The invention relates to an automatic system for monitoring the mixing of conglomerates. The inventive system can be used to monitor and measure the volume of a conglomerate, i.e. a concrete, mortar or other similar product, and the conditions in which the conglomerate is being mixed inside a mixer. The invention is characterised in that the system is provided with a sensor which rotates integrally with the mixer and which is fitted with a blade that is sensitive to the stresses exerted by the conglomerate thereon. The invention is also characterised in that the aforementioned information is transmitted to one or more terminals, by means of radio communication or other similar wireless communication means, for use in industrial processes.