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Passive Infrared Sensor (PIR sensor)

This technology is based on pyroelectric materials combined with dedicated optics and electronics. A passive infrared sensor is an electronic device which measures infrared light radiating from objects in its field of view. Motion or presence is detected when an infrared source with one temperature, such as a human being, passes in front of an infrared source with another temperature, such as the normal environment. As all objects emit what is known as black body radiation (i.e. heat), a dedicated PIR sensor can detect the emitted black body radiation.

This black body radiation being invisible to human eyes, however, can be detected by electronic devices designed for such a purpose, which convert the radiation into an electrical signal. This is then analyzed and – if requested – the sensor goes into “detection”.
L’infrarouge passif dispose de zones de détection réduites et modulables, mais, par définition, il est peu sensible aux objets.

*  “Infra” meaning below our ability to detect it visually, and “Red” because this colour represents the lowest energy level that our eyes can sense before it becomes invisible. Thus, infrared means below the energy level of the colour red.