18 • 65-2396RK CO
2
Transmitter
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.
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 0-20% volume,
0-50% volume, or 0-100% volume detector is being used.
1. Screw the regulator into the 100% nitrogen calibration cylinder.
2. Use the calibration kit sample tubing to connect the regulator to the calibration cup.
3. Turn the regulator’s on/off knob counterclockwise to open the regulator.
4. Allow the gas to flow for one minute and verify a reading of 100 mV (±2 mV). If necessary, use
the zero pot on the amplifier to adjust the reading to 100 mV (±2 mV).
5. Turn the regulator’s on/off knob clockwise to close the regulator.
6. Unscrew the regulator from the 100% nitrogen calibration cylinder.
7. 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’s on/off 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 pot on the amplifier to adjust
the reading to match the correct response reading.
4. Turn the regulator’s on/off knob clockwise to close the regulator.
5. Unscrew the regulator from the calibration cylinder.
Returning to Normal Operation
1. Remove the voltmeter leads from the amplifier test points.
2. Unscrew the calibration cup from the detector.
NOTE:
For convenience, leave the regulator and calibration cup connected by the sample tubing.
