Advances in Active Capacitive Sensing for Wearable Computing

Abstract: Capacitance measuring has already been used in industry area for a long time. Inrecent years, people start to invest it in physiological area, too. The object can still wear clothes (up to certain thickness) while being measured. It is also more comfortable because sensor can be directly integrated into clothes when using flexible metal textile. In formal study we measured from inner change like breathing and heartbeat to a broader range of activities including swallowing, head position and even walking pace. However, these are the first steps into a dark forest. To better understand and improve data quality before larger-scale experiments in various of application fields, we performed a detailed study to enhance raw data quality. In this presentation we will show our work in how to get the highest possible sensitivity, decided by sensitivity from structural change to capacitance change (E-field analyze) and sensitivity from capacitance change to voltage change (analog circuit analyze). The smallest measurable change is limited by overall sensitivity and circuit noise, about which we provide theoretical analyze, recommended device type, recommended parameters for different application fields, and basic result from real measurement.

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