Switching of the surface electrode array in A 16-electrode EIT system using 8-Bit parallel digital data

Modern sixteen electrode EIT system needs an automatic electrode switching module (ESM) developed with four 16:1 analog multiplexers. Sixteen parallel digital data are generally required to operate all the four 16:1 analog multiplexers switching at the same time. In this paper the surface electrode switching of a 16-electrode EIT system is studied using 8-bit parallel digital data. 8-bit parallel digital data are generated using a USB based data acquisition system (DAS) and a binary adder circuit (BAC) is used to convert it to the 16-bit digital data required for surface electrode switching of a 16-electrode EIT system. An automatic ESM is developed with four 16:1 analog multiplexers connected to sixteen surface electrodes. 8-bit parallel digital bits are generated using NI USB 6251 card using LabVIEW software and sent to the BAC which converts it into a 16-bit parallel digital data. BAC feeds the 16-bit digital data to the multiplexers in ESM and operates them to switch the surface electrodes. 1 mA, 50 kHz sinusoidal constant current is injected at the practical phantoms and the boundary potentials are collected. Resistivity images are reconstructed from the boundary data using EIDORS. Boundary data and reconstructed images are studied with contrast parameters to assess the electrode switching of the EIT system. Results show that the resistivity images of practical phantoms are successfully reconstructed from the boundary data collected with 8-bit parallel digital data sets.