At room temperature under the condition of anything radioactive. High temperature objects, infrared radiation is stronger. Humans are warm-blooded, infrared radiation is the most stable. We are called passive infrared, only the detector itself does not emit any energy passive receiving, detecting infrared radiation from the environment. Detectors installed after a few seconds have to adapt to the environment, in the absence of, or when the animal enters the detection area, constant field of infrared radiation, when infrared radiation in the human body, through an optical system focuses on making mutations signals of Pyroelectric devices, and alerts. Cordon formed passive infrared intrusion detectors usually can reach dozens of meters.
Passive infrared detector mainly consists of optical systems, thermal sensors (or infrared sensors) and alarm controller and other components. Its core is gone is an infrared detection device can be detected by a very closed system combined with a stereo to prevent change of thermal radiation in space. Detection wavelength of the infrared sensor is 8~14 μ m, the infrared radiation of human body peak wavelength of about 10 μ m, just within the range.