Non-contact electrocardiogram measuring method based on capacitance coupling electrodes with ultra-high input impedance

With the development of remote cardiac healthcare, wearable devices for electrocardiogram (ECG) monitoring are stringent requirements to cope with this rapid growth of demands. Due to the advantages of no-contact ECG measuring methods in safety, convenience, and comfortableness, it is more suitable for wearable long-term ECG monitoring than the conventional Ag/AgCl electrodes. The capacitance coupling printed circuit board (PCB) electrode with ultra-high input impedance proposed in this paper can realize non-contact ECG measurement through a multi-layer insulating medium. Then, an eight-channel ECG signal processing circuit is also designed and fabricated. In addition, the following important performance properties of the non-contact ECG measuring system, such as the input impedance, the phase-frequency characteristic, the amplitude-frequency characteristic, the coupling coefficient, and the input short-circuit input noise, were all experimentally measured. The synchronous comparison between the Ag/AgCl electrode and the PCB electrode was also conducted to verify the accuracy of the non-contact measuring method. Finally, the influence of the lead positions, coupling medium parameters, and the body motion states was also experimentally studied. The results demonstrate that the proposed non-contact ECG measuring method based on capacitance coupling PCB electrodes can effectively collect the main components of ECG signals and cardiac rhythm in various situations.