GMI Noise performance optimisation

Basile Dufay (1) , Michal Malatek (1) , Sébastien Saez (1) , Christophe Dolabdjian (1) , Arthur Yelon (2) , David Ménard (2)

1 Equipe Electronique - Laboratoire GREYC - UMR6072
2 Département de génie physique [Montréal]

1 INTRODUCTION The giant magnetoimpedance (GMI) effect has great potential for the design of highly sensitive magnetometers. It has previously been shown that the performance of GMI magnetometers is currently limited by the noise due to electronic conditioning [1, 2]. Therefore, an increase of the intrinsic sensitivity of the sensing element is a key point in the reduction of the impact of electronic noise on global performance. A promising approach to reaching that goal is to use a coupled pick-up coil wound around the GMI element in a twoport configuration [3]. Here, we propose a model for the equivalent output magnetic noise of a complete electronic circuit of a magnetometer using the two-port configuration as the sensing element. This allows us to clarify the main contributions to sensor noise performance, operating at the optimal sensor excitation working point. ------------------------------------------------ 2 NOISE MODEL The sensing element consists of a very thin two-layer pick-up coil wound on a 100μm diameter CoFeSiB soft amorphous ferromagnetic wire. The response of the device to magnetic field variation is fully described by its two-port network impedance matrix. The intrinsic sensitivity of each matrix component is then deduced from the differential impedance variation as a function of applied magnetic field. First, we quantify the contributions from all noise sources of the electronic chain. Then, we predict the output sensitivity, in V/T, of each of the matrix components. Finally, the output noise level, in T/√Hz, the ratio of the output electronic noise to the output sensitivity, is calculated. The model is in good agreement with noise measurements in which the measured white noise is at the pT/√Hz level. The two-port configuration, with the pick-up coil, clearly yields an improvement in noise performance, compared with the one-port measurement of the impedance of the wire. -------------------------------- REFERENCES: [1] L.G.C. Melo, D. Ménard, A. Yelon, L. Ding, S. Saez, C. Dolabdjian: Optimisation of the magnetic noise and sensitivity of giant magnetoimpedance sensors. Journal of Applied Physics, vol. 103, (2008), p.033903 [2] L. Ding, S. Nabily, S. Saez, J. Gieraltowski, C. Dolabdjian: Investigation of giant magnetoimpedance magnetic noise comparison. Sensors Letters, vol. 5, (2007), 171-175. [3] B. Dufay, S. Saez, C. Dolabdjian, D. Seddaoui, A. Yelon, D. Ménard: Improved GMI sensors using strongly coupled thin pick-up coils. Sensors Letters, vol. 7, (2009), 334-338.

Domaines: Electronique

Basile Dufay, Michal Malatek, Sébastien Saez, Christophe Dolabdjian, Arthur Yelon, et al.. GMI Noise performance optimisation. Magnetic Measurement Conference 2010, Sep 2010, Prague, Czech Republic. ⟨hal-01109718⟩