The present invention is directed to a measuring unit, for measuring characteristics of a sample liquid, comprising a support member, having at least one upper bearing arm, with an upper bearing unit, at least one lower bearing arm, with a lower bearing unit, and a base, for being attachable to a respective measuring system; a shaft, having shaft toes and being rotatably supported about a rotation axis, by said upper bearing unit, and said lower bearing unit, wherein said upper bearing unit, said lower bearing unit, and said shaft toes form toe bearings, respectively; an interface member, having a detecting element, and a drive element, said interface member, being fixed on said shaft, and being connected to a coupling shaft, with a probe connector section, for measuring characteristics of said sample liquid; wherein said interface member, and the coupling shaft, are coaxially aligned with said shaft.