Patent ID: 6476619
Filing Date: 2002-11-05
Classification: G01N

Abstract:
A method for continuously determining the density of a fibrous material, comprising the steps of:(a) continuously guiding the fibrous material through and parallel to height of a cylindrical microwave resonator having a microwave resonance frequency, said cylindrical microwave resonator includes: (i) an electrically conductive housing defining a cylindrical cavity having an input end and an output end; (ii) a plastic cylindrical tube spanning inside said cylindrical cavity from said input end to said output end, wherein ratio of length of said cylindrical cavity to length of said plastic cylindrical tube is about one, and wherein ratio of diameter of said cylindrical cavity to diameter of said plastic cylindrical tube is between about two and three to one, for said continuously guiding the fibrous material through and parallel to height of said cylindrical microwave resonator and for preventing contamination by residual fibrous material inside said cylindrical cavity; and (iii) a mechanism for measuring a shift in said resonance frequency caused by a presence of the fibrous material inside said cylindrical cavity; (b) measuring said shift in said resonance frequency caused by said presence of the fibrous material inside said cylindrical cavity; and (c) inferring the density of the fibrous material from said shift.