US 5,043,666 AGranted

Self-calibrating electromagnetic field sensor for locating buried conduits

AssigneeMetrotech Corporation

InventorsRussell E. Tavernetti, Paul W. Dodd

Life of this patent

Estimating the term…

Loading patent…

Abstract

An electromagnetic field sensing apparatus used for locating and determining the distance to buried conductive conduits including at least two receptor means, each adapted to receive a signal from the conduit and produce an output voltage proportional to the signal received, and also including a calibrating coil, with known relative coupling to the receptor means, and capable of inducing calibrating signals therein. Computing means are employed to calculate the relative sensitivities of each said receptor means using the voltage signals induced therein by the calibrating coil, and said known relative coupling relationships. The computing means further uses the output voltages from said receptor means, induced therein by the signal radiating from the conductive conduit, and said relative sensitivities to calculate the distance to and location of the conduit. Display means are provided to indicate this distance and location.

Claims9

Dependent claims

An apparatus for determining the distance to and location of a concealed conductive object radiating a first electromagnetic field induced by the application of an alternating current signal thereto, comprising:

first receptor means for receiving said first electromagnetic field and for providing a first output voltage proportional to the strength of the electromagnetic field at the position of said first receptor means;
second receptor means for receiving said first electromagnetic field and for providing a second output voltage proportional to the strength of the electromagnetic field at the position of said second receptor means;
third receptor means for receiving said first electromagnetic field and for providing a third output voltage proportional to the strength of the electromagnetic field at the position of said third receptor means;
support means for positioning said first, second and third signal receptor means at predetermined points relative to each other, said second and third receptor means being laterally spaced from each other and located beneath said first receptor means at points equidistant therefrom;
calibrating means supported by said support means and disposed in a predetermined spaced apart relationship to said first, second and third receptor means and having known relative coupling relationships with each of said receptor means, said calibrating means being operative to generate a second electromagnetic field for inducing calibrating voltage signals in each of said first, second and third receptor means;
computing means for calculating the relative sensitivities of each of said receptor means using the calibrating voltage signals, induced in each receptor means by said second electromagnetic field, and said known relative coupling relationships, said computing means further using said first, second and third output voltages and said relative sensitivities to calculate the distance to and location of said conductive object relative to said apparatus;
and
display means for indicating said calculated distance and location.

5 more elements

An apparatus for determining the distance to and location of a concealed conductive object radiating first electromagnetic field induced by the application of an alternating current signal thereto, said apparatus comprising:

first receptor means for receiving said first electromagnetic field and for providing a first output voltage proportional to the strength of the electromagnetic field at the position of said first receptor means;
second receptor means for receiving said first electromagnetic field and for providing second output voltages proportional to the strength of the first electromagnetic field at positions spaced vertically apart from said first receptor means;
support means for positioning said first and second signal receptor means at predetermined points relative to each other;
calibrating means disposed in spaced apart relationship to said first and second receptor means and operative to generate a second electromagnetic field for inducing calibrating voltage signals in each of said first and second receptor means;
computing means for calculating the relative sensitivities of each of said first and second receptor means using each said calibrating voltage signal induced by said calibrating means, and said known relative coupling relationships, said computing means further using said first and second output voltages and said relative sensitivities to calculate the vertical distance from said apparatus to said conductive object;
and
display means for indicating said calculated distance.

4 more elements

Dependencies are inferred from the claim text.