RKI Instruments 65-2391RK User Manual
Page 18
14 • 65-2391RK CO
2
Transmitter
the amplifier.
Plug the positive lead into the test point labeled TP+; plug the negative lead into the
test point labeled TP-.
5.
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% CO
2
and a fullscale setting of
5% CO
2
, the correct output is 300 mV.
300 (mV) = (2.5/5) X 400 +100
6.
Place the controller into its calibration program or disable external alarms.
NOTE:
Calibrating the CO
2
transmitter 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 100% nitrogen cylinder to set the zero signal of
a CO
2
transmitter with a low range detector. Fresh air can be used to zero the transmitter
if a 0-50 %volume or 0-100 %volume detector is being used.
1.
Screw the regulator into the 100% nitrogen cylinder.
2.
Turn the regulator knob counterclockwise to open the regulator.
3.
Allow the gas to flow for one minute and verify a reading of 100 mV (±2 mV). If
necessary, use the zero potentiometer on the amplifier to adjust the reading to 100 mV
(±2 mV).
4.
Turn the regulator knob clockwise to close the regulator.
5.
Unscrew the regulator from the 100% nitrogen cylinder. Leave the sample tubing
connected to the regulator and the calibration cup.
Setting the Response Reading
1.
Screw the regulator into the calibration cylinder. Verify that the calibration gas is
representative of the transmitter’s target gas.
2.
Turn the regulator knob counterclockwise to open the regulator.
3.
Allow the calibration gas to flow for one minute and verify that the reading matches
the response reading (±2 mV) you determined earlier. If necessary, use the span
potentiometer on the amplifier to adjust the reading to match the correct response
reading.
4.
Turn the regulator knob clockwise to close the regulator.
5.
Unscrew the regulator from the calibration cylinder.