The Timken Company
Hall effect sensor circuit with offset compensation

Abstract:

A method and apparatus for sensing magnetic field strength with a pair of Hall effect sensors includes sampling a sensed voltage for the Hall effect sensors during a first phase and combining the sensed voltage. During a second phase, obtaining sensed voltages for the Hall effect sensors and combining the sensed voltages. The sensed voltages from the first phase and the second phase are combined to obtain a summed voltage and remove the Hall effect sensor and amplifier offset error value. In one arrangement, the summed voltage corresponds to the sensed Hall voltage of the first Hall effect sensor added to the Hall voltage of the second Hall effect sensor. In another arrangement, the summed voltage corresponds to the sensed Hall voltage of the first Hall effect sensor subtracted by the sensed Hall voltage of the second Hall effect sensor. Changes in the summed voltage with respect to a reference voltage are counted to determine the speed of a rotating shaft having magnets or a similar arrangement.