Capacitive biopotential electrode with a ceramic dielectric layer

Abstract

This paper presents the design of an innovative active capacitive electrode with a ceramic dielectric layer. The electrode meets the requirements for contactless measurement, resistance to motion artefacts and possibility to make long and repeated recordings. The proposed capacitive electrode is distinguished from other capacitive electrodes by the construction of the capacitive coupling element, which is placed on the body surface. While common capacitive electrodes use a metal plate with a relatively large surface area as the capacitive coupling element, the proposed electrode uses a dielectric ceramic layer with high permittivity and a surface area no greater than a few cm(2). In order to test the electrode, an electrocardiography (ECG) measuring system was designed. Several different dielectric materials, different sizes of the electrode surface, as well as different electronics of the electrode were compared. The results show 26 dB signal to noise ratio (SNR) for the electrode with a ceramic dielectric layer, which was put on a skin over a cotton fabric, compared to 13 dB SNR for an electrode with a metal plate with a four times larger surface area.