bevægelsesdetektor

A bevægelsesdetektor, or motion detector, is a device that detects movement within a specified area. These sensors are commonly used in security systems, automated lighting, and energy-saving applications. They work by sensing various forms of energy that are altered by the presence of a moving object.

There are several types of motion detectors, each utilizing different technologies. Passive Infrared (PIR) detectors are the most common. They detect changes in infrared radiation, which is emitted by all objects with a temperature above absolute zero. When a warm body moves through the detector's field of view, it creates a change in the infrared pattern that the sensor registers as motion.

Microwave detectors, on the other hand, emit microwave pulses and measure the reflected waves. When an object moves, the frequency of the reflected waves changes due to the Doppler effect, which the detector interprets as motion. Ultrasonic detectors work similarly by emitting sound waves and analyzing the echoes.

Dual-technology detectors combine two different sensing methods, such as PIR and microwave, to reduce false alarms. This is particularly useful in environments where environmental factors like air currents or temperature fluctuations might otherwise trigger a single-technology detector.

Bevegelsesdetektorer find widespread use in homes and businesses for security purposes, triggering alarms or turning on lights when an intruder is detected. They also contribute to energy efficiency by automatically switching off lights in unoccupied rooms.