Magnetic rotary encoder for detection of absolute values of angular displacement

A magnetic rotary encoder having an rotary encoder unit and a housing for containing said unit, wherein said encoder unit comprises:

• first means fixedly attachable to a rotatable shaft;
• plural second means respectively retaining magnetic signals and being provided on said first means so as to form more than two tracks, each track having boundaries between said magnetic signals, said tracks being substantially parallel to the circumferential direction of said first means, said tracks producing respectively magnetic fields changing differently in magnitude and direction as said first means revolves;
• plural ferro-magneto-resistors fixedly provided in the vicinity of the rotating paths of said tracks and responsive to said magnetic field and producing analog signals indicative of changes in their electrical resistance, said plural ferro-magneto-resistors within 45.degree. of being parallel to said boundaries;
• and a rotary condition detector electrically connected to said magneto-resistors, receiving said analog signals and producing output signals indicative of the rotated angular distance of said first means in an absolute value;
• and
• wherein said housing comprises means for shielding magnetic fields applied externally.