Method and apparatus for locating buried conductors in the presence of plural conductors
First Claim
1. Apparatus for locating a conductor in a region suspected of containing a plurality of conductors all carrying respective alternating currents which differ in their current frequency spectra, said apparatus comprising an antenna for deriving an electrical signal in response to changing magnetic flux due to at least one of said conductors;
- signal processing means, coupled to said antenna, for analysing each respective frequency or frequency band of a multiplicity of different frequencies or frequency bands of said signal, for deriving, based on said analysing of each respective frequency or frequency band, respective data related to the apparent position of a conductor responsible for the particular respective frequency or frequency band and for comparing the respective data for the various frequencies or frequency bands to find coincidences which are taken as indicative that the frequencies or frequency bands are uniquely associated with individual conductors whose true positions correspond with the apparent positions corresponding to the data; and
means for displaying the respective data or data resulting from further processing of the respective data.
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Abstract
Buried conductors generally carry multi-frequency AC currents and are locatable by sensing the resulting varying magnetic flux. However the presence of several buried conductors makes location of individual conductors difficult. By investigating induced signals at a multiplicity of different frequencies it is possible to identify a frequency carried exclusively by a single conductor and use it to locate that conductor. E.g. an antenna array including three vertically spaced horizontal coils (A,B,C) is located over an apparent conductor position using vertical coils (D,E). For numerous frequencies, the terms SB/(A-B), 2SC/(A-C) and 2S (B-C)/ (A-B)-(B-C)! are determined (where S=coil spacing; X=signal strength of coil X). For an exclusive frequency the three values are identical and equal to the depth of the conductor.
41 Citations
15 Claims
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1. Apparatus for locating a conductor in a region suspected of containing a plurality of conductors all carrying respective alternating currents which differ in their current frequency spectra, said apparatus comprising an antenna for deriving an electrical signal in response to changing magnetic flux due to at least one of said conductors;
- signal processing means, coupled to said antenna, for analysing each respective frequency or frequency band of a multiplicity of different frequencies or frequency bands of said signal, for deriving, based on said analysing of each respective frequency or frequency band, respective data related to the apparent position of a conductor responsible for the particular respective frequency or frequency band and for comparing the respective data for the various frequencies or frequency bands to find coincidences which are taken as indicative that the frequencies or frequency bands are uniquely associated with individual conductors whose true positions correspond with the apparent positions corresponding to the data; and
means for displaying the respective data or data resulting from further processing of the respective data. - View Dependent Claims (2, 3)
- signal processing means, coupled to said antenna, for analysing each respective frequency or frequency band of a multiplicity of different frequencies or frequency bands of said signal, for deriving, based on said analysing of each respective frequency or frequency band, respective data related to the apparent position of a conductor responsible for the particular respective frequency or frequency band and for comparing the respective data for the various frequencies or frequency bands to find coincidences which are taken as indicative that the frequencies or frequency bands are uniquely associated with individual conductors whose true positions correspond with the apparent positions corresponding to the data; and
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4. A method of locating a conductor in a region suspected of containing a plurality of conductors all carrying respective alternating currents which differ in their current frequency spectra, said method comprising the steps of employing an antenna to derive an electrical signal in response to changing magnetic flux due to one or more of said conductors;
- and analysing the signal to determine data related to the true or apparent position of one or more of said conductors;
the analysing step comprising performing a multiplicity of like analytical steps each applied to a respective different frequency or frequency band, and each comprising deriving data relating to the apparent position of the conductor responsible for the particular frequency or frequency band, and comparing the data for the various frequencies or frequency bands to find coincidences which are taken as indicative that the frequencies or frequency bands are uniquely associated with individual conductors whose true positions correspond with the apparent positions corresponding to the data. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- and analysing the signal to determine data related to the true or apparent position of one or more of said conductors;
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15. An antenna having a support structure carrying three like horizontally extending parallel coils extending in a common vertical plane and spaced one above the other;
- and two like vertically extending horizontally spaced coils in the same plane as the horizontally extending coils.
Specification