Document
UMA 149
Rev
6
Page
6 (8)
Maintenance
The
aSENSE RL
is basically maintenance free. An internal self-adjusting calibration
function takes care of normal long term drift associated to the CO
2
sensor. To secure
the highest accuracy, a time interval of five years is recommended between CO
2
calibrations, unless some special situations have occurred.
A zero calibration can be performed by use of pure nitrogen or air that has passed
through a chemical absorber and a PC together with the
UIP software version 5
(or
higher) or by shortening of holes marked in figure 2 for at least 10 seconds. The
sensor needs stable gas flow for at least 3 minutes before zero calibration. The Zero
Calibration bag can be used to produce carbon dioxide free air. The software can be
free downloaded from
. The RS232-cable and the zero calibration
bag can be ordered from SenseAir. The cable is to be connected to the UART port
slide connector (see Fig. 7). For change of control parameters and re-calibration of
temperature this PC tool has to be used. Zero calibration can be done with PC and
UIP software version 5
or by shorting marked holes in figure 5. The check can be
done on site without interfering with the ventilation system.
A Back-ground calibration is an easy way to correct a sensor
’s zero point. The
sensor needs fresh air (380-420 ppm CO
2
). Shorten holes marked in figure 5 for at
least 10 seconds.
This is for sensors with measuring ranges between 0-3000 ppm and 0-4%:
When a zero calibration shall be executed a plastic tube with 2,2 mm outer diameter
and 0,8 mm inner diameter shall be inserted in marked holes of the sensor. A plastic
tubing is connected to the tube. The gas flow should be between 0,3 and 0,8 l/min.
The sensor needs stable gas flow for at least 3 minutes before zero calibration.
Shorten marked holes for at least 10 seconds. A successful calibration is
acknowledged by 5 flashes of the yellow LED. If unsuccessful, please release input
and waits at least 10 seconds before repeating the procedure again. Make sure that
the sensor environment is steady and calm!
Gas inlet
Figure 5 Part of the PCB with holes for gas inlets marked.
