US 6,204,667 B1Granted

Electromagnetic gradiometer having a primary detector and a plurality of secondary detectors

AssigneeGeophex, Ltd.

InventorI. J. Won

Life of this patent

Estimating the term…

Loading patent…

Abstract

An electromagnetic gradiometer generates a time varying primary electromagnetic field, such as by use of a transmitter coil attached to a waveform generator. The primary electromagnetic field induces a responsive, relatively weak, time varying secondary electromagnetic field about a hidden object. The combined primary and secondary electromagnetic field is measured simultaneously at two spaced apart detectors, such as at two distinct receiver coils. The detectors are configured such that they detect the primary field in equal magnitudes but in opposite sense and connected in series such that the primary electromagnetic field is automatically nulled. The difference in the secondary electromagnetic field measured at the two points is divided by the distance between the detectors to determine the electromagnetic field gradient therebetween. The electromagnetic gradiometer may have a pair of detectors for measuring the electromagnetic gradient along one line or may have an array of detectors for measuring a plurality of electromagnetic gradients by switching or otherwise pairing the detectors.

Claims16

Dependent claims

An electromagnetic field gradiometer, comprising:

a) a transmitter for generating a time varying primary electromagnetic field and inducing a secondary electromagnetic field about a hidden object;
b) a primary detector having a first sense and disposed at a first location for measuring the strength of the combined primary and secondary electromagnetic fields at said first location and for generating a first output based on said strength;
c) a plurality of secondary detectors having a sense and disposed at a plurality of secondary locations for measuring the strength of the combined primary and secondary electromagnetic fields at said secondary locations simultaneously with the measurement of said combined primary and secondary electromagnetic field at said first location by said primary detector;
wherein said sense of said secondary detectors is opposite said first sense;
each of said secondary detectors generating a secondary output indicative of said strength of the combined primary and secondary electromagnetic fields at the respective secondary location;
d) a logic circuit for selectively combining said first output with said secondary outputs;
and
e) wherein said electromagnetic gradiometer determines a plurality of gradients of said secondary electromagnetic field based on said combined first output and said selected secondary outputs and the distance between said first location and the respective secondary locations.

5 more elements

Dependencies are inferred from the claim text.