A novel dual modality sensor with sensitivities to permittivity and conductivity

In this paper, an electromagnetic (EM) sensor which can operate simultaneously in capacitive and inductive modalities is developed, and a novel measurement strategy is proposed accordingly. The sensor is composed of two planar spiral coils with large track width, which promotes its capacitive mode. The capacitive coupling is measured in common mode while the inductive coupling is measured in differential mode. In capacitive mode, the sensor is sensitive to the dielectric material distribution, i.e. changes in permittivity; while in inductive mode, it is sensitive to magnetically permeable material and electrically conductive material. Furthermore, it is demonstrated that the sensor can simultaneously measure dielectric and conductive materials. This novel sensor has been designed and implemented. Experimental results verified its effectiveness in dual modality measurement.