A Capacitive Sensor System for Measuring Laplacian Electromyogram through Cloth: A Pilot Study

A possibility for capacitive sensor system for measuring the surface Laplacian electromyogram (Laplacian EMG) was studied under conditions whereby a thin cloth was inserted between the electrodes and the skin of the subject. The system was designed based on a tri-polar concentric electrode unit and on a principle of the capacitive electrode involving the conductive electrodes, the cloth, and the skin. A pilot sensor and detecting circuit using this design were assembled and evaluated to explore the feasibility of this approach. The experimental results showed that the Laplacian EMG obtained in this way was comparable and synchronized with the surface EMG obtained using traditional bipolar electrodes, although its S/N was reduced. Though there are still a lot of challenges to be addressed to achieve practical performances, it seems promising for use in human-machine interfaces because the proposed approach eliminates discomfort due to conventional electrode-to-skin coupling.