In this paper, we present our new results of the high-sensitivity MI sensor and a feedback method to improve the dynamic range and the linearity of the magnetic sensing system. The DC bias current and the AC current flow in the coil directly.
There was no electrical connection with the amorphous wire. Using the (Fe 0.06Co 0.94) 72.5Si 12.5B 15 (FeCoSiB) amorphous wire with the diameter of 0.1 mm and the length of 5 mm, we developed a high-sensitivity magnetoimpedance (MI) sensor. Feedback methods are often used to increase the dynamic ranges of magnetic sensors and improve the linearity of magnetic sensors. Otherwise, the big background interferences may cause the distortion of the signal and increase the noise of the system.įor the NDE application of magnetic sensor, some ferromagnetic material samples may produce strong magnetic fields and cause the saturation of the magnetic sensors. To measure the small signal in the big background interferences, good linearity of the sensing system is important. These sensors are normally operated in unshielded environment with big background interferences, such as the power line interference. Room temperature-sensitive magnetic sensors have been developed and used in various areas of communication, geological exploration, medical diagnostics, nondestructive evaluation (NDE), and security control. An eddy current testing system using the magnetic sensor was developed, and the crack defects in steel plate and in 3D-printed titanium alloy plate were evaluated. Using the feedback method, the dynamic range was improved from ☐.7 Gauss to ☑0 Gauss and the linearity was also improved over 100 times better. The operation point of the magnetic field sensor was fixed by sending a feedback current to the coil. We developed a feedback method to improve the dynamic range and the linearity of the magnetic field sensor.
The linearity of the system was also not good when big magnetic field was applied, which will cause some noise when the system is used in unshielded environment. But the dynamic range of the magnetoimpedance magnetic field sensor was only about ☐.7 Gauss, which was not enough for some applications, such as the defect evaluation of steel plate. The magnetic field resolution of about 20 pT/√Hz was achieved. The amorphous wire had the diameter of 0.1 mm and the length of 5 mm. We developed a high-sensitivity magnetoimpedance magnetic field sensor using a FeCoSiB amorphous wire and a coil wound around it.
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