US 2003/0067293 A1 · Inductive Sensor arrangement and method for detecting of ferrous metal objects

Abstract

An inductive sensor arrangement for detecting ferromagnetic or non-ferrous electrically conducting objects hidden in a surrounding medium comprising three field coils arranged in essentially the same geometric plane and adjacently positioned at angular distances of usually 120° from each other around a central axis orthogonal to the plane for generating an alternating magnetic flux by a sequential excitation with an AC-current ramp. The sensor arrangement further comprises three sense coils respectively mounted inside each associated field coil and in an orientation to the axes of each of the field coils such that essentially no voltage is induced in the sensor coils in an environment free of a metallic object. When a ferromagnetic or non-ferrous electrically conducting object approaches the sensor, nine characteristic voltage value sets are produced by the three sense coils which are stored and processed by an algorithmic process for defining a distinct criterion with respect to the position of the hidden metallic object to be located. The sensor arrangement uses a single point measurement to provide an accurate position and depth discrimination of the hidden ferromagnetic or non-ferrous electrically conducting object such as a rebar (R), a copper pipe in concrete or the like.

Claims8

Dependent claims

An inductive sensor arrangement for detecting one of a ferromagnetic and non-ferrous electrically conducting object buried in a surrounding medium comprising at least one field coil for generating a penetrating alternating magnetic flux in said medium and at least one sense coil for sensing magnetic flux field disturbances caused by one of said ferromagnetic and non-ferrous electrically conducting object, wherein the sensor arrangement comprises

three field coils (1A, 1B, 1C) arranged in a geometric plane and adjacently positioned at defined angular distances from each other in relation to and around a central axis orthogonal to said plane, and
three sense coils (2A, 2B, 2C) cooperating with said three field coils to form three field/sense coil pairs, wherein each of said three sense coils is mounted inside a respective one of said three field coils in an orientation to the axis of the respectively associated field coil such that almost no voltage is induced in each of the sense coils from said respectively associated field coil in an environment free of one of the ferromagnetic and the non-ferrous electrically conducting object.

A method for detecting one of a ferromagnetic and non-ferrous electrically conducting object hidden in a surrounding medium by an inductive sensor arrangement comprising three field coils (1A, 1B, 1C) adjacently positioned at defined angular distances from each other around a central axis and three sense coils (2A, 2B, 2C), wherein each of said three sense coils is mounted inside a respective one of said three field coils in an orientation to the axis of the respectively associated field coil such that almost no voltage is induced in each of the sense coils from said respectively associated field coil in an environment free of one of the ferromagnetic and the non-ferrous electrically conducting object, the method comprising the steps of:

sequentially and individually applying defined current ramps to each of the three field coils to excite each of the three field coils by producing a changing magnetic flux penetrating said medium from three different physical positions to respond to said field coils arrangement;
collecting nine distinct output voltages from the three sense coils, comprising the steps of collecting a first output voltage from a first sense coil (2A) and second and third output voltages from the remaining second and third sense coils (2B, 2C), while a first field coil (1A) is excited by a first defined current ramp;
collecting a fourth output voltage from the second sense coil (2B) and fifth and sixth voltages from the remaining first and third sense coils while the second field coil (1B) is excited by a second defined current ramp;
collecting a seventh output voltage from the third sense coil (2C) and eighth and ninth voltages from the remaining first and second sense coils while the third field coil (1C) is excited by a third defined current ramp;
and
processing the nine distinct output voltages using an algorithm for determining whether one of a ferromagnetic object (R) and an electrically conducting object is present.

3 more elements

Dependencies are inferred from the claim text.

Inductive Sensor arrangement and method for detecting of ferrous metal objects

Life of this patent

Inductive Sensor arrangement and method for detecting of ferrous metal objects

Life of this patent

Abstract

Claims8