A new position sensor based on the MDL technique

In this paper we present a position sensor based on the magnetostrictive delay line (MDL) technique and the eddy currents induced on a soft magnetic material preferably in the form of a ribbon on top of the MDL, which generate elastic micro-strains on the MDL and consequently a pulsed voltage output across a search coil. These eddy currents are due to the pulsed current transmitted through a pair of pulsed current conductors parallel to the MDL, close to the soft magnetic material, and the presence of a permanent magnet, movable along the length of the MDL. The sensor output is the variation of the delay time of the MDL pulsed voltage output due to the motion of a moving magnet along the length of the MDL. The sensor response is by design linear, monotonic and anhysteretic. The sensor materials and characteristics are discussed. Some of the most important sensor applications are presented, namely the static measurement of the position of pneumatic pistons, liquid level and absolute ground velocity. Finally, a possible method of production is proposed.