Method and apparatus for detecting underground electrically conductive objects
US4994747A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 8, 1988 |
| Grant date | Feb 19, 1991 |
| Priority date | — |
| Expiry date | Aug 8, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/30
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus and method for detecting vertically or horizontally oriented underground electrical conductors such as electrical wiring or rails in tunnels thin conducting ore veins surrounded by less conducting rock, or boreholes filled with conductive water or lined with a conductive casing. The apparatus includes a surface or downhole transmitter and a downhole receiver connected to a coherent frequency source unit by fiber optic cables. The source unit generates two phase synchronized frequency signals in the range of one hundred to three hundred kHz. The receiver includes a vertical or horizontal magnetic dipole antenna, e.g. a ferrite rod antenna, and the transmitter includes a vertical or horizontal magnetic dipole antenna in the downhole configuration or at least one long cable or loop antenna in the surface configuration. The method includes generating a first electromagnetic field which induces current flow in the electrical conductor surround by the less conducting rock and then detecting a component of a second electromagnetic field generated by the induced current flowing in the conductor, as a received signal at the receiver. The received signal is processed by synchron…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.