Glass break detector

Glass break detectors are used to detect the breaking of a window to protect against break-ins. They are used for perimeter protection with intrusion detection systems.

There are different types of glass break detectors.

Passive sensors

Acoustic glass break detector

Acoustic glass break detectors react to airborne and be mounted in the space of the glass surface to be monitored. They have a built-in microphone and respond to characteristic frequencies that result from breaking a glass. As a rule, these are low frequencies ( hammering ) and then high frequencies ( glass fragments ) and possibly also infrasonic waves (air pressure changes ) that occur during disc breakdown. The typical minimum disk size for triggering is about 30 cm x 30 cm. This safely prevents tripping by shattering glasses. The maximum distance of the glass break detector to disk is seven to ten meters. There are monitored all disks within this radius. Acoustic glass break detectors require a supply voltage.

Passive glass -break detector

Passive glass -break detector also work acoustically, but are bonded directly to the glass surface to be monitored and register structure-borne noise. A piezo-electric sensor responsive to vibrations in the range typical of glass breakage to 100 kHz, resulting in destruction of the disk. Triggering by knocking on the glass window is not possible. The monitoring radius on the disc is one to two meters. Caused by glass cutters noise is usually not recognized. Passive glass-break detectors are available in four versions:

Active glass break detector

Active glass break detectors consist of an ultrasonic transmitter and one or more receivers. Transmitter and receiver are mounted on the disc and are nowadays often housed in the same housing. The disc is pressed or damaged, then the transfer medium (glass) between transmitter and receiver varies. Active glass break detectors require a separate power supply and conform to the highest safety class ( to VdS class C).

Glass break detector with alarm wires

In the alarm Glass is in a corner of the glass pane a network of electrical conductors, an "Alarm Spider", is applied to the glass or embedded in the glass. When the glass breaks, the head of the alarm spider be interrupted and an alarm is triggered.

Previously also found glass break detector with alarm alarm wires or foils (standard designation: surface protection, code: FÜ ) reporting an alarm for the protection of surfaces against breakthrough use. In this case, the alarm wire was being placed between the panes of glass to be backed glass surface. If the current-carrying wire tears, is triggered by the interruption of the current circuit of the alarm.