24
The Sensor ZERO Function
Zero and calibration functions should only be undertaken by trained competent
personnel. The effectiveness of a gas detection system is largely down to how well it is
maintained and this means how well it is calibrated.
Regulator to deliver a fixed flowrate (0.5-1 L/min)
Oliver IGD P/N 5022001
Hose delivers cal gas to the detector. Note a test
gas applicator is usually required. In some cases
weather protection guards or the detector itself
may include a gas applicator port.
ZERO
GAS
Cal Gas Adaptor
Ensure it is correctly
fitted
GAS RECOMMENDED ZERO GAS
Apply zero gas to the detector.
It is important that the detector zero point is correctly set. It must be considered that
there is the possibility that the gas to be detected is already present in the area of the
detector. For this reason never zero on just the ambient surroundings.
There are two possibilities
A. confirm there is no gas present by using a portable detector
B. Use a suitable ZERO gas as follows.
Zero gas should have a humidity between 0-90%RH
O2/CO2 NITROGEN
PELLISTOR INSTRUMENT AIR
TOXIC GASES NITROGEN
The following diagram shows a typical equipment set up.
Recommended Test 750 series Gas Applicators.
MK3 Gas Detector P/N 401101A
MK5 & MK6 Gas Detector P/N 401101E
TOC-750 Series
Tocsin 102 Series Detector P/N 401101A
IMPORTANT: Flow gas for a minimum of 60 Seconds. Some detectors with longer response
times may take longer to stabilise.
Procedure for check reaction time to gas
Ensure detector is at zero +/- 1% LEL
Use standard IGD professional gas introduction kit with 2M hose.
Connect calibration gas but do not turn on
Using a stop watch turn on the calibration gas and time to 50% and 90% LEL
Time to 50% should be less than 30 seconds
Time to 90% should be less than 60 seconds
Note on a 20% LEL bottle T50 point is 10% LEL and T90 point is 18% LEL
on a 50% LEL bottle T50 point is 25% LEL and T90 point is 45% LEL
replace non conforming sensors
Relative response to Methane @ 4.4%
Vol = 100% LEL
Equivalent to 55% LEL N-Butane
