Working principle of infrared probe:
Passive infrared probe works by detecting infrared rays emitted by the human body. The probe collects external infrared radiation and focuses it on the infrared sensing source. Infrared induction sources usually use pyroelectric elements. When the temperature of this element changes after receiving infrared radiation, it will release charges and generate an alarm after detection and processing.
1) This kind of probe is aimed at detecting human body radiation. Therefore, radiation-sensitive components must be sensitive to infrared radiation with a wavelength of about 10 μm.
2) In order to be sensitive only to the infrared radiation of the human body, its radiation exposure surface is usually covered with a special filter to significantly control environmental interference.
3) Passive infrared probe, its sensor contains two pyroelectric elements connected in series or parallel. Moreover, the polarization directions of the two electrodes produced are exactly opposite. The environmental background radiation has almost the same effect on the two pyrolysis elements, causing the discharge effects to cancel each other out, so the detector has no signal output.
4) Once a person invades the detection area, the infrared radiation of the human body is focused through part of the mirror and received by the pyroelectric element. However, the heat received by the two pyroelectric elements is different, and the pyroelectricity is also different. , cannot be offset, and an alarm is generated after signal processing.
5) To obtain multiple fields of view, one is the reflective focusing composed of multi-normal small mirrors, which focuses the light on the sensor, which is called a reflective optical system. The other is a transmissive optical system, which is a multi-faceted lens - a Fresnel lens focused on the infrared sensor.
6) It should be pointed out that several beams of passive infrared light represent several fields of view, not that passive infrared emits infrared light. The more fields of view, the tighter the control.