This paper presents an original concept for automatic determination of the time intervals for calculation of the mass flow rate of intermittent flow using a twin-plane electrical capacitance tomography system. The concept allows a solids mass flow rate to be calculated more accurately. It is based on images of instantaneous distributions of the material inside the measured volume by means of Electrical Capacitance Tomography (ECT), and extraction of the appropriate flow patterns, which are further used for calculation of the mass flow rate. The preliminary results of the mass flow rate measurement using the proposed concept for gas-solid flow during pneumatic conveying are presented.