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Description
The Giant Magneto-Impedance effect, which changes impedance of amorphous wire in response to the magnetic fields, is used in highly sensitive magnetometers for measuring biomagnetic fields, electronic compasses, and other applications. GMI sensor face a trade-off between sensitivity and wide dynamic range. GMI sensors with sensitivity on the order of pico-tesla, suitable for biomagnetic measurements, are limited to dynamic ranges of a few micro-tesla or less. One approach to achieving high sensitivity and wide dynamic ranges is to use magnetic field feedback, which is produced by feedback coil placed around the GMI sensor. Feedback coil can be integrated with the pickup coil of the GMI sensor, a configuration known as single coil feedback. This integration can make the GMI sensor smaller compared to designs where the feedback coil is separate from the pickup coil [1]. A gradiometer, which uses two different GMI sensor as sensing and reference element respectively, can reduce common mode noise represented by the geomagnetic field. A gradiometer combined with magnetic feedback functions as a common-mode magnetic field rejection-type (CMMFR-type) GMI gradiometer, which can more effectively reduce common mode noise [2].
In this study, we report the achievement of single coil feedback CMMFR type GMI gradiometer and conform the reduction of magnetic noise floor (Fig.1).
Fig. 1 Magnetic noise floor: Without Feedback and With Feedback.
References
[1] S. Gudoshnikov, N. Usov, A. Nozdrin, M. Ipatov, A. Zhukov, and V. Zhukova, “Highly sensitive magnetometer based on the off‐diagonal GMI effect in Co‐rich glass‐coated microwire,” physica status solidi (a), vol. 211, no. 5. Wiley, pp. 980–985, Feb. 14, 2014. doi: 10.1002/pssa.201300717.
[2] T. Takiya and T. Uchiyama, “Common-mode magnetic field rejection-type magneto-impedance gradiometer,” Journal of International Council on Electrical Engineering, vol. 7, no. 1. Informa UK Limited, pp. 1–6, Dec. 26, 2016. doi: 10.1080/22348972.2016.1271505.
