Method and device for contactless level and interface detection

process for determining the thickness of a layer of material, arranged in a container substance wherein the substance is one which is arranged in an upper layer of the first Material and disposed in a lower layer second material contains, comprising the steps of: - emitting a radio signal from a given in a distance of one container section arranged antenna device by the substance to the container portion down; - Receiving, in the antenna device of reflected signals from an upper first surface portion of the upper layer, by a second surface portion of the second layer and the container portion; - Changing Frequency of the transmitted signal over a frequency band for determining a phase shift between the transmitted signal and the reflected signals; - Determine optical distances from the antenna means to the first and second surface portion and the container portion dependent on of the phase shifts; - Determining the thickness of a the layers as a function of ...