page_title: Carbon dioxide sensor
section_title: Nondispersive Infrared (NDIR) CO2 Sensors
hierarchical_section_title: Carbon dioxide sensor / Nondispersive Infrared (NDIR) CO2 Sensors
caption_attribution_description: English: CO2Mini monitor for measuring atmospheric carbon dioxide concentration, manufactured for TFA Dostmann. The meter uses a nondispersive infrared sensor and can log data via USB.
context_page_description: A carbon dioxide sensor or CO₂ sensor is an instrument for the measurement of carbon dioxide gas. The most common principles for CO₂ sensors are infrared gas sensors and chemical gas sensors. Measuring carbon dioxide is important in monitoring indoor air quality, the function of the lungs in the form of a capnograph device, and many industrial processes.
context_section_description: NDIR sensors are spectroscopic sensors to detect CO₂ in a gaseous environment by its characteristic absorption. The key components are an infrared source, a light tube, an interference (wavelength) filter, and an infrared detector. The gas is pumped or diffuses into the light tube, and the electronics measure the absorption of the characteristic wavelength of light. NDIR sensors are most often used for measuring carbon dioxide. The best of these have sensitivities of 20–50 PPM. Typical NDIR sensors cost in the (US) $100 to $1000 range.
  NDIR CO₂ sensors are also used for dissolved CO₂ for applications such as beverage carbonation, pharmaceutical fermentation and CO₂ sequestration applications. In this case they are mated to an ATR (attenuated total reflection) optic and measure the gas in situ. New developments include using microelectromechanical systems (MEMS) IR sources to bring down the costs of this sensor and to create smaller devices (for example for use in air conditioning applications).
  Another method (Henry's Law) also can be used to measure the amount of dissolved CO₂ in a liquid, if the amount of foreign gases is insignificant.
caption: CO
  2 concentration meter using a nondispersive infrared sensor
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