RKI Instruments 65-2461RK - Manual (Page 19)

65-2461RK PPM Hexane Transmitter • 15
Calibration
This section describes how to calibrate the ppm hexane 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 0.5 LPM fixed flow regulator with an on/off knob, a
calibration cup for the detector, and a humidifier tube to connect the regulator to
the calibration cup.
Calibration Kit Humidifier Tube
The ppm hexane detector requires normal atmospheric humidity levels to respond
properly to hexane. Normal atmospheric humidity variations do not affect the detector’s
response to hexane in ambient air, but the ultra low humidity level of gas from a
calibration cylinder requires that the calibration sample be humidified for the detector to
respond properly. The calibration kit for the ppm hexane transmitter includes a
humidifier tube that is not normally included in other calibration kits. This humidifier
tube humidifies the calibration sample flowing through it by absorbing humidity from the
ambient air and adding it to the sample. The humidifier tube is included in the “Parts
List” on page 17.
WARNING: A humidifier tube must be used when calibrating the ppm hexane
transmitter test for the detector to respond properly to the calibration gas.
Failure to use a humidifier tube will result in an inaccurate calibration.
Preparing for Calibration
1. Screw the calibration cup onto the bottom of the hexane detector.
2. Use the humidifier tube to connect the regulator to the calibration cup.
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 red + test point; plug the negative lead into the black -
test point.
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 250 ppm hexane and a fullscale setting of
500 ppm hexane, the correct output is 300 mV.
300(mV) = (250/500) X 400 +100
6. Place the controller into its calibration mode or disable external alarms.