A motion detector
is a device that contains a physical mechanism or electronic sensor that quantifies motion
that can be either integrated with or connected to other devices that alert the user of the presence of a moving object within the field of view.
An electronic motion detector
contains a motion sensor that transforms the detection of motion into an electric signal. This can be achieved by measuring optical or acoustical changes in the field of view.
A motion detector may be connected to a burglar alarm that is used to alert the home owner or security service after it detects motion.
Such a detector may also be trigger a red light camera.
An occupancy sensor is a motion detector that is integrated with a timing device. It senses when motion has stopped for a specified time period in order to trigger a light extinguishing signal. These devices prevent illumination of unoccupied spaces like public toilets.
There are basically three types of sensors used in motion detectors spectrum.
- Passive infrared sensors (PIR)
- ''Looks for body heat. No energy is emitted from the sensor.
- Ultrasonic (Active)
- Sensor sends out pulses and measures the reflection off a moving object.
- Microwave (Active)
- Sensor sends out microwave pulses and measures the reflection off a moving object. Similar to a police radar gun.
Dual-technology motion detectors
Many modern motion detectors use a combination of different technologies. These dual-technology detectors benefit with each type of sensor, and false alarms
are reduced. All companies have the option to use PIR/Microwave Motion Detectors that have "Pet-Immune" functions which allow the detector to ignore pets that weigh up to 40 pounds (wireless models) or 80 pounds (hard-wired models).
Often, PIR technology will be paired with another model to maximise accuracy and reduce energy usage. PIR draws less energy than microwave detection, and so many sensors are calibrated so that when the PIR sensor is tripped, it activated a microwave sensor. If the latter also picks up an intruder, then the alarm is sounded.