Motion Detector's introduction

Motion Detector, type of electronic security device that senses movement and usually triggers an alarm. Many types of motion detectors can sense motion in total darkness, without an intruder becoming aware that an alarm has been triggered.

Motion detectors are an important part of most burglar alarm systems. They help alert security personnel, especially in situations where no obvious break-in has occurred. For instance, if an intruder steals a key to gain access to a protected site or hides within the site during normal business hours, the intruder’s entrance or presence could go unnoticed. A motion detector will detect the intruder’s movements as soon as he or she walks or otherwise moves within the area protected by the detector.

Motion detectors usually protect indoor areas, where conditions can be more closely controlled. Detectors for use in homes usually detect movement in spaces about 11 m × 11 m (35 ft × 35 ft) in area. Detectors for large warehouses can protect areas with dimensions as large as 24 m × 37 m (80 ft × 120 ft). Buildings with valuable or important assets, such as museums, also use motion detectors to detect break-ins at vulnerable points. Such points include walls, doors, windows, skylights, and even air ducts. Special motion detectors can protect the inside of exhibit cases where items such as diamonds are displayed. Others can be focused to a narrow area of coverage, somewhat like a curtain, that is projected in front of a painting to detect even the slightest touch.