Electrical Capacitance Tomography
“Electrical capacitance tomography (ECT) is a method for determination of the dielectric permittivity distribution in the interior of an object from external capacitance measurements. It is a close relative of electrical impedance tomography and is proposed as a method for industrial process monitoring, although it has yet to see widespread use. Potential applications include the measurement of flow of fluids in pipes and measurement of the concentration of one fluid in another, or the distribution of a solid in a fluid.”
“Although capacitance sensing methods were in widespread use the idea of using capacitance measuremnet to form images is attributed to Maurice Beck and co-workers at UMIST in the 1980s.”
“Although usually called tomography, the technique differs from conventional tomographic methods, in which high resolution images are formed of slices of a material. The measurement electrodes, which are metallic plates, must be sufficiently large to give a measureable change in capacitance. This means that very few electrodes are used and eight or twelve electrodes is common. An N-electrode system can only provide N(N-1)/2 independent measurements. This means that the technique is limited to producing very low resolution images of approximate slices. However, ECT is fast, and relatively inexpensive.”
(Wikipedia, Electrical Capacitance Tomography, 7/13/2011)
Recent Journal Articles
Electrical capacitance tomography as a monitoring tool for high-shear mixing and granulation
(4090-4100) Chemical Engineering Science 66 #18 (2011)
Rimpiläinen et al of the University of Eastern Finland, Finland, used electrical capacitance tomography (ECT) for monitoring high-shear mixing and high-shear granulation. A finite element method (FEM)-based reconstruction algorithm was utilized to take into account the specific geometrical characteristics of the experimental set-up. Two-dimensional ECT tomograms, mixing index curves and permittivity fractions were computed based on the measurements, and their suitability in the analysis of the processes was assessed. It was found that the different mixing processes and the different granulation processes could be analyzed based on these quantities. (RDC 7/12/2011)