RKI Instruments 65-2435RK - Manual (Page 19)

65-2435RK CO Transmitter • 19
Calibration
This section describes how to calibrate the CO transmitter. It includes procedures to prepare for
calibration, set the zero reading, set the response reading, and return to normal operation. It
describes calibration using a fixed flow regulator which has no on/off knob and allows sample to
flow as soon as it is screwed into a cylinder. RKI Instruments, Inc. recommends using a 0.5 LPM
(liters per minute) fixed flow regulator.
CAUTION: Do not adjust the null potentiometer during calibration. This will cause the hydrogen
compensation in the transmitter to operate improperly.
Preparing for Calibration
1. Screw the calibration cup onto the bottom of the CO detector.
2. Use the sample tubing to connect the fixed flow regulator to the calibration cup.
NOTE: Do not screw the regulator into the zero air calibration cylinder at this time.
3. Set a voltmeter to measure in the millivolt (mV) range.
4. Remove the junction box cover, then plug the voltmeter leads into the test points on 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 50 PPM CO and a fullscale setting of
300 PPM, the correct output is 167 mV.
167 (mV) = (50/300) X 400 +100
NOTE: Calibrating the CO transmitter may cause alarms. Be sure to put the controller into its
calibration program or disable external alarms before continuing.
Setting the Zero Reading
NOTE If you can verify that the CO transmitter is in a fresh air environment, you do not need to
apply zero air to the detector before adjusting the zero reading.
1. Screw the regulator into the zero air calibration cylinder. Gas will automatically begin to flow.
2. Allow the gas to flow for two minutes, then verify a reading of 100 mV (± 2mV). If necessary,
use the zero potentiometer on the amplifier to adjust the reading to 100 mV (± 2mV).
3. Unscrew the regulator from the zero air calibration 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. Gas will begin to flow.