Will My Pets Trigger My Motion Detector?

Motion sensors are a great addition to a home security system, triggering an alarm when motion is detected in your home.  Activated when you aren’t home, they will alert your monitoring station when unexpected activity is detected in your home, reacting to windows or doors being opened or closed, broken windows, and intruders crossing the floor.

There are a variety of different motion sensors available, each operating in a different way.

Passive infrared (or PIR) sensors detect body heat, and is the most common type available in homes today.  If the infrared energy levels change rapidly, indicating a heat source (like a warm human body) is present, it trips the alarm.

Microwave sensors send out microwave pulses, measuring the reflection off of a moving object.  If the time it takes for the microwaves to return changes, it’s an indication that something in the environment is moving, triggering the alarm.  You can also get systems that combine microwave and PIR sensors, requiring both sensors to be tripped to trigger an alarm, reducing the chance of false alarms.  These are called Dual Technology motion sensors.

Other motion sensor varieties include area reflective sensors or ultrasonic sensors.  These function similarly to microwave sensors, simply emitting infrared rays or ultrasonic waves rather than microwaves.   There are also vibration motion sensors, using a mass on a level which triggers an alarm when it vibrates.  These are generally less common and less effective than PIR or microwave sensors.

One of the most common questions we get, when installing home motion sensors, is whether the presence of a pet will set off the alarm.  After all, you don’t want to constantly send your monitoring company false alarms just because Fido is moving from one room to another!  Fortunately, pet-immune motion sensors do exist, thanks to advances in technology.

Pet-immune sensors use sophisticated algorithms, taking into account the mass, speed, movement patterns, body temperatures and infrared emissions of any moving objects to rule out household pets.  Weight is a major telling point; most pet-immune sensors simply won’t trigger if the moving object is below a certain weight, usually 40-80 pounds.  That’s enough to avoid any cat, bird or smaller pet from triggering the alarm, and only the largest of the large breeds of dog – your Great Danes or English Mastiffs – would find themselves detected by those sensors.

While pet-immune sensors do exist, there are some recommendations for set up. Where the motion sensors are located needs to be thoughtfully considered as you would not want them near a staircase or table where cats or small dogs may frequently jump up on and trigger the alarm.  Also, if your pet is too large for a pet-immune system to function properly, the alternative is to replace the motion sensors in your home with glass break detectors.

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