US Patent 7584663 Material stream sensors

A method of determining the content of a desired component in a stream of material including two or more types of component, includes causing or permitting a stream of a plurality of particles of material to impact a sensor member located in a path of the material thereby inducing vibration of the sensor member, analyzing vibrations of the sensor member and from the analysis determining whether individual impacts caused by the stream are one of any two or more types selected from three possible impact types, and performing an operation based on the result of the analysis.