Remotely Powered Two-Wire Cooperative Sensors for Biopotential Imaging Wearables

Abstract

Biopotential imaging (e.g., ECGi, EEGi, EMGi) processes multiple potential signals, each requiring an electrode applied to the body’s skin. Conventional approaches based on individual wiring of each electrode are not suitable for wearable systems. Cooperative sensors solve the wiring problem since they consist of active (dry) electrodes connected by a two-wire parallel bus that can be implemented, for example, as a textile spacer with both sides made conductive. As a result, the cumbersome wiring of the classical star arrangement is replaced by a seamless solution. Previous work has shown that potential reference, current return, synchronization, and data transfer functions can all be implemented on a two-wire parallel bus while keeping the noise of the measured biopotentials within the limits specified by medical standards. We present the addition of the power supply function to the two-wire bus. Two approaches are discussed. One of them has been implemented with commercially available components and the other with an ASIC. Initial experimental results show that both approaches are feasible, but the ASIC approach better addresses medical safety concerns and offers other advantages, such as lower power consumption, more sensors on the two-wire bus, and smaller size.

Wearable pulmonary monitoring system with integrated functional lung imaging and chest sound recording: a clinical investigation in healthy subjects

“…Multiple factors contributed to this improved EIT signal quality. The WELMO sensors were about 30% smaller and 40% lighter (Chételat et al 2022) than the old WELCOME sensors. Thanks to these reduced dimensions and weight the sensors could more easily establish and keep their position on the chest with a stable contact with the skin despite breathing movements.…”

“…These sensors were used to apply small excitation currents (100 μA, 40 kHz) to the body and measure the resulting voltages. Further technical details on these electrical bio-impedance measuring sensors are provided in Chételat et al (2022). Six sensors enabled the acquisition of chest sounds, two of these, located in the right and left subclavicular regions, were used exclusively for the acquisition of the acoustic signals.…”

“…It was powered by a rechargeable LiPo battery and secured the power supply of the cooperative sensors. (See (Chételat et al 2022) for further information.) The central unit was fixed to the outer front bottom part of the WELMO vest (figure 1).…”