Reference

Other Supplementary Information

Zero Calibration

• Method 1: Manual zero calibration
  
  Short circuit the HD and GND of the sensor to calibrate it. It always needs to last for over 7 seconds at a low level. Make sure that the sensor runs stably for over 20 minutes at a concentration of 400ppm before the calibration.
• Method 2: Automatic zero calibration
  
  The automatic calibration function means that the sensor will intelligently determine the zero point according to the ambient CO2 concentration and automatically calibrate it after a period of continuous operation. The calibration starts from power-on and is performed once every 24 hours. The zero point for automatic calibration is 400 ppm. This calibration is suitable for office and home enviornment.