Abstract
We report, theoretically and experimentally, the realization of a high detection performance in a novel magnetoelectric (ME) transverse gradient sensor based on the large ME effect and the magnetic field gradient (MFG) technique in a pair of magnetically-biased, electrically-shielded, and mechanically-enclosed ME composites having a transverse orientation and an axial separation. The output voltage of the gradient sensor is directly obtained from the transverse MFG-induced difference in ME voltage between the two ME composites and is calibrated against transverse MFGs to give a high detection sensitivity of 0.4–30.6 V/(T/m), a strong common-mode magnetic field noise rejection rate of <−14.5 dB, a small input-output nonlinearity of <10 ppm, and a low gradient noise of 0.16–620 nT/m/ in a broad frequency range of 1 Hz–170 kHz under a small baseline of 35 mm. An analysis of experimental gradient noise spectra obtained in a magnetically-unshielded laboratory environment reveals the domination of the pink (1/f) noise, dielectric loss noise, and power-frequency noise below 3 kHz, in addition to the circuit noise above 3 kHz, in the gradient sensor. The high detection performance, together with the added merit of passive and direct ME conversion by the large ME effect in the ME composites, makes the gradient sensor suitable for the passive, direct, and broadband detection of transverse MFGs.
Highlights
Magnetic field gradients (MFGs) are the variations of magnetic fields per unit length in three-dimensional space [1]
Magnetic gradient sensors are a key member of the magnetic sensor family, featuring a unique and strong ability to suppress ambient noise by detecting MFGs [1,2]
They generally consist of two magnetic field sensors spatially separated by a baseline to detect MFGs by differencing the output signals of the two magnetic field sensors over the baseline
Summary
Magnetic field gradients (MFGs) are the variations of magnetic fields per unit length in three-dimensional space [1]. In view of the above, we have developed and reported the basic detection performance of a small-scale and standalone ME transverse gradient sensor capable of detecting transverse MFGs into electrical voltages by combining the passive and direct ME conversion ability enabled by the ME effect with the ambient noise suppression ability facilitated by the MFG technique in a pair of plate-shaped and magnet-biased Terfenol-D/PZT/Terfenol-D trilayer ME composites [26]. This gradient sensor is essentially a transverse-type MFG sensor for detecting MFGs transverse to its length in the axial direction, which is analogous to transverse-type Hall probes for detecting magnetic fields, transverse to their length in the axial direction. Denotes the magnetization direction of the MS layers and P indicates the polarization direction of the PE layer
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