Method for determining and/or monitoring viscosity and corresponding apparatus

A method for determining and/or monitoring at least the viscosity of a medium, comprising the steps of:

• exciting at least one mechanically oscillatable unit to execute mechanical oscillations based on an exciter signal;
• receiving mechanical oscillations by the mechanically oscillatable unit and transducing them into a received signal;
• and
• ascertaining and/or monitoring the eigenfrequency of the mechanically oscillatable unit and/or the phase relationship between the exciter signal and the received signal, wherein:
• from changes in the eigenfrequency and/or from changes in the phase relationship between the exciter signal and the received signal, with oscillations of the mechanically osillatable unit at the resonance frequency, a change in viscosity is deduced;
• and/or
• based on dependencies of the oscillations of the mechanically oscillatable unit on the viscosity of the medium, from the eigenfrequency and/or phase relationship between the exciter signal and the received signal, with oscillations of the mechanically oscillatable unit at the resonance frequency, viscosity is ascertained.