Ultrasonic measurement of viscosity of liquids

This paper presents a cell to measure the dynamic viscosity of liquids using a wave mode conversion from longitudinal to shear waves and vice-versa. The method is based on the measurement of the complex reflection coefficient of shear waves at a solid-liquid interface. The reflected waves are measured in the longitudinal mode by a large aperture PVDF (Polyvinylidene Fluoride) membrane. Measurements of the viscosity of automotive oils (SAE90 and SAE140) and corn glucose were made in the range from 1 to 5 MHz. The experimental results are compared with the Maxwell model with two relaxation times.