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Inductive position sensor having plural phase windings on a support and a displaceable phase sensing element returning a phase indicating signal by electromagnetic induction to eliminate wire connections

  • US 5,003,260 A
  • Filed: 12/20/1989
  • Issued: 03/26/1991
  • Est. Priority Date: 05/28/1987
  • Status: Expired due to Term
First Claim
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1. A position sensor comprising, in combination:

  • a support extending along a certain direction over a certain range;

    electrically conductive windings mounted on said support, said electrically conductive windings including a first set of windings having a first and second electrically conductive windings, and a second set of windings having third and fourth electrically conductive windings;

    said first set of windings being disposed in a first periodic spatial pattern extending along said direction over said range, said first periodic spatial pattern having a first pitch, said first periodic spatial pattern having multiple cycles over said range,said second set of windings being disposed in a second periodic spatial pattern extending along said direction over said range, said second periodic spatial pattern having a second pitch, said second periodic spatial pattern having multiple cycles over said range, said second pitch being substantially different from said first pitch, said first and second sets of windings being disposed in close proximity to each other and being registered one over the other along said direction and over said range,said first and second windings being arranged to be connectable to a plural-phase source of alternating electrical current, when second pair of windings is disconnected, to establish along said direction and over said range a first electromagnetic field having a first phase that is a predetermined first periodic function of position within said range, said first periodic function having a predetermined first wavelength approximately equal to said pitch, such that said first phase varies continuously over two pi (2π

    ) radians over a distance of said first wavelength in said range and said first phase is proportional to position in said range but said first phase has the same value at two different positions in said range which are spaced apart by a distance of said first wavelength,said third and fourth windings being arranged to be connectable to a plural-phase source of alternating current, when said first set of windings is disconnected, to establish along said direction and over said range a second electromagnetic field that has a second phase that is a predetermined second periodic function of position within said range, said second periodic function having a predetermined second wavelength approximately equal to said second pitch, such that said second phase varies continuously over two pi (2π

    ) radians over a distance of said second wavelength in said range and said second phase is proportional to position in said range but said second phase has the same value at two different positions in said range which are spaced apart by a distance of said second wavelength, said first wavelength being different from said second wavelength so that every position within said range determines a unique combination of said first phase and said second phase but neither said first phase alone nor said second phase alone is sufficient to uniquely determine said position, and displaceable means located at a selected position along said direction and in said range for sensing the phase of the electromagnetic field at said selected position generated by said alternating electrical current and for electromagnetically inducing in said windings mounted on said support a signal indicating the sensed phase of said electromagnetic field at said selected position, whereby the phase of the electromagnetic field at the selected position is determinable from said signal without a wire connection between said displaceable means and said windings mounted on said support.

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