Abstract: A method and an apparatus have been found, with the aid of which important properties can be determined during the extrusion of polymer melts:continuous measurement of the density of pure polymers (density constancy)plotting of p, v, T diagrams of plastics determination of percentagesf by volume and weight in polymer/filler or polymer/reinforcing agent mixturesdetermination of proportions by weight of pigment in masterbatch preparationdetermination of measuring data for statements going further regarding mixing and thermal homogeneity of the material.Furthermore, the apparatus as a sensor is suitable as basic module for a closed control loop for monitoring and keeping constant porportions of filler.

Abstract: A system for measuring the density of a fluid stream by utilization of the gamma ray absorption method, including a flow channel through which the stream is conducted, a source of gamma radiation, which is directed through the channel, and a gamma radiation detector system disposed for receiving gamma radiation after it passes through the channel, with the radiation source being composed of at least two radiation sources disposed in a common plane perpendicular to the axis of the flow channel and angularly spaced about that axis and at least one beam channel associated with each source for forming the radiation from its source into a collimated beam directed into the flow channel, the beam channels being oriented for causing collimated beams from each source to intersect one another within the flow channel.