Advantages Of Vibration Sensors As First Line Of Defence.
Advantages of vibration sensors as a front line of defence – Just installing reed switches on doors or PIRs in rooms is not going to be sufficient – by the time they activate and a response is generated, it will be too late.
Vibration sensors detect the low frequency energy that emanates from a point of attack on a barrier, wall or door. The way it works is that transducers are directly attached to the structure being protected.
When an attack takes place, the vibrations excite transducers, which send electrical signals to a signal processor in a vibration sensor for analysis, buffering and then transmission to a controller. From there the signals pass on to a control room or monitoring station.
The ideal structures for low frequency detection are masonry walls and heavy well-fitted doors. Anything that flaps around, flexes or is lightly built in timber or metal is not going to do the job. There are a couple of types of transducers used to detect vibration – mechanical contact switches and piezoelectrics.
The latter convert the mechanical energy of an attack into electrical signals – the heavier the attack, the larger the wavelength of the electrical signal. Because the electrical signals are so minute, sometimes coaxial cable is used to protect and carry signals from vibration sensors to processor/controllers.
Same as PIR sensors, vibration sensors use a pulse count circuit to filter out false alarms. The circuit will tally up a particular number of pulses with a given wavelength threshold before an alarm signal is sent to the processor/controller.
Advantages Of Vibration Sensors
Advantages Of Vibration Sensors-Meanwhile, mechanical contact switches use a seismic mass to make an electrical connection between contacts, or to open a contact. There are spring-loaded switches and unrestricted switches. In unrestricted switches a tiny weight accelerates when hit by a low frequency vibration and momentarily opens a set of contacts – longer opens for bigger vibrations.
When the vibrations have ended, the mass returns to rest on the contacts. In comparison, spring-loaded switches use a spring to close the contacts. That means they can be mounted any old how – you aren’t forced to install them only vertically on a perfectly level axis.
In terms of their strengths, piezoelectrics are more finely adjustable in terms of vibration sensitivity and that means they can be more readily installed on less solid surfaces. Spring-loaded mechanical switches can be adjusted using a screw but it’s not as subtle or predictable as piezos can be.
Vibration sensors would be the perfect way to protect a space from external attack and they would give pre-warning. You’d have to back this up with a proper response, and be prepared to shell out for false alarms. And we’d still install a reed and a PIR in the room, just to give monitoring teams a greater understanding of event progression in the absence of CCTV support.
You can find out more about vibration sensors currently available here or read more SEN news here.
“Advantages Of Vibration Sensors As First Line Of Defence.”
