Planar coil-based differential electromagnetic sensor with null-offset

This paper focuses on the design and experimental test of a null-offset differential electromagnetic sensor characterized by simplicity, flexibility and low cost. This sensor consists of two planar excitation coils, which generate magnetic field and a planar acquisition coil, which senses the sample material. The differential configuration of the sensor improves signal conditioning and reduces the common-mode noise. We present analytical and numerical (simulation) studies of the working principle. Experiments were performed to test the ability of the sensor to detect non-invasively: (i) the presence of metallic samples and (ii) the variations of glucose in human blood.