Comparison of current measurement structures in voltage-driven tomographic systems

Front-end non-idealities determine the accuracy of impedance measurement systems and, consequently, the quality of the resulting images in impedance tomography systems. In current-driven systems, the finite output impedance of current sources gives load-dependent errors. In addition, in multiple-source systems, the mismatch between current sources gives a high common-mode voltage. In contrast, voltage-driven systems, with measurement of the applied current, are assumed to have better accuracy. In this work, we analyzed and tested two alternatives: 1. Replacing the op amp by a current feedback amplifier (CFA), given that this device has a reduced gain-bandwidth tradeoff; and 2. Using a current-conveyor (CCII) to apply the voltage to the load through the Y-X buffer. The resulting load current is copied to the Z node, then being converted into a voltage