1. Magnetostrictive effect Magnetostrictive effect: Under the action of an external magnetic field, the size of a ferromagnetic substance changes; after the external magnetic field is removed, it returns to its original length.
2. Magneto-mechanical coupling coefficient k When the permalloy thin strip is excited by an alternating magnetic field under a bias magnetic field, due to the magnetostrictive effect and piezomagnetic effect, alternate conversion between magnetic energy and mechanical energy occurs in the thin strip. The conversion of energy is called magneto-mechanical coupling. The magneto-mechanical coupling coefficient k is used to measure its size, and the k value is determined by the following method. The core element in the acousto-magnetic tag is a thin strip of permalloy.
3. Tuning fork effect The 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 ones).