Patent ID: 7945395

Claim:
Method for determining the density of a liquid by density meters with a flexural oscillator holding the liquid to be measured therein on the basis of measuring periods of oscillation at two different natural vibrations of the flexural oscillator and of at least a vibration damping value at one of the natural vibrations to find out whether air inclusions and/or other inhomogeneities are present in the liquid or not to decide if the measured density value is correct or not, the method comprising: (a) determining the periods of oscillation of the flexural oscillator when filled with inclusion-free samples of different densities ρ and viscosities η at two different natural vibrations and of at least one characteristic vibration damping value δ at one of the natural vibrations, (b) calculating from the measured period values at the natural vibration having the lower frequency the density values ρ G for each of the samples and from the measured period values at the natural vibration having the higher frequency density values ρ O , (c) calculating a functional dependence (δ,Δρ OG ) between the relative density differences Δ ⁢ ⁢ ρ OG ⁡ ( = ρ O - ρ G ρ O ) ⁢ ⁢ or ⁢ ⁢ Δ ⁢ ⁢ ρ OG ⁡ ( = ρ O - ρ G ρ G ) in which the density values ρ O and ρ G are respectively viscosity-corrected or not viscosity-corrected, and the measured vibration damping values δ of the samples to define an inclusion-free curve KB reflecting the functional dependency (δ,Δρ OG ) over a desired density and viscosity range, (d) expanding the inclusion-free curve KB to provide an inclusion-free curve area KF having a deviation bandwidth on both sides of the curve KB and a constant distance in a direction normal to the curve KB, (e) storing the inclusion-free curve area KF, (f) for each subsequent liquid sample the density of which is to be measured with the flexural oscillator, determining the actual functional value (δ,Δρ OG ) from the actual values of ρ G ,ρ O and δ, and (g) testing whether the actual functional value F (δ,Δρ OG ) falls within the boundaries of the inclusion-free curve area KF or not and therewith deciding whether the measured density value of the liquid sample is correct.