METAL DETECTOR

• US 20120049850A1
• Filed: 05/18/2010
• Published: 03/01/2012
• Est. Priority Date: 05/18/2009
• Status: Active Grant

• Current Assignee: Gerd Reime
• Original Assignee: Gerd Reime
• Inventors: Reime, Gerd
• Granted Patent: US 9,835,752 B2
• Time in Patent Office: Days
• US Class Current: 324/329
• CPC Class Codes: G01V 3/00 Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
• CPC Class Codes: 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
• 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
• CPC Class Codes: G01V 3/10 using induction coils
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence
• CPC Class Codes: G01V 3/107 using compensating coil or loop arrangements
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat

Abstract

A sensor for the location of metallic objects and also an associated method comprise a plurality of transmitting coils (2.1, 2.2) and at least one receiving coil (1.9) which are arranged such as to be inductively coupled to one another and overlap to a partial extent for the purposes of decoupling the interaction therebetween, whereby there can be obtained a point of optimal cancellation of the interaction. Due to the fact that a flow of current is passed through the transmitting coils (2.1, 2.2) by a sensor electronic system, equal flows of current through the transmitting coils have an effect upon the at least one receiving coil (1.9) which results in a local point of optimal cancellation which moves in a first direction when there is a flow of current in a first transmitting coil (2.1), whereas it moves in another direction when there is a flow of current in a further transmitting coil (2.2), and due to the fact that there is provided a control circuit for the regulation of the currents in the transmitting coils which leads to a displacement of the local point of optimal cancellation which causes cancellation of the received signal, a simple and effective sensor is thereby produced.

Claims

1. A sensor for the location of metallic objects, comprising:

at least one transmitting coil and at least one receiving coil which are inductively coupled to one another and are arranged in partly overlapping manner for decoupling an interaction therebetween, whereby there can be obtained a point of optimal cancellation of the interaction;

a sensor electronic system for passing a flow of current through the transmitting coil and for evaluating a signal received by the receiving coil;

a plurality of transmitting coils through which a flow of current is passed by the sensor electronic system;

wherein, in the case of equal current flows, the transmitting coils have an effect upon the at least one receiving coil such that a local point of optimal cancellation occurs;

wherein, in the case of a flow of current through a first transmitting coil, the point of optimal cancellation moves in a first direction, whereas in the case of a flow of current through a further transmitting coil, the point of optimal cancellation moves in a further direction, and;

the sensor further comprising a control circuit for regulating currents through the transmitting coils which leads to a movement of the local point of optimal cancellation which causes cancellation of the received signal.

2. A sensor in accordance with claim 1, wherein the transmitting coils and the at least one receiving coil are arranged in co-planar manner.

3. A sensor in accordance with claim 1, wherein the transmitting coils are formed by a plurality of transmitting coil parts which together have an approximate shape of a transmitting coil that corresponds to the at least one receiving coil.

4. A sensor in accordance with claim 1, wherein at least two transmitting coils overlap the receiving coil with differing surface areas.

5. A sensor in accordance with claim 1, wherein a plurality of receiving coils and a plurality of transmitting coils are provided, wherein at least one transmitting coil and at least one receiving coil are arranged in a first plane and at least one further transmitting coil and at least one further receiving coil are arranged in at least one further plane wherein the coils arranged in the first plane are rotated relative to the coils arranged on the at least one further plane through a central angle with respect to their notional common central axis for the purposes of cancelling the interaction of the coils, wherein the central axes are offset or displaced relative to each other.

6. A sensor in accordance with claim 5, wherein the periphery of the transmitting coils is approximately congruent with the periphery of the receiving coils.

7. A sensor in accordance with claim 5, wherein at least one of the transmitting coils or the at least one receiving coils are formed by a plurality of coil parts.

8. A sensor in accordance with claim 1, wherein the transmitting coils or the at least one receiving coils are formed by two coil halves of substantially the same size.

9. A sensor in accordance with claim 1, wherein an axis of symmetry of the transmitting coils is tilted through an angle with respect to an axis symmetry of the receiving coil.

10. A sensor in accordance with claim 1, wherein central points of an arrangement of the transmitting coils and the receiving coil are spaced from each other by a distance which determines the range within which the local point will lie in the case of equal currents through the transmitting coils.

11. A sensor in accordance with claim 1, wherein there is provided a comparator for comparing voltage signals associated with the transmitting coils for the purposes of determining a control value, and in that there is provided at least one regulated current source in which the control value for the regulation of an amplitude of current supplied to the transmitting coils regulates the amplitude in such a way that amplitudes of the voltage signals at inputs of the comparator are substantially equal or such that that there is no difference in the voltage signals at the inputs of the comparator from two clock sections of a clock cycle.

12. A sensor in accordance with claim 11, wherein a change of the control value which leads to the local displacement of the point of optimal cancellation when approaching a metal is a measured value.

22. A sensor in accordance with claim 1, wherein it is a metal detector operated in the PI mode.

13. A method for the location of metallic objects utilising a sensor, the sensor comprising at least one transmitting coil and at least one receiving coil which are inductively coupled to one another and are arranged in partly overlapping manner for decoupling the interaction therebetween, whereby there can be obtained a point of optimal cancellation at which cancellation of a received signal is caused, the method comprising:

passing a flow of current through the at least one transmitting coil;

evaluating a signal received by the receiving coil,

wherein the flow of current is passed through a plurality of transmitting coils by the sensor electronic system,

wherein, in the case of equal current flows, the transmitting coils have an effect upon the at least one receiving coil such that a local point of optimal cancellation occurs,

wherein, in the case of a flow of current through one transmitting coil, the point of optimal cancellation moves in a first direction, whereas in the case of a flow of current through a further transmitting coil, the point of optimal cancellation moves in a further direction, and

wherein currents through the transmitting coils are regulated in such a way that there results a displacement of the local point of optimal cancellation which causes cancellation of the received signal.

14. A method in accordance with claim 13, wherein there are used as transmitting coils a plurality of transmitting coil parts, which together have the shape of a transmitting coil that corresponds to the receiving coil.

15. A method in accordance with claim 13, wherein two transmitting coil halves of substantially the same size are used as transmitting coils.

16. A method in accordance with claim 13, wherein an axis of symmetry of the transmitting coils, is arranged such that it is tilted through an angle with respect to an axis of symmetry the receiving coil.

17. A method in accordance with claim 13, wherein the receiving coil is overlapped by the at least two transmitting coils with differing surface areas.

18. A method in accordance claim 13, wherein for the production of the sensor there are provided a plurality of receiving coils and a plurality of transmitting coils, of which at least one transmitting coil and at least one receiving coil are arranged in a first plane and at least one further transmitting coil and at least one further receiving coil are arranged in at least one further plane, wherein coils arranged in the first plane are rotated relative to coils arranged on the at least one further plane through a central angle with respect to their notional common central axis until the interaction of the coils is cancelled, wherein the central axes are then displaced relative to each other by a spacing.

19. A method in accordance with claim 13, wherein voltage signals associated with the transmitting coils are compared for the purposes of determining a control value, and in that the control value regulates an amplitude of the current supplied to the transmitting coils by means of at least one regulated current source in such a way that amplitudes of the voltage signals at the inputs of the comparator are substantially equal.

20. A method in accordance with claim 13, wherein a change of the control value which leads to the local displacement of the point of optimal cancellation is used as a measured value.

21. A method in accordance with claim 13, wherein the transmitting coils are controlled at a clock rate of a clock pulse generator and in that the signals received by the receiving coil are sampled at the clock rate, wherein the sampling time points are freely selectable, are controlled in steps of nanoseconds and are located at predefined positions in a clock period in order to obtain specific information from the received signal.

23. A method in accordance with claim 13, wherein the sensor is operated in a PI Mode as metal detector.