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Glass Break Sensor – How It Works


In the future, it’s easy to imagine a home security system that works perfectly. A full scan of a home would allow the system to detect any unknown or unwanted intruders before they were even able to cause any damage. Cameras would be able to pick up movement even in low-light and nighttime conditions. Monitored security systems would be able to run even if a theif attempted to scramble their transmission signals. Also, every entry point (windows and doors) in a home would be under 24/7 surveillance of an intrusion.

You may not realize it, but some of this technology already exists. To detect a breaking window, many monitored security systems have the option of installing “glass break sensors”. Glass break sensors (also commonly called “window break sensors”) are designed to be activated when certain parameters are met. Depending on the type of sensor, these parameters may be designed around specific sound pitch requirements, or a vibration signaling that a window has been broken. They are classified as being “perimeter devices”, since they function to help alert you of unauthorized entry around the “perimeter” of your home.

How do Glass Break Sensors Work?

Acoustic glass break sensor units are usualy placed in an area where they are within a specific “detection range”. The sensor is designed to monitor for special frequencies that usually occur when glass is broken. The frequencies monitored are usually from the infrasonic level (which is defined as being 20 hertz or less) to the ultrasonic level (which is above 20 kHz. Because many of these sensors have a “range”, they may not need to be placed directly in front of the window that is being monitored. This can allow a single sensor to monitor several windows, as long as they are within range of the sensor. However, this only refers to glass break detectors which have a built-in microphone that monitors for sound.

Seismic glass break detectors, on the other hand, are installed directly onto the pane of glass that is being monitored. This type of window break sensor is able to detect a break-in by monitoring for special shock frequencies. In most cases, these shock frequencies will be between 3 kHz and 5 kHz. The sensor is able to detect these shock frequencies, which usually will travel though the glass pane, window frame and sometimes the surrounding wall paneling. Once a break is detected, the seismic window break detector will alert you of the break-in.

Wired vs. Wireless

Depending on the type of home security system that you have, you can choose to either install wired or wireless devices. In most cases, having a wireless glass break sensor offers you the greatest advantage. Wireless sensors have flexible placement, allowing you to install them in an optimum location without worrying about the length of a connecting wire. Though wireless window break sensors may be affected by some interference, this can be avoided by placing them within a designated radius of your security system’s control panel. Be sure to account for any other types of interference, such as thick walls or other wireless signals in your home.