Dokument
UMA 148
Rev
1
Page
4 (
5
)
Automatic Zero Point Calibration
The
CF8-D/W-IN
sensors have a function for easy automatic zero point calibration. The calibration
should be done after installation and at least once every year. The calibration can be done on site. It is
only necessary to connect the zero gas without any further action required from the operator, but to
check the verification signal offered from the system.
1.
Unscrew one of the filters from the sensor housing and replace it with a hose nipple.
2.
Connect the zero gas to the nipple. The sensor automatically enters phase 1 of the calibration
procedure when the CO
2
concentration drops sharply. See figure 2. Do not remove the zero gas
during calibration.
3.
When the calibration starts the yellow LED starts to flash. The sensor continues the procedure
until the readings of the sensor are stable enough and are below the limit of Automatic Zero Point
Calibration. If the conditions are not good enough for calibration within eight minutes the sensor
returns to normal measuring operation without calibration.
4.
When the calibration is successfully executed the yellow LED flashes four times, pauses and
flashes another four times for an eight minutes acknowledgement period, phase 2. During the
acknowledgement period the relay is closed and the red LED is lit.
5.
Remove the zero gas during the acknowledgement period. The sensor returns to normal
measuring mode as soon as the calibration is ready. The yellow LED continues flashing, the red
LED is lit and the relay is closed independent of gas removal.
The zero gas can be generated by passing air through the chemical absorber in the service bag
F0005 or by using nitrogen in a gas bottle. Not more than three minutes shall pass before the yellow
LED starts to flash. If the yellow LED does not start to flash the zero gas is not good enough or the
sensor is not stable enough. Wait ten minutes before another attempt to calibrate the sensor.
If the sensor does not enter phase 1 even if the conditions are good push the push button on the PCB
until the red LED is lit to force a manual zero point calibration. Push the push button for at least ten
seconds.