Detection principle of passive infrared detector
Add Date：2018/12/5 Hits：4154 Font Size：S M L Back
Any temperature above absolute in nature (-273o) infrared radiation will produce objects, objects of different temperatures are released from different wavelengths of infrared energy. The body has a constant temperature, there is a difference with the surrounding ambient temperature. When the body moves, change the background infrared energy resulting temperature difference caused by passing through the Fresnel lens onto the pyroelectric sensor, allowing the detector alarm signal is detected.
The various objects within the detection area of the radio waves emitted or reflected by the Fresnel lens will be focused on the infrared sensor, when the object does not change within the environment, the infrared light energy received by the sensor is constant, the conversion to the detector electrical circuit is on a stable value, the detector does not alarm.
When someone within the detection area through the body of the large wavelength of the emitted microwave of about 10 microns due to inhibition of the sensor so that the white light of infrared light a larger proportion of energy, especially when the body is in the bright areas and dark areas of the Fresnel lens when moving between the Fresnel lens is focused on the signal of the infrared sensor will be a series of distinct intensity change, the conversion to an electrical signal detection circuit also has a distinct pulse signal, if this reaches a peak pulse alarm detection standard, the detector will be triggered police.
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