Vibetek performance is unaffected by temperature.Vibetek cables available to suit most applications.Vibetek shows minimal variation in sensitivity with length.Vibetek performance is predictable, quantifiable and guaranteed.Vibetek cables do not “pressure age”, so they can be attached with a tie wrap gun. ![]() There are many reasons why Vibetek sensor cables have been so successful in perimeter security: It is usually possible to confirm the alarm event by “listening in” to the audio signals When the latter is detected, the analyser signals the event to the central alarm system. An electronic signal analyser continuously monitors the the sensor cable and automatically discriminates between environmentally generated noises, caused by wind and rain etc, and signals caused by attempts to breach the fence by, for example, someone climbing over or cutting the fence fabric. The Vibetek cable is simply attached to the fence, using cable ties, and effectively converts the entire fence into a microphone that “listens” for any sounds that may be related to intrusion events. Vibetek cable has been in continuous use in the perimeter security industry for many years - mainly as a microphonic sensor on perimeter fences. Distributed vibration, pressure & impact sensing.Vibetek has many practical applications, including: A charge amplifier can also provide a suitable interface for use with Vibetek, but care needs to be taken with the design of this type of circuit if it is to be used at very low frequencies. This will prevent damage by the high voltage spikes that can be generated when the cable experiences an impact. It is recommended, particularly when using Vibetek 10, that transient protection be provided for interface circuits, using, eg, back to back diodes. This should be a high resistance, ideally >10M. When using non inverting op-amps with capacitive sources, R3 is necessary to provide a DC bleed path to earth. A low noise, non inverting JFET voltage amplifier is the simplest interface option, using, for example, a TL071 op-amp. This clearly requires the input impedance of the interface circuit to be high also. For example, a 1 metre length of Vibetek 10, with a capacitance of 700pF, has an effective output impedance of 22M at a frequency of 10Hz. This means that Vibetek cables have a very high source impedance, and care needs to be taken when designing interface amplifier/buffer circuits. The cable effectively behaves as an extended microphone, converting stress, strain, vibration, impact, sound or pressure change into minute electrical signals.Īs with all piezoelectric sensors, Vibetek displays a linearly increasing electrical output as the level of mechanical disturbance increases, and will monitor signals ranging in frequency from a few mHz to hundreds of kHz or more.Ī Vibetek sensor cable can be modeled as a voltage source in series with a capacitance, where the capacitance represents the total capacitance of the Vibetek cable. Vibetek cables are coaxial in configuration and use polyvinylidene fluoride (PVDF) as the dielectric between the inner core and the outer braiding. ![]() This meant that flexible piezoelectric sheet, film and cables could be made, so paving the way for the development of the Vibetek range of microphonic sensor cables in the 1980s. However, in the 1970s it was discovered that certain thermoplastics could be processed to make them piezoelectric. Most piezoelectric materials are hard and brittle examples are crystal quartz and certain ceramics such as lead zirconate titanate (PZT). ![]() Piezoelectric materials have the interesting property of converting mechanical energy into electrical energy and vice versa. All Vibetek cables utilise the piezoelectric effect, discovered in 1880 by the famous French physicist Pierre Curie and his brother Jacques.
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