System and method for detecting a concealed current carrying conductor

• US 6,777,923 B2
• Filed: 02/19/2003
• Issued: 08/17/2004
• Est. Priority Date: 02/19/2002
• Status: Active Grant

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Pearson, Richard David
• Primary Examiner(s): TANG, MINH NHUT
• Application Number:
  US10/367,983
• Publication Number:
  US 20030155906A1
• Time in Patent Office: 545 Days
• Field of Search: 324/67, 324/127, 324/207.17, 324/213, 324/263, 324/326-329, 324/345-346, 175/45
• US Class Current: 324/127
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A system and method for detecting a concealed current carrying conductor is presented. A first and a second field strength signal proportional to an electromagnetic field is generated. A value is determined for the first field strength signal. This value is used to divide the second field strength signal and form an indicator signal. A value for the indicator signal is determined. If the value of the indicator signal is equal to or greater than a predetermined value (i.e., not less than the predetermined value), a conductor detection signal is generated and used to alert a user to the presence of a concealed current carrying conductor.

Claims

1. A system for detecting a concealed current carrying conductor, comprising:

means for generating a first and a second field strength signal proportional to an electromagnetic field of the concealed current carrying conductor;

means for determining a value for the first field strength signal;

means for dividing the second field strength signal by the value of the first field strength signal to form an indicator signal;

means for determining a value for the indicator signal;

means for determining whether the value of the indicator signal is less than a predetermined value; and

means for generating a conductor detection signal for a user if the value of the indicator signal is not less than the predetermined value.

2. The system of claim 1, further comprising:

means for adjusting at least one of the first and the second field strength signals to decrease the value of the indicator signal.

3. The system of claim 1, further comprising:

means for multiplying the second field strength signal by a value between 0 and 1 to decrease the value of the indicator signal.

4. The system of claim 1, further comprising:

means for multiplying the first field strength signal by a value greater than 1 to decrease the value of the indicator signal.

5. The system of claim 1, wherein said means for generating a conductor detection signal produces an audible signal.

6. The system of claim 1, wherein said means for generating a conductor detection signal produces a visual signal.

7. The system of claim 1, further comprising:

means for multiplying the value of the conductor detection signal by the value of the indicator signal, to produce a second indicator signal; and

means for generating a visual indication for a user based on the second indicator signal.

8. A system for detecting a concealed current carrying conductor, comprising:

a first and a second electromagnetic field detector arranged to detect an electromagnetic field of a current carrying conductor, said first and said second electromagnetic field detector each having an output signal;

a first and a second signal level detector that each produces an output signal at an output port that is proportional to an input signal at an input port;

a signal divider that produces an output signal at an output port that is proportional to a first input signal at a first input port divided by a second input signal at a second input port;

a comparator that produces an output value at an output port equal to a first control value, if an input signal at an input port is less than a predetermined value, and equal to a second control value, if the input signal is not less than the predetermined value;

a switch having an input port, an output port, and a control port that controls the operation of said switch; and

an indicator that provides an indication to a user of an input signal at an input port;

wherein the output signal of said first electromagnetic field detector is electromagnetically coupled to said input port of said first signal level detector,

the output signal of said second electromagnetic field detector is electromagnetically coupled to said first input port of said signal divider,

the output signal of said first signal level detector is electromagnetically coupled to said second input port of said signal divider,

the output signal of said signal divider is electromagnetically coupled to said input port of said switch and to said input port of said second signal level detector,

the output signal of said second signal level detector is electromagnetically coupled to said input port of said signal comparator,

the output signal of said signal comparator is electromagnetically coupled to said control port of said switch, and

the output signal of said switch is electromagnetically coupled to said input port of said indicator.

9. The system of claim 8, further comprising:

a system sensitivity control that produces an output signal at an output port proportional to a first input signal at a first input port multiplied by a second input signal at a second input port,

wherein the output signal of the second electromagnetic field detector is electromagnetically coupled to said first input port of said system sensitivity control,

a signal having a nominal value between 0 and 1 is electromagnetically coupled to said second input port of said system sensitivity control, and

the output signal of said system sensitivity control is electromagnetically coupled to said first input port of said signal divider.

10. The system of claim 8, wherein each of said first and said second electromagnetic field detectors comprises:

a coil that develops an output signal proportional to a strength of a sensed alternating electromagnetic field.

11. The system of claim 10, wherein each of said first and said second electromagnetic field detectors further comprises:

a matched filter electromagnetically coupled to said coil.

12. The system of claim 8, wherein each of said first and said second signal level detectors comprises:

an averaging filter.

13. The system of claim 8, wherein said indicator comprises:

a mixer having a first and a second input port that produces an output signal at an output port, said first input port of said mixer electromagnetically coupled to said output port of said switch;

an oscillator electromagnetically coupled to said second input port of said mixer; and

a speaker electromagnetically coupled to the output signal of said mixer.

14. The system of claim 8, wherein said indicator further comprises:

a further comparator that produces an output value at an output port equal to a first control value, if an input signal at an input port is less than a predetermined value, and equal to a second control value, if the input signal is not less than the predetermined value

a signal multiplication network that produces an output signal at an output port proportional to a first input signal at a first input port multiplied by a second input signal at a second input port; and

a second indicator network that provides an indication of an input signal at an input port,

wherein the output signal of said second signal level detector is electromagnetically coupled to said first input port of said signal multiplication network,

the output signal of said further comparator is electromagnetically coupled to said second input port of said signal multiplication network, and

the output signal of said signal multiplication network is electromagnetically coupled to the input port of said second indicator network.

15. The system of claim 8, wherein each of said first and second signal level detectors comprises an RMS filter.

16. A method for detecting a concealed current carrying conductor, comprising:

generating a first and a second field strength signal proportional to an electromagnetic field of the concealed current carrying conductor;

determining a value for the first field strength signal;

dividing the second field strength signal by the value of the first field strength signal to form an indicator signal;

determining a value for the indicator signal;

determining whether the value of the indicator signal is less than a predetermined value; and

generating a conductor detection signal for a user if the value of the indicator signal is not less than the predetermined value.

17. The method of claim 16, further comprising:

adjusting at least one of the first and the second field strength signals to decrease the value of the indicator signal.

18. The method of claim 16, further comprising:

multiplying the second field strength signal by a value between 0 and 1 to decrease the value of the indicator signal.

19. The method of claim 16, further comprising:

multiplying the first field strength signal by a value greater than 1 to decrease the value of the indicator signal.

20. The method of claim 16, wherein the step of generating a conductor detection signal comprises generating an audible signal.

21. The method of claim 16, wherein the step of generating a conductor detection signal comprises generating a visual signal.

22. The method of claim 16, further comprising:

multiplying the value of the conductor detection signal by the value of the indicator signal, to produce a second indicator signal; and

generating a visual indication for a user based on the second indicator signal.