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picture of a motion detector

Motion Detectors in a Security System

picture of a motion detector

A motion detector is designed to detect any kind of motion and uses heat patterns in a room to detect movement. We’ll walk you through a wireless motion detector installation and explain how motion detectors work.


Looking for Heat

Technician Adam begins to install a motion detector.

Motion detectors look for heat, but certain wired kinds can also look for microwave reflections or bounce back. Wireless motion detectors are also known as passive infrared detectors (PIR) and look for heat only.

Because wired motion detectors look for heat and microwave reflections, they are less susceptible to false alarms. False alarms can occur from any change in the heat pattern of a room, such as from balloons, ceiling fans, open windows, and curtains.


Pets and False Alarms

Technician Adam installs a wireless motion detector
Technician Adam installs the motion detector.

Human heat patterns are different from the heat patterns of small animals, such as dogs or cats. Besides this, to avoid false alarms from pets, motion detectors divide areas into quadrants and pie wedges, detecting a “pulse count” every time a wedge is crossed. Most detectors have a two- or three-step catch and trigger an alarm after a breach of this kind.


Line of Sight

Technician Adam finishes installing a wireless motion detector
Technician Adam finishes installing a wireless motion detector.

Motion detectors need a direct line of sight to function best, so you’ll want to place them in an area that is unobscured by large objects or walls.

Since motion detectors use heat to detect motion in a room, they are not recommended for unheated spaces such as sheds, garages, some entryways, or some unfinished basements.


We recommend motion detectors as a part of any security system. For more information on motion detectors and how they can help protect you, contact us.

Read more about other sensors & detectors available in a security system.

Updated August 8, 2016