High-Resolution Magneto-Impedance Sensor With TAD for Low Noise Signal Processing

We propose a new measurement system using a magnetoimpedance (MI) sensor with a time analog-to-digital (TAD) converter for a very weak magnetic field measurement and for a low noise signal processing. To demonstrate magnetic characteristics of the proposed measurement system of MI sensor with TAD, we measured the magnetic field sensitivity of the new MI sensor measurement system. In addition, we also investigated the noise level of this proposed measurement system owing to verification on the possibility of the detection of very weak magnetic signals. The gradiometer of MI sensor with TAD was applied to reduce extrinsic noise, such as geomagnetism and commercial power supply noise. We demonstrated that the newly developed MI sensor measurement system has 3 pT/LSB resolution without an amplifier. This shows that the proposed measurement system of MI sensor with TAD is suitable for a low-noise measurement.