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International audience; The impact of the influence quantitiessensors has become a hot topic of interest in the last years [versus the temperature changes in a real measurement environmentmanufacturers and industrial buyersrich amorphous wires(Co-Fecomponent, Z21, of the impedance tensorintrinsic sensitivity and offsetimplementation.The sample was awire was supplied by an AC current of 1 MHz frequency and 5 mA amplitude.about 800 turns was also wound around the wirecase, a DC current of 10 mAwires with circumferential anisotropy) was also supplied to the wireinside a regulated thermal chamber. Experiments were conducted in the temperatures range of[-20 °C, 120 °C].The impedance For the componentZ11, the results have showed afield, of -0.13 (A/m)/°C (170 nT/°C)between -20 °C and +40 °C, and then itdecreaseddiagonal component, Z21, the change of the offset near the zero(A/m)/°C or-19 nT/°C), while tthe range of [-20 °C, 120 °C].

International audience; Giant-Magneto-Impedance (GMI)sensors measure the magnetic field produced by the currentconfiguration of the sensor, the GMI element (a wire for example) circles the conductormeasured current, Im[1] & [2]. Tresulting in a modification ofthe sensor response and consequently incan be encountered when the sensor is subjectedfield and those produced by otheanalytical model to explain the effect of the conductorthe GMI response. In the case ofobtained. This response is modified when the conductor is eccentric. The analytical developed modelallows predicting this modified response.the eccentric conductor, along the sensitive wireresponse which is calculated and predicted by1(a) illustrates a reference GMI cuthe calculated curve when the conductor is eccentric.Fig.1. Analytical prediction of the responseFigure 1(b) shows the experimentaldeformed. This deformation, attributed to the extended to also take into account the effect of the surrounding magorigins of disturbance, along the sensitiresponse as it will be presented in the full paper.

International audience; In some applications of Giant Magnetosensors where the sensitive element must be deformed to be aligned with the magnetic fieldproduced by the measured current. This deformation inducesstress which was addressed in [1impact on the GMI characteristics washas beenstudiedin Co-rich amorphous wirescomponent, Z21, of the impedance tensor were consideredμ diameter and 90 mm length from Unitika.around the wire. The later DC current (necessary for the apparition of the offcircumferential anisotropy) was anegative angles with respect to the reference position corresponding to theposition of the wire. For comparison purposes only,function of the rotation anglerelated to the modification the magnetoof this the induced torsion at this anglesensitivity and offset were measured as a function of the rotation angle.The results showed that, for a DC current of 5 mA,the sensitivity of the diagonal combias field was slightly increased for angles betwee-90° to °+90, while this sensitivity wasconstant for the off-diagonal component at zerofield. The intrinsic offset in the diagonalconfiguration was almost constant for theconsidered rotation angles, while this offset wasincreased in the off-diagonal configuration.

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The GMI effect displays several advantages, such as high sensitivity, high detection resolution and bandwidth, and mechanical flexibility. These advantages predispose this technology to the implementation of flexible contactless current sensors measuring both DC and AC currents.This thesis work aims at exploring the feasibility of a flexible GMI current sensor. A particular attention to the impact of influence parameters which largely condition the design solutions of the sensor has been paid.The effects of temperature and mechanical constraints such as bending and torsion, which apply in a real measuring environment, are characterized by taking into account the intrinsic features which are necessary to the design of the sensor. The impact of the general measuring configuration and electronics are also studied. The effects of magnetic disturbances and of the position of the current-carrying conductor in the measuring loop are quantified and an adequate shielding method is proposed. Finally, the sensor prototype obtained at the end of this work is described with its performances and the possible optimization and enhancement ways., La Magnéto-Impédance Géante (GMI pour Giant Magneto-Impedance) présente un certain nombre d’avantages, tels la haute sensibilité, la haute résolution de détection, la large bande passante et la flexibilité de l’élément sensible qui rendent cette technologie très prometteuse pour la réalisation de capteurs de courant flexibles, sans contact, capables de mesurer à la fois les courants continus (DC) et alternatifs (AC).Ce travail de thèse vise à explorer la faisabilité d’un capteur de courant flexible à base de GMI, en portant une attention particulière sur l’impact des paramètres d’influence qui conditionnent largement les solutions de mise en œuvre du capteur.Les effets de la température et des contraintes mécaniques de flexion et de torsion, qui s’appliquent dans un environnement de mesure réel, sont caractérisés en prenant en compte les grandeurs intrinsèques du fil nécessaires à la réalisation d’un capteur industriel. L’impact de la mise en œuvre et du conditionnement électronique vis-à-vis de ces grandeurs d’influence est aussi étudié. Les effets des perturbations magnétiques externes et de l’excentration du conducteur sous test dans la boucle de mesure sont quantifiés et une solution de blindage est proposée. Enfin, le prototype de capteur obtenu à l’issue de ces travaux est présenté, ainsi que ses performances, en dégageant les pistes d’optimisation et d’amélioration.

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International audience; Giant Magneto-Impedance (GMI) is a large change of the high frequency impedance of somesoft magnetic materials when they are subjected to an external magnetic field. This effect can beused to realizemagnetic sensors based on the impedance measurement of the sensitiveelement.Despite the great advantages of the GMI such as the high sensitivity, the potential ofminiaturization as well as the large bandwidth, there is still only a few concrete or industrialachievements of these sensors.One of the key features of these GMI sensors is their ability to measure both DC and ACmagnetic fields by the same sensitive element. This feature is of great value for a large palette ofapplications like the contactless current measurement(based on the measurement of the magneticfield produced by the measured current [1]).For this application, the mechanical flexibility ofsome GMI elements (like amorphous wires) is also another key andvery useful feature forrealizing toroidal flexible sensors (the sensing element forms a loop around the conductor ofinterest). Such flexible sensors are needed in many industrial environments where rigid toroidalstructures of the current sensor are not convenient.This paperpresents an overview of a full attempt of design andrealization of a quasi-industrialGMI-based currentsensor. The sensor combines DC/AC measurements in a same flexiblesensitive element. The paper addresses several practical problems encountered in a realmeasurement environment. In this context, main attention is paid to the impact of the influencequantities that largely condition the implementation strategies and solutions of the sensor. For theintended industrialapplication,these influence quantitiesfirstly include the operating temperature[2]. Its impact on the intrinsic sensor response is addressed in a quasi-industrial temperaturerange. Secondly, bending stress on the sensitive element is another involved influence parameterin the toroidal and flexible structure. This constraint effect is also characterized [3] - [4]. Finally,the third considered influence parameter is the effect of magnetic disturbances such as theeccentricity of the conductor of interest and the impact of the surrounding magnetic fields (earthfield or fields produced by others conductors in close proximity to the sensor). Differentstrategies of implementation and solutions, taking into account the impact of influenceparameters, are proposed and compared. A sensor prototype is realized and its performances aregiven and discussed .

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