Front End Instrumentation Modeling of Electrical Tomography Systems

Electrical tomography refers to imaging methods based on electrical measurements. Examples are given by electrical impedance tomography, or electrical impedance tomography. The instrumentation of an electrical tomography sensor refers to all components for the measurement system, including excitations sources, cables, and dedicated measurement circuits for data acquisition. The following step of image reconstruction is based on a model of the sensor. It is common at this point to apply simplifications for the model of the measurement process. Differences between the model and the measurement system are compensated by means of calibration measurements. In this paper we present the modeling of the front end instrumentation for electrical tomography systems and discuss the influence of the instrumentation on the measurements. We present a framework for sensor and component modeling based on scattering parameter technique to evaluate the mutual interactions between the components of the instrumentation. The approach can be used in combination with existing simulation models for inverse problems. In a case study we analyze the impact of the instrumentation system for the behavior of an electrical capacitance tomography system for low contrast and high contrast imaging problems. In the case study we compare two different measurement circuits and analyze the capabilities of calibration, as well as the influence of transmission lines.