How Does a Glass Break Sensor Work?

A glass break sensor works by listening for the sounds associated with breaking glass. The device must detect both the low-pitch "thud" of an object striking against the glass and the high-pitch "shattering" of the glass itself. Only if both sounds are present, will the device activate.

Glass break sensors are primarily used to monitor windows that an intruder could potentially use to break into the building. If the window is broken, the sensor will activate and cause a faulted zone on the system. The system will then respond according to the response type for that zone. This could include requiring a system disarm or triggering an immediate alarm event.

However, glass break sensors are not always used to monitor windows. Some people use glass break sensors to monitor glass casings and other glass objects. This could include a trophy case or a glass painting. Many stores that use protective glass casings to house their products also use glass break sensors. These often include jewelry stores and gun shops that must monitor their expensive goods at all costs.

Ideally a glass break sensor should be installed near the glass that it is monitoring, along with a direct line of sight to the glass. However, these devices should never be placed directly on the glass itself. This is because the sensor could become damaged if the glass were to become broken. Still, they should be mounted fairly close to the glass so that they can properly pickup any important sounds.

Remember, glass break sensors are sound-based devices that respond to the sound of breaking glass, not the associated shockwaves. That said, there are shock sensors that will respond to these shockwaves. These devices can be used as an alternative to standard glass breaks. Keep in mind though that shock sensors are known to be considerably more sensitive than sound-based glass break sensors. For instance, a shock sensor could activate by someone merely tapping against the glass. For that reason, most users prefer sound-based glass break sensors over shock sensors.