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Abstract

A magnetostrictive waveguide position measuring apparatus includes a waveguide extending between opposed anchored ends. A magnet is displaceable along the waveguide and generates torsional strain in the waveguide in response to an electrical excitation signal transmitted along the waveguide. A piezoelectric film element is coupled to the waveguide to sense the torsional strain signal on the waveguide. A signal processor determines the relative elapsed time between the excitation signal and the output signal of the piezoelectric film element to determine the position of the magnet along the waveguide. The piezoelectric film element is coupled to the waveguide along an axis transverse to the axis of stretch of the element. Alternately, a differential piezoelectric film element formed of two piezoelectric elements contacts a waveguide, with the two elements connected in differential parallel or series configuration and in or out of phase to double the output current or the output voltage. The output of the differential piezoelectric elements are connected to an amplifier in either charge or voltage mode for noise, EMI and transient signal suppression.

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First Claim