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In modern EAS systems articles are affixed with security labels which, if not deactivated, respond to electromagnetic fields generated from pedestals at the store's exit. The response is picked up by an antenna thereby triggering an alarm. One of the most widespread systems is the Acousto-Magnetic system.

courtesy of Sensormatic/ Tyco Fire & Security


The security label consists of an amorphous magnetostrictive sensor element which is housed in a small cavity such that it can vibrate freely. The resonant frequency is the fingerprint of an active label. An additional strip of a ductile bias magnet serves for activation and deactivation of the label.

In order to guarantee a unique signal identity of the label both the soft magnetic amorphous material and the bias material have to fulfill specific requirements. 

In close cooperation with the customer, VAC has developed a new amorphous VITROVAC® alloy in order to optimize the required sensor properties with a maximum of consistency and yet possibly low raw material and processing costs.

The resonant frequency of the amorphous sensor can be varied by applying a magnetic field which is used for activating and deactivating the label. This is the task of the adjacent bias field strip which is magnetized or demagnetized accordingly. For this purpose the corresponding state of magnetization must be stable and insensitive to accidental changes on the one hand, but easily changeable with appropriate equipment on the other hand in order to ensure proper activation or deactivation of the label. Our specifically designed Co-free alloy SENSORVAC® with high remanence, closely controlled coercivity and low magnetostriction best fulfills these requirements for the bias magnet.

Last update: 03.12.2012


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