Patent ID: 6906528
Filing Date: 2005-06-14
Classification: G01D

Abstract:
1. An electronic non-contacting linear position measuring system, comprising: an electrical transmission line of at least two parallel conductors helically twisted with a pitch wavelength that is large compared to the spacing between said two parallel conductors, wherein said pitch wavelength is constant along said line and defines a characteristic unit of distance; a radio-frequency (RF) current source configured to provide RF current into said transmission line, wherein a time-varying magnetic field having both azimuthal and radial components will be induced in the vicinity of said transmission line; at least one nested coil comprising a first coil and a second coil orthogonally nested together, and attached to an object, wherein said first coil and said second coil have about the same area and the same number of turns of wire, wherein said first coil has its axis pointing toward the symmetry axis of said transmission line and thus will intercept said radial component to produce a corresponding radial signal, wherein said second coil has its axis oriented at 90 degrees to said first coil so that it will intercept said azimuthal component to produce a corresponding azimuthal signal; and means for calculating the instantaneous position of said object with respect to said transmission line based on said azimuthal signal and said radial signal.