Dynamic Sensitivity and Noise Floor of a Bonded Magneto(Elasto)Electric Laminate for Low Frequency Magnetic Field Sensing under Strain Modulations
Résumé
The low frequency performances of a layer-bonded Magneto(elasto)Electric (ME) magnetic sensor have been investigated for an in-plane excitation. This technique is based on the strain modulation at the first longitudinal mechanical resonance of the ME magnetic sensor, where the magnetoelastic properties can be controlled by an applied low frequency magnetic field. Its sensitivity can be derived from the elastic coupling equations with nonlinear factors for the excitation [1]. The equivalent magnetic noise results mainly from mechanical instabilities, due to the arbitrary rotation of elastic domain walls [2]. This modulation relies on the change of either the direct or the converse transfer function as a function of the low frequency magnetic field. Because of the symmetrical magnetic and electric behaviors of the magnetoelectric composite, the direct and converse ME modulations are similar in performances. The magnetoelastic coupling parameter is controlled by the external low frequency magnetic field and dominated by the piezomagnetic coefficient [3]. The mechanical impedance of the composites can also vary as a function of external mechanical stress (this stress can result from the applied magnetic field). However, this is not regarded as a dominant effect for low frequency field sensing. By using the strain modulation based on the direct or converse ME effects, the layer-bonded ME multilayer exhibits a measured limit of the order of 10 to 100 pT/√Hz at 1 Hz, as well as a direct current (DC) detection capability under an excitation close to the resonant frequency. The results for both the direct and converse modulation were investigated and compared with the help of an equivalent circuit modeling.
Domaines
Electronique
Origine : Fichiers produits par l'(les) auteur(s)
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