High sensitive magnetic sensor with amorphous wire

Using a FeCoSiB amorphous wire and a coil wrapped around it, we developed a sensitive magnetic sensor. To improve the linearity of the field response, a feedback method was used. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise of the sensor was about 30 pT per root Hz above 30 Hz. An eddy current testing (ECT) system using the GMI sensor was developed and a defect in a 2 mm thick aluminum plate was successfully detected.