Abstract: The actual density of liquids is determined with a flexural oscillator that is excited at two different natural vibrations. The presence of air/gas inclusions or other inhomogeneities in a liquid is detected and their influence can be eliminated. In an initial step, the periods of the inherent vibrations and of at least one vibration damping value of the natural vibrations are determined for liquids having different densities ? and viscosities. Liquid densities as well as the difference between them and between the vibration damping values are determined from this. An inclusion-free curve (KB) which reflects the functional dependence F(??) between the relative density differences and the vibration damping differences is calculated and the exact function determined; i.e. the gas/air inclusion-free curve (KB) is expanded by introducing a deviation bandwidth (ab) to form an inclusion-free curve area (KF), which is stored.

Abstract: The actual density of liquids is determined with a flexural oscillator that is excited at two different natural vibrations. The presence of air/gas inclusions or other inhomogeneities in a liquid is detected and their influence can be eliminated. In an initial step, the periods of the inherent vibrations and of at least one vibration damping value of the natural vibrations are determined for liquids having different densities ? and viscosities. Liquid densities as well as the difference between them and between the vibration damping values are determined from this. An inclusion-free curve (KB) which reflects the functional dependence F(??) between the relative density differences and the vibration damping differences is calculated and the exact function determined; i.e. the gas/air inclusion-free curve (KB) is expanded by introducing a deviation bandwidth (ab) to form an inclusion-free curve area (KF), which is stored.

Abstract: A device for determining a physical quantity of a sample, in particular for determining the density of a fluid, is implemented as an optical measuring device which allows an evaluation the reliability of the measured value in the measurement of the physical quantity of the sample.