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Apparatus for magnetically detecting position or speed or moving body utilizing bridge circuit with series connected MR elements

  • US 4,818,939 A
  • Filed: 02/26/1987
  • Issued: 04/04/1989
  • Est. Priority Date: 03/05/1986
  • Status: Expired
First Claim
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1. An apparatus for magnetically detecting the relative position or speed between moving and stationary bodies, comprising:

  • a magnetic medium provided on either one of the moving and stationary bodies, and having a plurality of magnetic poles arranged continuously thereon at a constant pitch λ

    ;

    sensing means including plural MR elements, provided on the other of the moving and stationary bodies in opposition to said magnetic medium, for sensing a magnetic field generated by said magnetic poles to thereby cause variation in the electric resistance thereof, in which said MR elements constitute k sets of element pairs, each set consisting of two MR elements arranged at positions spaced at (m+1/2)λ

    from one another, where m is an integer, and said element pairs being spaced by (n+1/3λ

    from each other, wherein n is an integer; and

    output circuit means, including said MR elements connected in a bridge circuit so that said two MR elements of each element pair are connected in series and said k sets of series connections of said MR elements are connected in parallel with each other with respect to a power source of the bridge circuit, for synthesizing k sets of voltages appearing at nodes of said two MR elements connected in series and which include third harmonic components having a phase difference of 2 π

    /k from each other so as to produce an output signal.

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