Analyze the working principle and characteristics of various infrared sensors
June 15,2022
12v infrared motion sensor, high speed infrared sensor, outdoor infrared motion sensor
Infrared is a kind of light invisible to the human eye, so it has all the properties of light, and all substances above absolute zero, ie -273 °C, can generate infrared. According to the characteristics of infrared rays, infrared rays are used in various sensors, such as infrared temperature and humidity sensors, human infrared detectors and so on.
12v infrared motion sensors are also classified into different types based on how they are emitted and how energy is converted. Let's take a closer look at how the different 12v infrared motion sensors work and their features. According to different emission methods, infrared sensors can be divided into two types: active and passive.
1. Active infrared sensor The transmitter of the active infrared sensor emits a modulated infrared beam, which is received by the infrared receiver, thereby forming a warning line composed of infrared beams. When it is blocked by leaves, rain, small animals, snow, sand, and fog, the alarm should not be reported, and the alarm will be issued when people or objects of a considerable size are blocked.
The active high speed infrared sensor technology mainly uses one transmission and one reception, which belongs to linear prevention. Now it has developed from the original single beam to multiple beams, and it can also be dual-transmitted and dual-received to minimize the false alarm rate, thereby enhancing the product's performance. Stability, reliability.
Since infrared is a detection medium with good incoherence of environmental factors (for sound, lightning, vibration, various artificial light sources and electromagnetic interference sources in the environment, it has good incoherence); it is also a product with good coherence of target factors ( Only the target that blocks the infrared beam will trigger the alarm), so the active high speed infrared sensor will be further promoted and applied.
2. Passive infrared sensor Passive infrared sensor works by detecting the infrared rays emitted by the human body. The sensor collects the infrared radiation from the outside world and concentrates it on the infrared sensor.
Outdoor infrared motion sensors usually use pyroelectric elements, which release electric charges when they receive changes in infrared radiation temperature, and generate an alarm after detection and processing. This outdoor infrared motion sensor is aimed at detecting human radiation.
Therefore, the radiation-sensitive element must be very sensitive to infrared radiation with a wavelength of about 10 μm. In order to be sensitive to the infrared radiation of the human body, its radiation surface is usually covered with a special filter, so that the interference of the environment is obviously controlled. A passive infrared sensor consists of two pyroelectric elements connected in series or parallel to each other.
Moreover, the polarization directions of the two electrodes are opposite, and the background radiation of the environment has almost the same effect on the two pyroelectric elements, so that the electric discharge effects cancel each other out, so the detector has no signal output.
Once the intruder enters the detection area, the infrared radiation of the human body is focused by part of the mirror and received by the pyroelectric element, but the heat received by the two pyroelectric elements is different, and the pyroelectricity is also different, which cannot be cancelled. After signal processing And call the police.
Passive 12v infrared motion sensor, high speed infrared sensor, outdoor infrared motion sensor are widely used in human infrared detectors.