An in-Line Ultrasonic Viscometer

Abstract

The ultrasonic viscometer described in this paper is a nonintrusive in-line device that measures both fluid density and viscosity. The principle of the viscometer is based on acoustic- and shear- impedance measurements. Normal-incident ultrasonic shear (1-10 MHz) and longitudinal waves (1 MHz) are launched to two wedge surfaces that are in contact with the fluid, and their reflections are measured. The reflection coefficients, along with the sound speed in the fluid, are used to calculate the fluid density and viscosity. A laboratory prototype has been built and tested. Results agree with a model calculation and show an accuracy of 1 % in density measurement and 5% in viscosity measurement for viscosities greater than 100 cPo