US 2017/0248662 A1Published application

Hall effect sensor circuit with offset compensation

AssigneeThe Timken Company

InventorsAlfred J. Santos, Lei Wang, Mark E. Lacroix

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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.

Claims32

Dependent claims

A method for sensing a magnetic field with at least one Hall effect sensor connected to a Hall effect sensing circuit, the method comprising the steps of:

applying a drive current to the at least one Hall effect sensor during a first phase;
sampling a sensed phase one voltage for the at least one Hall effect sensor during the first phase;
providing the sensed phase one voltage to an amplifier;
outputting from the amplifier a positive voltage output of the sensed phase one voltage and a negative voltage output of the sensed phase one voltage to a hold circuit during the first phase, the positive voltage output and the negative voltage output corresponding to a magnetic field strength value and a Hall effect sensor and amplifier offset error value;
switching terminals of the at least one Hall effect sensor and applying the drive current to different terminals of the at least one Hall effect sensor to begin a second phase;
sampling a sensed phase two voltage for the at least one Hall effect sensor during the second phase at the different terminals of the at least one Hall effect sensor than during the first phase;
providing the sensed phase two voltage to the amplifier;
outputting from the amplifier a positive voltage output of the sensed phase two voltage and a negative voltage output of the sensed phase two voltage to the hold circuit during the second phase, the positive voltage output and the negative voltage output corresponding to a magnetic field strength value and a Hall effect sensor and amplifier offset error value;
and
summing the positive output and negative output voltages from the first phase with the positive output and negative output voltages from the second phase to remove the Hall effect sensor and amplifier offset error value and to obtain a summed voltage corresponding to a summed magnetic field strength value.

7 more elements

A method for sensing a magnetic field with at least one pair of Hall effect sensors connected to a Hall effect sensing circuit, the method comprising the steps of:

applying a drive current to the at least one pair of Hall effect sensors during a first phase;
sampling a sensed voltage for each of the Hall effect sensors during the first phase;
combining the sensed voltage from the Hall effect sensors during the first phase to obtain a first combined sensed voltage corresponding to a magnetic field strength value and a Hall effect sensor and amplifier offset error value;
switching terminals of the Hall effect sensors and applying the drive current to different terminals of the at least one pair of Hall effect sensors to begin a second phase;
sampling a sensed voltage for each of the Hall effect sensors during the second phase at different terminals of the at least one pair of Hall effect sensors than during the first phase;
combining the sensed voltage from the Hall effect sensors during the second phase to obtain a second combined sensed voltage corresponding to a magnetic field strength value and Hall effect sensor and amplifier offset error value, and
summing the first combined sensed voltage from the first phase with the second combined sensed voltage during the second phase to remove the Hall effect sensor and amplifier offset error value and to obtain a summed voltage corresponding to a summed magnetic field strength value.

4 more elements

A Hall effect sensing circuit arrangement comprising:

first and second Hall effect sensors having terminals;
first and second amplifiers;
a first switching unit configured to selectively connect the terminals of the first Hall effect sensor to inputs of the first amplifier, and the first switching unit configured to selectively connect the terminals of the second Hall effect sensor to inputs of the second amplifier;
first and second adders for receiving outputs from the first and second amplifiers;
a second switching unit configured to connect an output of the first adder to a hold circuit and alternately to connect an output of the second adder to the hold circuit, wherein the hold circuit comprises capacitors and switches;
an output amplifier for receiving a voltage input from the hold circuit and the adders to obtain a combined sensed voltage, and
a controller configured to control the first switching unit and the second switching unit.

4 more elements

Dependencies are inferred from the claim text.