Patent ID: 7680614

Claim:
A method for determining the humidity and/or density of a dielectric material in a resonator filled with the material, the resonator including a sender and a receiver, the method comprising: emitting a signal by the sender; sweeping a resonance curve of the filled resonator; measuring appropriate signal strength values of the receiver signal at respective different frequencies; determining a resonant frequency and a bandwidth for the filled resonator from points corresponding to the signal strength values of the receiver signal at the respective different frequencies measured; and calculating at least one of humidity or density of the material by solving a second system of equations comprising the resonant frequencies and respective bandwidths of the empty and of the filled resonator and known calibration coefficients of the resonator, wherein, from the points for determining the bandwidth of the filled resonator, cut-off frequencies are determined and the resonant frequency and the bandwidth are calculated therefrom, and wherein the cut-off frequencies of the resonator are determined by: determining a one of the points having a highest signal strength value, and, starting from said one of the points, calculating a threshold value; determining two proximate points for positive and negative slope sections, the signal values of said two proximate points lying below and above the threshold value, respectively; and calculating first and second cut-off frequencies therefrom by respectively interpolating between the two proximate points.