Adaptive Readout Schemes for Thin-Film Magnetoelectric Sensors Based on the delta-E Effect

Thin-film magnetoelectric sensors, i.e., composites of magnetostrictive and piezoelectric materials, are able to measure very low magnetic fields. As a consequence, an application of such sensors could be, e.g., the measurement of biomagnetic fields in the near future. To measure these signals, typically characterized by low-frequency components, techniques, such as the delta-E effect, are utilized. The limit of detection (LoD) of such sensor systems did not reach the required level until now. In order to improve this, an adaptive readout scheme is proposed for sensor systems based on the delta-E effect. The basis is a simultaneous measurement with a single sensor at different frequency ranges close to the resonance frequencies. The signals are combined optimally in regard to their signal-to-noise ratio. Two combination approaches are presented and evaluated. An improvement up to 6 dB in terms of LoD is achieved. Due to an adaption of the weighting coefficients with time, the proposed method can be interpreted as a noise reduction technique, which increases the usability of such sensors in realistic measurement scenarios.