Gas Sensors

Metal Oxide Gas Sensors

Gas sensors can be segmented according to their operating mechanism (catalytic, electro-chemical, chemFET, resonant, metal oxide semiconductor (MOS), infrared (IR), chromatography, photoionization, chemi-luminescence, etc.). MOS based sensors are the most suitable for cost sensitive, low-power applications such as disposable medical, smart home, and consumer. MOS sensors detect concentration of various types of gases by measuring the resistance change of the metal oxide due to adsorption of gases. 

Semiconductor sensors are commonly used to detect hydrogen, oxygen, alcohol vapor, and harmful gases such as carbon monoxide. One of the most common uses for semiconductor sensors is in carbon monoxide sensors. They are also used in breathalyzers. Because the sensor must come in contact with the gas to detect it, semiconductor sensors work over a smaller distance than infrared point or ultrasonic detectors.

Infrared Gas Detection

Infrared gas detection is based upon the ability of some gases to absorb IR radiation. Many hydrocarbons absorb IR at approximately 3.4 micrometers and in this region H2O and CO2 are relatively transparent. This type of sensor is advantageous because it does not have to be placed into the gas to detect it and can be used for remote sensing. Infrared point sensors can be used to detect hydrocarbons and other infrared active gases such as water vapor and carbon dioxide. IR sensors are commonly found in waste-water treatment facilities, refineries, gas turbines, chemical plants, and other facilities where flammable gases are present and the possibility of an explosion exists. The remote sensing capability allows large volumes of space to be monitored.