Broad-band spectral electrical impedance tomography (sEIT) measurements with a centralized multiplexer and coaxial cables

SUMMARY Spectral electrical impedance tomography (sEIT) has attracted increasing interest in hydrogeology, biogeosciences, agriculture and environmental studies. However, broad-band sEIT measurements, particularly at frequencies above 50 Hz, have long been challenging due to electromagnetic (EM) coupling effects. Recent advances in instrumentation, data correction and filtering have improved sEIT measurements at higher frequencies, yet many of these developments rely on a customized system with distributed amplifiers. Extending these advancements to more universally applicable methods is necessary, as sEIT measurements are often acquired using systems with centralized multiplexers. This study aims to bridge this gap by developing model-based data correction methods to mitigate EM coupling effects in sEIT measurements acquired with such a set-up. For this, the differences in EM coupling effects between measurements with a centralized multiplexer and distributed amplifiers were discussed, and the required correction methods in case of a centralized multiplexer were developed. The effectiveness of the developed corrections was tested using sEIT measurements acquired with a centralized multiplexer. A data set obtained using distributed amplifiers and corrected using previously developed approaches served as a reference. Finally, inversion results of all data sets were compared. It was shown that cable capacitance dominates the capacitive coupling in the sEIT measurements acquired with a centralized multiplexer when coaxial cables are used. Improvements were observed after each correction step using the developed methods. It was concluded that broad-band sEIT imaging results can be obtained using measurements with a centralized multiplexer and coaxial cables using the proposed data correction and filtering methods.