RKI Instruments 35-3001A-11 - Manual (Page 22)

18 • 35-3001A-11 Hydrogen Sample-Draw Detector
If the low flow alarm is set too low, turn the pressure switch adjustment screw slightly
clockwise. Repeat steps 3 and 4 if necessary.
5. Use the sensor flow control valve to set the flow to 1.0 SCFH.
6. Make sure the sample-draw detector’s Fail LED is off.
Calibration Frequency
Although there is no particular calibration frequency that is correct for all sample draw detector
applications, a calibration frequency of every 9 to 12 months is adequate for most applications.
Unless experience in a particular application dictates otherwise, RKI Instruments, Inc. recommends
a calibration frequency of every 9 months.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment where hydrogen is not normally present and calibration adjustments are minimal at
calibration, then a calibration frequency of every 12 months is adequate.
If an application is very demanding, for example if hydrogen is present often and in significant
concentrations or the environment is not well controlled, then more frequent calibration than every
9 months may be necessary.
Calibration
This section describes how to calibrate the hydrogen 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.
Preparing for Calibration
1. Follow the instructions in the controller’s operator’s manual for entering calibration mode.
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.
2. Screw the regulator into a zero air calibration cylinder.
3. Open the housing door.
4. Set a voltmeter to measure in the millivolt (mV) range.
5. Plug the positive lead into the red (+) amplifier test point; plug the negative lead into the black
(-) amplifier test point.
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 4% vol and a fullscale setting of 10% vol, the correct
output is 260 mV.
260 (mV) = (4/10) X 400 +100