Magnetic position detector

Claim 1

A magnetic position detector including: a magnetic field generating element including first, second and third longitudinally axially aligned magnets, said first magnet having opposed ends, said second magnet being adjacent to one opposed end of said first magnet, said third magnet being adjacent the other opposed end of said first magnet, said first magnet having a longitudinal face with a selected magnetic polarity, said second and third magnets having longitudinal faces adjacent said longitudinal face of said first magnet with a magnetic polarity opposite the polarity of said adjacent longitudinal face of said first magnet, and said magnets being spaced apart from each other so as to define inter-magnet gaps between said magnets; and a magnetic field detecting assembly located adjacent said magnetic field generating element, said magnetic field generating element and said magnetic field detecting assembly being configured to shift positions relative to each other along a line of travel parallel to the longitudinal axis of said magnetic field generating element, said magnetic field detecting assembly including a Hall element positioned to detect magnetic fields generated by said magnetic field generating element magnets, said Hall element producing an output signal representative of the magnetic fields, and a power supply for providing a bias voltage to the output signal produced by said Hall element, said power supply bias voltage being adjusted so as to cause said Hall element to produce a biased output signal such than when said Hall element crosses positions subtended by said magnetic field generating element inter-magnet gaps, said output signal changes polarity.