Patent ID: 6933846
Filing Date: 2005-08-23
Classification: G01D,G01V,G08C

Abstract:
1. A protected object comprising: an object having associated therewith a displacement sensing system including: an oscillator circuit having a characteristic frequency which varies as a function of a magnetic field in the vicinity thereof; an element whose position relative to said oscillator circuit is varied by a displacement to be sensed, said element being operative to vary the magnetic field in the vicinity of said oscillator circuit as a function of said displacement; and circuitry for sensing a change of frequency of said oscillator circuit over time (Δf/Δt) and for providing an output indication when the change in frequency of said oscillator circuit over time exceeds a threshold; and a locator operative for determining the location of at least one of said oscillator circuit, said element and said circuitry for sensing, wherein one but not both of said oscillator circuit and said element is fixedly mounted onto said object.