Abstract: A method for determining a corrected value for a viscosity-dependent sonic velocity in a fluid under test includes generating and transmitting sound pulses to the fluid under test, registering the sound pulses after traversing a predetermined measuring distance in the fluid under test, and ascertaining a first arrival of a first sound pulse received after traversing the measuring distance and determining the transit time of the first received sound pulse in the fluid under test. A viscosity is predetermined or ascertained for the fluid under test, and a transit time of the first received sound pulse and the viscosity are used to determine the sonic velocity in the fluid under test. An apparatus for determining a corrected value for a viscosity-dependent sonic velocity in a fluid under test is also provided.

Abstract: A method determines the filling quality of a frequency oscillator where a measured fluid is passed through an oscillator tube. The relationship between the viscosity-dependent density of the measured fluid and the quality and/or attenuation of the oscillator tube is determined. The relationship between the dynamic viscosity and the attenuation and/or quality of the measured fluid is determined, and these values are used to create a calibration table that reproduces the functional relationship between a parameter relevant for the quality and/or the attenuation of the frequency oscillator and the viscosity of the measured fluid. An independent measuring apparatus determines a measured value for the dynamic viscosity of the measured fluid. The obtained measurement value for the viscosity coincides in the calibration table with a specific function value, and the result of this comparison with respect to the presence of any filling errors is used to determine a possible filling error.