RKI Instruments 35-3010RKA-04 - Manual (Page 25)

35-3010RKA-04 Sample-Draw Detector • 21
5. Store the components of the calibration kit in a safe and convenient place.
Calibration, Oxygen Detector
This section describes how to calibrate the oxygen detector in the sample-draw detector. It
includes procedures to prepare for calibration, set the zero reading, set the fresh air
reading, and return to normal operation.
NOTE: This procedure describes calibration using a demand flow regulator, a zero air
calibration cylinder, and a 3-gas calibration cylinder to set the zero reading. A 3-
gas cylinder is used to set the zero since it is already used to calibrate the LEL
channel. A 100% nitrogen calibration cylinder could also be used to set the zero
reading.
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. Plug the voltmeter into the test points on the oxygen transmitter. Plug the positive
lead into the test point labeled TP+; plug the negative lead into the 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 12% and a fullscale setting of 25%, the
correct output for the oxygen test points is 292 mV.
292 (mV) = (12/25) X 400 +100
Setting the Zero Reading
NOTE: The 3-gas calibration cylinder included in the calibration kit may be used to zero
the oxygen channel. Keep in mind that the oxygen concentration in that cylinder
is 12%, not 0%. Be sure to set the controller appropriately.
1. Screw the regulator into the 3-gas calibration cylinder.
2. Connect the calibration kit sample tubing to the regulator.
3. Allow the sample-draw detector to respond to the calibrating sample for
approximately 1 minute.
4. After one minute, check the mV output on the oxygen transmitter test points and
verify that the reading matches the response reading (±2 mV) you determined earlier
(292 mV for 12% oxygen).
5. If necessary, use the span pot on the transmitter to adjust the reading to match the
correct response reading.
6. Disconnect the sample tubing from the inlet line.