Calibration frequency, Calibration – RKI Instruments 65-2396RK User Manual
Page 18
14 • 65-2396RK CO
2
Transmitter
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 CO
2
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 CO
2
transmitter. 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.
NOTE:
The following procedure assumes the use of a calibration kit which includes a
calibration gas cylinder, a 100% nitrogen cylinder, 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.
Unscrew and remove the junction box cover.
2.
Set a voltmeter to measure in the millivolt (mV) range.
3.
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.
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 2.5 %Vol. and a fullscale setting of
5 %Vol., the correct output is 300 mV.
300(mV) = (50/100) X 400 +100
5.
Screw the calibration cup onto the detector housing.
6.
Place the controller into its calibration mode or disable external alarms.
NOTE:
Calibrating the CO
2
transmitter may cause alarms. Be sure to put the controller
into its calibration mode or disable external alarms before continuing.