An apparatus for determining and/or monitoring at least one flow parameter of a medium, wherein the medium flows through at least one measuring tube essentially along an imaginary flow axis, wherein at least one exciter transducer element is provided, which, based on an exciter signal, excites the measuring tube to mechanical oscillations, and wherein at least one receiver transducer element is provided, which receives mechanical oscillations of the measuring tube as a received signal. The invention includes that at least one separating unit is provided, and that the separating unit is embodied and arranged in the measuring tube in such a manner, that at least two sub measuring tubes result in the measuring tube, wherein the medium flows through the at least two sub measuring tubes essentially along the imaginary flow axis.