Magnetic rotary encoder system having a multi-element magnetoresistive sensor

Claim 1

A magnetic rotary encoder system for encoding the position of a rotating member, said system comprising: an encoder wheel having one of a number of different diameters d and at least a first circumferentially running track wherein plural pieces of magnetic information representative of incremental positioning of said encoder wheel are recorded at predetermined spaced intervals along the first track to produce a desired pole count of a number of predetermined possible pole counts; a magnetoresistive displacement sensor disposed adjacently opposite to and in close proximity with the circumferentially running track of said encoder wheel, said sensor being arranged with an arraya of magnetoresistive elements on a non-magnetic substrate and facing said track for sensing the magnetic information recorded on said track, each of said elements in said array having means extending on said substrate to an associated output terminal for selective connection to an electrical conduit wherein said conduit provides electrical connection means between said sensor and a circuit means comprising said system; means for selectively connecting said magnetoresistive elements of said sensor in an interleaved arrangement to provide a corresponding predetermined element spacing in accordance with one of a number of predetermined connecting arrangements each of which correspond to an encoder wheel having a given diameter and pole count, said selectively connected elements providing at least a one pair of bridge terminals; said circuit means having first means for selective coupling to one of said at least one pair of bridge terminals and said circuit means generating an output signal representative of the incremental position of said encoder wheel in response to a change in resistance of said selectively connected elements in the presence of a magnetic field generated by said recorded magnetic information on said encoder wheel.