RKI Instruments 35-3001-09 - Manual (Page 24)

20 • 35-3001-09 Oxygen/Hydrogen Sulfide Sample-Draw Detector
Returning to Normal Operation
1. Wait 1 to 2 minutes to allow the oxygen reading at the controller to return to normal, then
return the controller to normal operation.
NOTE: If you do not allow the oxygen reading to return to normal, then unwanted alarms may
occur.
2. Verify that the controller display reading stabilizes at 20.9%.
3. Store the components of the calibration kit in a safe and convenient place.
Calibration, H
2
S Sensor
This section describes how to calibrate the hydrogen sulfide sensor of 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.
Preparing for Calibration
1. Follow the instructions in the controller’s operator’s manual for entering calibration mode.
NOTE: If you can verify a fresh air environment, it is not necessary to use the zero air calibration
cylinder to set the zero reading.
2. Screw the regulator into a zero air calibration cylinder.
3. Set a voltmeter to measure in the millivolt (mV) range and plug the leads into the H
2
S
amplifier.
Plug the positive lead into the red (+) amplifier test point; plug the negative lead into the black
(-) amplifier test point.
4. Use the following formula to determine the correct test points output for the test
sample.
Output (mV) = (calibrating sample/fullscale) X 400 + 100
For example, with a test sample of 25 ppm and a fullscale setting of 100 ppm, the
correct output is 200 mV.
200 (mV) = (25/100) X 400 +100
Setting the Zero Reading
1. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet
line. This step is not necessary if you verified a fresh air environment earlier in this
procedure.
2. Allow the sample-draw detector to draw sample for one minute.
3. Verify a voltmeter reading of 100 mV (± 2 mV).
4. If necessary, use a small flat-blade screwdriver to adjust the zero potentiometer until the
voltmeter reading is 100 mV (± 2 mV). If you used a zero air calibration cylinder to set the
zero reading, proceed to step 5. If you verified a fresh air environment, proceed to the next