Lock-in integration for detection of tiny bioimpedance variations

It is often desirable to detect tiny variations on top of larger static base value. Synchronous or lock-in measurement related problems are discussed in the current paper, and new solution is proposed for detection of bioimpedance variations. Proposed method is believed to be simpler, and more robust compared to known solutions. In the heart of the method is lockin integrator, used as differentiating peak detector. The base component of the signal is rejected, giving better dynamic range for the information carrying variable component of the bioimpedance due to the apparent differentiation. Reduction of the additive off band signals and noise is considered as well.