- Motion detector
-
A motion detector attached to a garage
A motion detector is a device for motion detection. That is, it 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. They form a vital component of comprehensive security systems, for both homes and businesses.
Contents
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. Most motion detectors can detect up to 15 – 25 meters (50–80ft).
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 trigger a red light camera or outdoor lighting.
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. They are widely used for security purposes.
Sensors
There are basically four types of sensors used in motion detectors spectrum:
- Passive infrared sensors (Passive)
- Looks for body heat. No energy is emitted from the sensor.
- Ultrasonic (active)
- Sends out pulses of ultrasonic waves 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.
- Tomographic Detector (active)
- Senses disturbances to radio waves as they travel through an area surrounded by mesh network nodes.
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. Placement of the sensors can be strategically mounted so as to lessen the chance of pets activating alarms.
Often, PIR technology will be paired with another model to maximize 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 activates a microwave sensor. If the latter also picks up an intruder, then the alarm is sounded. As interior motion detectors do not ‘see’ through windows or walls, motion-sensitive outdoor lighting is often recommended to enhance comprehensive efforts to protect your property.
False alarms are those usually caused by technical errors such as electrical and mechanical failures. Nuisance alarms are system activations not commonly caused by attackers or intruders but rather from wind blown debris, animals, insects and foliage.
Sequencing alarm systems to trip the alert mechanism only when both alarm sensors have been activated will reduce nuisance alarms, but may also cause the probability of detection to decrease.
See also
- Smoke detector
- Heat detector
- Pickup (music technology)
- Motion detection
- Motion controller for video game consoles
External links
Categories:- Security technology
Wikimedia Foundation. 2010.
