24 • 35-3010A-11 Sample-Draw Detector
Returning to Normal Operation
1.
Remove the voltmeter leads from the test points.
2.
Reconnect the incoming sample line.
3.
Wait 1 to 2 minutes to allow the calibration gas to be drawn out and the reading to
stabilize.
4.
Close the housing door.
5.
Store the components of the calibration kit in a safe and convenient place.
Calibration, H
2
S and IR CO
2
Detectors
This section describes how to calibrate the H
2
S and IR CO
2
detectors in the sample-draw
detector. It includes procedures to prepare for calibration, set the zero reading, set the
response reading, and return to normal operation.
NOTE:
This procedure describes calibration using a demand flow regulator, a zero air
calibration cylinder, a 4-gas calibration cylinder, and a CO
2
calibration cylinder.
Preparing for Calibration
CAUTION:
This procedure may cause alarms at the controller. Take appropriate action to avoid
this, such as entering the calibration mode at the controller.
1.
Open the housing door.
2.
Set a voltmeter to measure in the millivolt (mV) range.
3.
For H
2
S detector calibration: Plug the voltmeter leads into the test points in the AMP 2
section of the main circuit board. Plug the positive lead into the test point labeled
CAL+2
; plug the negative lead into the test point labeled CAL-2.
4.
For IR CO
2
detector calibration: Plug the voltmeter into the test points on the IR CO
2
transmitter. Plug the positive lead into the test point labelled TP+; plug the negative
lead into the test point labelled TP-.
5.
Use the following formula to determine the correct test points output for the H
2
S and
CO
2
calibrating samples.
Output (mV) = (calibrating sample/fullscale) X 400 + 100
For example, with a calibrating sample of 25 ppm H
2
S and a fullscale setting of 100
ppm H
2
S, the correct output for the H
2
S test points is 200 mV.
200 (mV) = (25/100) X 400 +100
Setting the Zero Reading
1.
Screw the regulator into the zero air cylinder. If you are sampling a fresh air
environment, you don’t need to use a zero air cylinder to zero the H
2
S channel.
However, even if you are sampling a fresh air environment, since CO
2
is always
present in fresh air, you must use either a zero air cylinder, a 4-gas cylinder, or a CO
2
scrubber to zero the CO
2
channel.
2.
Connect the calibration kit sample tubing to the regulator.
