Density and Viscosity Sensor

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 memorizing a determined number (n) of resonant frequency, quality factor and associated correlation coefficient,
• 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.