65-2321RK Oxygen Transmitter • 13
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a
calibration frequency of every 3 months is adequate for most oxygen transmitter
applications. Unless experience in a particular application dictates otherwise, RKI
Instruments, Inc. recommends a calibration frequency of every 3 months for the oxygen
transmitter.
If an application is not very demanding, for example detection in a clean, temperature
controlled 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 transmitter. It includes procedures to
prepare for calibration, set the fresh air reading, set the zero reading, and return to normal
operation. It describes calibration using a calibration kit that includes a calibration cup,
calibration gas, sample tubing, and a fixed flow regulator with an on/off knob. RKI
Instruments, Inc. recommends using a 0.5 LPM (liters per minute) fixed flow regulator
Preparing for Calibration
1.
Place the controller into its calibration mode or disable external alarms.
2.
Unscrew and remove the junction box cover.
3.
Set a voltmeter to measure in the millivolt (mV) range.
4.
Plug the voltmeter leads into the test points on the amplifier. Plug the positive lead
into the red + test point; plug the negative lead into the black - test point.
5.
Use the following formula to determine the correct test points output for the
calibrating sample.
Output (mV) = (calibrating sample/fullscale) X 400 + 100
The concentration of oxygen in the atmosphere is 20.9%, so when setting the fresh air
reading, you will set the test points output to 434 mV (±2 mV).
434(mV) = (20.9/25) X 400 +100
NOTE:
Calibrating the oxygen transmitter may cause alarms. Be sure to put the
controller into its calibration program or disable external alarms before
continuing.
6.
Screw the calibration cup onto the detector housing cap.
Setting the Fresh Air Reading
NOTE:
If you can verify that the oxygen transmitter is in a fresh air environment, you do
not need to apply zero air to the detector before adjusting the fresh air reading.
1.
Screw the regulator into the zero air calibration cylinder.
2.
Use the sample tubing to connect the regulator to the calibration cup.
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