Patent ID: 6437558
Filing Date: 2002-08-20
Classification: G01R

Abstract:
A system for detecting rotational speed of a rotor, the system comprising:a sensor comprising at least one multilayer material located adjacent to, but separate from, a rotatable rotor, the multilayer material comprising a layer of a first selected thickness of a selected magnetostrictive material, connected across an interface to a layer of a second selected thickness of a selected piezoelectric material and configured so that, when the magnetostrictive material is subjected to a change in magnetic field from rotation of the rotor, a change in at least one dimension of the magnetostrictive material induces a strain in, and produces a non-zero voltage signal in, the piezoelectric material, where the rotor comprises one or more selected magnetic materials located at N locations (N &gE;1) on a circumference of the rotor, and the N locations are approximately equally spaced along the circumference; and voltage sensing means connected to the piezoelectric material layer to sense and count a number of times the voltage signal attains or exceeds a selected value in a selected time interval as the rotor wheel rotates.