RKI Instruments 35-3010RKA-07 - Manual (Page 25)

35-3010RKA-07 Sample-Draw Detector • 21
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 fresh air reading, set the zero
reading, and return to normal operation.
NOTE: This procedure describes calibration using a demand flow regulator, a zero air
calibration cylinder, and a 4-gas calibration cylinder to set the zero reading. A 4-
gas cylinder is used to set the zero reading since it is already used to calibrate the
IR CH
4
and oxygen channels. 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 4-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 4-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.
7. Unscrew the regulator from the 4-gas calibration cylinder.