Elektromagnetische Feuchtemessung für mineralische Schüttgüter

The ability to measure the moisture of a material by using electromagnetic waves is caused by interaction between water particles and microwaves. In this thesis the theoretical background of the dielectric water and its detection via microwaves through polarization mechanisms is shown. Thereby, the different measuring methods reflection, transmission and resonance are compared in their coupling and basic structure. The obtained parameters (amplitude attenuation and phase shift or resonance frequency and bandwidth of the resonance curve) are described and the mathematical connection to the moisture-dependent dielectric constant is given. The focus is also placed on possible influencing parameters of the moisture measurement of mineral bulk material. These include fluctuation of the temperature, the bulk density, the frequency, the binding strength of the water, the composition of the material (iron species, additives) and the operating conditions (statics and dynamics, on a conveyor belt). The origin of the influence is described theoretically and is evaluated concerning its importance. Furthermore, compensation possibilities of relevant influencing values are discussed. As the main part of this thesis, several different examples (concrete, bauxite, coal, etc.) of reflection/transmission and resonator measurements are used to show the theoretical creation of linear and non-linear calibration functions. Further on, their accuracy is analyzed and determined. In addition, two possible methods from self-development are presented. A conclusion of all theoretically and from the application examples gathered information is merged in the last part of this thesis, and additionally recommendations for further use in moisture measurement are given.