Abstract: The generator for the microwave measuring arrangement consists of a frequency-modulated oscillator which feeds a cavity measuring resonator in a transmission arrangement. The sample to be examined is located in the center of the resonator. The microwave signal allowed through the resonator is detected as the peak amplitude of a detector circuit, the change in the signal corresponding to the change in the quality factor due to the presence of the sample introduced. The average frequency of the microwave oscillator can be switched over several stages in order to expand the range of measurement. Each time the frequency is switched over, a different field mode is excited in the measuring resonator so that the sample is located in a mode region of the electrical measuring field for measuring high water contents and in a maximum of the electrical measuring field for measuring low water contents.

Abstract: The water content of electrically non-conductive powders, granulates, pastes and fibrous materials may be measured on the basis of microwave absorption. A frequency-modulated microwave oscillator supplies a closed multimode measuring resonator charged with the sample in a transmission arrangement. The sample charged into a container almost completely fills the multimode resonator. The sample container is rotatable about its longitudinal axis. A substantial homogeneity of the field distribution in the sample is thus obtained so that even in the case of variations in the bulk density, accurate measurements are still possible.

Abstract: The principle of measurement is based on the microwave absorption by the water content of a sample. The sample is located in a closed single-reflection measurement cell which is fed by a microwave oscillator which is frequency-modulated within the absorbing frequency range of the sample. The sample partially or completely fills the end section of a circular or rectangular waveguide forming the measurement cell. The waveguide is sealed off with a short circuit plate so that two planar travelling waves with a homogeneous field distribution are present in the measurement cell.

Abstract: The measuring arrangement consists of a frequency-modulated microwave oscillator which supplies a closed resonator charged with the sample in a transmission circuit. The change in the quality factor induced by the water content of the sample is used as the unknown. The sample is located in the substantially homogeneous range of the electrical field maximum of a stationary wave in a cylindrical single mode cavity resonator of the E.sub.010 mode, the diameter of the sample being not more than 25% of the internall diameter of the resonator and the length of the sample being not more than 50% of the height of the resonator.