20 • 35-3001-05-XX CO
2
Sample-Draw Detector
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a calibration
frequency of every 6 months is adequate for most infrared combustible gas transmitter applications. Unless
experience in a particular application dictates otherwise, RKI Instruments, Inc. recommends a calibration
frequency of every 6 months.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment where calibration adjustments are minimal at calibration, then a calibration frequency of every
9 to 12 months is adequate.
If an application is very demanding, for example if the environment is not well controlled, then more
frequent calibration than every 6 months may be necessary.
Calibration
This section describes how to calibrate the carbon dioxide 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.
Setting the Zero Reading
Since there is a background of CO
2
in air of typically 300 - 600 ppm (0.03 - 0.06% volume), it is necessary
to use a calibration kit with a 100% nitrogen cylinder to set the zero signal for the
0 - 5,000 ppm and 0 - 5% volume versions. Fresh air can be used to set the zero signal for the
0 - 50% and 0 - 100% volume versions.
1. Screw the regulator into a 100% nitrogen calibration cylinder.
2. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet line.
3. Allow the sample-draw detector to draw sample for one minute.
4. Follow the directions in the controller’s operator’s manual for setting the zero reading.
5. Disconnect the sample tubing from the inlet line.
6. Unscrew the regulator from the 100% nitrogen calibration cylinder.
Setting the Response Reading
1. Screw the regulator into the carbon dioxide calibration cylinder.
2. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet line.
3. Allow the sample-draw detector to draw sample for one minute.
4. Follow the directions in the controller’s operator’s manual for setting the span.
www.
.com
1.800.561.8187