A CO₂ sensor is an instrument for the measurement of carbon dioxide gas. The most common principles for CO₂ sensors are infrared gas sensors (NDIR) and chemical gas senors. Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ...

Nondispersive Infrared (NDIR) CO₂ Sensors

These are the simplest of the spectroscopic sensors.^{[citation needed]} 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 measures the absorption of the characteristic wavelength of light. NDIR sensors are most often used for measuring carbon dioxide.^[1] The best of these have sensitivities of 20-50 PPM.^[1] Typical NDIR sensors are still in the (US) $100 to $1000 range. Most are used for carbon dioxide, because no other sensing method works reliably for this gas. New developments include using MEMS to bring down the costs of this sensor and to create smaller devices (for example for use in air conditioning applications). Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength. ... The wavelength is the distance between repeating units of a wave pattern. ... PPM can stand for more than one thing: Pages per minute, a measure of speed often used to market printers or photocopiers the Portable Pixmap file format the PPM compression algorithm (Prediction by partial matching) used in computer science Parts per million, a measure of concentration Portable People Meter peak... A mite next to a gear set produced using MEMS. Courtesy Sandia National Laboratories, SUMMiTTM Technologies, www. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ...

Chemical CO₂ Sensors

Chemical CO₂ gas sensors with sensitive layers based on polymer- or heteropolysiloxane have the principal advantage of a very low energy consumption and can be reduced in size to fit into microelectronic-based systems. On the downside, short- and long term drift effects as well as a rather low overall lifetime are major obstacles when compared with the NDIR measurement principle^[2].

References

1. ^ ^a b Carbonate Based CO2 Sensors with High Performance, Th. Lang, H.-D. Wiemhöfer and W. Göpel, Conf.Proc.Eurosensors IX, Stockholm (S) (1995); Sensors and Actuators B, 34, 1996, 383-387.
2. ^ Reliable CO2 Sensors Based with Silicon-based Polymers on Quartz Microbalance Transducers, R. Zhou, S. Vaihinger, K.E. Geckeler and W. Göpel, Conf.Proc.Eurosensors VII, Budapest (H) (1993); Sensors and Actuators B, 18-19, 1994, 415-420.