Infrared sensor is a sensor that utilizes the physical properties of infrared radiation for measurement. Infrared, also known as infrared light, has properties such as reflection, refraction, scattering, interference, and absorption. Any substance, as long as it has a certain temperature (above absolute zero), can radiate infrared radiation. Infrared sensors do not directly contact the measured object during measurement, thus there is no friction, and they have the advantages of high sensitivity and fast response. IR sensor haves two types as active infrared and passive infrared sensors.

PF21 series photoelectric sensor

1 Active infrared sensor technology mainly adopts one receiver and one transmitter, which belongs to line defense. It has evolved from a single beam to multiple beams, and can achieve dual reception and dual transmission, minimizing false alarm rates and enhancing the stability of the product.

Advantages of active infrared sensor : good non coherence of environmental factors, good non coherence for sound, thunder, vibration, various artificial light sources and electromagnetic interference sources in the environment; At the same time, it is also a product with good coherence of target factors. The alarm will be triggered only when the target of infrared beam is blocked

Disadvantages of active infrared sensor: High cost. Due to the narrow beam of the active infrared detector, the installation point of the receiving and transmitting end must be firm and cannot be moved by ground vibration, otherwise it will cause false alarms. The optical system also needs to be kept clean, and need regular maintenance.

2 Passive infrared sensors work by detecting the infrared radiation emitted by the human body. The sensors collect external infrared radiation and gather it onto the infrared sensor.

Advantages of passive infrared sensor: It does not emit any type of radiation, and the device has low power consumption, good concealment, and low price.

Disadvantages of passive infrared sensor: Easy to be disturbed by various heat sources and sunlight sources; Passive infrared penetration is poor and the infrared radiation of the human body is easily blocked; Susceptible to radio frequency radiation interference; When the ambient temperature is close to the human body temperature, the detection and sensitivity significantly decrease.