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What is Pyroelectric Infrared?

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  • Written By: Heather Phillips
  • Edited By: Michelle Arevalo
  • Last Modified Date: 19 September 2016
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Pryoelectric infrared is a passive infrared (PIR) technology that can sense a change in radiation emitted by living organisms and inanimate matter. It converts infrared light waves, which are below the light range that humans can see, to electricity via special crystalline material. When the frequency of the light waves changes, the electrical change can be utilized to power a relay on a circuit, sending a signal that can sound an alarm, among other uses.

The crystalline material used in pyroelectric infrared products can be made of various substances. Some of them include gallium nitride, caesium nitrate, cobalt phthalocyanine, and polyvinyl fluorides. All of these substances are capable of generating a low level electrical current when infrared radiation around them increases.

The most common use of this technology is in motion detection sensors. Many of these detectors and sensors are used in burglar alarms. They can be configured to sense the specific amount of infrared radiation that human beings generate — in the range of 9.4 microns — millionths of a meter. Typically, a pyroelectric infrared motion detector will pick up any infrared radiation in the eight to 14 micron range.

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The usual configuration of a pyroelectric infrared detector often includes a Fresnel lens, which focuses the infrared light onto the crystalline material. When the amount of light is in the right range to indicate the possible presence of an intruder, the crystalline material becomes charged. This charge is usually very low and is then amplified by a field effect transistor (FET). The amplified power level can then be sent, via electrical circuitry, to a siren, lights, or an automated call, which can contact local law enforcement.

Other uses of pyroelectric infrared technology often occur in industrial settings. PIR sensors can be used to detect the presence of various gases and petroleum leaks. Hence, they often form part of the safety systems at oil refineries, in steel mills, and other industries that utilize or refine gases. In addition, PIR sensors can be used to detect flames, in breath analyzers that check for the presence of alcohol, in some kinds of medical equipment, and for water safety testing.

Improvements in nanotechnology have allowed for the development of pyroelectric infrared detectors with built-in cameras. These can be employed to capture images of intruders, which can then be relayed to law enforcement. The images can also act as evidence in cases where an alleged burglary or attempted break-in has occurred.

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