RKI Instruments 35-3000RKA-H2S - Manual (Page 14)

14 • Sample-Draw Hydrogen Sulfide Gas Detection
Calibration
This section describes how to calibrate the sample-draw combustible gas detector. It
includes procedures to assemble the calibration kit, set the zero reading, set the response
reading, and return to normal operation.
NOTE: This procedure describes calibration using a gas collection bag. A demand-flow
calibration kit is also available for calibrating the hydrogen sulfide gas sample-
draw detector.
Preparing for Calibration
1. Open the housing door.
2. Set a voltmeter to measure in the millivolt (mV) range.
3. Plug the positive lead into the transmitter test point labeled TP+; plug the negative
lead into the transmitter test point labeled TP-.
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 hydrogen and a fullscale setting of
100 ppm hydrogen, the correct output is 200 mV.
200 (mV) = (25/100) X 400 +100
Assembling the Calibration Kit
NOTE: If you can verify a fresh air environment, it is not necessary to use a zero air
calibration cylinder to set the zero reading. Go to the next section, “Setting the
Zero Reading.”
1. Connect the calibration kit sample tubing to the fitting on the gas collection bag.
2. Connect the sample tubing from the gas collection bag to the inlet line at or near the
INLET fitting.
Allow the sample-draw pump to draw out any residual gas in the gas collection bag.
3. Disconnect the calibration kit sample tubing from the inlet line.
4. Close the clamp right away. The clamp is attached to the calibration kit sample
tubing.
5. Connect the tubing from the gas collection bag to the fixed flow regulator, then open
the clamp.
6. Screw the fixed flow regulator onto the zero air calibration cylinder. The gas
collection bag begins to fill.
7. When the bag is full, unscrew the fixed flow regulator form the cylinder.
8. Close the clamp, then disconnect the sample tubing from the fixed flow regulator.