RKI Instruments 61-0191RK - Manual (Page 15)

61-1004RK/61-0191RK Carbon Dioxide Detector • 11
then more frequent calibration than every 6 months may be necessary.
Calibration
This section describes how to calibrate the CO
2
detector. It includes procedures to prepare
for calibration, set the zero reading, set the response reading, and return to normal
operation.
WARNING: The controller is not an active gas monitoring device during the calibration
procedure.
The following procedure assumes the use of a calibration kit which includes a 100%
nitrogen calibration gas cylinder for setting the zero reading, a CO
2
calibration gas
cylinder for setting the response reading, a 0.5 LPM fixed flow regulator with an on/off
knob, a calibration cup for the detector, and a short piece of sample tubing to connect the
regulator to the calibration cup.
Preparing For Calibration
1. Screw the calibration cup onto the detector.
2. Use the sample tubing to connect the regulator to the calibration cup.
3. Place the controller into its calibration program or disable external alarms.
NOTE: Calibrating the CO
2
detector may cause alarms. Be sure to put the controller into
its calibration program or disable external alarms before continuing.
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 CO
2
free gas to set the zero signal of a low
range CO
2
detector. Fresh air can be used to zero the detector if a 0-50 %volume or 0-100
%volume detector is being used.
1. Follow the directions in the controller’s operator’s manual for setting the zero reading
(sometimes called the fresh air reading).
2. When the directions call for exposing the detector to zeroing gas, screw the regulator
into the cylinder, turn the on/off knob counterclockwise to open the regulator, and
allow the gas to flow to the detector for 1 minute.
3. Turn the regulator’s on/off knob clockwise to close the regulator.
4. Set the zero reading according to the controller’s operator’s manual.
5. Unscrew the 100% nitrogen cylinder from the regulator.
Setting the Response Reading
1. Follow the directions in the controller’s operator’s manual for setting the response
reading (span).
2. When the directions call for exposing the detector to calibration gas, screw the CO
2
cylinder onto the regulator, turn the on/off knob counterclockwise to open the
regulator, and allow the gas to flow to the detector for 1 minute.
3. Turn the regulator’s on/off knob clockwise to close the regulator.