A Measurement System for Electrical Impedance Tomography

The authors present a measurement system designed to facilitate tests within electrical impedance tomography (EIT). More concretely, this system provides the input data for EIT-based conductivity image reconstruction. The realized setup includes a generator, a voltage-to-current converter, a switching unit, an accurate AC multimeter, and a measuring vessel. This vessel contains 16 stainless steel electrodes; a pair of the directly opposed electrodes is connected to the converter, and voltage is measured on the other electrodes. The current electrodes are periodically excited. For each instance of current excitation, a set of voltages is measured; thus, we obtain n(n - 1) of measured voltage values, where n expresses the number of the electrodes. The measurement system is fully automated. To control the measurement, we created a program in the HP VEE environment. The measured sample consists in a saline solution, in which agar-based objects exhibiting different conductivity are placed; these objects then form defects. The applied intermittent excitation prevents the occurrence of electrolysis. The measurement is realized with several conductivity values as well as with various locations and number of defects in the saline solution.