Electrical Resistance Tomography (ERT) is a technique employed in the industrial environment that reconstructs images formed by the impedance distributions inside a vessel. The method relies on measures from a data acquisition system, responsible to inject a current inside the vessel and measures the voltage on the boundaries, and sequentially an inverse problem solution. This paper introduces a low-cost design of an acquisition system that can obtain 30 images/s with a signal-to-noise ratio of 57.47 dB and a maximum error of 3.79%. It utilizes a simple RMS-to-DC converter demodulation scheme to provide good accessibility to researchers aimed at investigating flow patterns of multiphase flow applications.

The film thickness of a two-phase flow is a parameter of interest since it is of importance to the heat and mass transfer phenomena. A novel method is proposed based on electrical impedance tomography (EIT) and conductance sensors to measure this quantity. An analytical equation is developed to relate the differential voltage associated with a current injection on the domain and the angular film thickness profile. A characteristic of the measuring procedure is that it presents a high sensitivity when the thickness is small, with the possibility of adjustment using different magnitudes of current. This model is compared experimentally and by the complete electrode model (CEM), solved by finite elements method (FEM). Results presented a good agreement with the FEM simulations, and the experimental results presented systematic error caused by the fringe effect.

Electrical Impedance Tomography (EIT) is a technique that enables the reconstruction of the impedance distributions inside a vessel in a multiphase flow of industrial processes. Such a technique combines a data acquisition (DAQ) system to inject a current and to measure the voltages on the sensors and an inverse problem technique to reconstruct the image properly. This problem is highly ill-conditioned, causing errors to produce instabilities. Therefore, when performing the acquisition, the DAQ system must have adequate accuracy to allow the reconstruction of images with good quality. To avoid these measurement inaccuracies, this paper introduces a methodology that aid in the process of development of low-cost systems. It consists of investigating the errors in the current version of the system. Further, predicting the systematic errors of each subsystem by modeling its frequency response by Simulation Program with Integrated Circuit Emphasis (SPICE). From this information, it is possible to perform critical analysis, aiding design decisions.