The tuning fork effect acousto-magnetic label is composed of a small plastic box with a length of about 40mm, a width of 8"14mm, and a thickness of 1mm (the existing thinner). In the small box, two metal strips form a structure similar to a tuning fork One is a hard magnetic metal strip fixed on a plastic box, and the other is a soft magnetic permalloy strip that can vibrate freely.
According to the special material and structure of the label, it has a certain resonant frequency; when an alternating current is applied When the frequency of the magnetic field is the same as the resonant frequency of the tag, resonance will occur. Due to the magnetostrictive effect and piezomagnetic effect, when the applied alternating magnetic field disappears, the tag will still produce damped oscillation, forming a mode of alternating magnetic field energy and mechanical energy conversion. Attenuated resonance signal, which is a kind of acousto-magnetic composite signal.
The working frequency of a typical acousto-magnetic tag is 58kHz, and the tuning fork resonance signal is similar to ultrasound. Therefore, it has strong anti-interference ability and penetrating power, which is different from other tags The biggest advantage. In the process of using the tuning fork effect to identify, it is actually a process of mutual conversion between electromagnetic energy and mechanical energy. However, due to the low transduction efficiency of magneto-sensitive devices, strong transmission power is required. For example, the typical value of the minimum activation magnetic field strength is greater than 16A/m, so the antenna detector of the acoustic magnetic system is relatively large.