Designing a Cost-Effective Multiplexer for Electrical Impedance Tomography

Electrical impedance tomography as a nondestructive, non-invasive diagnostic method finds wide application within multiple fields and disciplines. Measuring the electrical voltage on the surface of an investigated object then constitutes a procedure that facilitates the reconstruction of the inner specific electrical conductivity. The accuracy of such measurement, together with elimination of the noise and uncertainties, embodies a central factor for any precise specific conductivity reconstruction. This paper discusses a novel multiplexer to switch between the supply source, measuring electrodes, and devices that automatize the tomographic procedure. In general terms, the design of the measuring card has to respect not only the accuracy and speed requirements but also the fabrication costs. The concept proposed herein exploits the MOSFET technology, utilizing galvanic separation of the current source and the electrodes that potential-measuring electrodes; significantly, the design is compared with commercially available solutions.