Patent ID: 6651513
Filing Date: 2003-11-25
Classification: G01F,G01N

Abstract:
A method of measuring a viscosity of a fluid flowing through a pipe, using a vibration meter comprising:a transducer assembly with at least one flow tube inserted into the pipe which in operation oscillates relative to a position of rest at an adjustable excitation frequency, with an electromechanical excitation arrangement for producing spatial deflections of the flow tube, and with a sensor arrangement, responsive to lateral deflections of the flow tube, for sensing an inlet-side and an outlet-side deflection of the flow tube; and meter electronics with an excitation circuit which generates an excitation current feeding the excitation arrangement, and an evaluating circuit, the vibration meter providing a density value, representative of a density of the fluid, and an excitation frequency value, representative of the excitation frequency, said method comprising the steps of:generating vibrations of the flow tube at the excitation frequency to produce viscous friction in the fluid; sensing the excitation current feeding the excitation arrangement to generate a friction value representative of the viscous friction; sensing an inlet-side and/or an outlet-side deflection of the flow tube to generate an estimate representative of a velocity of a motion of the fluid, which causes the viscous friction; dividing the friction value by the estimate to obtain a quotient value representative of a damping of the oscillating flow tube caused by the viscous friction; deriving from the density value and the excitation frequency value a correction value dependent on the density of the fluid and on the excitation frequency; and deriving from the quotient value and the correction value a viscosity value representative of the viscosity of the fluid.