Home Security Systems - Motion Sensors

• Motion sensors come in a variety of flavors, including microwave and infared; they operate in distinct ways and are ideal for different scenarios.




• Microwave Sensors

  Microwave Sensors operate by bouncing electromagnetic waves in the microwave spectrum off objects and checking the frequency of the waves that bounce back. This is the same as radar speed checking; as the doppler effect compresses sound waves and make them sound different, microwaves give off differing frequencies when the object they're bounced off is moving. These sensors are very sensitive, which can result in the occasional false positive, but microwaves penetrate walls, allowing them to be placed in hidden locations so that they cannot be evaded. Their primary drawback is their periodic interference with other electronic equipment.




• Infrared Sensors

  Infrared Sensors are more common and inexpensive; these are the sensors you see on cheaper installations like porch lights. Infrared sensors actually check temperature, with a methodology not unlike microwave sensors. As consequence, infrared sensors are much more accurate in their detections; however, infrared signals do not penetrate walls in the same way as microwave sensors, and their range is limited. Some of the better sensors on the market combine microwave and infrared sensors to reduce false positives.