EP0830733A1 - Capteur electromagnetique pour la detection d'une cible - Google Patents
Capteur electromagnetique pour la detection d'une cibleInfo
- Publication number
- EP0830733A1 EP0830733A1 EP96920891A EP96920891A EP0830733A1 EP 0830733 A1 EP0830733 A1 EP 0830733A1 EP 96920891 A EP96920891 A EP 96920891A EP 96920891 A EP96920891 A EP 96920891A EP 0830733 A1 EP0830733 A1 EP 0830733A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- target
- electromagnetic sensor
- coil
- core
- matrix
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/945—Proximity switches
- H03K17/95—Proximity switches using a magnetic detector
- H03K17/9505—Constructional details
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
- G01D5/204—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils
- G01D5/2046—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils by a movable ferromagnetic element, e.g. a core
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
- G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
- G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
- G01D5/204—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils
- G01D5/2053—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the mutual induction between two or more coils by a movable non-ferromagnetic conductive element
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
- G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
- G01V3/104—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils
- G01V3/105—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops
Definitions
- the present invention relates to an electromagnetic sensor and to a method for simultaneously determining the magnetic permeability and the conductivity of a metal target as well as the distance of this target relative to an electromagnetic sensor.
- an electromagnetic sensor comprises a coil associated with a core with high magnetic permeability.
- a target i.e. a metallic object
- the impedance of the electromagnetic sensor varies according to parameters which are the frequency of the excitation current, the magnetic permeability of the target, the electrical conductivity of the target and the distance of the sensor from the target.
- the magnetic permeability and the electrical conductivity of a target are known, it is therefore possible to use an electromagnetic sensor to determine the distance of the electromagnetic sensor from the target, in particular to perform dimensional measurements of parts. metallics.
- the magnetic permeability and the electrical conductivity depend not only on the metal used, but also on the various treatments to which the metal is subjected during manufacture so that it does not It is not possible to consider that different parts produced successively from the same metal will have the same magnetic permeability and the same electrical conductivity.
- the magnetic permeability varies with temperature.
- the electromagnetic sensors currently known generally have a magnetic circuit U-shaped, the measuring coil then being placed on a branch of the U, or pot-shaped comprising a central stud on which the coil is arranged.
- the large number of interfaces between the different media which make up the electromagnetic sensor which makes it unusable in practice to produce a model making it possible to simultaneously determine the different parameters which influence the impedance. of the electromagnetic sensor.
- the object of the invention is to propose an electromagnetic sensor which can be modeled, and a method for the simultaneous determination of the magnetic permeability and the conductivity of a metal target as well as the distance of this target relative to an electromagnetic sensor.
- an electro-magnetic sensor comprising at least one coil associated with a core with high magnetic permeability, in which the core is a flat plate, the coil is' fixed on one face of the core and has an axis of symmetry. extending perpendicularly to the face of the core on which it is fixed, and the core has a thickness greater than the dimension of the coil taken along its axis of symmetry so that the lines of magnetic fields resulting from the excitation of the coil are substantially in their entirety included in the core.
- An electromagnetic sensor is thus obtained which, while having sufficient sensitivity to carry out measurements, has a reduced number of interfaces and sufficiently low magnetic leaks to allow modeling.
- the core and the coil are coaxial circular cylinders, the core having a diameter greater than an outer diameter of the coil so that the magnetic field lines are close substantially entirely in the space delimited by the core and the opposite target.
- a sensor is thus obtained having very low magnetic leaks even when the latter is placed opposite a very conductive target and having a low magnetic permeability such as brass.
- a method for simultaneously determining the magnetic permeability and the conductivity of a metal target as well as the distance of this target with respect to an electro-magnetic sensor, this method comprising the steps of: a) determining complex normalized impedance,
- ZN RN + j XN of the electromagnetic sensor at different excitation frequencies (fj, f 2 , ... f k ,. "" * F Q ) I and for different calibration examples each defined by a magnetic permeability and a conductivity of the target as well as by a distance of the electromagnetic sensor from the target, with
- RN * (f k ) is the normalized resistive component of the impedance for the example of calibration of order i at the excitation frequency of order k
- XN * (f k ) is the compo ⁇ normalized reactive health of the impedance for the example of calibration of order i at the frequency of exc tation of order k.
- FIG. 1 is a schematic sectional view of an electromagnetic sensor according to the invention facing a target;
- FIG. 2 is a perspective view illu ⁇ - trant embodiment of the coil in the particular embodiment of the invention.
- FIG. 3 is an enlarged partial view in section along line III-III of Figure 2 of an electromagnetic sensor according to the embodiment of the invention.
- the electro-magnetic sensor comprises a core 1 of high magnetic permeability, for example a ferrite core, in the form of a circular flat cylinder, one face of which carries an annular coil 2 of fixed circular shape. coaxially with the core 1.
- the axis of symmetry of the coil 2 extends perpendicular to the face of the core on which the coil is fixed.
- the electromagnetic sensor thus formed is placed opposite a metal target 3.
- the core 1 has an absolute magnetic permeability ⁇ u and a conductivity ⁇ n .
- the surrounding air has an absolute magnetic permeability ⁇ a and a conductivity ⁇ a and the target has an absolute permeability ⁇ c and a conductivity ⁇ c .
- D the diameter of the core 1
- L the thickness of the core 1
- r the internal radius of the coil 2
- r 2 the external radius of the coil 2
- c the distance from the face of the sensor electromagnetic facing the target with respect to the target
- 1 the dimension of the coil 2 taken along its axis of symmetry
- d the distance from the target with respect to the opposite face of the coil 2.
- We have also shown in phantom 4 the representation of a line of the magnetic field created by the coil 2 when the latter is subjected to an alternating excitation current.
- the thickness L of the core is much greater than the dimension 1 of the coil 2-taken along its longitudinal axis so that the lines of magnetic fields 4 resulting from the excitation of the coil are substantially in their all included in the core, that is to say that they close inside the core without leaving the face of the core opposite the face carrying the coil 2.
- the field lines magnetic tend to penetrate all the more deeply into the magnetic core as the opposite target has a higher magnetic permeability.
- a thickness of the core ten times greater than the dimension 1 of the coil has been found to be satisfactory whatever the type of target.
- the target itself has a thickness sufficient for the magnetic field lines 4 to close inside the target.
- the diameter of the core is preferably greater than the external diameter of the coil so that the magnetic field lines close in the space delimited by the core and the opposite target, that is to say do not escape through the side wall of the core 1. It will be recalled in this connection that the magnetic field lines 4 close at a distance all the greater from the axis of the coil as the target has a conductivity. quickly higher.
- a diameter of the core equal to twice the external diameter of the coil has been found to be sufficient even for very conductive targets such as brass.
- FIG. 2 and 3 illustrate a particular embodiment of the invention in which the coil 2 consists of an excitation winding 5 and a measurement winding 6 nested one inside the other and each formed by a sheet of wires 7 arranged parallel to each other and joined together, for example by a resin.
- the plies of wires After the plies of wires have been produced, these are placed on the wafer and wound in a spiral as illustrated in FIG. 2 where the plies have been shown spaced apart from one another for a better understanding of the structure of the coil 2.
- FIG. 3 illustrates in a very enlarged manner the final structure of the coil 2 in which the different turns of the excitation coil 5 are interposed with the turns of the measuring coil 6.
- the wires 7 are connected in parallel by a strip 8 conveniently connected to a connection wire 9.
- an experiment plan matrix is established by determining the impedance ZN at different excitation frequencies fj f 2 ... f k ... f M for different examples of calibration E 1 # E 2 , ... E-, E Q , each defined by a relative magnetic permeability ⁇ and a conductibi ⁇ ity j of the target, as well as by a distance d j of the electromagnetic sensor relative to the target.
- This experience plan matrix is associated with a matrix of calibration values P e with:
- ⁇ ri , ⁇ and t are respectively the relative magnetic permeability, the conductivity of the target and the distance of the target from the sensor in the example of calibration of order i.
- the calibration examples could be carried out using real targets having a relative magnetic permeability and a conductivity. well defined, the normalized impedance then being obtained by a measurement of the voltage obtained at the terminals of the measurement winding during a supply of the excitation winding at each of the calibration frequencies.
- the experiment plan matrix from a modeling of the impedance of the electromagnetic sensor according to the invention, the modeled impedance associated with the sensor according to the invention being reproduced in FIG.
- r and a are integration variables
- N is the number of turns of the excitation winding
- ⁇ k 2 ⁇ f k
- ⁇ ⁇ 4 ⁇ x 10 "7
- J t ( ⁇ r) is the Bessel function of the first species of order 2
- r ,, r 2 , and 1 are such that defined previously and ⁇ ⁇ ⁇ ir d ⁇
- Ci are for the calibration example of order i the values of ⁇ , ⁇ , d and c as defined above with regard to the description of the sensor.
- impedance Z ⁇ f .. thus modeled we can extract the resistive part Ri (f j ) and the reactive part Xi (f j ) and deduce the values of RN ⁇ f ..) and XNiff j ) to insert in the matrix .
- the experimental design matrix is established on the basis of calibration examples defined by different combinations of the initial estimates ⁇ ro , ⁇ 0 and d 0 , and framing values ⁇ o + ⁇ ⁇ , ⁇ ro - ⁇ ( _; s7 0 + ⁇ ⁇ , ⁇ 0 - ⁇ ⁇ ; d 0 + ⁇ d , d 0 - ⁇ d , where ⁇ ⁇ f ⁇ ⁇ and ⁇ d are the deviations defining the range of evolution estimated of each of the parameters.
- RN and XN being determined in a manner known per se from the measurement of the impedance.
- the senor according to the invention has been illustrated with a coil 2 comprising two windings nested one inside the other, provision may be made for using a single winding serving at the same time for the exci ⁇ tation and measurement, the excitation being provided by a current generator, while the measurement is carried out by measuring the voltage across the single winding.
- any modeling which can be deemed appropriate depending on the precise structure of the sensor used can be used and simplify the modeling when certain parameters are constant for a target. to the other.
- RN and XN no longer vary linearly as a function of the influencing parameters, it is also possible to provide for changes in variables to linearize the input-output relationship of the sensor, for example by replacing RN and XN in the experiment design matrix with values ln (RN) and ln (XN).
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Electromagnetism (AREA)
- Geophysics (AREA)
- Measuring Magnetic Variables (AREA)
- Geophysics And Detection Of Objects (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9506763A FR2735224B1 (fr) | 1995-06-08 | 1995-06-08 | Capteur electromagnetique et procede de determination simultanee de differents parametres d'une cible associee |
FR9506763 | 1995-06-08 | ||
PCT/FR1996/000834 WO1996042138A1 (fr) | 1995-06-08 | 1996-06-03 | Capteur electromagnetique et procede de determination simultanee de differents parametres d'une cible associee |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0830733A1 true EP0830733A1 (fr) | 1998-03-25 |
Family
ID=9479743
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96920891A Withdrawn EP0830733A1 (fr) | 1995-06-08 | 1996-06-03 | Capteur electromagnetique pour la detection d'une cible |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0830733A1 (fr) |
FR (1) | FR2735224B1 (fr) |
WO (1) | WO1996042138A1 (fr) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2439558A1 (fr) * | 2010-10-07 | 2012-04-11 | Klaus Ebinger | Sonde de détecteur et procédé de fabrication d'une sonde de détecteur |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3120522C2 (de) * | 1981-05-22 | 1985-02-28 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., 8000 München | Verfahren zur Bestimmung von Werkstoffeigenschaften |
JPS59190719A (ja) * | 1983-04-13 | 1984-10-29 | Omron Tateisi Electronics Co | 近接スイツチ |
SU1170339A1 (ru) * | 1983-08-25 | 1985-07-30 | Научно-Исследовательский Институт Интроскопии | Способ вихретокового контрол ферромагнитных металлических объектов |
EP0258468B1 (fr) * | 1986-08-28 | 1990-01-24 | Vickers Systems GmbH | Procédé de mesure de déplacement inductif et capteur de déplacement |
JPH02312316A (ja) * | 1989-05-26 | 1990-12-27 | Omron Corp | 高周波発振型近接スイッチ |
-
1995
- 1995-06-08 FR FR9506763A patent/FR2735224B1/fr not_active Expired - Fee Related
-
1996
- 1996-06-03 EP EP96920891A patent/EP0830733A1/fr not_active Withdrawn
- 1996-06-03 WO PCT/FR1996/000834 patent/WO1996042138A1/fr not_active Application Discontinuation
Non-Patent Citations (1)
Title |
---|
See references of WO9642138A1 * |
Also Published As
Publication number | Publication date |
---|---|
FR2735224B1 (fr) | 1997-07-18 |
WO1996042138A1 (fr) | 1996-12-27 |
FR2735224A1 (fr) | 1996-12-13 |
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