Apparatus is provided featuring a signal processor or processing module configured at least to: receive signaling containing information about coded and multiplexed voltages measured across pairs of electrodes in an array of electrodes configured in relation to a fluid processing structure, including a pipe, tank, vessel, vat or container, having a process fluid therein; and determine using a tomographic signal processing algorithm a tomographic indication of the process fluid, based at least partly on the signaling received. The signal processor module may be configured to provide corresponding signaling containing information about the tomographic indication of the process fluid. The tomographic indication includes a 2D or 3D image or visualization of the process fluid, including an analysis of mixing in multiphase flows, liquid interfaces or liquid-froth layers detected in the process fluid.