20 • 65-2330RKSS H
2
S Transmitter
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 a calibration cup, 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 junction box cover while the
circuits are energized unless the area is determined to be non-hazardous.
Keep the detector housing cap and junction box cover tightly closed during
operation.
1. Unscrew and remove the junction box 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. Screw the calibration cup onto the detector housing.
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 sample tubing 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 two minutes, then verify a reading of 100 mV (± 2mV). If
necessary, use the zero pot on the amplifier to adjust the reading to 100 mV (± 2mV).
