Method and apparatus including spaced antennas for determining the trace and depth of underground metallic conductors
First Claim
1. A method for determining the horizontal position and depth of an underground metallic conductor in which there exists an alternating current of a basic frequency which generates a corresponding electromagnetic field having horizontal and vertical components, said method comprising:
- (a) detecting the electromagnetic field by ferrite antennas at an upper and a lower level, at least one of which is rotatable in a vertical plane, wherein the ferrite antennas are inductive elements of first and second band pass filter circuits, respectively, the capacitance of such circuits being selected such that each of the circuits has a resonant frequency equal to the Nth upper harmonic of the basic frequency when a separate generator is not used to generate the alternating current in the conductor, and each of the circuits has a resonant frequency equal to the Mth upper harmonic of the basic frequency when a separate generator is used to generate the alternating current in the conductor, wherein (i) N is equal to (CP±
1) or (2C±
1), (ii) M is equal to CP or 2C, (iii) C is a properly selected integer greater than 1, (iv) P is 1, 2, 3, or 6, and (v) the product CP is an even number;
(b) determining the horizontal position of the conductor from sensing the vertical component of the magnetic field at either one of the upper and the lower levels, sensing the horizontal component of the magnetic field at the other of the levels, and forming the ratio of the two sensed components; and
(c) determining the depth of the conductor from sensing the horizontal component of the magnetic field at both the upper and lower levels.
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Abstract
Method and apparatus for determining the horizontal position and depth of a buried metallic conductor. An upper and a lower ferrite antenna, at least one rotatable in the vertical plane, and each coupled to a band-pass filter, detect the horizontal and vertical components of an electromagnetic field associated with the buried conductor. The electromagnetic field may be induced in the conductor by a portable generator, or alternatively, by alternating current already present in the conductor. The horizontal position of the conductor is determined by measuring the vertical component of the electromagnetic field at an upper or lower level and the horizontal component of the electromagnetic field at a lower or upper level. On the basis of the ratio of the two components the approximate horizontal position of the conductor is determined. The depth of the conductor is determined by measuring the horizontal component of the electromagnetic field at both the upper and the lower level. Circuit elements in the apparatus convert the voltages induced in the antennas into suitable indications of the horizontal position and depth of the buried conductor.
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Citations
15 Claims
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1. A method for determining the horizontal position and depth of an underground metallic conductor in which there exists an alternating current of a basic frequency which generates a corresponding electromagnetic field having horizontal and vertical components, said method comprising:
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(a) detecting the electromagnetic field by ferrite antennas at an upper and a lower level, at least one of which is rotatable in a vertical plane, wherein the ferrite antennas are inductive elements of first and second band pass filter circuits, respectively, the capacitance of such circuits being selected such that each of the circuits has a resonant frequency equal to the Nth upper harmonic of the basic frequency when a separate generator is not used to generate the alternating current in the conductor, and each of the circuits has a resonant frequency equal to the Mth upper harmonic of the basic frequency when a separate generator is used to generate the alternating current in the conductor, wherein (i) N is equal to (CP±
1) or (2C±
1), (ii) M is equal to CP or 2C, (iii) C is a properly selected integer greater than 1, (iv) P is 1, 2, 3, or 6, and (v) the product CP is an even number;(b) determining the horizontal position of the conductor from sensing the vertical component of the magnetic field at either one of the upper and the lower levels, sensing the horizontal component of the magnetic field at the other of the levels, and forming the ratio of the two sensed components; and (c) determining the depth of the conductor from sensing the horizontal component of the magnetic field at both the upper and lower levels. - View Dependent Claims (2, 3, 4, 5, 6, 14, 15)
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7. Apparatus for determining the horizontal position and depth of an underground metallic conductor in which there exists an alternating current of a basic frequency which generates a corresponding electromagnetic field having vertical and horizontal components, comprising:
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(a) a measuring receiver comprising a transducer, which transducer comprises a first ferrite antenna and a second ferrite antenna, at least one of which is rotatable in a vertical plane, for converting the magnetic field strength into voltage signals; (b) a horizontal position locating unit electrically connected to the transducer for sensing the voltage signals corresponding to the magnetic field and for pointing out a corridor of a predetermined half-width depending on the depth of the conductor; and (c) a depth measuring unit, comprising analog circuits, electrically connected to the transducer for sensing the voltage signals corresponding to the magnetic field and for determining the depth of the conductor; wherein the transducer comprises; first and second band-pass filters, each comprising inductive elements and capacitive elements in electrical parallel, and further comprising active and passive filter elements, wherein the first ferrite antenna is an inductive element of the first filter and the second ferrite antenna is an inductive element of the second filter and the capacitive elements of the filters comprise capacitors selected such that the resonant frequency of both filters is the Nth harmonic of the basic frequency when a separate generator is not used to generate the alternating current in the conductor, and the resonant frequency of both filters is the Mth harmonic of the basic frequency when a separate generator is used to generate the alternating current in the conductor, wherein (i) N is equal to (CP±
1) or (2±
C1), (ii) M is CP or 2C, (iii) C is a properly selected integer greater than 1, (iv) P is 1, 2, 3, or 6, and (v) the product CP is an even number. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification