Displacement sensor including a magnetically responsive member and a pair of piezoelectric elements

Claim 1

A displacement sensor for sensing displacement of a magnetic material comprising: a first piezoelectric element and a second piezoelectric element, each said piezoelectric element having two ends; a pair of electrodes being provided, one each, respectively, at one end and at the other end of each of said first and second piezoelectric elements; a permanent magnet mechanically fixed at a base end thereof to one end of said first piezoelectric element so as to be attracted or repulsed as magnetic material is temporarily brought into proximity therewith, thereby consequentially temporarily physically distorting said first piezoelectric element; a weight piece mechanically fixed at a base end thereof to one end of said second piezoelectric element and having approximately the same weight as said permanent magnet but a substantially lesser propensity to be attracted or repulsed as magnet material is temporarily brought into proximity therewith, whereby said first and second piezoelectric elements will tend to be similarly distorted when exposed in common to vibrational effects, but will tend to be differentially distorted when exposed to the proximity of magnetic material; and a base plate having said other ends of said first and second piezoelectric elements mechanically fixed thereto; said electrodes provided at the other end of each of said first and second piezoelectric elements being electrically connected to one another, and said electrodes provided at one end of each of said first and second piezoelectric elements being adapted to be used as output terminals for a monitor of the difference in electrical potential between said one ends of said first and second piezoelectric elements.