Flexible blade for in-line measurement of low-range viscosity

A new type of viscometer is proposed for measuring viscosity in low viscosity fluids. Viscosity is determined by rotating a flexible blade at a constant angular velocity within a cylindrical vessel. As the blade rotates a torque transducer measures changes in strain or deflection of the flexible blade. We show that the deflection during rotation is directly proportional to the sample viscosity. We provide measurements in standard materials and show that blade strain monotonically increases with rotational rate. The rate of increase of the blade strain with rotation rate provides the viscosity through a calibration curve. The measurements performed here are inherently fast, averaging about 3 min per sample. The instrument presented here can be used for simple, fast, and inexpensive in-line viscosity measurements.