Motion detector

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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.

1 Overview
2 Sensors
3 Dual-technology motion detectors
4 See also

[edit] Overview

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.

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.

[edit] Sensors

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.

[edit] 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. ^[1] 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 later also picks up an intruder, then the alarm is sounded.