Method and apparatus for tracing conductors using an alternating signal having two components related in frequency and phase
DCFirst Claim
1. A method of tracing a conductor, comprising the following steps:
- applying an alternating signal to the conductor at a first point;
detecting at a second point and at a third point the field produced by said alternating signal in said conductor;
wherein said alternating signal alternates at substantially less than radio frequency and has first and second continuously present sinusoidal components related in frequency and phase whereby said field has first and second continuously present sinusoidal field components; and
determining any change in phase difference in said first and second sinusoidal field components between said second and third points;
wherein a determination of a predetermined phase relationship traces said conductor from said second point to said third point, while determination of a change in said phase relationship indicates that a different conductor is being traced from said second point.
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Abstract
A system for tracing routes of conductors is disclosed. An alternating signal is applied to the object to be traced (12), and the field produced by this signal is detected remotely from the object. In order to distinguish between signals produced by the object being traced and those produced by nearby conductors (14) due to capacitive coupling, the alternating signal has first and second components, related in frequency and phase, and the field is detected at a plurality of positions. The phase relationship of the detected signals is investigated to determine unambiguously the position of the object concerned. In one embodiment, the second frequency component is a harmonic of the other. In another embodiment the frequency of the second component is the frequency of the first, plus or minus a sub-harmonic of the first.
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Citations
10 Claims
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1. A method of tracing a conductor, comprising the following steps:
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applying an alternating signal to the conductor at a first point; detecting at a second point and at a third point the field produced by said alternating signal in said conductor; wherein said alternating signal alternates at substantially less than radio frequency and has first and second continuously present sinusoidal components related in frequency and phase whereby said field has first and second continuously present sinusoidal field components; and determining any change in phase difference in said first and second sinusoidal field components between said second and third points; wherein a determination of a predetermined phase relationship traces said conductor from said second point to said third point, while determination of a change in said phase relationship indicates that a different conductor is being traced from said second point. - View Dependent Claims (2, 3, 4, 5, 6, 7, 10)
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10. An apparatus according to claim 7 or claim 8 wherein said detection means is arranged to multiply the frequency of said second component of said field by a predetermined multiple prior to said determining of changes of phase by said determination means.
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8. An apparatus for tracing a conductor, comprising:
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generation means for applying an alternating signal to the conductor at a first point; and detection means for detecting the field produced by said signal on said conductor; wherein said generation means applies an alternating signal alternating at substantially less than radio frequency having first and second continuously present sinusoidal components related in frequency and phase, thereby to generate a field having first and second continuously present sinusoidal field components; and said detection means detects said first and second sinusoidal field components produced by said signal at second and third points, and includes determination means for determining changes in phase difference of said first and second sinusoidal field components between said second and third points; wherein a determination of a predetermined phase relationship traces said conductor from said second point to said third point, while determination of a change in said phase relationship indicates that a different conductor is being traced from said second point. - View Dependent Claims (9)
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Specification