Blood pulse measurement based on capacitive sensing

Abstract

A capacitive sensing system is adapted for noninvasive measurement of blood pulse (hear rate). A capacitive sensor is located near a skin pulse point exhibiting pulse displacement of skin tissue from vascular pulsation (for example, the temple area of the head), and includes a sensor electrode disposed over and spaced from the skin pulse point, such that the distance between sensor electrode and the skin pulse point cycles between a proximal and a distal displacement distance based on vascular pulsation. A capacitance-to-digital conversion (CDC) unit includes excitation circuitry providing sensor excitation to generate a sensor E-field between the sensor electrode and the skin pulse point based on sensor self-capacitance, and capacitance acquisition/conversion circuitry that acquires capacitance measurements for proximal and distal self-capacitance (for example, by multi-phase capacitive charge transfer using a switched capacitor arrangement), and converts these capacitance measurements into sensor data representative of vascular pulsation.