Detector for calculating a depth of a buried conductor

• US 8,183,851 B2
• Filed: 03/02/2009
• Issued: 05/22/2012
• Est. Priority Date: 03/03/2008
• Status: Active Grant

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Royle, John Mark, Pearson, Richard David
• Primary Examiner(s): TANG, MINH NHUT
• Application Number:
  US12/396,414
• Publication Number:
  US 20100001732A1
• Time in Patent Office: 1,177 Days
• Field of Search: None
• US Class Current: 324/67
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12

Abstract

A detector for calculating a depth of a buried conductor is provided. The detector includes first, second and third antennas and a microprocessor. The second antenna has an axis parallel to an axis of the first antenna and is spaced a distance s from the first antenna. The third antenna has an axis parallel to the axes of the first and second antennas and is spaced a distance 2s from the first antenna and a distance s from the second antenna. The microprocessor is configured to compare magnetic fields at the first and second antennas to produce a first compared value, compare magnetic fields at the first and third antennas to produce a second compared value, and calculate the depth of said buried conductor based on the first and second compared values.

Claims

1. A detector for calculating a depth of a buried conductor, the detector comprising:

a first antenna;

a second antenna having an axis parallel to an axis of the first antenna and spaced a distance s from the first antenna;

a third antenna having an axis parallel to the axes of the first and second antennas and spaced a distance 2s from the first antenna and a distance s from the second antenna;

means for comparing magnetic fields at the first and second antennas to produce a first compared value;

means for comparing magnetic fields at the first and third antennas to produce a second compared value; and

means for calculating the depth of said buried conductor based on the first and second compared values.

2. A detector as claimed in claim 1, wherein the magnetic fields at the first and second antennas and the magnetic fields at the first and third antennas are compared using the relationship:

3. A detector as claimed in claim 1, wherein each antenna outputs an analogue field strength signal representative of the electromagnetic field at the antenna.

4. A detector as claimed in claim 3, further comprising means for amplifying the field strength signals.

5. A detector as claimed in claim 4, further comprising:

means for converting the analogue field strength signals into digital signals; and

means for processing the digital signals to isolate signals of predetermined frequency bands.

6. A detector as claimed in claim 5, wherein the means for converting the analogue field strength signals into digital signals is a delta-sigma stereo CODEC.

7. A detector as claimed in claim 1, wherein each pair of first and second antennas and first and third antennas is calibrated to an accuracy of at least 1 part in 600,000.

8. The detector of claim 1, wherein said comparing magnetic fields at the first and second antennas includes subtracting a second magnetic field value from a first magnetic field value.

9. The detector of claim 1, wherein said comparing magnetic fields at the first and third antennas includes subtracting a third magnetic field value from a first magnetic field value.

10. A method of calculating a depth of a buried conductor, the method comprising:

providing a first antenna;

providing a second antenna having an axis parallel to an axis of the first antenna and spaced a distance s from the first antenna;

providing a third antenna having an axis parallel to the axes of the first and second antennas and spaced a distance 2s from the first antenna and a distance s from the second antenna;

comparing magnetic fields at the first and second antennas to produce a first compared value;

comparing magnetic fields at the first and third antennas to produce a second compared value; and

calculating the depth of said buried conductor based on the first and second compared values.

11. A method as claimed in claim 10, wherein the magnetic fields at the first and antennas and the magnetic fields at the first and third antennas are compared using the relationship:

12. A method as claimed in claim 10, wherein each antenna outputs an analogue field strength signal representative of the electromagnetic field at the antenna.

13. A method as claimed in claim 12, further comprising amplifying the field strength signals.

14. A method as claimed in claim 13, further comprising:

converting the analogue field strength signals into digital signals; and

processing the digital signals to isolate signals of predetermined frequency bands.

15. A method as claimed in claim 10, wherein each pair of first and second antennas and first and third antennas is calibrated to an accuracy of at least 1 part in 600,000.

16. A carrier medium carrying computer readable code for controlling a microprocessor to carry out the method of claim 10.

17. A detector for calculating a depth of a buried conductor, the detector comprising:

a first antenna;

a second antenna having an axis parallel to an axis of the first antenna and spaced a distance s from the first antenna;

a third antenna having an axis parallel to the axes of the first and second antennas and spaced a distance 2s from the first antenna and a distance s from the second antenna; and

a microprocessor, configured to;

compare magnetic fields at the first and second antennas to produce a first compared value;

compare magnetic fields at the first and third antennas to produce a second compared value; and

calculate the depth of said buried conductor based on the first and second compared values.

18. A detector as claimed in claim 17, wherein the magnetic fields at the first and second antennas and the magnetic fields at the first and third antennas are compared using the relationship:

19. A detector as claimed in claim 17, wherein each antenna outputs a field strength signal representative of the electromagnetic field at the antenna.

20. A detector as claimed in claim 19, further comprising amplifiers arranged to amplify the field strength signals.

21. A detector as claimed in claim 20, further comprising:

analogue to digital converters to convert the field strength signals into digital signals; and

a digital signal processor arranged to process the digital signals and to isolate signals of predetermined frequency bands.

22. A detector as claimed in claim 21, wherein the analogue to digital converter is a delta-sigma stereo CODEC.

23. A detector as claimed in claim 17, wherein each pair of first and second antennas and first and third antennas is calibrated to an accuracy of at least 1 part in 600,000.