Measuring device for determining the density, the mass flow rate and/or the viscosity of a flowable medium, and method for operating same

A measuring device for determining density, mass flow rate and/or viscosity of a flowable medium, the measuring device comprising:

• an oscillator including at least one oscillatable measuring tube adapted to convey the medium and to have at least one oscillatory mode, whose eigenfrequency depends on a density of the medium, wherein a type of the measuring device is defined by a configuration of the oscillator;
• an exciter configured to excite the at least one oscillatory mode;
• at least one oscillation sensor configured to detect oscillations of the oscillator and to generate signals representing the detected oscillations;
• and
• an operating-evaluating circuit configured to:
• supply the exciter with an excitation signal;
• register the signals of the oscillation sensor;
• ascertain current values of the eigenfrequency of the oscillator and fluctuations of the eigenfrequency based on the signals of the oscillation sensor;
• and
• determine a value characterizing density fluctuations of the medium, which density fluctuations arise from inhomogeneities in the medium, wherein the value depends on a function which is proportional to the fluctuations of the eigenfrequency and is normalized by a reciprocal of the third power of the eigenfrequency such that the value is substantially independent of the type of measuring device.