Calibration circuits and methods for a proximity detector using a first rotation detector for a determined time period and a second rotation detector after the determined time period
First Claim
1. A proximity detector, comprising:
- a magnetic field transducer for providing a magnetic field signal indicative of a changing magnetic field;
a first peak detector circuit responsive, during a determined time period, to the magnetic field signal, for providing a first tracking signal, which, at a first time, holds a first value corresponding to a positive peak of the magnetic field signal, and which holds, at a second different time, a second value corresponding to a negative peak of the magnetic field signal;
a second peak detector circuit responsive, during the determined time period and also after the determined time period, to the magnetic field signal, for providing a second tracking signal, which holds a third value corresponding to a positive peak of the magnetic field signal, and for providing a third tracking signal, which holds a fourth value corresponding to a negative peak of the magnetic field signal, wherein the second tracking signal has an upward excursion limit and a downward excursion limit, wherein the upward excursion limit of the second tracking signal is smaller than the downward excursion limit of the second tracking signal, and wherein the third tracking signal has an upward excursion limit and a downward excursion limit, wherein the upward excursion limit of the third tracking signal is larger than the downward excursion limit of the third tracking signal; and
an output control circuit coupled to the first and second peak detector circuits and coupled to receive the magnetic field signal, wherein the output control circuit is configured to provide an output signal, which, during the determined time period, changes state in response to the first peak detector circuit, and which, after the determined time period, changes state in response to the second peak detector circuit.
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Abstract
A proximity detector employs a first peak detector circuit and a second peak detector circuit, both responsive to a magnetic field signal. The second peak detector circuit includes a positive peak detector circuit and a negative peak detector circuit, each of which have a predetermined excursion limit in an outward direction away from a center voltage of the magnetic field signal so as to be less affected by a large signature region in the magnetic field signal. The proximity detector also includes an output control circuit. The output control circuit is configured to provide an output signal, which, during a determined time period, changes state in response to the first peak detector circuit, and which, after the determined time period, changes state in response to the second peak detector circuit.
41 Citations
20 Claims
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1. A proximity detector, comprising:
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a magnetic field transducer for providing a magnetic field signal indicative of a changing magnetic field; a first peak detector circuit responsive, during a determined time period, to the magnetic field signal, for providing a first tracking signal, which, at a first time, holds a first value corresponding to a positive peak of the magnetic field signal, and which holds, at a second different time, a second value corresponding to a negative peak of the magnetic field signal; a second peak detector circuit responsive, during the determined time period and also after the determined time period, to the magnetic field signal, for providing a second tracking signal, which holds a third value corresponding to a positive peak of the magnetic field signal, and for providing a third tracking signal, which holds a fourth value corresponding to a negative peak of the magnetic field signal, wherein the second tracking signal has an upward excursion limit and a downward excursion limit, wherein the upward excursion limit of the second tracking signal is smaller than the downward excursion limit of the second tracking signal, and wherein the third tracking signal has an upward excursion limit and a downward excursion limit, wherein the upward excursion limit of the third tracking signal is larger than the downward excursion limit of the third tracking signal; and an output control circuit coupled to the first and second peak detector circuits and coupled to receive the magnetic field signal, wherein the output control circuit is configured to provide an output signal, which, during the determined time period, changes state in response to the first peak detector circuit, and which, after the determined time period, changes state in response to the second peak detector circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of detecting a ferromagnetic article, comprising:
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generating a magnetic field signal indicative of changing magnetic field; generating, with a first peak detector circuit, during a determined time period, a first tracking signal, which holds, at a first time, a first value corresponding to a positive peak of the magnetic field signal, and which holds, at a second different time, a second value corresponding to a negative peak of the magnetic field signal; generating, with a second peak detector circuit, during the determined time period and also after the determined time period, a second tracking signal, which holds a third value corresponding to a positive peak of the magnetic field signal, wherein the second tracking signal has an upward excursion limit and a downward excursion limit, wherein the upward excursion limit of the second tracking signal is smaller than the downward excursion limit of the second tracking signal; generating, with the second peak detector circuit, during the determined time period and also after the determined time period, a third tracking signal, which holds a fourth value corresponding to a negative peak of the magnetic field signal, wherein the third tracking signal has an upward excursion limit and a downward excursion limit, wherein the upward excursion limit of the third tracking signal is larger than the downward excursion limit of the third tracking signal; and generating an output signal, which, during the determined time period, changes state in response to the first peak detector circuit, and which, after the determined time period, changes state in response to the second peak detector circuit. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification