Magnetic field energy responsive position sensing apparatus and method

Magnetic field energy responsive position sensing apparatus comprising:

• a) a Hall sensor having an element defining a generally planar active face and circuitry coupled to said Hall sensor for producing a two state electrical output signal in response to magnetic field energy in a region of said active face;
• b) a ring magnet having spaced apart annular end walls adjacent a north pole and south sole of said ring magnet wherein said ring magnet defines a magnetic field in a center region of the ring magnet;
• c) structure for mounting said ring magnet and said Hall sensor for relative substantially linear movement in a direction substantially normal to the active face of the Hall sensor element to move said active face through the center region of the ring magnet, the magnet moving along a path of travel such that one annular end wall of the magnet moves past said active face while avoiding mechanically contacting said active face and causes the electrical output signal to change state as the one end wall of the ring magnet moves past the active face of the Hall sensor element;
• and
• d) latch circuitry coupled to the Hall sensor for maintaining said signal output from said sensor subsequent to initiation of said output signal.