Magnetic gear tooth sensor with Hall cell detector
First Claim
Patent Images
1. A sensor, comprising:
- a Hall cell for providing an output signal having a first signal component corresponding to a background field from a magnet and a second signal component corresponding to rotations of a ferrous gear; and
a compensation circuit coupled to the Hall cell, the compensation circuit including a subtractor for subtracting a steady state compensation signal corresponding to the background field signal from the Hall cell output signal, the compensation circuit further including a counter circuit for providing the compensation signal by counting up until the compensation signal reaches a level corresponding to the background field.
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Abstract
A sensor includes a Hall cell and a compensation circuit for subtracting a magnet background field from the Hall cell output to provide a signal corresponding to rotations of a toothed ferrous gear.
30 Citations
16 Claims
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1. A sensor, comprising:
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a Hall cell for providing an output signal having a first signal component corresponding to a background field from a magnet and a second signal component corresponding to rotations of a ferrous gear; and
a compensation circuit coupled to the Hall cell, the compensation circuit including a subtractor for subtracting a steady state compensation signal corresponding to the background field signal from the Hall cell output signal, the compensation circuit further including a counter circuit for providing the compensation signal by counting up until the compensation signal reaches a level corresponding to the background field. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A Hall sensor, comprising:
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a magnet producing a background field;
a Hall cell proximate the magnet, the Hall cell providing an output responsive to the background field and a ferrous gear rotating in proximity to the Hall cell; and
a compensation circuit receiving the Hall cell output, the compensation circuit including a subtractor having first and second inputs and an output, wherein the first input is coupled to the Hall cell output;
a comparator having first and second inputs and an output, wherein the first input receives a signal corresponding to a signal from the subtractor output;
a logic circuit having first and second inputs and an output, the first input receiving a clock signal and the second input receiving a signal from the subtractor ouput;
a counter receiving a signal from the logic circuit output; and
a digital-to-analog circuit converting a digital count value from the counter to an analog value provided to the second input of the subtractor. - View Dependent Claims (11)
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12. The sensor according to claim A, further including a flip-flop circuit coupled to the comparator output.
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13. A method of extracting a signal, comprising:
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receiving a Hall cell output voltage, which includes a first component corresponding to a background field from a magnet and a second component corresponding to rotations of a ferrous gear proximate the Hall cell;
generating a steady state compensation voltage using a counter, wherein the compensation voltage corresponds to the background field; and
subtracting the compensation voltage from the Hall cell output voltage. - View Dependent Claims (14, 15)
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16. A method of providing a Hall sensor, comprising:
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securing a Hall cell to a magnet; and
coupling a compensation circuit to the Hall cell, the compensation circuit generating a steady state compensation signal corresponding to a background field of the magnet that is subtracted from an output of the Hall cell, wherein the compensation circuit includes a counter circuit for providing the compensation signal by counting until the compensation signal reaches a level corresponding to the background field.
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Specification