The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 15, 2001
Filed:
May. 07, 1997
Kristann L. Moody, Barrington, NH (US);
Ravi Vig, Bow, NH (US);
P. Karl Scheller, Rochester, NH (US);
Jay M. Towne, Newbury, NH (US);
Teri L. Tu, Bow, NH (US);
Allegro Microsystems Inc., Worcester, MA (US);
Abstract
A magnetic-field-to-voltage transducer includes a Hall element and a digitally gain-controlled Hall-voltage amplifier that produces an analog voltage Vsig having excursions of one polarity corresponding to the passing of magnetic articles. Vsig is applied to the input of a peak-referenced-threshold signal detector that generates a binary proximity-detector output voltage, Vout, having transitions of one direction upon approaches of gear teeth down to zero speed. A digitally gain-controlled amplifier is connected to the Hall element. A comparator circuit generates a binary signal Vbig (or V,) that changes from one to another binary level each time that Vsig exceeds a DC target voltage, V,. The AGC circuit incrementally changes the transducer gain in the direction to bring the peaks in Vsig to just below the target value T,. Reference voltages V,and V,are generated that are equal respectively to the most recent peak positive and negative going excursion in Vsig. DC off-set-limit voltages V,and V,are provided that are respectively above and below the center of the dynamic voltage range of the detector, and the entire signal Vsig at the output of the amplifier is biased in a negative direction when the median value, Vos, of Vsig is greater than V,and moving the entire signal Vsig in a less positive direction when Vos is less than V,to keep Vos within the range from V,to V,.