Patent ID: 7191667

Claim:
A method of measuring a viscosity and a density of a fluid flowing through a pipe, said method comprising the steps of: using an electromechanical excitation arrangement for driving a flow tube being inserted into the pipe and conducting said fluid; feeding said excitation arrangement by an oscillating excitation current and driving said flow tube to vibrate in a bending mode at least partially, said bending mode vibrations causing lateral deflections of said flow tube and said bending mode vibrations producing viscous friction within said fluid; sensing oscillations of said flow tube by using a sensor arrangement being responsive to lateral oscillations of the flow tube and generating at least one sensor signal being representative of lateral oscillations of the flow tube; using said at least one sensor signal and said excitation current to determine a viscosit value representative of said viscosit to be measured and using said at least one sensor signal to determine a density value representative of said density to be measured; wherein the step of determining the viscosity value further comprises a step of using said density value for determining said viscosity to be measured; and wherein the step of determining the viscosity value comprises the step of deriving from the density value and the excitation frequency value a correction value depending on the density of the fluid and the excitation frequency.