NDIR CO2 gas sensor with improved temperature compensation

This paper describes a Non-Dispersive Infrared (NDIR) CO2 gas sensor with auto-temperature compensation in order to apply HVAC systems. The developed gas sensor amplifies differentially both the output of thermopile and output of temperature sensor that has linear output characteristics. With differential amplification circuits, the output voltage of sensor module according to the CO2 concentration shows the independent temperature output characteristics from 10 ∘C to 40 ∘C. The developed sensor module shows ±30 ppm error at 1,000 ppm and ±50 ppm error at 2,000 ppm CO2 concentration regardless of temperature variations.