Door & window contact sensors – what are they and where to put them?

Boundary door & window contact sensor

Most modern alarm systems incorporate them and Boundary is no different. Ours come in two parts, the sensor and the magnet, which sit on either side of the door or window gap. When the door or window is opened the connectivity between sensor and magnet is broken, which may represent a burglar breaking in.

Cheaper contact sensors can be defeated by holding a second magnet up to the sensor. You can then open the door, without the sensor realising the (real) magnet has moved. Premium contact sensors, like ours, have technology to detect this type of tampering.

Lifestyle Uses

Knowing which doors and windows are open is quite handy, above and beyond security. Those with young children can check that doors to off-limit rooms are closed. If you’ve got a cupboard full of Christmas presents you can make sure nosey teenagers don’t spoil the surprise!

Similarly, if you have a cat or dog, you can make sure they the don’t enter rooms they shouldn’t, and you can keep your furniture free from bite and scratch marks.

False Alarms

Cheap contact sensors tend to be less reliable and more likely to cause a false alarm.

There have been cases of alarms sounding because of the vibrations caused by a truck or bin lorries driving past, or a football hitting the window.

Properly-designed contact sensors will meet Grade 2 EN50131 standards, hence having gone through the testing required to ensure reliability. This means they’re designed to minimise false alarms and will only notify you when necessary.

Where to install them

1. Doors

  • The front and back doors are the two most important entry points to put contact sensors on. If you have other home entry doors, like one via the Garage, a contact sensor should be installed here too.
  • Internal doors are optional. We would advise installing them on any rooms with a high number of valuables.
  • Many top floor apartments have hatches into the attic. Criminals have been known to break in via these hatches. We’d recommend adding a contact sensor if there’s a hatch entry.

2. Windows

  • Contact sensors can be installed on most windows, including slider, casemount and Velux windows. As ours come with both sticky pads and screws, you can install them on most surfaces.

3. Garage, shed and garden side-doors.

We’ve had some users ask about installing contact sensors on mechanical garage doors, shed doors and garden side doors.

In these 3 places, there’s the risk of exposure to wet weather. Therefore, we don’t recommend installing contact sensors on these doors and the warranty does’t cover them if you do. However, our alarm system Z-Wave 700 has long range connectivity, therefore it’s possible that the signal would reach areas outside your home. If you choose to install contact sensors in the places mentioned, you must test them and be fully aware of the implications on your warranty.

Why is the word “contact” in the name?

It’s a historical term, which refers to the electrical contact taking place on the circuit board. If we take a light switch as an example, when the light is off there is no contact between wires which carry electricity. When the light switch is turned on, contact takes place and electricity can travel to the lightbulb.

In old contact sensors, the magnet controlled whether small wires were connected in the circuit board. If this connection was disturbed, it meant the door or window had been opened!

The Boundary contact uses a new detection approach, by sensing the magnetic field directly. This helps to minimise false alarms or tampering.