RKI Instruments 35-3001A-02 - Manual (Page 22)

18 • 35-3001A-02 Oxygen Sample-Draw Detector
environment, and calibration adjustments are minimal at calibration, then a calibration frequency of
every 6 months is adequate.
If an application is very demanding, for example if the environment is not well controlled, then
more frequent calibration than every 3 months may be necessary.
Calibration
This section describes how to calibrate the oxygen sensor 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: Calibrating the sample draw detector may cause alarms. Be sure to put the controller into
its calibration program or disable external alarms before continuing.
NOTE: This procedure describes calibration using a demand flow regulator.
Preparing for Calibration
NOTE: If you can verify a fresh air environment, it is not necessary to use a zero air calibrating
sample to set the fresh air reading at the controller.
1. Follow the instructions in the controller’s operator’s manual for entering calibration mode.
2. Screw the regulator into the zero air calibration cylinder.
3. Open the housing door.
4. Set a voltmeter to measure in the millivolt (mV) range.
5. Plug the positive lead into the red (+) amplifier test point; plug the negative lead into the black
(-) amplifier test point.
Setting the Fresh Air Reading
1. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet
fitting. 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 434 mV (± 2 mV).
4. If necessary, use a small flat-blade screwdriver to adjust the span potentiometer until the
voltmeter reading is 434 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
section, Setting the Zero Reading.
5. Disconnect the sample tubing from the inlet fitting.
6. Unscrew the regulator from the zero air calibration cylinder.
Setting the Zero Reading
1. Screw the demand flow regulator onto the 100% N
2
calibration cylinder.
2. Connect the sample tubing from the regulator to the inlet line.
3. Allow the sample-draw detector to draw the calibrating sample for 1 minute.