What is the measurement principle of the CO2 sensor?

The measurement principle of a CO2 sensor includes three main methods: infrared, chemical adsorption, and electrochemical. Among them, the most commonly used method is the infrared sensor, which detects the absorption of infrared energy by CO2 molecules to measure CO2 concentration. For instance, Gravity: I2C SCD41 Infrared CO2 Sensor (400 - 5000 ppm)andGravity: PWM Infrared Carbon Dioxide Sensor (400-5000 ppm) are examples of infrared CO2 sensors.