User Manual

20 • 35-3010RKA-02 Sample-Draw Detector
Calibration Frequency
Although there is no particular calibration frequency that is co rrect for all applications, a
calibration frequency of every 3 months is adequate for mo st sample d raw detector
applicatio ns. Unless experience in a particular application dictates otherwise, RKI
Instruments, Inc. recommends a calibration frequency of every 3 months for the sample
draw detector.
If an application is not very demanding, for example detection in a clean, temperature
controlled environment, and calibration adjustments are minimal at calibration, th en a
calibration frequency of every 6 months is adequate for the sample draw detector.
If the application is very demand ing, for example if the environment is no t well
controlled, then more frequent calibration than every 3 months may be necessary for the
sample draw detector.
Calibration, LEL Detector
This section describes how to calibrate the LEL sensor in the sample draw detector. It
includes procedures to prepare for calibration, set the zero reading, set the response
reading, and return to normal operation.
NOTE: This procedure describes calibration using a demand flow regulator, a zero air
calibration cylinder, a nd a 4-gas calibration cylind er.
Preparing for Calibration
CAUTION: This proce dure may cause alarms at the controller. Take appropriate action to avoid
this, such as entering the calibration mode at the controller.
1. Open the housing door.
2. Set a voltmeter to measure in the millivolt (mV) range.
3. Plug the voltmet er into the test points on the LEL transmit ter. Plug the positive lead
into the test point labeled TP+; plug the negat ive lead into the test point labeled TP-.
4. Use the following formula to determine the correct test points output for the
calibrating sample.
Output (mV) = (calibratin g sample/fullscale) X 400 + 100
For example, with a calibrating sample of 50 %LEL methane and a fullscale setting of
100%LEL, the correct output for the LEL test points is 300 mV.
300 (mV) = (50/100) X 400 +100
Setting the Zero Reading
NOTE: If you can verify a fresh air environment, it is not necessary to use the zero air
calibration cylinder to set the zero reading.
1. Screw the regulator into the zero air calibration cylinder.
2. Connect the calibration kit sa mple tubing to the regulator.