WO2009136116A2 - System for measuring a magnetic field and corresponding method for suppressing a magnetic field sensor shift - Google Patents

System for measuring a magnetic field and corresponding method for suppressing a magnetic field sensor shift Download PDF

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Publication number
WO2009136116A2
WO2009136116A2 PCT/FR2009/050665 FR2009050665W WO2009136116A2 WO 2009136116 A2 WO2009136116 A2 WO 2009136116A2 FR 2009050665 W FR2009050665 W FR 2009050665W WO 2009136116 A2 WO2009136116 A2 WO 2009136116A2
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WO
WIPO (PCT)
Prior art keywords
sensor
frequency
excitation
measurement signal
magnetic field
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PCT/FR2009/050665
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French (fr)
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WO2009136116A3 (en
Inventor
Christophe Pierre Coillot
Joël MOUTOUSSAMY
Gérard Marcel CHANTEUR
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Centre National De La Recherche Scientifique (C.N.R.S)
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Publication of WO2009136116A2 publication Critical patent/WO2009136116A2/en
Publication of WO2009136116A3 publication Critical patent/WO2009136116A3/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/07—Hall effect devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices

Definitions

  • the present invention relates to a system for measuring a magnetic field comprising a magnetic sensor having an electrical measurement signal characteristic as a function of the even measured field and an electronic device for suppressing the offset of the sensor.
  • It also relates to a method of suppressing the offset of a corresponding magnetic field sensor.
  • the invention relates to magnetic field measuring sensors which utilize an AC excitation source and which have an electrical measurement signal characteristic as a function of the even-measured field.
  • Such sensors are generally used in magnetometry applications.
  • the criteria used to compare their performances are: - the smallest measurable magnetic field at a given frequency;
  • anisotropic magneto-resistance (AMR) and giant magneto-impedance (GMI) are the most promising.
  • the AMR sensors and their variants GMR (magneto-resistance giant) and TMR (magnetoresistance tunnel) are of small size and low consumption and have a sensitivity that can be flush 1 nT / VHz at 1 Hz.
  • the GMI sensors are low consumption and present possibilities of miniaturization and evolution suggesting a potential low mass and sensitivities below 1 nT / VHz at 1 Hz. Major research efforts are currently underway to improve these magnetic sensors.
  • This offset is also called the sensor offset and represents the value of the electrical measurement signal at the output of the zero magnetic field sensor.
  • Such an offset has the effect of producing a measurement bias which reduces the measurement dynamics and makes the operation of the measurement signal difficult without providing information on the magnetic field and is therefore a limiting factor of the sensitivity of the magnetic sensors.
  • the object of the invention is to solve these problems.
  • the invention aims to provide a solution for the suppression of the offset in a magnetic sensor having a characteristic of the electrical measurement signal as a function of the even-measured field.
  • the subject of the invention is a system for measuring a magnetic field comprising a magnetic sensor having an electrical measurement signal characteristic as a function of the even measured field and an electronic device for eliminating the sensor offset, characterized in that the offset removal device comprises symmetrical AC bias means of the sensor at a determined polarization frequency.
  • the system comprises one or more of the following features, taken alone or in any technically possible combination:
  • the system comprises an alternating current source for exciting the sensor at an excitation frequency determined so as to maximize the sensitivity of said sensor, the excitation frequency of the sensor is an integer multiple of the polarization frequency of the sensor,
  • the system comprises means for reducing the low frequency noise of the excitation current source;
  • the noise reduction means of the excitation current source comprise a selective filter for filtering the measurement signal at the frequency; excitation,
  • the noise reduction means of the excitation current source comprise a piezoelectric transformer; the noise reduction means of the excitation current source comprise a direct-alternating AC converter,
  • the AC-AC direct converter comprises a transformer
  • the system comprises synchronous demodulation means at the excitation frequency of the measurement signal and a high-pass filter for filtering the measurement signal demodulated at the excitation frequency,
  • the system comprises means of demodulation at the polarization frequency of the measurement signal demodulated at the excitation frequency and filtered high-pass and a low-pass filter for the filtering of the measurement signal demodulated at the polarization frequency; the system comprises means for increasing the linearity range of the magnetic sensor,
  • the means for increasing the linearity range of the magnetic sensor comprise a counter-reaction
  • the magnetic sensor is a giant magneto-impedance effect sensor
  • the magnetic sensor is a giant magneto-resistance effect sensor.
  • the subject of the invention is also a method for suppressing the offset of a magnetic field sensor, said sensor having an electrical measurement signal characteristic as a function of the even measured field, characterized in that it comprises an alternative polarization step. symmetrical sensor at a determined polarization frequency.
  • the invention makes it possible to overcome the drawbacks of the usual solution for eliminating the offset by making it possible to eliminate the offset of a single magnetic sensor in an intrinsic manner thus avoiding the need to associate with this sensor another polarized sensor in an opposite manner.
  • the invention makes it possible to reduce the noise of the excitation current source of the sensor, which is a factor limiting the low frequency sensitivity of the sensor.
  • FIG. 1 is a block diagram illustrating the structure of a magnetic sensor with a GMI effect
  • FIG. 2 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a first embodiment of the invention
  • FIG. 3 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a second embodiment of the invention
  • FIG. 4 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a third embodiment of the invention.
  • FIG. 5 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a fourth embodiment of the invention.
  • FIG. 6 is a flowchart illustrating the operation of the offset removal method of a magnetic sensor according to the invention.
  • the invention particularly relates to GMI effect sensors and GMR effect sensors.
  • FIG. 1 illustrates the structure of a magnetic sensor with a GMI effect of the state of the art.
  • the magnetic sensor is designated by the general reference 2.
  • the magnetic sensor 2 comprises an electrical conductor 4 (for example a copper ribbon) sandwiched between two ferromagnetic strips 6 and 8 of planar shape having a magneto effect -giant impedance.
  • the ribbons 6 and 8 are composed of a nanocrystalline material but other magnetic materials are also used in the state of the art.
  • An exc excitation alternating current is injected through the sensor 2.
  • GMI or giant magneto-impedance is referred to in this sensor 2 since when a magnetic field H ex t 12 is applied near the sensor 2, the impedance variation of the sensor 2 can be modified. to be measured.
  • the polarization field is conventionally created by a so-called polarization winding or by the leakage field of a magnet.
  • the useful part of the measured signal 16 is contained in dZ gm ⁇ / dH (H b ⁇ a s) x Uxc while the part Z gm ⁇ 0 (H b ⁇ a s) x Uxc is an offset which has the effect of reducing the dynamic of measurement without making any difference. information on the magnetic field 12.
  • the offset or offset is a continuous signal which is superimposed on the measurement signal.
  • An excessively large offset relative to the measurement signal makes it difficult to use the measurement signal because the measurement signal consists, in this case, in small variations around a constant signal of high amplitude.
  • An offset in a magnetic sensor is therefore often a source of measurement bias and variations in this offset, particularly because of the temperature, limit the resolution of the sensor.
  • the offset is manifested in the signal 16 in the form of small variations of the impedance dzgmax / dH (H b ⁇ a s) xlexc about the impedance of the GMI sensor.
  • the invention makes it possible to eliminate this shift, in particular by means of an alternating polarization of the magnetic sensor.
  • FIG. 2 illustrates the structure of a measurement system of a magnetic field according to a first embodiment of the invention.
  • the system further comprises the GMI effect sensor 2 and the AC excitation source exc 10 the frequency F 0, means for symmetrical alternating bias designated by the general reference 20 and to obtain the bias field H b ⁇ a
  • This polarization means consist, according to the embodiment of FIG. 2, in a polarization winding.
  • the bias field H b ⁇ as 14 is an alternating field of frequency l ⁇ b ⁇ as-
  • excitation frequencies F 0 and polarization F b ⁇ as are determined according to the invention as follows:
  • the excitation frequency F 0 is determined, by performing preliminary tests, so as to maximize the sensitivity of the sensor 2. It depends on the configuration, that is to say, the material and the shape of the sensor 2; and
  • the polarization frequency F b ⁇ as is chosen lower than the frequency F 0 and such that the difference (F 0 - F b ⁇ as ) is greater than the frequency range to be measured which depends on the application.
  • the magnetic field measuring system comprises a bandpass-type selective filter 22 for filtering the measurement signal 16 at the excitation frequency F 0 .
  • the selective filter 22 thus makes it possible to reduce the noise of the excitation current source 10 around the frequency F 0 .
  • the polarization frequency F b ⁇ as is set so that (F 0 - F b ⁇ as ) is sufficiently high for the selective filter 22 to attenuate the noise of the excitation current source. 10 of the desired amount for the application.
  • the order of the selective filter 22 is also set according to the desired application of the system.
  • the measurement system illustrated in FIG. 2 comprises synchronous measurement demodulation means illustrated in FIG. 2 at the excitation frequency F 0 designated by the reference 24 and a high-pass filter 26 enabling the signal to be suppressed.
  • measurement U 16 the component related to the shift.
  • the synchronous demodulation means 24 comprise a multiplier by a signal at the frequency F 0 and the high-pass filter 26 has a cut-off frequency Fci "(F b ⁇ a s-BU) where BU represents the useful band of the measurement signal 16.
  • the measurement system also comprises demodulation means at the bias frequency F b ⁇ as designated by the reference 28 and a low-pass filter 30 for removing the undesirable components of the measurement signal.
  • the demodulation means at the bias frequency F b ⁇ as designated by the reference 28 and a low-pass filter 30 for removing the undesirable components of the measurement signal.
  • the low-pass filter 30 has a cutoff frequency Fc 2 > BU.
  • the order of the filter 30 is chosen as a function of the application and in particular of the desired attenuation or of the modulation residue at F b ⁇ as .
  • amplifiers 32, 34 and 36 are also provided. They make it possible to improve the performance of the system and to adapt the dynamics of the sensor 2 to the intended application.
  • V 8 corresponds to the measurement signal 16 from which the offset is suppressed and whose noise is attenuated, which has the consequence of having a more precise measurement and a more sensitive sensor.
  • FIG. 3 illustrates a second embodiment of the magnetic field measuring system according to the invention.
  • the system illustrated in FIG. 3 differs from that of FIG. 2 by adding means for increasing the linearity range of the sensor 2 comprising a corrector 38 and a feedback 40.
  • the corrector 38 is a corrector of the proportional (P), proportional integral (P1) or proportional integral derivative (PID) type.
  • the feedback 40 consists of an additional winding which creates, in the GMI sensor 2, a magnetic field which opposes the measured magnetic field so as to operate the magnetic field sensor almost zero.
  • the feedback 40 does not use an additional winding, but the polarization winding.
  • FIG. 4 illustrates a third embodiment of the magnetic field measuring system according to the invention.
  • the system illustrated in Figure 4 differs from that of Figure 2 by replacing the selective filter 22 by a piezoelectric transformer 42 placed at the entrance of the system.
  • the piezoelectric transformer 42 is a quadrupole consisting of two terminals to which the excitation source 10 is connected at the input and two terminals to which the GMI sensor 2 is connected.
  • the piezoelectric transformer combines voltage amplification and a filter. selective.
  • FIG. 5 illustrates a fourth embodiment of the magnetic field measuring system according to the invention in which the magnetic polarization means 20 are represented by a polarization current source 1 bias 43.
  • the system illustrated in FIG. 5 differs from FIG. that of FIG. 4 by the replacement of the piezoelectric transformer 42 by a direct-alternating direct converter comprising a transformer 44 of smaller volume than that of the transformer 42.
  • the reduction of the size of the transformer is obtained by means of a modulation of the polarization current l b ⁇ as 43 at a frequency higher than the frequency F b ⁇ as , for example at the excitation frequency F 0 .
  • the modulation of the polarization current I Bias 43 is performed by a modulation circuit 47 at the excitation frequency F 0 placed at the input of the transformer 44.
  • a demodulation circuit 48 at the frequency of F 0 excitation is provided to demodulate the bias current l b ⁇ as 43.
  • the circuits 47 and 48 comprise a plurality of switches controlled by the excitation source 10 (not shown in FIG. 5).
  • the polarization current I Bias 43 then passes through a resistor 49 before passing through the polarization means 20.
  • This fourth embodiment allows the reduction of the consumption of the transformer.
  • the magnetic sensor 2 is exited by the alternating current source Uxc 10. It is then polarized at 52 with the symmetrical alternating polarization means 20.
  • the measurement signal U 16 is filtered by the selective bandpass filter 22 at the frequency F 0 .
  • the signal obtained at the output of the selective filter 22 is then amplified at 56 by the amplifier 32 and demodulated at the frequency F 0 at 58 by the demodulation means 24.
  • the amplified signal obtained is filtered high-pass at 60 by the pass filter.
  • -High 26 then amplified at 62 by the amplifier 34.
  • the amplified signal obtained is demodulated at the frequency F b ⁇ as at 64 by the demodulation means 28.
  • the demodulated signal obtained is low-pass filtered at 66 by the low-pass filter 30, then amplified at 68 by the amplifier 36 to adapt its dynamics to the intended application.
  • the signal V 8 38 is obtained.
  • the invention makes it possible, thanks to the alternating polarization and to the high-pass filter 26, to eliminate the offset of a magnetic sensor without having recourse to two sensors mounted in differential and subjected to opposite magnetic polarizations, as is the case. in the usual solution of offset removal.
  • the system proposed in the invention makes it possible, by using the selective filter 22 or the piezoelectric transformer 42 or the direct alternating-AC converter comprising the transformer 44, to reduce the noise. from the excitation source of the sensor and thereby increase the sensitivity of the magnetic sensor.

Abstract

The invention relates to a system for measuring a magnetic field (12) that includes a magnetic sensor (2) characterized in that the system has a signal for electrical measurement on the basis of the paired field (12) being measured and an electronic device (2) for suppressing sensor shift, and is further characterized in that the shift suppression device includes a symmetrical AC biasing means (20) for the symmetrical AC bias of the sensor (2) to a predetermined bias frequency.

Description

Système de mesure d'un champ magnétique et procédé de suppression du décalage d'un capteur de champ magnétique correspondant Magnetic field measuring system and offset suppression method of a corresponding magnetic field sensor
La présente invention concerne un système de mesure d'un champ magnétique comprenant un capteur magnétique présentant une caractéristique de signal de mesure électrique en fonction du champ mesuré paire et un dispositif électronique de suppression du décalage du capteur.The present invention relates to a system for measuring a magnetic field comprising a magnetic sensor having an electrical measurement signal characteristic as a function of the even measured field and an electronic device for suppressing the offset of the sensor.
Elle concerne également un procédé de suppression du décalage d'un capteur de champ magnétique correspondant.It also relates to a method of suppressing the offset of a corresponding magnetic field sensor.
Plus particulièrement, l'invention se rapporte aux capteurs de mesure de champs magnétiques qui utilisent une source d'excitation alternative et qui présentent une caractéristique de signal de mesure électrique en fonction du champ mesuré paire.More particularly, the invention relates to magnetic field measuring sensors which utilize an AC excitation source and which have an electrical measurement signal characteristic as a function of the even-measured field.
De tels capteurs sont généralement utilisés dans les applications de magnétométrie. Les critères employés pour comparer leurs performances sont : - le plus petit champ magnétique mesurable à une fréquence donnée ;Such sensors are generally used in magnetometry applications. The criteria used to compare their performances are: - the smallest measurable magnetic field at a given frequency;
- la masse et les dimensions du capteur ;- the mass and dimensions of the sensor;
- la bande passante ; et- bandwidth ; and
- la consommation du capteur.- the consumption of the sensor.
En fonction des applications, l'ordre de préférence pour ces critères diffère. Ainsi pour les applications concernant la mesure de la composante magnétique des ondes dans les plasmas spatiaux, il est souhaitable d'avoir des capteurs sensibles à des champs magnétiques ayant une densité spectrale inférieure à 100 à 1 Hz, de faible masse et de faible consommation.Depending on the applications, the order of preference for these criteria differs. Thus, for applications relating to the measurement of the magnetic component of the waves in the spatial plasmas, it is desirable to have sensors sensitive to magnetic fields having a spectral density of less than 100 to 1 Hz, of low mass and of low consumption.
Parmi les technologies de capteurs magnétiques utilisés en magnétométrie, la magnéto-résistance anisotrope (AMR) et la magnéto-impédance géante (GMI) sont les plus prometteuses.Among the magnetic sensor technologies used in magnetometry, anisotropic magneto-resistance (AMR) and giant magneto-impedance (GMI) are the most promising.
Les capteurs AMR et leurs variantes GMR (magnéto-résistance géante) et TMR (magnéto-résistance tunnel) sont de faible taille et de faible consommation et présentent une sensibilité pouvant affleurer 1 nT/VHz à 1 Hz. Les capteurs GMI sont de faible consommation et présentent des possibilités de miniaturisation et d'évolution laissant entrevoir une potentielle faible masse et des sensibilités en-deçà de 1 nT/VHz à 1 Hz. De grands efforts de recherche sont actuellement menés afin d'améliorer ces capteurs magnétiques.The AMR sensors and their variants GMR (magneto-resistance giant) and TMR (magnetoresistance tunnel) are of small size and low consumption and have a sensitivity that can be flush 1 nT / VHz at 1 Hz. The GMI sensors are low consumption and present possibilities of miniaturization and evolution suggesting a potential low mass and sensitivities below 1 nT / VHz at 1 Hz. Major research efforts are currently underway to improve these magnetic sensors.
L'une des voies de recherche s'intéresse au problème du décalage dans les capteurs. Ce décalage est également appelé offset du capteur et il représente la valeur du signal électrique de mesure en sortie du capteur à champ magnétique nul.One of the lines of research is concerned with the problem of the shift in the sensors. This offset is also called the sensor offset and represents the value of the electrical measurement signal at the output of the zero magnetic field sensor.
Un tel décalage a pour effet de produire un biais de mesure qui réduit la dynamique de mesure et rend l'exploitation du signal de mesure difficile sans apporter d'informations sur le champ magnétique et constitue donc un facteur limitant de la sensibilité des capteurs magnétiques.Such an offset has the effect of producing a measurement bias which reduces the measurement dynamics and makes the operation of the measurement signal difficult without providing information on the magnetic field and is therefore a limiting factor of the sensitivity of the magnetic sensors.
La solution usuelle pour supprimer le décalage d'un magnétomètre consiste à associer dans ce même magnétomètre deux capteurs les plus identiques possibles montés en différentiel et polarisés de manière opposée.The usual solution to eliminate the offset of a magnetometer is to combine in the same magnetometer two identical sensors possible differential mounted and polarized in opposite manner.
Cette solution présente l'inconvénient de la nécessité d'utiliser deux capteurs dans un même magnétomètre afin de compenser le décalage des deux capteurs.This solution has the disadvantage of the need to use two sensors in the same magnetometer to compensate for the offset of the two sensors.
Le but de l'invention est de résoudre ces problèmes.The object of the invention is to solve these problems.
Plus particulièrement, l'invention vise à fournir une solution pour la suppression du décalage dans un capteur magnétique présentant une caractéristique du signal de mesure électrique en fonction du champ mesuré paire.More particularly, the invention aims to provide a solution for the suppression of the offset in a magnetic sensor having a characteristic of the electrical measurement signal as a function of the even-measured field.
A cet effet, l'invention a pour objet un système de mesure d'un champ magnétique comprenant un capteur magnétique présentant une caractéristique de signal de mesure électrique en fonction du champ mesuré paire et un dispositif électronique de suppression du décalage du capteur, caractérisé en ce que le dispositif de suppression du décalage comprend des moyens de polarisation alternative symétrique du capteur à une fréquence de polarisation déterminée.For this purpose, the subject of the invention is a system for measuring a magnetic field comprising a magnetic sensor having an electrical measurement signal characteristic as a function of the even measured field and an electronic device for eliminating the sensor offset, characterized in that the offset removal device comprises symmetrical AC bias means of the sensor at a determined polarization frequency.
Suivant d'autres modes de réalisation, le système comprend une ou plusieurs des caractéristiques suivantes, prises isolément ou suivant toutes les combinaisons techniquement possibles :According to other embodiments, the system comprises one or more of the following features, taken alone or in any technically possible combination:
- le système comprend une source de courant alternatif d'excitation du capteur à une fréquence d'excitation déterminée de manière à maximiser la sensibilité dudit capteur, - la fréquence d'excitation du capteur est un multiple entier de la fréquence de polarisation du capteur,the system comprises an alternating current source for exciting the sensor at an excitation frequency determined so as to maximize the sensitivity of said sensor, the excitation frequency of the sensor is an integer multiple of the polarization frequency of the sensor,
- le système comprend des moyens de réduction du bruit basse fréquence de la source de courant d'excitation, - les moyens de réduction du bruit de la source de courant d'excitation comprennent un filtre sélectif pour le filtrage du signal de mesure à la fréquence d'excitation,the system comprises means for reducing the low frequency noise of the excitation current source; the noise reduction means of the excitation current source comprise a selective filter for filtering the measurement signal at the frequency; excitation,
- les moyens de réduction du bruit de la source de courant d'excitation comprennent un transformateur piézo-électrique, - les moyens de réduction du bruit de la source de courant d'excitation comprennent un convertisseur direct alternatif-alternatif,the noise reduction means of the excitation current source comprise a piezoelectric transformer; the noise reduction means of the excitation current source comprise a direct-alternating AC converter,
- le convertisseur direct alternatif-alternatif comprend un transformateur,the AC-AC direct converter comprises a transformer,
- le système comprend des moyens de démodulation synchrone à la fréquence d'excitation du signal de mesure et un filtre passe-haut pour le filtrage du signal de mesure démodulé à la fréquence d'excitation,the system comprises synchronous demodulation means at the excitation frequency of the measurement signal and a high-pass filter for filtering the measurement signal demodulated at the excitation frequency,
- le système comprend des moyens de démodulation à la fréquence de polarisation du signal de mesure démodulé à la fréquence d'excitation et filtré passe-haut et un filtre passe-bas pour le filtrage du signal de mesure démodulé à la fréquence de polarisation, - le système comprend des moyens d'augmentation de la plage de linéarité du capteur magnétique,the system comprises means of demodulation at the polarization frequency of the measurement signal demodulated at the excitation frequency and filtered high-pass and a low-pass filter for the filtering of the measurement signal demodulated at the polarization frequency; the system comprises means for increasing the linearity range of the magnetic sensor,
- les moyens d'augmentation de la plage de linéarité du capteur magnétique comprennent une contre-réaction,the means for increasing the linearity range of the magnetic sensor comprise a counter-reaction,
- le capteur magnétique est un capteur à effet de magnéto-impédance géante,the magnetic sensor is a giant magneto-impedance effect sensor,
- le capteur magnétique est un capteur à effet de magnéto-résistance géante.the magnetic sensor is a giant magneto-resistance effect sensor.
L'invention a également pour objet un procédé de suppression du décalage d'un capteur de champ magnétique, ledit capteur présentant une caractéristique de signal de mesure électrique en fonction du champ mesuré paire, caractérisé en ce qu'il comprend une étape de polarisation alternative symétrique du capteur à une fréquence de polarisation déterminée. Ainsi, l'invention permet de pallier les inconvénients de la solution usuelle de suppression du décalage en permettant de supprimer le décalage d'un capteur magnétique unique de manière intrinsèque évitant ainsi la nécessité d'associer à ce capteur un autre capteur polarisé de manière opposée. Par ailleurs, l'invention permet de réduire le bruit de la source de courant d'excitation du capteur qui est un facteur limitant la sensibilité basse fréquence du capteur.The subject of the invention is also a method for suppressing the offset of a magnetic field sensor, said sensor having an electrical measurement signal characteristic as a function of the even measured field, characterized in that it comprises an alternative polarization step. symmetrical sensor at a determined polarization frequency. Thus, the invention makes it possible to overcome the drawbacks of the usual solution for eliminating the offset by making it possible to eliminate the offset of a single magnetic sensor in an intrinsic manner thus avoiding the need to associate with this sensor another polarized sensor in an opposite manner. . Furthermore, the invention makes it possible to reduce the noise of the excitation current source of the sensor, which is a factor limiting the low frequency sensitivity of the sensor.
On va maintenant décrire des modes de réalisation de l'invention de façon plus précise mais non limitative en regard des dessins annexés sur lesquels : - la figure 1 est un schéma synoptique illustrant la structure d'un capteur magnétique à effet GMI,Embodiments of the invention will now be described in a more precise but nonlimiting manner with reference to the accompanying drawings in which: FIG. 1 is a block diagram illustrating the structure of a magnetic sensor with a GMI effect,
- la figure 2 est un schéma synoptique illustrant la structure d'un système de mesure d'un champ magnétique selon un premier mode de réalisation de l'invention ; - la figure 3 est un schéma synoptique illustrant la structure d'un système de mesure d'un champ magnétique selon un deuxième mode de réalisation de l'invention ;FIG. 2 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a first embodiment of the invention; FIG. 3 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a second embodiment of the invention;
- la figure 4 est un schéma synoptique illustrant la structure d'un système de mesure d'un champ magnétique selon un troisième mode de réalisation de l'invention ;FIG. 4 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a third embodiment of the invention;
- la figure 5 est un schéma synoptique illustrant la structure d'un système de mesure d'un champ magnétique selon un quatrième mode de réalisation de l'invention, etFIG. 5 is a block diagram illustrating the structure of a measurement system of a magnetic field according to a fourth embodiment of the invention, and
- la figure 6 est un organigramme illustrant le fonctionnement du procédé de suppression du décalage d'un capteur magnétique selon l'invention.FIG. 6 is a flowchart illustrating the operation of the offset removal method of a magnetic sensor according to the invention.
Parmi les capteurs magnétiques présentant une caractéristique de signal de mesure électrique en fonction du champ magnétique paire, l'invention concerne particulièrement les capteurs à effet GMI et les capteurs à effet GMR.Among the magnetic sensors having an electrical measurement signal characteristic as a function of the even magnetic field, the invention particularly relates to GMI effect sensors and GMR effect sensors.
Les modes de réalisation décrits dans la suite de la description concernent plus particulièrement les capteurs à effet GMI.The embodiments described in the following description relate more particularly to GMI effect sensors.
On a illustré sur la figure 1 la structure d'un capteur magnétique à effet GMI de l'état de la technique. Sur cette figure 1 , le capteur magnétique est désigné par la référence générale 2. Le capteur magnétique 2 comprend un conducteur électrique 4 (par exemple un ruban de cuivre) en sandwich entre deux rubans ferromagnétiques 6 et 8 de forme plane présentant un effet de magnéto-impédance géante. Généralement, les rubans 6 et 8 sont composés d'un matériau nanocristallin mais d'autres matériaux magnétiques sont également utilisés dans l'état de la technique.FIG. 1 illustrates the structure of a magnetic sensor with a GMI effect of the state of the art. In this FIG. 1, the magnetic sensor is designated by the general reference 2. The magnetic sensor 2 comprises an electrical conductor 4 (for example a copper ribbon) sandwiched between two ferromagnetic strips 6 and 8 of planar shape having a magneto effect -giant impedance. Generally, the ribbons 6 and 8 are composed of a nanocrystalline material but other magnetic materials are also used in the state of the art.
Un courant alternatif dit d'excitation lexc 10 est injecté à travers le capteur 2.An exc excitation alternating current is injected through the sensor 2.
On parle d'effet GMI ou de magnéto-impédance géante dans ce capteur 2 étant donné que lorsqu'un champ magnétique Hext 12 est appliqué à proximité du capteur 2, il y a modification de la variation d'impédance du capteur 2 pouvant être mesurée.GMI or giant magneto-impedance is referred to in this sensor 2 since when a magnetic field H ex t 12 is applied near the sensor 2, the impedance variation of the sensor 2 can be modified. to be measured.
Dans les applications nécessitant la mesure de champs magnétiques 12 faibles, il est indispensable de polariser magnétiquement le capteur 2 avec un champ de polarisation Hbιas 14.In applications requiring the measurement of weak magnetic fields 12, it is essential to magnetically bias the sensor 2 with a polarization field H bιas 14.
Le champ de polarisation est classiquement créé par un bobinage dit de polarisation ou par le champ de fuite d'un aimant.The polarization field is conventionally created by a so-called polarization winding or by the leakage field of a magnet.
Le signal de mesure du champ magnétique 12 est une tension U 16 de la forme U = Zgmιo(Hbιas) X lexc+dZgm/dH (Hbias) X Uxc-The measurement signal of the magnetic field 12 is a voltage U 16 of the form U = Zgmιo (Hbιas) X lexc + dZgm / dH (Hbias) X Uxc-
La partie utile du signal mesuré 16 est contenue dans dZgmι / dH(Hbιas) x Uxc tandis que la partie Zgmι0 (Hbιas)x Uxc est un décalage qui a pour effet de réduire la dynamique de mesure sans apporter d'informations sur le champ magnétique 12.The useful part of the measured signal 16 is contained in dZ gmι / dH (H bιa s) x Uxc while the part Z gmι0 (H bιa s) x Uxc is an offset which has the effect of reducing the dynamic of measurement without making any difference. information on the magnetic field 12.
Ainsi, le décalage ou offset est un signal continu qui se superpose au signal de mesure. Un décalage trop important relativement au signal de mesure rend l'exploitation du signal de mesure difficile car le signal de mesure consiste, dans ce cas, dans de faibles variations autour d'un signal constant d'amplitude élevée.Thus, the offset or offset is a continuous signal which is superimposed on the measurement signal. An excessively large offset relative to the measurement signal makes it difficult to use the measurement signal because the measurement signal consists, in this case, in small variations around a constant signal of high amplitude.
Un décalage dans un capteur magnétique est donc souvent source de biais de mesure et les variations de ce décalage, notamment à cause de la température, limitent la résolution du capteur.An offset in a magnetic sensor is therefore often a source of measurement bias and variations in this offset, particularly because of the temperature, limit the resolution of the sensor.
Dans le cas d'un capteur à effet GMI, le décalage se manifeste dans le signal 16 sous forme de petites variations de l'impédance dZgmi/dH(Hbιas)xlexc autour de l'impédance du capteur à effet GMI. L'invention permet de supprimer ce décalage notamment grâce à une polarisation alternative du capteur magnétique.In the case of a GMI effect sensor, the offset is manifested in the signal 16 in the form of small variations of the impedance dzgmax / dH (H bιa s) xlexc about the impedance of the GMI sensor. The invention makes it possible to eliminate this shift, in particular by means of an alternating polarization of the magnetic sensor.
La figure 2 illustre la structure d'un système de mesure d'un champ magnétique selon un premier mode de réalisation de l'invention. Le système comporte outre le capteur à effet GMI 2 et la source de courant alternatif d'excitation lexc 10 de fréquence F0, des moyens de polarisation alternative symétrique désignés par la référence générale 20 et permettant d'obtenir le champ de polarisation Hbιas 14 statique dans les deux directions en exploitant la parité de la caractéristique du capteur 2. Ces moyens de polarisation consistent selon le mode de réalisation de la figure 2 dans un bobinage de polarisation.FIG. 2 illustrates the structure of a measurement system of a magnetic field according to a first embodiment of the invention. The system further comprises the GMI effect sensor 2 and the AC excitation source exc 10 the frequency F 0, means for symmetrical alternating bias designated by the general reference 20 and to obtain the bias field H bιa This polarization means consist, according to the embodiment of FIG. 2, in a polarization winding.
Le champ de polarisation Hbιas 14 est un champ alternatif de fréquence l~bιas-The bias field H bιas 14 is an alternating field of frequency l ~ bιas-
Les fréquences d'excitation F0 et de polarisation Fbιas sont déterminées selon l'invention de la manière suivante :The excitation frequencies F 0 and polarization F bιas are determined according to the invention as follows:
- la fréquence d'excitation F0 est déterminée, en effectuant des tests préalables, de manière à maximiser la sensibilité du capteur 2. Elle dépend de la configuration, c'est-à-dire du matériau et de la forme du capteur 2 ; et- The excitation frequency F 0 is determined, by performing preliminary tests, so as to maximize the sensitivity of the sensor 2. It depends on the configuration, that is to say, the material and the shape of the sensor 2; and
- la fréquence de polarisation Fbιas est choisie inférieure à la fréquence F0 et telle que la différence (F0 - Fbιas) est supérieure à la gamme de fréquences à mesurer qui dépend de l'application.- The polarization frequency F bιas is chosen lower than the frequency F 0 and such that the difference (F 0 - F bιas ) is greater than the frequency range to be measured which depends on the application.
Selon un mode de réalisation de l'invention, la fréquence de polarisation est une fréquence sous-multiple entier de la fréquence d'excitation soit Fbιas = F0 /n.According to one embodiment of the invention, the polarization frequency is an integer sub-multiple frequency of the excitation frequency, ie F bιas = F 0 / n.
Selon le premier mode de réalisation de l'invention, le système de mesure de champ magnétique comprend un filtre sélectif 22 de type passe-bande pour le filtrage du signal de mesure 16 à la fréquence d'excitation F0. Le filtre sélectif 22 permet ainsi de réduire le bruit de la source de courant d'excitation 10 autour de la fréquence F0.According to the first embodiment of the invention, the magnetic field measuring system comprises a bandpass-type selective filter 22 for filtering the measurement signal 16 at the excitation frequency F 0 . The selective filter 22 thus makes it possible to reduce the noise of the excitation current source 10 around the frequency F 0 .
Selon un mode de réalisation de l'invention, la fréquence de polarisation Fbιas est fixée de manière à ce que (F0 - Fbιas ) soit suffisamment élevée pour que le filtre sélectif 22 atténue le bruit de la source de courant d'excitation 10 de la quantité souhaitée pour l'application. L'ordre du filtre sélectif 22 est également fixé selon l'application souhaitée du système.According to one embodiment of the invention, the polarization frequency F bιas is set so that (F 0 - F bιas ) is sufficiently high for the selective filter 22 to attenuate the noise of the excitation current source. 10 of the desired amount for the application. The order of the selective filter 22 is also set according to the desired application of the system.
Par ailleurs, le système de mesure illustré sur la figure 2 comprend des moyens de démodulation synchrone de mesure illustrés sur la figure 2 à la fréquence d'excitation F0 désignés par la référence 24 et un filtre passe-haut 26 permettant de supprimer du signal de mesure U 16 la composante liée au décalage.Furthermore, the measurement system illustrated in FIG. 2 comprises synchronous measurement demodulation means illustrated in FIG. 2 at the excitation frequency F 0 designated by the reference 24 and a high-pass filter 26 enabling the signal to be suppressed. measurement U 16 the component related to the shift.
Selon un mode de réalisation de l'invention, les moyens de démodulation synchrone 24 comprennent un multiplicateur par un signal à la fréquence F0 et le filtre passe-haut 26 présente une fréquence de coupure Fci«(Fbιas - BU) où BU représente la bande utile du signal de mesure 16.According to one embodiment of the invention, the synchronous demodulation means 24 comprise a multiplier by a signal at the frequency F 0 and the high-pass filter 26 has a cut-off frequency Fci "(F bιa s-BU) where BU represents the useful band of the measurement signal 16.
Le système de mesure comprend également des moyens de démodulation à la fréquence de polarisation Fbιas désignés par la référence 28 et un filtre passe- bas 30 permettant de supprimer les composants indésirables du signal de mesure. Selon un mode de réalisation de l'invention, les moyens de démodulationThe measurement system also comprises demodulation means at the bias frequency F bιas designated by the reference 28 and a low-pass filter 30 for removing the undesirable components of the measurement signal. According to one embodiment of the invention, the demodulation means
28 comprennent un multiplicateur par un signal à la fréquence Fbιas en phase avec le signal alternatif de polarisation et le filtre passe-bas 30 présente une fréquence de coupure Fc2 >BU.28 comprise a multiplier by a signal at the frequency F bιas in phase with the alternating polarization signal and the low-pass filter 30 has a cutoff frequency Fc 2 > BU.
Par ailleurs, l'ordre du filtre 30 est choisi en fonction de l'application et notamment de l'atténuation souhaitée ou du résidu de modulation à Fbιas.Moreover, the order of the filter 30 is chosen as a function of the application and in particular of the desired attenuation or of the modulation residue at F bιas .
Dans le système de la figure 2, des amplificateurs 32, 34 et 36 sont également prévus. Ils permettent d'améliorer les performances du système et d'adapter la dynamique du capteur 2 à l'application envisagée.In the system of Figure 2, amplifiers 32, 34 and 36 are also provided. They make it possible to improve the performance of the system and to adapt the dynamics of the sensor 2 to the intended application.
En sortie du système représenté dans la figure 2, une tension V8 38 est obtenue. Elle correspond au signal de mesure 16 duquel le décalage est supprimé et dont le bruit est atténué ce qui a pour conséquence d'avoir une mesure plus précise et un capteur plus sensible.At the output of the system shown in FIG. 2, a voltage V 8 is obtained. It corresponds to the measurement signal 16 from which the offset is suppressed and whose noise is attenuated, which has the consequence of having a more precise measurement and a more sensitive sensor.
La figure 3 illustre un deuxième mode de réalisation du système de mesure de champ magnétique selon l'invention. Le système illustré dans la figure 3 diffère de celui de la figure 2 par l'ajout de moyens d'augmentation de la plage de linéarité du capteur 2 comprenant un correcteur 38 et une contre-réaction 40. Le correcteur 38 est un correcteur de type proportionnel (P), proportionnel intégral (Pl) ou proportionnel intégral dérivé (PID). La contre-réaction 40 consiste en un bobinage supplémentaire qui crée, dans le capteur GMI 2, un champ magnétique qui s'oppose au champ magnétique mesuré de manière à faire fonctionner le capteur à champ magnétique quasi-nul.FIG. 3 illustrates a second embodiment of the magnetic field measuring system according to the invention. The system illustrated in FIG. 3 differs from that of FIG. 2 by adding means for increasing the linearity range of the sensor 2 comprising a corrector 38 and a feedback 40. The corrector 38 is a corrector of the proportional (P), proportional integral (P1) or proportional integral derivative (PID) type. The feedback 40 consists of an additional winding which creates, in the GMI sensor 2, a magnetic field which opposes the measured magnetic field so as to operate the magnetic field sensor almost zero.
Dans une variante, la contre-réaction 40 n'utilise pas un bobinage supplémentaire, mais le bobinage de polarisation.In a variant, the feedback 40 does not use an additional winding, but the polarization winding.
La figure 4 illustre un troisième mode de réalisation du système de mesure de champ magnétique selon l'invention. Le système illustré dans la figure 4 diffère de celui de la figure 2 par le remplacement du filtre sélectif 22 par un transformateur piézo-électrique 42 placé à l'entrée du système.FIG. 4 illustrates a third embodiment of the magnetic field measuring system according to the invention. The system illustrated in Figure 4 differs from that of Figure 2 by replacing the selective filter 22 by a piezoelectric transformer 42 placed at the entrance of the system.
Le transformateur piezo-électrique 42 est un quadhpôle constitué de deux bornes auxquelles est connectée la source d'excitation 10 à l'entrée et de deux bornes auxquelles est connecté le capteur GMI 2. Le transformateur piézoélectrique, combine une amplification en tension et un filtre sélectif.The piezoelectric transformer 42 is a quadrupole consisting of two terminals to which the excitation source 10 is connected at the input and two terminals to which the GMI sensor 2 is connected. The piezoelectric transformer combines voltage amplification and a filter. selective.
La figure 5 illustre un quatrième mode de réalisation du système de mesure de champ magnétique selon l'invention dans lequel les moyens de polarisation magnétique 20 sont représentés par une source de courant de polarisation lbιas43. Le système illustré dans la figure 5 diffère de celui de la figure 4 par le remplacement du transformateur piézo-électrique 42 par un convertisseur direct alternatif-alternatif comprenant un transformateur 44 de volume plus réduit que celui du transformateur 42.FIG. 5 illustrates a fourth embodiment of the magnetic field measuring system according to the invention in which the magnetic polarization means 20 are represented by a polarization current source 1 bias 43. The system illustrated in FIG. 5 differs from FIG. that of FIG. 4 by the replacement of the piezoelectric transformer 42 by a direct-alternating direct converter comprising a transformer 44 of smaller volume than that of the transformer 42.
La réduction de la taille du transformateur est obtenue grâce à une modulation du courant de polarisation lbιas 43 à une fréquence plus élevée que la fréquence Fbιas, à titre d'exemple à la fréquence d'excitation F0.The reduction of the size of the transformer is obtained by means of a modulation of the polarization current l bιas 43 at a frequency higher than the frequency F bιas , for example at the excitation frequency F 0 .
La modulation du courant de polarisation lbιas 43 est réalisée par un circuit 47 de modulation à la fréquence d'excitation F0 placé à l'entrée du transformateur 44. A la sortie du transformateur 44, un circuit 48 de démodulation à la fréquence d'excitation F0 est prévu pour démoduler le courant de polarisation lbιas 43. Les circuits 47 et 48 comprennent une pluralité d'interrupteurs commandés par la source d'excitation 10 (non représentée sur la figure 5).The modulation of the polarization current I Bias 43 is performed by a modulation circuit 47 at the excitation frequency F 0 placed at the input of the transformer 44. At the output of the transformer 44, a demodulation circuit 48 at the frequency of F 0 excitation is provided to demodulate the bias current l bιas 43. The circuits 47 and 48 comprise a plurality of switches controlled by the excitation source 10 (not shown in FIG. 5).
Le courant de polarisation lbιas 43 passe ensuite à travers une résistance 49 avant de traverser les moyens de polarisation 20. Ce quatrième mode de réalisation permet la réduction de la consommation du transformateur.The polarization current I Bias 43 then passes through a resistor 49 before passing through the polarization means 20. This fourth embodiment allows the reduction of the consumption of the transformer.
Dans la suite de la description, le fonctionnement du procédé de suppression du décalage d'un capteur magnétique selon l'invention est décrit en référence à l'organigramme de la figure 6. Plus particulièrement, l'organigramme de la figure 6 détaille le fonctionnement du système de mesure selon le mode de réalisation illustré dans la figure 2.In the remainder of the description, the operation of the offset correction method of a magnetic sensor according to the invention is described with reference to the flowchart of FIG. 6. More particularly, the flowchart of FIG. 6 details the operation of the measuring system according to the embodiment illustrated in FIG. 2.
En 50, le capteur magnétique 2 est exité par la source de courant alternatif Uxc 10. Il est ensuite polarisé en 52 avec les moyens de polarisation alternative symétrique 20.At 50, the magnetic sensor 2 is exited by the alternating current source Uxc 10. It is then polarized at 52 with the symmetrical alternating polarization means 20.
En 54, le signal de mesure U 16 est filtré par le filtre passe-bande sélectif 22 à la fréquence F0.At 54, the measurement signal U 16 is filtered by the selective bandpass filter 22 at the frequency F 0 .
Le signal obtenu en sortie du filtre sélectif 22 est alors amplifié en 56 par l'amplificateur 32 et démodulé à la fréquence F0 en 58 par les moyens de démodulation 24. Le signal amplifié obtenu est filtré passe-haut en 60 par le filtre passe-haut 26 puis amplifié en 62 par l'amplificateur 34.The signal obtained at the output of the selective filter 22 is then amplified at 56 by the amplifier 32 and demodulated at the frequency F 0 at 58 by the demodulation means 24. The amplified signal obtained is filtered high-pass at 60 by the pass filter. -High 26 then amplified at 62 by the amplifier 34.
Le signal amplifié obtenu est démodulé à la fréquence Fbιas en 64 par les moyens de démodulation 28. Le signal démodulé obtenu est filtré passe-bas en 66 par le filtre passe-bas 30, puis amplifié en 68 par l'amplificateur 36 pour adapter sa dynamique à l'application envisagée. En 70, le signal V8 38 est obtenu.The amplified signal obtained is demodulated at the frequency F bιas at 64 by the demodulation means 28. The demodulated signal obtained is low-pass filtered at 66 by the low-pass filter 30, then amplified at 68 by the amplifier 36 to adapt its dynamics to the intended application. At 70, the signal V 8 38 is obtained.
Ainsi l'invention permet, grâce à la polarisation alternative et au filtre passe- haut 26, de supprimer le décalage d'un capteur magnétique sans avoir recours à deux capteurs montés en différentiel et soumis à des polarisations magnétiques opposées comme c'est le cas dans la solution usuelle de suppression du décalage.Thus the invention makes it possible, thanks to the alternating polarization and to the high-pass filter 26, to eliminate the offset of a magnetic sensor without having recourse to two sensors mounted in differential and subjected to opposite magnetic polarizations, as is the case. in the usual solution of offset removal.
En outre, le système proposé dans l'invention permet, grâce à l'utilisation du filtre sélectif 22 ou du transformateur piézo-électrique 42 ou du convertisseur direct alternatif-alternatif comprenant le transformateur 44, de réduire le bruit provenant de la source d'excitation du capteur et d'augmenter ainsi la sensibilité du capteur magnétique. In addition, the system proposed in the invention makes it possible, by using the selective filter 22 or the piezoelectric transformer 42 or the direct alternating-AC converter comprising the transformer 44, to reduce the noise. from the excitation source of the sensor and thereby increase the sensitivity of the magnetic sensor.

Claims

REVENDICATIONS
1.- Système de mesure d'un champ magnétique (12) comprenant un capteur magnétique (2) présentant une caractéristique de signal de mesure électrique (16) en fonction du champ mesuré (12) paire et un dispositif électronique de suppression du décalage du capteur (2), caractérisé en ce que le dispositif de suppression du décalage comprend des moyens de polarisation alternative symétrique (20) du capteur (2) à une fréquence de polarisation déterminée. 1. A magnetic field measurement system (12) comprising a magnetic sensor (2) having an electrical measurement signal characteristic (16) as a function of the even measured field (12) and an electronic offset suppression device. sensor (2), characterized in that the offset removal device comprises symmetrical AC biasing means (20) of the sensor (2) at a determined polarization frequency.
2.- Système selon la revendication 1 , caractérisé en ce qu'il comprend une source de courant alternatif d'excitation (10) du capteur (2) à une fréquence d'excitation déterminée de manière à maximiser la sensibilité dudit capteur (2).2.- System according to claim 1, characterized in that it comprises an alternating current source excitation (10) of the sensor (2) at a given excitation frequency so as to maximize the sensitivity of said sensor (2) .
3.- Système selon la revendication 2, caractérisé en ce que la fréquence d'excitation du capteur (2) est un multiple entier de la fréquence de polarisation du capteur (2).3. System according to claim 2, characterized in that the excitation frequency of the sensor (2) is an integer multiple of the polarization frequency of the sensor (2).
4.- Système selon la revendication 2 ou 3, caractérisé en ce qu'il comprend des moyens de réduction du bruit basse fréquence de la source de courant d'excitation (10).4. System according to claim 2 or 3, characterized in that it comprises means for reducing the low frequency noise of the excitation current source (10).
5.- Système selon la revendication 4, caractérisé en ce que les moyens de réduction du bruit de la source de courant d'excitation (10) comprennent un filtre sélectif (22) pour le filtrage du signal de mesure (16) à la fréquence d'excitation.5. System according to claim 4, characterized in that the noise reduction means of the excitation current source (10) comprise a selective filter (22) for filtering the measurement signal (16) at the frequency excitation.
6.- Système selon la revendication 4, caractérisé en ce que les moyens de réduction du bruit de la source de courant d'excitation (10) comprennent un transformateur piézo-électrique (42). 6. The system of claim 4, characterized in that the noise reduction means of the excitation current source (10) comprise a piezoelectric transformer (42).
7.- Système selon la revendication 4, caractérisé en ce que les moyens de réduction du bruit de la source de courant d'excitation (10) comprennent un convertisseur direct alternatif-alternatif.7. System according to claim 4, characterized in that the noise reduction means of the excitation current source (10) comprise a direct-alternating AC converter.
8.- Système selon la revendication 7, caractérisé en ce que le convertisseur direct alternatif-alternatif comprend un transformateur (44). 8.- System according to claim 7, characterized in that the AC-AC direct converter comprises a transformer (44).
9.- Système selon l'une quelconque des revendications 2 à 8, caractérisé en ce qu'il comprend :9. System according to any one of claims 2 to 8, characterized in that it comprises:
- des moyens de démodulation synchrone (24) à la fréquence d'excitation du signal de mesure (16); et - un filtre passe-haut (26) pour le filtrage du signal de mesure (16) démodulé à la fréquence d'excitation.synchronous demodulation means (24) at the excitation frequency of the measurement signal (16); and a high-pass filter (26) for filtering the measurement signal (16) demodulated at the excitation frequency.
10.- Système selon la revendication 9, caractérisé en ce qu'il comprend :10. System according to claim 9, characterized in that it comprises:
- des moyens de démodulation (28) à la fréquence de polarisation du signal de mesure (16) démodulé à la fréquence d'excitation et filtré passe-haut ; etdemodulation means (28) at the polarization frequency of the measurement signal (16) demodulated at the excitation frequency and filtered high-pass; and
- un filtre passe-bas (30) pour le filtrage du signal de mesure (16) démodulé à la fréquence de polarisation.a low-pass filter (30) for filtering the measurement signal (16) demodulated at the polarization frequency.
11.- Système selon l'une quelconque des revendications 1 à 10, caractérisé en ce qu'il comprend des moyens d'augmentation de la plage de linéarité du capteur magnétique (2).11. System according to any one of claims 1 to 10, characterized in that it comprises means for increasing the linearity range of the magnetic sensor (2).
12.- Système selon la revendication 11 , caractérisé en ce que les moyens d'augmentation de la plage de linéarité du capteur magnétique (2) comprennent une contre-réaction (40).12. System according to claim 11, characterized in that the means for increasing the linearity range of the magnetic sensor (2) comprise a feedback (40).
13.- Système selon l'une quelconque des revendications 1 à 12, caractérisé en ce que le capteur magnétique (2) est un capteur à effet de magnéto-impédance géante.13.- System according to any one of claims 1 to 12, characterized in that the magnetic sensor (2) is a giant magneto-impedance effect sensor.
14.- Système selon l'une quelconque des revendications 1 à 12, caractérisé en ce que le capteur magnétique (2) est un capteur à effet de magnéto-résistance géante. 14.- System according to any one of claims 1 to 12, characterized in that the magnetic sensor (2) is a giant magneto-resistance effect sensor.
15.- Procédé de suppression du décalage d'un capteur (2) de champ magnétique (12), ledit capteur (2) présentant une caractéristique de signal de mesure électrique (16) en fonction du champ mesuré (12) paire, caractérisé en ce qu'il comprend une étape de polarisation alternative symétrique (52) du capteur (2) à une fréquence de polarisation déterminée. A method of suppressing the offset of a magnetic field sensor (12), said sensor (2) having an electrical measurement signal characteristic (16) as a function of the same measured field (12), characterized in that it comprises a symmetrical AC bias step (52) of the sensor (2) at a determined bias frequency.
PCT/FR2009/050665 2008-04-14 2009-04-10 System for measuring a magnetic field and corresponding method for suppressing a magnetic field sensor shift WO2009136116A2 (en)

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CN112307779A (en) * 2020-11-06 2021-02-02 北京航空航天大学 Method for optimizing ultra-high-precision GMI superconducting composite magnetometer
US20220199308A1 (en) * 2020-12-21 2022-06-23 Methode Electronics Malta Ltd. Device for Correcting an External Stress Overload Affecting a Ferromagnetic Component

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