WO2019196998A1 - Détecteur de courant de foucault et procédé d'étalonnage d'un tel détecteur de courant de foucault - Google Patents

Détecteur de courant de foucault et procédé d'étalonnage d'un tel détecteur de courant de foucault Download PDF

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Publication number
WO2019196998A1
WO2019196998A1 PCT/DK2019/050110 DK2019050110W WO2019196998A1 WO 2019196998 A1 WO2019196998 A1 WO 2019196998A1 DK 2019050110 W DK2019050110 W DK 2019050110W WO 2019196998 A1 WO2019196998 A1 WO 2019196998A1
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Prior art keywords
eddy
coil
magnetic field
current detector
calibration
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PCT/DK2019/050110
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English (en)
Inventor
Kasper JENSEN
Eugene Simon Polzik
Jens ARNBAK
Hans Christian STÆRKIND
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Københavns Universitet
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Københavns Universitet
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
    • G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
    • G01N27/9073—Recording measured data
    • G01N27/9086—Calibrating of recording device

Definitions

  • the present invention relates in a first aspect to an eddy-current detec- tor comprising a magnetometer configured to measure a magnetic field and gen- erate a signal indicative of the measured magnetic field, at least one alternating current, AC, power source, an excitation coil for inducing an eddy-current in an electrically conductive object and a calibration coil, the at least one AC power source being electrically coupled to the excitation coil and to the calibration coil.
  • the invention furthermore relates to a method for calibrating such an eddy-current detector.
  • excitation coil is intended to refer to the coil of the eddy-current detector used for inducing eddy-currents in an object to be examined during normal operation of the eddy-current detector.
  • calibration coil is intended to refer to the coil of the eddy-current detector used for calibrating the eddy-current detector prior to detecting eddy-currents during normal operation of the eddy- current detector.
  • detection range is intended to refer to the range or distance from the eddy-current detector, and in particular from the excitation coil, within which it is possible to actually measure an eddy- current induced in an electrically conductive object by means of the eddy-current detector.
  • Detection and imaging of eddy-currents is a useful way to examine elec- trically conductive objects in a non-destructive and non-invasive way. Also, the presence of objects may be detected in this way.
  • Detection of eddy-currents in biological tissue is one such use.
  • optical magnetometers for non-invasive im- aging of the conductivity of the human heart. The ability to do so may help in diagnosing people suffering from heart diseases such as atrial fibrillation. Howev- er, detection of eddy-currents in biological tissue is difficult as the conductivity is low.
  • Cardiac tissue for instance has a conductivity, s, of 0.2 S/m (Sie- mens/meter).
  • Metals generally have high conductivity.
  • copper has a conductivity, s, of 6 x 10 7 S/m.
  • s conductivity
  • Yet another use is underground exploration.
  • an eddy- current detector By means of an eddy- current detector, it is possible to induce and detect eddy-currents in the ground. Based on the detected signals, one can get information about what is below the ground, whether it is minerals, ground water, metals, hidden objects such as bunkers or something else.
  • Standard prior art eddy-current detectors comprise a magnetometer and a single excitation coil.
  • the electri- cally conductive object is exposed to a magnetic field B oscillating with frequency f produced by the single excitation coil.
  • This magnetic field induces eddy-currents in the object, which create a magnetic field B eddy , and the total magnetic field B + B eddy is measured with the magnetometer.
  • the field produced by the single excitation coil
  • eddy-current detector comprises a magnetometer, a magnetic device, such as a magnetic core, for providing an excitation magnetic field and a calibration unit.
  • the calibration unit comprises a calibration coil arranged around a pole of the magnetic core, a switching means and a reference impedance or resistance.
  • the magnetic calibra- tion field is non-zero and is a pulsed magnetic field.
  • a further object of the invention is to provide an eddy-current detector and a method for calibrating such an eddy-current detector, by means of which it becomes possible to avoid saturation of the measurements and to improve the dynamic range of the measurements.
  • the eddy-current detector of the type mentioned by way of introduction in which the excitation coil and the calibration coil are arranged in such positions with respect to the magne- tometer and each other that when the at least one AC power source delivers an AC current to the excitation coil and to the calibration coil, the resulting total magnetic field at the position of the magnetometer is approximately zero in the absence of any electrically conductive object to be examined within a detection range of the eddy-current detector while the resulting total magnetic field is measured by the magnetometer, and in which the eddy-current detector fur- thermore comprises control electronics, the control electronics being configured to receive a first signal, S ci , indicative of a first magnetic field, Bl, generated by the excitation coil, receive a second signal, S C2 , indicative of a second magnetic field, B2, generated by the calibration coil, and analyze said first signal and said second signal to obtain calibration of the eddy-current detector.
  • Oscillating magnetic fields can be generated by the excitation coil and the calibration coil by running an alternating (AC) electrical current through them.
  • AC alternating
  • the magne- tometer detects the sum of the magnetic fields generated by the excitation coil and the calibration coil.
  • eddy-currents are generated in the electrically conductive ob- ject and the magnetometer detects a non-zero signal. It is noted that the eddy- currents generated in the electrically conductive object are mainly due to the field from the excitation coil, as the object is placed closer to the excitation coil than to the calibration coil.
  • the excitation coil and the calibration coil in such positions with respect to the optically pumped magnetometer and each oth- er that when the AC power source delivers an AC current to each of the excitation coil and the calibration coil, the total magnetic field at the position of the optically pumped magnetometer is approximately zero in the absence of any electrically conductive object to be examined within a detection range of the eddy-current detector, an improved signal-to-noise ratio is obtained when detecting eddy- currents and imaging electrically conductive objects. In turn, faster examination of electrically conductive objects, and also detection of small signals is made pos- sible.
  • the above configuration enables detecting the magnetic field, B eddy , generated by the eddy-current directly, instead of measuring small changes in the total magnetic field as is done in the prior art.
  • the magnetometer will predominantly measure the magnetic field, B eddy , in- pokerd by the eddy-current, when an electrically conductive object is subsequent- ly placed within the detection range of the eddy-current detector.
  • the electrically conductive object should be placed closer to the excitation coil than to the calibration coil.
  • the above configuration also enables providing an eddy- current detector by means of which it becomes possible to avoid saturation of the measurements and to improve the dynamic range of the measurements.
  • the excitation coil and the calibration coil are ar- ranged in such positions with respect to the magnetometer and each other that when the AC power source delivers an AC current II to the excitation coil and the same AC current II to the calibration coil, a first magnetic field B1 is generated by the excitation coil and a second magnetic field B2 is generated by the calibra- tion coil, wherein the first magnetic field B1 and the second magnetic field B2 have the same magnitude and mutually opposite directions at the position of the magnetometer.
  • the eddy-current detector further comprises a detection side adapted for, when inducing an eddy-current in and detecting an eddy-current from an electrically conductive object, facing said electrically con- ductive object, and a calibration side adapted for, when inducing an eddy-current in and detecting an eddy-current from a electrically conductive object, facing away from the electrically conductive object, the detection side and the calibra- tion side being mutually opposite sides of the eddy-current detector, where the excitation coil is arranged on the detection side, and the calibration coil is ar- ranged on the calibration side.
  • an eddy-current de- tector with an improved signal-to-noise ratio when detecting eddy-currents and imaging electrically conductive objects, and with which faster examination of electrically conductive objects, and also detection of small signals is made possi- ble, is achieved in a particularly simple manner.
  • the excitation coil and the calibration coil are ar- ranged on mutually opposite sides of the magnetometer.
  • the excitation coil and the calibration coil are arranged in the same distance, d, from the magnetometer.
  • an eddy-current de- tector having a particularly simple structure with very few and simple compo- nents and simultaneously being especially noise insensitive is provided.
  • the magnetometer is an optically pumped magne- tometer.
  • an optically pumped magnetometer may be an opti cally pumped magnetometer based on Caesium vapor or Potassium vapor or Ru- bidium vapor or Nitrogen-vacancy centers in diamond or on room-temperature Caesium vapor or room-temperature Potassium vapor or room-temperature Ru- bidium vapor or room-temperature Nitrogen-vacancy centers in diamond.
  • an eddy-current detector with a particularly improved signal- to-noise ratio and with which a particularly fast examination of electrically con- ductive objects, and also detection of particularly small signals is provided for.
  • the above and other ob- jects are achieved by a method for calibrating an eddy-current detector according to the first aspect of the invention, the method comprising the following steps:
  • Fig. 1 shows a schematic illustration of a first embodiment of an eddy- current detector according to the invention.
  • Fig. 2 shows a schematic illustration of a second embodiment of an ed- dy-current detector according to the invention.
  • Fig. 3 shows a schematic illustration of a third embodiment of an eddy- current detector according to the invention.
  • Figs. 4A to 4C show schematic illustrations of a method for calibrating an eddy-current detector according to the invention.
  • Figs. 5A to 5F show graphs illustrating the difference between meas- urements performed with a prior art eddy-current detector with one single excita- tion coil (Figs. 5A, 5C and 5E) and measurements performed with an eddy- current detector according to the invention (Figs. 5B, 5D and 5F).
  • Figs 5A and 5B show measurements with shot noise.
  • Figs 5C and 5D show measurements with shot noise and classical noise.
  • Figs 5E and 5F show measurements with shot noise and magnetic field noise.
  • the measurements are illus- trated by means of vectors illustrating an out-of-phase component on the Y-axis and an in-phase component on the X-axis, the units used being arbitrary units (a.u.).
  • in-phase means in phase with the sig nal from the one single coil or the excitation coil
  • out-of-phase means out of phase with the signal from the one single coil or the excitation coil
  • Fig. 6 shows an illustration of the main part of an experimental setup used for establishing pro of- of- concept.
  • Figure 7A illustrates a measurement of the signal from a prior art eddy- current detector with one single coil only illustrating the phase noise in the measurement.
  • Fig 7B shows the results of differential measurements without (Sn a ) and with (Su b ) an object in the form of salt-water to be detected for an eddy-current detector according to the present invention.
  • Each data-point in Figs. 7A and 7B corresponds to the average value of X and Y integrated over 40 ms. Each data-set has 500 data-points. The meas- urements were done using an applied magnetic field oscillating at around 2 MHz.
  • Fig. 8 shows a plot of the Y-component of a measurement signal as a function of time illustrating measurements made as real-time imaging of an ob- ject using the experimental setup shown in Fig. 6 by scanning the position of the object across the excitation coil of the eddy-current detector.
  • Fig. 9 shows a modification of the embodiment of Fig. 2 adapted for far field detection.
  • Fig. 1 shows an eddy-current detector 1 according to the invention.
  • the eddy-current detector 1 comprises a magnetometer 2, which in a preferred em- bodiment is an optically pumped magnetometer.
  • the eddy-current detector 1 further comprises an excitation coil 3.
  • the excitation coil 3 is configured or adapted to, in operation, inducing an eddy-current 9 in an electrically conductive object 8.
  • the eddy-current detector 1 further comprises a calibration coil 4.
  • the eddy-current detector 1 also comprises at least one power source, preferably at least one AC power source 5.
  • the at least one AC power source 5 is configured to deliver an AC current to the excitation coil 3 and to the calibration coil 4.
  • the at least one AC power source 5 is electrically coupled to the excitation coil 3 and to the calibration coil 4 by means of electrical lines 51 and 52.
  • the AC current delivered to the excitation coil 3 and to the calibration coil 4, respectively, should be AC currents with the same or identical frequencies.
  • the AC power source 5 should furthermore provide the AC current delivered to the excitation coil 3 and to the calibration coil 4, respectively, with a stable phase.
  • one AC power source 5 is provid- ed.
  • the one AC power source 5 may have one output terminal connected to both the excitation coil 3 and the calibration coil 4, whereby the AC current delivered to the excitation coil 3 and the calibration coil 4 may be synchronized.
  • the one AC power source 5 may have two output terminals, of which one is connected to the excitation coil 3 and one to the calibration coil 4, whereby the AC current delivered to the excitation coil 3 and the calibration coil 4 may be ad- justed separately from one another.
  • two AC power sources 5a, 5b are provided.
  • One AC power source 5a is connected to the excitation coil 3
  • the other AC power source 5b is connected to the calibration coil 4.
  • the excitation coil 3 and the calibration coil 4 are arranged in such a manner with respect to the optically pumped magnetometer 2 and with respect to each other that, when the AC power source 5 delivers an AC current to each of the excitation coil 3 and the calibration coil 4, the total magnetic field at the posi- tion of the optically pumped magnetometer 2 is approximately zero or precisely zero in the absence of any electrically conductive object 8 to be examined, for instance detected or measured, within a detection range of the eddy-current de- tector 1. It is noted that in this connection "approximately zero" is intended to encompass at least the value zero itself and values within ordinary and/or statis- tical uncertainties thereof.
  • the excitation coil 3 and the calibration coil 4 may additionally be ar- ranged in such a manner with respect to the optically pumped magnetometer 2 and with respect to each other that, when the AC power source 5 delivers an AC current to each of the excitation coil 3 and the calibration coil 4, the total mag- netic field at the position of the optically pumped magnetometer 2 is approxi- mately zero or precisely zero also in the absence of any ambience electrically conductive object being introduced within a detection range of the eddy-current detector 1 while the resulting total magnetic field is measured by the magnetom- eter 2, or in other words when no electrically conductive object is moved with respect to the eddy-current detector 1 or vice versa within a detection range of the eddy-current detector 1 while the resulting total magnetic field is measured by the magnetometer 2.
  • stationary electrically conductive objects such as for instance stationary electrically conductive objects forming a part of the eddy-current detector 1 or a corresponding measurement setup, such as e.g. a housing, a holder or the like, may be present within a de- tection range of the eddy-current detector 1 while the resulting total magnetic field is measured by the magnetometer.
  • the eddy- current detector 1 comprises a magnetometer 2, which in a preferred embodi- ment is an optically pumped magnetometer.
  • the eddy-current detector 1 further comprises an excitation coil 3.
  • the excitation coil 3 is configured or adapted to, in operation, inducing an eddy-current 9 in an electrically conductive object 8.
  • the eddy-current detector 1 further comprises a calibration coil 4.
  • the eddy-current detector 1 also comprises a power source, preferably an AC power source 5, of any of the types described above.
  • the AC power source 5 is electrically coupled to the excitation coil 3 and to the calibration coil 4.
  • the excitation coil 3 and the calibration coil 4 are arranged in such positions with respect to the magnetometer 2 and each other that when the AC power source 5 delivers an AC current II to the excitation coil 3 and the same AC current II to the calibration coil 4, a first magnetic field B1 is generated by the excitation coil 3 and a second magnetic field B2 is generated by the calibration coil 4, where the first magnetic field B1 and the second magnetic field B2 have the same magnitude and mutually opposite directions at the position of the magnetometer.
  • the eddy-current detector 10 comprises a magnetometer 2, which in a preferred embodiment is an optically pumped mag- netometer.
  • the eddy-current detector 10 further comprises an excitation coil 3.
  • the excitation coil 3 is configured or adapted to, in operation, inducing an eddy- current 9 in an electrically conductive object 8.
  • the eddy-current detector 10 fur- ther comprises a calibration coil 4.
  • the eddy-current detector 10 also comprises two power source, preferably two AC power sources 5a and 5b, of any of the types described above in connection with Fig. 1.
  • the eddy-current detector 10 comprises a detection side 6 and a calibration side 7.
  • the detection side 6 is adapted for, during operation of the eddy-current detector, and thus when induc- ing an eddy-current 9 in and detecting an eddy-current 9 from an electrically conductive object 8, facing the electrically conductive object 8.
  • the calibration side 7 is adapted for, during operation of the eddy-current detector, and thus when inducing an eddy-current 9 in and detecting an eddy-current 9 from an electrically conductive object 8, facing away from the electrically conductive ob- ject 8.
  • the detection side 6 and the calibration side 7 are mutually opposite sides of the eddy-current detector.
  • the detection side 6 and the calibration side 7 are arranged on a central axis A of the eddy-current detector 10.
  • the central axis A extends through the excitation coil 3, the calibration coil 4 and the magnetometer 2.
  • the detection side 6 and the calibration side 7 are arranged symmetrically on opposite sides of a plane B extending perpendicular to the central axis A and through the center of the eddy-current detector 10 and the middle of the magnetometer 2.
  • the detection side 6 and the calibration side 7 are or are arranged on mutually opposite sides of the magnetometer 2.
  • the excitation coil 3 is in this connection arranged on the detection side 6, while the calibration coil 4 is arranged on the calibration side 7.
  • the exci- tation coil 3 and the calibration coil 4 may be arranged in the same distance, d, from the optically pumped magnetometer 2.
  • the mag- netometer 2 may be an optically pumped magnetometer.
  • the optically pumped magnetometer may be based on Caesium or Rubidium vapor, particularly room- temperature Caesium or Rubidium vapor.
  • Other feasible types of optically pumped magnetometers include optically pumped magnetometers based on Po- tassium vapor, vapor of an alkali-metal or on Nitrogen-vacancy centers in dia- mond.
  • the excitation coil 3 and the calibration coil 4 are arranged on mutually opposite sides of the optically pumped magnetometer 2.
  • the excitation coil 3 and the calibration coil 4 may be arranged in a different configuration than on mutually opposite sides of the optically pumped magnetometer 2
  • the eddy-current de- tector may also comprise control electronics 11. This is illustrated in Fig. 3 show- ing an eddy-current detector 100 according to a third embodiment of the inven- tion.
  • the control electronics 11 may be coupled electrically and/or in a data transfer enabling relationship, by means of a wired or a wireless connection, with any one or more of the magnetometer 2, the excitation coil 3, the calibration coil 4 and the AC power source 5.
  • the control electronics 11 may be configured to perform any one or more of regulating the output of the AC power source 5, re- ceiving from the magnetometer 2 a first signal, S ci , indicative of a magnetic field, Bl, generated by the excitation coil 3, receiving from the magnetometer 2 a sec- ond signal, S C 2, indicative of a magnetic field, B2, generated by the calibration coil 4, analyzing said first signal and said second signal to obtain calibration of the eddy-current detector, receiving from the magnetometer 2 a third signal in- dicative of an eddy-current 9 induced in an electrically conductive object 8 by the excitation coil 3, and analyzing said third signal to obtain information regarding said electrically conductive object 8.
  • the eddy-current de- tector may also comprise a display (not shown) configured for displaying infor- mation relating to a measurement performed with the eddy-current detector and/or a calibration process, such as an image of the eddy-current.
  • the control electronics 11 may also be coupled electrically and/or in a data trans- fer enabling relationship, by means of a wired or a wireless connection, with the display.
  • the display may be integrated in the eddy-current detector.
  • the display may be an external element.
  • the eddy-current de- tector may also comprise a housing (not shown) in which one or more of the above-described components of the eddy-current detector may be arranged and shielded from the outside.
  • an oscillating signal can be written as
  • the method for calibrating the eddy- current detector 1 comprises the following steps.
  • step 100 an eddy-current detector 1 according to the first aspect of the present invention is provided.
  • step 101 it is ensured that no electrically conductive object to be ex- amined is present within a detection range of the eddy-current detector 1 during the performance of steps 102 and 103 to be described in the following.
  • step 102 an AC current is delivered from the AC power source 5 to each of the excitation coil 3 and the calibration coil 4 such that a first magnetic field B1 is generated by the excitation coil 3 and a second magnetic field B2 is generated by the calibration coil 4.
  • step 103 the amplitude and the phase of the second magnet- ic field B2 generated by the calibration coil 4 is adjusted such as to ensure that that the total magnetic field, B1+B2, at the position of the optically pumped magnetometer 2 is approximately zero or precisely zero.
  • the magnetic fields generat- ed by the excitation coil 3 and the calibration coil 4, respectively, are continuous- ly on.
  • the step 102 of delivering may comprise continuously delivering an AC current from the AC power source 5 to each of the excitation coil 3 and the calibration coil 4.
  • the step 102 of delivering may comprise deliver- ing a pulsed AC current from the AC power source 5 to each of the excitation coil 3 and the calibration coil 4.
  • the calibration method may furthermore comprise one or more of the following optional and/or additional steps.
  • the step 104 with sub-steps 104a-104c may be com- bined with or performed together with the step 103 with sub-steps 103a-103c. Inclusion of the step 104 with sub-steps 104a-104c ensures an even further im- proved calibration of the eddy-current detector.
  • Figs. 5A to 5F an exemplary comparison between the noise sensitivity of a prior art eddy-current detector with one single excitation coil and the noise sensitivity of an eddy-current detector according to the present invention will be made. It is noted that besides noise and drifts in the applied magnetic field, there may be noise in the measurement itself as carried out with the magnetometer. As will be clear the eddy-current detector according to the present invention exhibits an improved signal-to-noise ratio as compared to the prior art.
  • the magnetic field at the position of the magnetometer may be written as Bci COS(GOI t + cpi), where B ci is the amplitude and f i is the phase of the field. It is here assumed that the magnetometer provides a signal which is proportional to the magnetic field.
  • the one single coil induces an eddy-current in any nearby electrically conductive object.
  • the magnetic field from the eddy-currents at the position of the magnetometer is B eddy,ci cos(c i t + cpe ddy ). Note that the induced field has a phase cpe ddy relative to the applied field.
  • the phase cp eddy is expected to be -90 degrees when the thickness of the electrically conductive object is much smaller than the skin depth d and to be -180 degrees when the thickness of the electrically conductive object is much larger than the skin depth.
  • Fig. 5A shows an example of simulated data for the case when only one coil is used.
  • the magnetometer signals are plotted in phase-space (i.e., plotted with X and Y on the coordinate axes).
  • the excitation coil gives a signal S ci and the calibration coil gives a signal S C 2-
  • Fig. 5B shows simulated data for the situation where one uses an eddy- current detector according to the present invention with a magnetometer and two coils.
  • the eddy-current detector according to the present invention makes it possible to measure the signal from the eddy-currents directly.
  • FIGs. 5A and 5B show simulated data for this type of noise for a prior art eddy-current detector and an eddy-current detector accord- ing to the invention, respectively.
  • the noisy data are presented in Figs. 5A to 5F as a set of points that have a certain distribution in X-Y phase-space.
  • FIGs. 5C and 5D show simulated data for this situation.
  • an optical magnetometer based on room-temperature caesium vapor was used.
  • the caesium atoms were placed in a static bias magnetic field B o , and the caesium atoms were optically pumped and probed with laser light.
  • FIG. 6 An illustration of the main part of the experimental setup used is shown in Fig. 6. The goal was to detect the presence of salt-water with 2 cm 3 volume placed inside a container 80.
  • An eddy-current detector 101 according to the in- vention with two coils (excitation coil 3 on the top and calibration coil 4 on the bottom) and a caesium vapor cell 20 are placed in a holder. The holder is not shown for the sake of simplicity. Magnetic fields are measured by shining several laser beams through the caesium vapor cell 20 and detecting the transmitted light. The caesium vapor cell 20 thus acts as magnetometer. Laser beams and detector are not shown in Fig. 6. Experiments are performed inside a cylindrical magnetic shield 90.
  • the conductivity of salt-water depends on the concentration of salt.
  • Figure 7A the measurement of the signal from a prior art eddy- current detector with one single coil only with the salt-water placed far away is illustrated.
  • the expected signal from eddy-currents in salt-water is much smaller than this, and for that reason one will not be able to detect such eddy-currents with a prior art eddy-current detector with one single coil.
  • Fig 7B shows the results of differential measurements without (Sn a ) and with (Su b ) the salt-water.
  • the eddy-current detector according to the present inven- tion can be used to detect the presence of objects with low conductivity.
  • the inventors have also performed real-time imaging of the salt- water in the container 80 of the setup shown in Fig. 6 by scanning the position of the container 80 with salt-water across the excitation coil 3. The measurement results are shown in Fig. 8.
  • the inventors have furthermore realized that the invention is also appli- cable for detection of an electrically conductive object 8, even if the electrically conductive object 8 is far away from the eddy current detector 1.

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Abstract

La présente invention concerne un détecteur de courant de Foucault (1) comprenant un magnétomètre (2) conçu pour mesurer le champ magnétique et générer un signal indiquant le champ magnétique mesuré, au moins une source d'alimentation en courant alternatif (5), une bobine d'excitation (3) conçue pour, en fonctionnement, induire un courant de Foucault (9) dans un objet électriquement conducteur (8) et une bobine d'étalonnage (4), la ou les sources de courant alternatif (5) étant couplées électriquement à la bobine d'excitation (3) et à la bobine d'étalonnage (4), et la bobine d'excitation (3) et la bobine d'étalonnage (4) étant agencée dans des positions telles par rapport au magnétomètre (2) et l'une par rapport à l'autre que, lorsque la source de courant alternatif (5) distribue un courant alternatif à la bobine d'excitation (3) et à la bobine d'étalonnage (4), le champ magnétique total à la position du magnétomètre (2) est approximativement nul en l'absence de tout objet électroconducteur dans une plage de détection du détecteur de courant de Foucault (1) tandis que le champ magnétique total résultant est mesuré par le magnétomètre (2).
PCT/DK2019/050110 2018-04-09 2019-04-08 Détecteur de courant de foucault et procédé d'étalonnage d'un tel détecteur de courant de foucault Ceased WO2019196998A1 (fr)

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Cited By (2)

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WO2023280748A1 (fr) * 2021-07-09 2023-01-12 Endress+Hauser Flowtec Ag Capteur de conductivité
US12405248B2 (en) * 2022-09-25 2025-09-02 Anhui Guosheng Quantum Technology Co., Ltd. Eddy current flaw detection system based on NV color center quantum sensing technology and detection method thereof

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