Patent ID: 7958772
Filing Date: 2011-06-14
Classification: G01N

Abstract:
1. A method for measuring density and viscosity of a fluid comprising the steps of: a) applying an excitation signal to a resonating arrangement comprising an actuating/detecting element and a resonating element arranged to be immersed in the fluid (F), the excitation signal having a first frequency (f), b) detecting a reception signal provided by the resonating arrangement, c) repeating the excitation signal applying step and the reception signal detecting step at various frequencies so that a range of frequencies is swept according to a frequency increment (Δf), d) determining an in-phase sensor actual response and a quadrature sensor actual response based on the reception signal detected in the range of frequencies, wherein the method further comprises the steps of: e) calculating an in-phase sensor model response and a quadrature sensor model response based on an initial resonant frequency and an initial quality factor of the resonating element, f) comparing the in-phase sensor model response to the in-phase sensor actual response, and the quadrature sensor model response to the quadrature sensor actual response by determining an associated correlation coefficient, g) repeating the calculating step and the comparing step with a modified resonant frequency and a modified quality factor and storing a determined number (n) of resonant frequencies, quality factors and associated correlation coefficients, h) determining a resulting resonant frequency and a resulting quality factor of the resonating element in the fluid (F) based on the determined number (n) of associated correlation coefficient, and i) determining density and viscosity of the fluid (F) based on the resulting resonant frequency, the resulting quality factor and a sensibly exact analytical modelling of the resonating element.