Is a perimeter alarm system the best way to protect your home?

What is a perimeter alarm system?

Your perimeter is your first layer of defence. The perimeter is essentially the outer boundary of your property. No-one can get into your home without going through the outer perimeter. A secure perimeter alarm system covers all points where an intruder could cross your perimeter. These points are known as access points.

How do motion sensors work?

Motion sensors are an essential part of any perimeter alarm system. You’ll want to combine motion sensors and security cameras for maximum protection. There are two types of motion sensors: active motion sensors and passive motion sensors.

Active motion sensors send out ultrasonic sound waves. These ultrasonic soundwaves travel out from the device and bounce back to the device when they hit something. The motion sensor measures the sound waves bouncing back. If something comes in range of the motion sensor (e.g. a person walks past), the ultrasonic waves do not bounce back correctly. This triggers the device.

Passive motion sensors work by detecting either heat or light. Passive infrared motion sensors detect infrared heat. Humans emit infrared heat through their body heat. So a passive infrared motion sensor is triggered when a human (or animal) emitting infrared heat comes into a range.

The other type of passive motion sensor detects light. They’ll generally emit a laser beam and they’ll monitor the beam with a light detector. When something crosses the beam, the sensor will detect the change to the light and trigger.

As you can see, each type of motion sensor has unique characteristics. What works for one property might not be appropriate for another. Talk to a security expert about which types of motion detector will work best.

What’s a false positive?

A false positive is when a motion sensor is triggered but there’s no intruder on the property. This is not only really annoying; it’s also a security problem! If your alarm goes off all the time, you’ll stop trusting it to tell you when there’s a genuine threat.

The different types of motion sensor give different types of false positive. As you might imagine, an infrared motion sensor can be tripped by changes in temperature. Sunlight on a warm day can trip this kind of motion sensor, so it’s best used in an environment where the temperature is stable.

For both ultrasonic and photo (light) motion sensors, the alarm can be tripped by anything that comes into range — not necessarily a human!

What about cameras that detect motion?

Security cameras have come a long way recently. A smart security camera can be controlled by a smartphone app. Camera sensors can often record in 4K resolution. Clever software allows cameras to follow subjects as they move across the field of vision and zoom in on faces. Ideally, your camera will also be smart enough to be able to tell the difference between pets and humans. This will stop you from getting false alarms every time your dog goes for a walk!