Home Alarm Sensors - What Are the Options?

A home alarm system is an integral part of a complete home security system. A good home alarm is a deterrent to would-be thieves, but it is also a mechanism by which to slow them down and lower the possibility that they make of your things in the event of a break-in.

Perhaps the most crucial element of a home alarm is the sensor. These can sense activity in and around the house by taking various observations and relaying them back to a central control panel. Understanding the different types of sensors and their different functions is an important step in planning your own home security system. What follows is a brief primer on the basic types of sensors available to homeowners.

Magnetic Detectors are commonly used for windows and doors and are composed of two magnetic elements, one on the window or door frame and the other on the window or door itself. When the door or window is opened, the elements are separated and, if the system is armed, an alarm is triggered. A sensor such as this would not trigger the alarm system if a thief broke the window and entered without separating the elements.

Pressure Sensors can add an extra layer of security to window entrances. Mats with pressure-sensitive elements are placed beneath carpet or another flooring at the base of the window. When the system is armed, the weight of a person on the hidden mat will trigger an alarm.

Glass breakage detectors use highly developed acoustic technology to trigger an alarm on detection of breaking of glass windows or doors. These detectors have highly attuned audio sensors that can distinguish the sound of an object striking glass and the sound of glass breaking that immediately follows. Generally one device is sufficient to cover one room.

Passive Infrared Sensors use advanced technology to detect the presence of an intruder by identifying changes in air temperature due to body heat.

Ultrasonic sensors send out sound waves which are returned to the sensor. Movement in the room will alter the pattern of waves returning to the sensor and trigger the alarm. The sound waves sent out by ultrasonic sensors can be moved by strong air currents, such as those from a heating and cooling system, so a careful assessment of the air currents in the space should be made before installation.

Microwave sensors operate similarly to ultrasonic ones but use microwave radio waves instead of sound waves. These waves are not affected by air currents and can thus be used as an alternative to ultrasonic systems in rooms with powerful air-con or heating units. Microwave radio waves are powerful, however, and may trigger alarms due to movement detected beyond the boundary you have chosen. As such, careful assessment and consultation with a professional are advisable if using such a system.