Magnetostrictive position indicator

摘要

The position of a movable member is measured without the establishment of physical contact with such member. A magnetic field generator, which provides a localized field of special geometry, is mounted on the movable member and an elongated ferromagnetic member is positioned adjacent and parallel to the path of movement of the member. The magnetic field will produce a change in the Young's modulus of elasticity in an adjacent region of the ferromagnetic member and sonic strain pulses launched along the ferromagnetic member will be partly reflected from this region of Young's modulus discontinuity. The time required for a strain pulse to travel from a given point on the ferromagnetic member to the region of Young's modulus discontinuity and be partially reflected therefrom and returned to a known detection point will provide a measure of the position of the field generator along the elongated ferromagnetic member.