# Design of Three-Dimensional Electrical Impedance Tomography System for Rock Samples
## 1 Introduction  
The electrical properties of rocks and ores constitute fundamental prerequisites for electrical (and electromagnetic) field surveys in geophysical exploration [1]. Through these electrical properties, we can understand the differences in resistivity and polarization between mineralized bodies and surrounding rocks, which serve as essential criteria for selecting appropriate geophysical exploration methods. Furthermore, the electrical parameters of rocks and ores provide an objective basis for forward calculations and inversion interpretations, as well as a physical foundation for result explanations [2]. In addition to laboratory-based investigations, the study of rocks and ores often necessitates field-based research. For example, the practice of metal ore exploration often involves splitting key core samples along the core axis, reserving one portion for laboratory analysis while preserving the other as evidence of exploration. Consequently, there are situations where it becomes imperative to conduct measurements on specific core samples within their original field environment before the splitting procedure takes place [3]. Consequently, the development of a highly precise, portable, and efficient instrument system for obtainingaccurate and reliable electrical information from rock and ore specimens represents a crucial foundational research area in geophysical instrument development [4]. Currently, the focus of researchers lies predominantly on the measurement of the overall electrical properties of rock and ore specimens, while the study of three-dimensional impedance imaging techniques capable of reconstructing the internal impedance distribution within such specimens remains relatively limited. In 2009, GDD Instrumentation Company in Canada developed the Sample Core IP Tester (SCIP), a rock core testing instrument, with the operating software installed on a PDA. This instrument enables rapid real-time measurement of the resistivity and chargeability of sampled specimens, core samples, outcrop rocks, and borehole surrounding rocks [5]. [PERSON] et al. (2014) studied theoretical methods for testing the true electrical parameters of rock and ore specimens and subsequently developed the WXE type test system electrical parameters of rocks and minerals [6]. In 2016, [PERSON] et al., from Central South University, designed a spectral induced polarization measurement system for high-impedance rock and ore samples in laboratory settings [7]. [PERSON] et al. (2021) developed a precise current encoding signal transmitting system for measuring electrical parameters of rock and ore specimens [8]. In 2022, [PERSON] et al. conducted high-precision laboratory measurements of spectral induced polarization (SIP) on rock samples using the multi-functional electrochemical P-40\(\times\) potentiostat-galvanostat instrument [9]. However, the aforementioned instruments can only conduct overall measurements of the electrical parameters of rock and ore specimens and lack the capability to obtain a visual three-dimensional distribution of electrical impedance. Electrical impedance tomography (EIT) refers to a non-invasive imaging technique that involves applying electrical signals to a target object, observing boundary voltage data on the surface of the object, and then using inversion algorithms to reconstruct the internal conductivity distribution of the target object [10]. This efficient and non-destructive imaging technique has been widely applied in medical diagnostics [11; 12] (such as lung and breast examinations) and material inspections [13]. Additionally, it is increasingly being used to characterize the structure of underground systems. For example, in 2022, [PERSON] et al., from the University of Bonn in Germany, designed spectral electrical impedance tomography (sEIT) to characterize the structure of subsurface systems [14]. Therefore, EIT technology provides a new approach for studying rock and ore specimens.