Method and apparatus for metal target proximity detection at long distances
First Claim
1. A method of detecting a position of a metallic object, the method comprising:
- (a) exciting a coil with an electrical signal to produce an electromagnetic field enveloping the metallic object;
(b) allowing a frequency of the electrical signal to be at the resonant frequency of the coil as affected by the metallic object;
(c) adjusting a control signal controlling a characteristic of the electrical signal so that the amplitude of oscillation substantially equals a predetermined standard level;
(d) periodically coupling and decoupling a resistive element in parallel with the coil while performing (a) through (c); and
(e) deriving a signal based upon the adjusted control signal during at least a first time period, wherein the derived signal is indicative of a difference between at least one first value of an intermediate signal functionally related to the adjusted control signal obtained when the resistive element is coupled in parallel with the coil and at least one second value of the intermediate signal obtained when the resistive element is decoupled, and wherein the derived signal is further indicative of the position of the metallic object.
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Abstract
A method and system for detecting a position of a metallic object are disclosed. The method includes (a) exciting a coil with an electrical signal to produce an electromagnetic field enveloping the object, (b) allowing a frequency of the electrical signal to be at the resonant frequency of the coil as affected by the object, and (c) adjusting a control signal controlling a characteristic of the electrical signal so that the characteristic substantially equals a predetermined standard level. The method further includes (d) periodically coupling and decoupling a resistive element in parallel with the coil while performing (a)-(c), and (e) deriving a signal based upon the control signal. The derived signal is indicative of a difference between first and second values of an intermediate signal functionally related to the control signal, which are obtained when the resistive element is coupled in parallel with the coil and decoupled, respectively.
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Citations
20 Claims
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1. A method of detecting a position of a metallic object, the method comprising:
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(a) exciting a coil with an electrical signal to produce an electromagnetic field enveloping the metallic object;
(b) allowing a frequency of the electrical signal to be at the resonant frequency of the coil as affected by the metallic object;
(c) adjusting a control signal controlling a characteristic of the electrical signal so that the amplitude of oscillation substantially equals a predetermined standard level;
(d) periodically coupling and decoupling a resistive element in parallel with the coil while performing (a) through (c); and
(e) deriving a signal based upon the adjusted control signal during at least a first time period, wherein the derived signal is indicative of a difference between at least one first value of an intermediate signal functionally related to the adjusted control signal obtained when the resistive element is coupled in parallel with the coil and at least one second value of the intermediate signal obtained when the resistive element is decoupled, and wherein the derived signal is further indicative of the position of the metallic object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A sensor for detecting a position of a metallic object, the sensor comprising:
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a conductive coil;
an oscillator connected to the conductive coil to;
(1) drive the conductive coil with an oscillating current based upon an external control signal;
(2) to receive feedback from the conductive coil and allow a frequency of the oscillating current to vary in accordance with a varying resonant frequency of the conductive coil as affected by the metallic object;
an amplitude control circuit connected to the oscillator to provide the external control signal to adjust the oscillating current;
an additional circuit coupled to the conductive coil, wherein the additional circuit operates to couple and decouple a resistive element in relation to the conductive coil at first and second times, respectively; and
a processing circuit coupled to the amplitude control circuit, wherein the processing circuit derives an output signal based upon the external control signal, and wherein the output signal is derived, at least during some periods of operation of the sensor, based upon a difference between a first sample of at least one of the external control signal and an intermediate signal functionally related to the external control signal obtained at the first time and a second sample of at least one of the external control signal and the intermediate signal obtained at the second time. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A sensor for detecting a position of a metallic object, the sensor comprising:
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an antenna circuit capable of transmitting and receiving electromagnetic signals, wherein the antenna circuit further provides an intermediate signal indicative of a characteristic of operation of the antenna circuit;
a secondary circuit capable of periodically adjusting an effective resistance of at least a portion of the antenna circuit; and
a processing circuit capable of determining an output signal indicative of the position of the metallic object based upon the intermediate signal;
wherein the processing circuit determines the output signal at least in part based upon differences that occur in the intermediate signal between first and second times at which the effective resistance is adjusted to first and second levels, respectively. - View Dependent Claims (20)
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Specification