Abstract: TDR limit level switch determines whether or not the measuring probe is surrounded by the filling material on the basis of the positions relative to the transmission pulse that can be read out from the detected measuring signal and on the basis of the associated amplitudes of the reflections of the transmission pulse on the coupling point and on the end of the measuring probe. In this way, a limit level message can be formed in a simpler, more secure and more reliable manner.

Abstract: Described is a method and an apparatus of directly digitizing microwave signals reflected at a filling product surface of a filling product present in a receptacle, in which method the microwave signals reflected at the filling product surface are sampled unmodified in their frequency, and the therefrom resulting analog values are converted into digital values, with successive digital values being stored in various intermediate memories, and the intermediately stored digital values are read out from the intermediate memories and are stored in a terminal memory unit, to which accesses an evaluation arrangement which determines the filling level height.