Bioimpedance monitoring with improved accuracy using three-level stimulus

Operation principles, modeling, and practical design of a novel system for bioimpedance (BI) measurement and monitoring are introduced in this paper. The system employs excitation and reference signals in a form of three-level rectangular waveforms with specially shortened duty cycles for eliminating some higher harmonics from the measured response. It enables to decrease systematic errors and ensures simplicity and power efficiency for wearable devices at the same time. The system is designed as a four-channel instrument, while both, the analog and digital approaches are discussed.