Comfort Chek
400 Operation Manual
10
1509-9000 Rev 4
Figure 4-9. P3.1 Temperature Scale
Figure 4-10. Temperature Units
4.11. CO
2
Calibration
The instrument defaults to be calibrated manually in ambient air where CO
2
concentration outdoors is around 400 ppm.
NOTE:
Though not required, it is recommended that you calibrate the instrument
prior to each use. It is also recommended that the instrument be calibrated annually
by a trained technician or the factory using calibration gas.
NOTE:
Do not calibrate the instrument in air with unknown CO
2
concentration
otherwise it will be calibrated as 400 ppm by default and the CO
2
readings displayed
will be inaccurate.
It is suggested to calibrate the instrument in fresh outdoor air that is well ventilated
and it is better in sunny weather. Do not calibrate the instrument in places crowed with
people or close to areas where CO
2
concentrations may be high such as ventilation
outputs, near exhaust, idling cars, garages, transportation depots, traffic, etc.
Set the instrument in the calibration site, switch it on and hold down the CAL Esc and
MODE (arrow up) buttons simultaneously to enter the CO
2
calibration mode. CAL and
400 ppm are blinking on the LCD while performing calibration.
Figure 4-11. CO
2
Calibration Mode
NOTE:
Ensure either the wall adapter or fresh batteries are used for the calibration
procedure because the infrared CO
2
sensor draws a fairly high current. Low battery
voltage may result in an interruption or failed calibration.
Wait about 10 minutes until the blinking stops and the calibration is completed
automatically. The instrument returns to normal operation mode. To abort the
calibration, switch the instrument off at any time.
