A Low-powered Capacitive Device for Detection of Heart Beat and Cardiovascular Parameters

Contact-based skin measurements represent the standard setup for biopotential acquisition in clinical practice. The techniques for ECG, EMG, EOG or EEG recordings have remained largely unchanged for the past decades, apart from electronic circuit miniaturization and ease of connectivity to the Internet of Things. Electrode placement over the skin needs to consider the endogenous currents generated by the body flowing into the terminal inputs of an external amplifier. Although much effort has been devoted lately to the design of electrodes with better conductivity and signal-to-noise ratios, a physical connection between the skin and electronics is still necessary to accommodate the circulation of these currents. In this paper, we present a capacitive sensor for distant ECG acquisition without physical contact with the skin, combining the non-invasiveness nature of the method with contact-less measurements. A high impedance front-end amplifier assures a deviation of the corner frequency to the mHz range for the high-pass filter generated between body surface and amplifier, thus allowing the detection of cardiac events produced by slowly moving AC currents.