Correlation and Interference of Velocity Measurement in Electrical Capacitance Tomography

Electrical Capacitance Tomography (ECT) is widely applied in various industrial fields, such as oil extraction and transportation. One method to calculate flow velocity is through the cross-correlation technique. This study focuses on analyzing the mutual interference of electric fields in capacitive sensors with dual plane electrodes and the correlation of capacitance data measurements. Firstly, by examining the difference in capacitance between a dual plane electrodes and a single plane-electrodes as the distance between plane <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d$</tex> changes, it is found that when <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d$</tex> is twice the length of the measuring electrodes, the electric fields between the dual plane electrodes exhibit minimal interference. Subsequently, under this optimal distance condition, the cross-correlation in velocity measurement is investigated. When a small ball passes through either the upper or lower plane of electrode, it generates two signals. By analyzing the difference between these signals, the cross-correlation velocity can be determined. Compared to the calculated cross-correlation velocity of the ball in free fall, the error in the measured velocity is within 1%.