Distance Sensors Using Domain Wall Propagation Driven by a Wire Current Pulse Train in Amorphous Magnetostrictive Wires

A new distance sensor described in this paper uses stepwise propagation of a domain wall by a pulse wire current train in a twisted magnetostrictive amorphous wire. A distance sensor of simple construction and with a length of 1000 mm was obtained. The sensor characteristics are controlled by applying torsion, and a suitable amount of torsion, with minimal nonlinearity, was identified. To improve the resolution of the sensor while preserving the good linearity, we tried changing the pulse shape of the driving current by adding a bias current to the pulse train current. A digital type distance sensor with a resolution of about 1 mm and nonlinearity of about 1% over the length of the 1000 mm long wire was achieved.