Abstract: In a process for measuring the equilibrium moisture in hygroscopic, laminar material coated on both sides, preferably in raw paper coated on both sides used as support for a photographic paper, by determining the relative moisture of the air in contact with the material, samples are removed from the material by a process which forms cut surfaces on the material and are introduced into a container which can be sealed off against the outer atmosphere, and after establishment of the equilibrium moisture in this container the relative moisture of the air contained therein is measured.

Abstract: A process for measuring the relative equilibrium moisture content, particularly of surface samples such as papers, films, woven material or the like, with which the sample is introduced into a hermetically sealable measuring tube and then the equilibrium moisture content arising from a temperature which is predetermined and adjustable by means of a thermostat is measured by a moisture sensor inserted into the measuring tube and not touching the sample. An apparatus serves to carry out the process which has a measuring tube which can be sealed on both sides and can be inserted into a thermostat, in which measuring tube frames are arranged for holding the sample to be examined, and which has a moisture sensor provided at the side sealing the measuring tube.

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.