The working principle of infrared detector:

Infrared detectors work by detecting infrared light emitted by the human body. The detector collects infrared radiation from the outside world and concentrates it on the infrared sensor. Pyroelectric infrared sensors usually use pyroelectric elements, which release charges outward when receiving changes in infrared radiation temperature, and generate alarms after detection and processing. Infrared detector This detector is designed to detect radiation from the human body. Therefore, the radiation sensitive element must be very sensitive to infrared radiation with a wavelength of about 10μm.

In order to be sensitive to the infrared radiation of the human body, the radiation surface is usually covered with a special filter, so that the interference of the environment is obviously controlled. An infrared detector whose sensor consists of two pyroelectric elements connected in series or parallel. Moreover, the two electric polarization directions made are opposite, and the environmental background radiation has almost the same effect on the two pyroelectric elements, so that the pyroelectric effect is offset by each other, so the detector has no signal output.

Once the intruder enters the detection area, the infrared radiation of the human body is focused through part of the mirror, so that it is received by the pyroelectric element, but the heat received by the two pyroelectric elements is different, the pyroelectric is also different, can not be offset, and the alarm is reported by signal processing. The acquisition of multiple fields of view, one is the reflection focusing composed of a multi-normal small mirror, and the light is concentrated on the sensor, which is called a reflective optical system. The other is a transmissed-optical system, which combines multiple lenses together - Fresnel lenses, and focuses on the infrared sensor through the Fresnel lens. It should be pointed out that several beams of light on the infrared surface indicate that there are several fields of view, not infrared infrared light, the more field of view, the more tightly controlled.

Advantages of infrared detectors:

It does not emit any type of radiation, the device power consumption is small, and the concealment is good. Low price

Disadvantages of infrared detector:

Easy to be disturbed by various heat sources and sunlight sources.

The infrared penetration power is poor, and the infrared radiation of the human body is easy to be blocked and not easy to be received by the detector.

Susceptible to interference from radio frequency radiation.

When the ambient temperature is close to the human body temperature, the detection and sensitivity decrease significantly, sometimes resulting in short-term failure.