What is the working principle of smart home Mid-IR detectors?

Infrared detectors are commonly used in smart homes and play a crucial role in smart home security systems. However, many people do not know what the working principle of infrared detectors is, so today Xiaobian will popularize it for everyone.

The infrared detector works

Infrared detectors work by detecting infrared radiation emitted by the human body. The detector collects infrared radiation from the outside and collects it on the infrared sensor. Infrared sensors usually use pyroelectric elements, which release charge when they receive a change in the infrared radiation temperature, and generate an alarm after detection processing. The detector is aimed at detecting human radiation. Therefore, the radiation sensitive element must be very sensitive to infrared radiation having a wavelength of about 10 μm.

In order to be sensitive to human body's infrared radiation, a special filter is usually covered on its radiation surface, so that the environmental interference is obviously controlled.

Infrared detectors, whose sensors contain two pyroelectric elements connected in series or in parallel. In addition, the two polarization directions produced are exactly the opposite. The ambient background radiation has almost the same effect on the two pyroelectric elements, causing them to cancel each other's charge generation effect. Thus, the detector has no signal output.

Once the intruder enters the detection area, the infrared radiation of the human body is focused by the partial mirror and is thus received by the pyroelectric element. However, the pyroelectric element received by the two pyroelectric elements is different in heat, and the pyroelectricity is also different and cannot be canceled. And the alarm.

The infrared body temperature detector is another form of light detector that can be triggered by the thermal energy emitted by the intruder. This detector does not respond to changes in room temperature rise or fall. However, when the target whose temperature is approximately equal to the human body temperature enters the elbow in the non-sensitive area from the sensitive area, the alarm can detect the difference in radiation and trigger an alarm. Infrared body temperature detectors have high sensitivity and are not easily damaged. However, if the intruder's body temperature matches the room's ambient temperature, the alarm will fail.

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