System for sensing the angular position of a rotatable member using a hall effect transducer

Apparatus for sensing the angular position within a preselected angle of a rotatable member supported by a housing, the apparatus having annular magnet means coaxially secured for rotation with the rotatable member and including a magnetic pole pair for generating a magnetic field of corresponding arcuate length about the magnet means, comprising:

• magnetic field transducing means including a Hall Effect device secured in close and constant proximity to a given surface of the magnet means to provide a constant gap therebetween, said Hall Effect device being selectively disposed within the magnetic field between adjacent magnetic poles thereof when the rotatable member is at a preselected angular position;
• said Hall Effect device further being disposed in a magnetic null region between the magnetic poles of the magnetic field in angular coincidence with the preselected angular position of the rotatable member;
• circuit means including offset adjusting means coupled to the magnetic field transducing means for generating a substantially linear range of voltages indicative of corresponding angular deviations of the tension arm from the preselected annular position;
• and
• said offset adjusting means being set at a preselected nulled voltage corresponding to a zero point in the slope in the linear range of voltage when the rotatable member is at the preselected angular position.

Apparatus for sensing the angular position of a rotatable member supported by a housing, comprising:

• magnet means of preselected annular length, coaxially secured for rotation with the rotatable member and having a magnetic pole pair for generating a magnetic field of corresponding arcuate length about the magnet means;
• wherein the magnet means includes a ring magnet having a selected portion removed from the cross section thereof to define confronting ends of the ring magnet;
• magnetic field transducing means secured in constant proximity to a given surface of the magnet means at a preselected location within the arcuate length of the magnetic field when the rotatable member is at a preselected angular position;
• wherein the magnetic field transducing means is a Hall Effect device secured in close and constant proximity relative to the magnet means to provide a constant gap therebetween, said Hall Effect device being selectively disposed within the magnetic field between adjacent magnetic poles thereof and disposed in the close and constant proximity to the ring magnet in diametrically opposed relation to the selected removed portion when the rotatable member is at the preselected angular position;
• and
• circuit means including offset adjusting means coupled to the magnetic field transducing means for generating a substantially linear range of voltages indicative of corresponding angular positions of the rotatable member;
• and
• wherein the offset adjusting means is set at a preselected nulled voltage when the rotatable member is at the preselected angular position.