# US 6,724,191 B1 · Systems and methods useful for detecting presence and/or location of various materials

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- Number: US 6,724,191 B1
- Document ID: US6724191B1
- Status: Granted
- Kind: B1
- Application number: 09/852,255
- Filed: 2001-05-09
- Granted: 2004-04-20
- Earliest claimed: 2000-05-09
- Assignees: Admiralty Corporation
- Inventors: James Wagner Larsen
- Web page: https://patentgrep.com/patent/US6724191B1

## CPC

- G01V 3/104: {using several coupled or uncoupled coils (G01V3/101 takes precedence)}
- 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)
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)

## Abstract

The present invention provides systems and methods which can be employed to locate or detect presence of various materials, including nonferrous metals. These systems include new and useful sensors, circuits, systems and devices which power and/or interoperate with the sensors, and methods of making, operating and using such systems. Any or all of the systems, devices or processes can be combined with other systems, devices or processes disclosed.

## Claims

### Claim 1

Apparatus for sensing and providing information relating to position of and material forming an object, the apparatus comprising:
a. at least one emitter, the emitter adapted to emit a plurality of primary electromagnetic fields, at least some fields varying in time relative to other of the fields,
b. a plurality of sensors, the sensors adapted to sense amplitude and gradients in secondary electromagnetic fields, the secondary electromagnetic fields produced by the object responsive to the primary electromagnetic fields, and to sense difference in phases between at least one of the secondary electromagnetic fields and its corresponding primary electromagnetic field;
c. said sensors coupled to processing circuitry, the processing circuitry adapted to use said secondary field amplitude, gradient and phase difference information in order to provide information relating to material forming the object and position of the object relative to at least one of the sensors, and
d. wherein at least one of said sensors is positioned relative to said emitter whereby the field quantity of at least one field emitted by the emitter at the position of said at least one sensor, in the direction sensed by said at least one sensor, is near zero.

### Claim 2 (depends on 1)

Apparatus according to claim 1 in which the processing circuitry draws inferences from said phase differences relating to permeability and conductivity of material forming the object, and uses said inferences to identify said material.

### Claim 3

A method for sensing and providing information relating to position of and material forming an object, the method comprising:
a. emitting a plurality of primary electromagnetic fields, at least some fields varying in time relative to other of the fields;
b. positioning a plurality of sensors relative to said plurality of primary electromagnetic fields, including positioning at least one of said sensors relative to at least one of the primary electromagnetic fields such that the field quantity of said at least one field, in the direction sensed by said at least one sensor, is near zero;
c. sensing, using at least some of said sensors, amplitude and gradients in secondary electromagnetic fields, the secondary electromagnetic fields produced by the object responsive to the primary electromagnetic fields;
d. sensing, using at least some of said sensors, differences in phases between at least one of the secondary electromagnetic fields and its corresponding primary electromagnetic field; and
e. providing relating to material forming the object and position object relative to at least one of the sensors, using processing circuitry coupled to said sensors, the processing circuitry adapted to use said secondary field amplitude, gradient and phase difference information in order to generate said information.

### Claim 4 (depends on 3)

The method of claim 3, further comprising:
a. sensing amplitude of the secondary electromagnetic field; and
b. determining information relating to location of the object based at least in part on information relating to said amplitude sensing.

### Claim 5 (depends on 3)

The method of claim 3, further comprising:
a. sensing amplitude and gradients in said secondary electromagnetic field using at least two sensors; and
b. determining, based at least in part on the amplitude and gradient sensing, information relating to position of the object relative to at least one of the sensors.

### Claim 6 (depends on 3)

The method of claim 3, further comprising:
a. sensing, in the secondary electromagnetic field, difference relating to permeability and conductivity of material forming the object, and
b. based on said sensing of said difference, generating information relating to identification of the material.

### Claim 7 (depends on 3)

The method of claim 3, wherein a plurality of primary electromagnetic fields are transmitted and a plurality of secondary electromagnetic fields are received, at least some of the said fields varying in at least one property from other of said fields.