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Motion transducer

  • US 5,399,967 A
  • Filed: 03/15/1993
  • Issued: 03/21/1995
  • Est. Priority Date: 03/13/1992
  • Status: Expired due to Term
First Claim
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1. A motion transducer comprising magnetised ferromagnetic material which is capable of motion past an array of Hall-effect sensors positioned in a common plane at points on a circle, said motion being along a straight axis transverse to said plane in which said circle lies, said axis being displaceable from a true position normal to said plane through the centre of said circle to a displaced position within said circle, said magnetised material being in the form of a hollow cylinder having a central longitudinal axis coincident with said straight axis, and comprising external and internal faces, and said material being magnetised so that said external face everywhere presents a magnetic pole of a first polarity and said internal face everywhere presents a magnetic pole of a second polarity, each sensor having an output when the magnetised material moves past the sensors and the transducer also comprising means by which said output may be combined with each other said output to yield a combined output representative of said motion, the value of said combined output being unaffected by any rotation of said hollow cylinder of magnetised material about said straight axis either in said true position or in said displaced position, said sensors being located in the array such that each said output is equal to each other said output in response to said motion along said straight axis in said true position and said combined output being unaffected by said motion along said straight axis in said displaced position, any increase in said output from any sensor or sensors closer to said displaced position of said straight axis being compensated for by reduced output from a sensor or sensors more remote from said displaced position of said straight axis, said output having the form of part of a sine wave and said motion being such that said output has a substantially linear relationship with said motion.

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