An Evaluation Study of Various Excitation Signals for Electrical Impedance Spectroscopy

Electrical Impedance Spectroscopy (EIS) is a popular method for investigating tissue properties. Implementing the signal generator for EIS measurements with a suitable excitation signal type is thereby one of the two system components. The choice of the excitation signal defines the measurement speed, signal-to-noise ratio (SNR), total area and power consumption of the system, and many more properties. Signal types such as analog single-tone, analog multi-tone, linear feedback shift registers (LFSR), and single-tone Sigma Delta Modulated (ΣΔM) are proposed in the state of the art. In this work an EIS setup is implemented and successfully tested with all the mentioned signal types to evaluate their properties on impedance models as well as in vitro cell layers. It is proposed to combine the ΣΔM with the multi-tone excitation signal yielding a very versatile excitation generator. Multi-tone ΣΔM are as fast as analog multi-tones, while benefiting from a binary output and thus less system complexity. The implemented EIS setup is used to perform EIS measurement for biological samples. The results show a very good matching with the reference for all the excitation signals.