PIR sensor-based alarms can be designed to ignore certain shapes of moving objects, or only detect motion above a certain height. It is important to seal the PIR sensor itself inside material that can reduce the outside influences of temperature or humidity, such as metals like silicon. These differentials are what the PIR sensor uses to detect movement, sending a message to the alarm panel and sounders if active. The minute an object, person or animal moves through the detecting area, it is sensed by one of the slots before the other, causing a positive differential as it passes by, and a negative differential change as it leaves the area. While ‘idle’, the ambient level of infrared detected in the room (naturally emitted by all objects) is the same on both slots. Two IR-sensitive slots sit in front of the lens, with their field of “vision” determining the range of detection. When the PIR sensor detects motion, it opens the relay, breaking the circuit and triggering the alarm.Īt a basic level, PIR sensors operate using positive differential change. In the case of PIR sensors in burglar alarms, a relay comprises part of a circuit that runs across twin contacts.

It is also important to remember that PIR sensors detect the emission of infrared radiation, and not heat. They are referred to as “passive” due to the fact that no heat or energy is emitted by the sensor itself.

They are sometimes referred to as ‘motion-based detectors’, as they sense the presence of people, animals and objects through the movement of their infrared wavelengths. This type of emission is not visible to the human eye, but sensors that operate using infrared wavelengths can detect such activity. PIR (passive infrared) sensors utilise the detection of infrared that is radiated from all objects that emit heat. But what is a PIR Sensor? And what makes them so effective? What is a PIR Sensor? One of the most successful to date is the PIR sensor method found in many of the burglar alarm systems installed in domestic and commercial properties alike. The PIR detection technology involved in security systems has changed over the years, with top manufacturers constantly finding new and innovative ways to sense the presence of intruders. What is a PIR Sensor and How does it Work?

Pir sensor