7. Apply the nitrogen gas for about one and a half (1 ½) minute.
8. After minute and a half the sensor will display Adj for 5 to 15 seconds while
making adjustments and recording the calibration data into memory. When
completed the display will starts flashing rapidly. At this time remove the
calibration gas and allow the sensor to clear. Do not remove the nitrogen
gas while Adj is being displayed. Remove the gas only when the adjustment
is completed and the display is rapidly flashing with calibration gas value.
9. The sensor calibration has been successfully completed
10. While the gas from the sensor housing is being cleared the 4-20mA analog
output will be held at 2.0mA and alarm relay will not be activated until the
sensor has returned to ambient oxygen air reading which is 20.9%. Once
nitrogen has been cleared from the head assembly the unit will return to its
normal operation. The 2mA level on the analog output line is an indication to
any connected gas monitor that the sensor is in calibration mode thus
avoiding any false alarm.
Also refer to “Sensor calibration Flow Chart” for quick calibration review and
“Calibration Error and remedies”
Recommended Calibration Gas for Target Gas Sensor
Gas Sensor Recommended Calibration gas
Hydrogen Sulfide 50 ppm H2S Balanced in Air
Carbon Monoxide
Range 100 ppm
50 ppm CO balanced in Air
Carbon Monoxide
Range 1000 ppm
400 ppm CO balanced in Air
Sulfur Dioxide 25 ppm SO2 Balanced in Air
25 ppm Ammonia balanced in Air
Pure Nitrogen (for zeroing)
100 ppm Hydrogen balanced in Air
50 ppm HCL balanced in air
50 ppm NO balanced in air
10 ppm NO2 balanced in air
Chlorine 5 ppm CL2 air balanced
PT295 Series Toxic Sensor Rev 5.1
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