These devices are a type of burglar alarm. They react to breaking glass through sounds or vibrations. As they are simple to install and consume little space, they constitute a popular choice for many homeowners.
Technological Evolution of Glass Breakage Alarms
The first model of these types of detectors consisted of metal foil encasing circuits wrapped around or adhered to glass. Upon rupturing, the circuits in the foil would trigger the alarm. However, this technology is difficult to install, requiring precise adherence to the window surface and also is aesthetically unappealing.
Many residents thus opted for other alarm types. An advance in technology witnessed the creation of small devices attached to glass. Commonly called bugs or piezos, these objects are sensitive to vibrations. The obvious logic entails a window breaking vibrates before breaking.
Electric and non-electric models are available, however the electric models are prone to false alarms as any vibration may trigger the device. In addition, a separate device is required for each window pane.
Glassbreak and Audio Verification Detectors
Acoustics represented another advance in technology for these devices. An audio detector is sensitive to the sound of breaking glass and only one is needed for a single room. Sounds travel from the breakpoint outward at a high frequency. When the sound reaches the sensors, the sensors transmit the sound to a filter which triggers the alarm, if necessary.
However, like the piezo, the audio detector may react to other similar sounds such as a breaking mirror, clinking glasses, and other similar sounds. Keep in mind that audio detectors are able to detect sounds with a thirty-five foot radius.
A more recent advance combines two types of sensor technology. This dual-technology sensor uses a microphone and filter attuned to two sounds. Examining the physics of glass breaking reveals a process. First, when an object strikes glass, the relatively dull, low-frequency sound of a flex wave emanates from the point of breakage, traveling outward. A high-frequency sound, about five kilohertz, then follows. The dual-technology detector requires both sounds to transmit to the processor and trigger the alarm.
Installation of Glass Breakage Window Alarms
In contrast to the foil wraps, newer technologies are simpler to install, often requiring simple mounting. The sensor unit can be placed on a window, window frame, wall or ceiling. If you choose to mount the unit on a window, it should be placed about two inches from the window frame. However, windows are more susceptible to temperature fluctuations than walls, so window mounting also requires protecting the unit from heat and cold.
In addition, improper calibration of the detector may cause false alarms. As with many types of sensors, experts recommend using a variety of measures to ensure an optimal amount of security. Some of the more common measures used in conjunction with glass-break sensors include volumetric detectors, and magnetic switches.
Common Problems to Look Out For with a Glass Break Detector
Items such as drapes, shutters, blinds may obfuscate sound and inhibit detection. Thus, installing these detectors may entail compromising aesthetic considerations for one's home. Background noise, like machinery, radio interference, sudden impact noises may also trigger false alarms.
These detectors will also not operate correctly if the glass is cracked. An easy way to circumvent glass-break detectors is to cut the glass, using special glass-cutting instruments, and then removing the cut section. Muffling the break sound with a towel or other soft casing may also obfuscate the break sound.
These devices represent a popular choice for many homeowners. Homeowners who choose to purchase one of these devices you should be aware of its disadvantages and consider using it in conjunction with other measures.