Types of Motion Sensors
Passive Infrared (PIR)
Detects body heat (infrared energy). Passive infrared sensors are the most widely used motion in home security systems. When your system is armed, your motion sensors are activated. Once the sensor warms up, it can detect heat and movement in the surrounding areas, creating a protective “grid.” If a moving object blocks too many grid zones and the infrared energy levels change rapidly, the sensors are tripped.
Sends out microwave pulses and measures the reflection off a moving object. They cover a larger area than infrared sensors, but they are vulnerable to electrical interference and are more expensive.
Dual Technology Motion Sensors
Motion sensors can have combined features in an attempt to reduce false alarms. For example, a passive infrared (PIR) sensor could be combined with a microwave sensor. Since each operates in different areas of the spectrum, and one is passive and one is active, Dual Technology motion sensors are not as likely as other types to cause false alarms, because in order for the alarm to be triggered, both sensors have to be tripped. However, this does not mean that they never cause false alarms.
Area Reflective Type
Emits infrared rays from an LED. Using the reflection of those rays, the sensor measures the distance to the person or object and detects if the object is within the designated area.
Measures the reflection off a moving object and sends out pulses of ultrasonic waves.
These can be purchased or easily made at home. Detects vibration. A homemade vibration sensor uses a small mass on a lever, which is activated by a switch to an alarm when it vibrates. Homemade motion sensors can work, but they can also be unreliable.
Other Motion Sensor Features
Wireless Motion Sensors
Today, most motion sensors are wireless. Wireless sensors are very easy to set up. They do not require drilling, and they communicate with the other security system components wirelessly.
Contact Motion Sensors (door/window)
Most contact motion sensors are passive infrared sensors. They trigger an alarm if the protected door or window is opened while the system is armed.
Pet Immune Motion Sensors
A passive infrared sensor can be set up to ignore animals up to a certain weight. A dual technology motion sensor is more resistant to false alarms caused by animals because it requires two sensors to be triggered in a manner determined by the manufacturer. They can be set up to ignore a large animal or multiple small animals without setting off a false alarm. Some pet immune motion sensors have a sensitivity level that can be adjusted for families with very active animals.
Video Motion Sensors
Combines video cameras with advanced signal processing. Some recordable motion sensors start recording when they sense motion. Cameras controlled by motion sensors can save you memory storage by not recording hundreds of hours of useless footage—they only capture the important stuff.