Patent ID: 7434482

Claim:
An improved external force measuring apparatus, comprising: a) a piezoelectric force generating element having one fixed end attached to a fixed frame and the other, free end, to receive force from a force input mechanism, b) first means for sensing the position of said free end of said force generating element, and for generating a signal proportional to a position of said free end of said element; said means comprising: i) an electrical conductive element mounted on said force generating element, and ii) one or more inductive coils mounted on said fixed frame adjacent to or near said conductive element means, c) second means for using said signal to generate a voltage to control the position of said piezoelectric force generating element's free end, such that said free end maintains a substantially constant location, despite existence of externally applied forces, via closed-loop feedback position control and d) third means to interpret said voltage applied to said piezoelectric element in terms of a scaled measure to said external force.