Infrared gas sensor

Infrared gas sensors and controllers for both stand-alone operations and integration in other systems... 

Comparison of sensor response to varying concentrations of carbon monoxide for both a SnOj sensor (top) and an infrared gas sensor (bottom). Reproduced with permission (Wiegleb and Heitbaum, 1994). 

Lambrecht A, Hartwig S, Schweizer SL, Wehrspohn RB (2007) Miniature infrared gas sensors using photonic crystals. Proc SPIE 6480 64800D... 

Table 14.15 Various infrared detectors used in optical nondispersive infrared gas sensors...

In context with methane detection during offshore oil drilling, another infrared fiber optic methane sensor was reported25. The detector comprises 3 main units a microcomputer-based signal processing and control unit, a nonconducting fiber optic gas sensor, and an optical fiber cable module. The system operates at an absorption line of methane where silica fibers have very low losses. 

Inaba H., Chan K., Ito H., All-optical remote gas sensor system over a 20 km range based on low-loss optical fibers in the near infrared region, Proc. SPIE-Int. Soc. Opt. Eng. 1984 514 211. 

Stewart G., Jin W., Culshaw B., Prospects for fibre-optic evanescent-field gas sensors using absorption in near-infrared, Sensors and Actuators B 1997 38-39 42-47. 

We expect these micromachined sensors to become more and more important in the household industry, in many domestic applications of silicon pressure sensors, acceleration sensors, tilt sensors, infrared detectors and thermopiles, flow meters, as well as gas sensors and liquid constituent sensors. 

This can be realized with modem sensors such as infrared thermopiles, thermopile arrays, microspectrometers and color sensors, several types of humidity sensors, artificial noses and multi-gas sensors. 

Detailed studies were conducted by infrared, TPD, XPS but also by more sophisticated techniques such as CP-MAS solid state NMR or EXAFS, on the various steps by which molybdenum can be deposited on alumina supports starting from [Mo(CO)e]. Indeed, thin films of molybdenum or of its oxides have wide application as gas sensors or solar cell catalysts. 

The covalent chemistry of fullerenes has developed very rapidly in the past decade in an effort to modify fuUerene properties for a number of applications such as photovoltaic cells, infrared detectors, optical limiting devices, chemical gas sensors, three-dimensional electroactive polymers, and molecular wires [8, 25, 26, 80-82]. Systematic studies of the redox properties of Cgo derivatives have played a crucial role in the characterization of their unique electronic properties, which lie at the center of these potential applications. Furthermore, electrochemical techniques have been used to synthesize and separate new fullerene derivatives and their isomers as well as to prepare fullerene containing thin films and polymers. In this section, to facilitate discussion of their redox properties, Cgo derivatives have been classified in three groups on the basis of the type of attachment of the addend to the fullerene. In group one, the addends are attached via single bonds to the Cgo surface as shown in Fig. 6(a) and are referred to as singly bonded functionalized derivatives. The group includes... 

When rebreathing systems are used for the delivery of xenon, its concentration within the system needs to be closely monitored. Infrared gas analysers cannot detect xenon, since it is a single atom, and as it is chemically inert its physical properties must be utilised. Mass spectrometry is the most accurate method but it is expensive and it is impractical for clinical use. A calibrated katharometer combined with a galvanic oxygen sensor is a satisfactory alternative which provides a reasonably accurate measure ( 1%). 

A variety of chemical gas sensors are or could be used in electronic nose instruments. So far, successful results have been reached with conductive polymer (CP) sensors, metal oxide semiconductor (MOS) sensors, metal oxide semiconductor field effect transistor (MOSFET) sensors, quartz crystal microbalance (QCM) sensors, and infrared sensors. 

The pyroelectric response of ferroelectrics may be exploited to detect tem-peratnre changes with extremely high sensitivity. The most common devices are nncooled infrared (IR) detectors, which may be used for spectroscopic analysis as well as imaging apphcations. Pyroelectric thin films based on perovskite-type complex oxides, including Pb(Sc,Ta)03 have been deposited by CSD for intruder alarms, gas sensors, and IR cameras. It is anticipated that these thin-film devices will be substantially less expensive to manufacture than existing bulk polycrystaUine devices, which require labor-intensive manufacturing procedures. 

Chan K, Ito H, Inable H (1984) An optical fiber based gas sensor for remote adsorption measurement of low level methane gas in near infrared region. J Lightwave Technol 2 234—237... 

Mizaikoff B et al (1995) Infrared fiber optic gas sensor for chlorofluorohydrocarbons. Vib Spectrosc 8 103-108... 

One of the most common types of gas sensor sold is the electrochemical gas sensor however, although these are low power, it is not possible to integrate this type of sensor and the necessary circuits on the same chip. This is because it requires signihcant volumes of liquid electrolytes and non-CMOS catalytic materials, such as platinum or silver electrodes. Another common gas sensor is based on infrared absorption but these require high power for the source and non-CMOS optical band-pass filters. They are also even more expensive than electrochemical sensors at 50 or more. 

Optional dual-range infrared combustible gas sensor... 

The GD-888 SERIES of portable and wall-mounted. Infrared Carbon Dioxide Gas analyzers are available from as low as 0-9990 ppm up to 0-100.0% full scale. Bectrochemical oxygen and toxic gas sensors can also be added inline with the built-in air pump. Most units come with backlit LCD display, adjustable alarm, 0-1 VDC output, and rechargeable batteries that allow for portable use or continuously on AC power with the battery charger. 

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