zero since it is already used to calibrate the LEL
and oxygen channels. A 100% nitrogen calibration cylinder could also be used to
set the zero reading.
Setting the Zero Reading
NOTE:
The 4-gas calibration cylinder included in the calibration kit may be used to zero
the oxygen channel. Keep in mind that the oxygen concentration in that cylinder
is 12%, not 0%. Be sure to set the controller appropriately.
1.
Screw the regulator into the 4-gas calibration cylinder.
2.
Connect the calibration kit sample tubing to the regulator.
3.
Follow the directions in the controller’s operator’s manual for setting the zero reading
for the oxygen channel.
4.
When the instructions call for applying gas to the detector, connect the sample tubing
from the regulator to the inlet line at or near the INLET fitting.
5.
Allow the gas to flow for one minute.
6.
Set the zero reading according to the controller operator’s manual.
7.
Disconnect the sample tubing from the inlet line.
8.
Unscrew the regulator from the 4-gas calibration cylinder.
9.
For convenience, leave the regulator attached to the sample tubing.
Setting the Fresh Air Reading
CAUTION:
This procedure may cause alarms at the controller. Take appropriate action to avoid
this, such as entering the calibration mode at the controller.
NOTE:
If you suspect the sampling area to not be a fresh air environment (free of
combustible or toxic gases and of normal oxygen content, 20.9%), it is necessary
to use a zero air cylinder when setting the zero reading.
1.
Open the housing door.
2.
The fresh air reading for the oxygen channel is set at the controller. See the controller
operator’s manual for instructions to set the zero reading.
3.
When the instructions call for applying gas to the detector, make sure the inlet line is
sampling fresh air.
4.
Allow the detector to sample fresh air for one minute.
