65-2331-04 H
2
S Transmitter • 19
Calibration
This section describes how to calibrate the H
2
S transmitter. It includes procedures to
prepare for calibration, set the zero reading, set the response reading, and return to
normal operation. It describes the test using a calibration kit that includes calibration gas,
sample tubing, and a fixed flow regulator with an on/off knob. RKI Instruments, Inc.
recommends using a 0.5 LPM (liters per minute) fixed flow regulator.
Preparing for Calibration
NOTE:
Calibrating the H
2
S transmitter may cause alarms. Be sure to put the controller
into its calibration program or disable external alarms before calibration.
WARNING: Do not remove the detector housing cap or either of the junction box covers
while the circuits are energized unless the area is determined to be non-
hazardous. Keep the detector housing cap and junction box covers tightly
closed during operation.
1.
Unscrew and remove the amplifier junction box’s cover.
2.
Set a voltmeter to measure in the millivolt (mV) range.
3.
Plug the voltmeter leads into the test points on the amplifier. Plug the positive lead
into the red (+) test point; plug the negative lead into the black (-) test point.
4.
Use the following formula to determine the correct test points output for the
calibrating sample.
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, the correct output is 200 mV.
200 (mV) = (25/100) X 400 +100
5.
Place the controller into its calibration mode or disable external alarms.
NOTE:
Calibrating the H
2
S transmitter may cause alarms. Be sure to put the controller
into its calibration mode or disable external alarms before continuing.
Setting the Zero Reading
NOTE:
If you can verify that the H
2
S transmitter is in a fresh air environment, you do not
need to apply zero air to the detector before adjusting the zero reading.
1.
Screw the regulator into the zero air calibration cylinder.
2.
Use the flexible tubing coming from the calibration adapter/splash guard to connect
the regulator to the calibration cup.
3.
Turn the regulator knob counterclockwise to open the regulator.
4.
Allow the gas to flow for the length of time determined in “Determining Response
Time” on page 18.
5.
Verify a reading of 100 mV (± 2mV). If necessary, use the zero pot on the amplifier to
