RKI Instruments 65-2400RK - Manual (Page 18)

14 • 65-2400RK Combustible Gas Transmitter
adjustments are minimal at calibration, then a calibration frequency of every 6 months is
adequate.
If an application is very demanding, for example if combustible gas is present often and in
significant concentrations or the environment is not well controlled, then more frequent
calibration than every 3 months may be necessary. If potential catalyst poisons are known
or likely to be present, more frequent calibration than every 3 months will be necessary.
Calibration
This section describes how to calibrate the combustible gas transmitter. It includes
procedures to prepare for calibration, set the zero reading, set the response reading, and
return to normal operation. It describes the test using a calibration kit that includes a
calibration cup, calibration gas, sample tubing, and a fixed flow regulator with an on/off
knob. RKI Instruments, Inc. recommends using a 0.5 LPM (liters per minute) fixed flow
regulator.
Preparing for Calibration
NOTE: Calibrating the combustible transmitter may cause alarms. Be sure to put the
controller into its calibration program or disable external alarms before
continuing.
1. Screw the calibration cup onto the bottom of the combustible gas detector.
2. Screw the regulator into the zero air calibration cylinder.
3. Use the sample tubing to connect the regulator to the calibration cup.
4. Set a voltmeter to measure in the millivolt (mV) range.
5. 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-.
6. 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% LEL and a fullscale setting of
100% LEL, the correct output is 300 mV.
300 (mV) = (50/100) X 400 +100
Setting the Zero Reading
NOTE: If you can verify that the combustible transmitter is in a fresh air environment,
you do not need to apply zero air to the detector before adjusting the zero
reading.
1. Turn the regulator’s on/off knob counterclockwise to open it. The sample will begin
to flow.
2. Allow the gas to flow for two minutes.
3. Verify a reading of 100 mV (±2 mV).