Abstract: The invention relates to an automatic system for collecting, weighing and releasing solid particles comprising a leak-tight weighing chamber (1) which houses a container (5), whereon the particles entering said chamber (1) via an inlet (4) come to rest. The weight of the container (5) is transmitted to a weighing sensor (7) which is also located inside the weighing chamber (1) but which does not come into contact with the walls of said chamber. Once the sample has been weighed, it is removed from the chamber through the injection of compressed air. The inventive system can be used directly to determine the mass flow of solid particles in pneumatic conveyor lines by means of the integration thereof in automatic sampling systems. For this purpose, a signal is emitted which can be integrated in flow regulation loops in order to control said flow.