The Working Principle, Type, And Application Of Photocell

- Nov 05, 2018 -

Types of infrared sensors: According to different ways of sending, infrared sensors can be divided into active and passive.

The working principle and characteristics of the active infrared sensor: The transmitter of the active infrared sensor emits a modulated infrared beam, which is received by the infrared receiver to form a warning line composed of an infrared beam. When encountering leaves, rain, small animals, snow, sand, and fog, it should not be alarmed. If a person or a considerable volume of objects is blocked, an alarm will occur.

Active infrared detector technology mainly adopts one-shot and one-receipt, which belongs to linear prevention. Now it has developed from the original beam to multiple beams, and it can also double-shot and double-receive, minimizing the false alarm rate, thus enhancing the stability of the product. Sex, reliability. Because infrared is a non-coherent environmental factor (for sound, lightning, vibration, various types of artificial light sources and electromagnetic interference sources in the environment, with good incoherence), it is also a product with good coherence of target factors ( The alarm will only be triggered if the target of the infrared beam is blocked, so the active infrared sensor will be further promoted and applied.

The working principle and characteristics of the passive infrared sensor: The passive infrared sensor works by detecting the infrared rays emitted by the human body. The sensor collects infrared radiation from the outside and collects it on the infrared sensor. Infrared sensors usually use pyroelectric components, which release the charge outward when the temperature of the infrared radiation is received, and an alarm is generated after the detection process. This sensor is aimed at detecting human radiation. Therefore, the radiation sensitive component must be very sensitive to infrared radiation having 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 environmental interference is obviously controlled. A passive infrared sensor consists of two pyroelectric elements connected in series or in parallel. Moreover, the two polarization directions are exactly opposite. The ambient background radiation has almost the same effect on the two pyroelectric elements, so that the discharge effect is mutually canceled, so that 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 received by the pyroelectric element, but the two pieces of pyroelectric elements receive different heat, and the pyroelectric power is different, which cannot be cancelled, and is processed by signal. And the alarm.

Infrared sensor application:

1. Environmental adaptability is superior to visible light, especially at night and in harsh weather;

2, good concealment, generally passive signal receiving target, more secure than radar and laser detection and confidentiality, not easy to be interfered;

3. The ability to identify camouflage targets is better than visible light due to the detection of infrared radiation characteristics caused by the temperature difference between the target and the background and the difference in emissivity;

4. Compared with the radar system, the infrared system is small in size, light in weight, and low in power consumption