Infrared Gas Sensor Physics - a brief introduction by our CSO, Dr.techn. S. O. Kanstad

IR sensor physics

Infrared (IR) radiation is "redder than red", and so cannot easily be seen, but otherwise it is just like ordinary light. This fact will be familiar to anyone who has ever felt the heat radiated from a hot oven, and has observed the dark red glow arising when the heat becomes stronger: Some of the heat radiation becomes visible when the temperature increases. Thus, infrared radiation is essentially heat radiation. And yet, though in its nature it is invisible to the eye, it is fully visible to our SmartScan sensors!

Indeed, any body that has a temperature emits infrared radiation. For instance, the well-known IR intruder alarm relies on observing the heat radiation from a moving "hot" body (the intruder) against a colder background (the walls). For these reasons, infrared technology has been intensively researched and developed over the last few decades for military (seeing in the dark) and space (observing faint stars and planets) applications, and an extensive range of IR components exist as standard industry items, such as windows, mirrors, lenses, prisms, "color" filters etc, even IR cameras and IR-TV. Today, IR radiation can be treated and manipulated by the same kind of optical components as are known for visible light - and almost as easily.

Almost - but not quite. The reason being that simple and powerful IR radiation sources have been scarce or even non-existent, or else too complex, too expensive, too weak, too slow. This has now all changed with the introduction of our InfraRapid source of IR radiation.

The InfraRapid radiation source can be made to suit essentially any particular application. Whatever its shape or size, however, it will emit many times more useful IR radiation than comparable thermal IR sources. The InfraRapid can be easily manipulated at will by electric means, to turn electrical energy into IR radiation at unprecedented efficiency.

The InfraRapid source will precipitate a major revolution in IR technology, to transform IR equipment from being an exclusive, high level industrial, space, and military luxury into everyday items. And the most important of those changes will affect all of us profoundly, through the very air we breathe, because IR radiation has the ability to measure accurately and selectively the presence of gases in the air. The reason for this is in the nature of the gases.

As it happens, most gases have their characteristic spectra in the infrared. Those spectra derive from the molecule's composition in such a way that no two molecular gases have the same IR spectrum. IR spectra are the fingerprints of gases, and thus allow gases to be uniquely identified. Indeed, were our eyes tuned to the IR, the sky would be wonderfully colored all day, not only at sunset. Some colors might even be so strong as to make the air opaque in that spectral range.

By transmitting a beam of IR radiation through the air, or through any particular gas volume, and recording how much is transmitted at selected spectral lines, one may decide which gases are present and how much of each. This is a standard and well-proven principle, routinely used in laboratory analyses of chemical species, and is also the basis on which our sensors are made.

However, our SmartScan IR sensor modules do it better, faster, and more precisely and without failure, since our sensors - as well as the molecules - depend directly on the basic physical laws of nature for their operation, - and those laws never fail. It is just that simple.

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