A simple mechanical spring-driven rheometer for measurement of Newtonian and non-Newtonian fluids—Design, validation, and input correction

This paper deals with the construction and validation of a new, very simple purely mechanical rheometer, which is assembled from a syringe and a steel spring. This rheometer does not require any expensive measuring equipment and yet can measure the viscosities of common Newtonian and non-Newtonian liquids with satisfactory results. By determining the temporary position of the piston, the force applied by the spring and the piston velocity can be ascertained and the viscosity of a given sample of Newtonian liquid can be calculated with repeatability of better than 2%. When measuring non-Newtonian and viscoelastic liquids, a camera is used to record the time course of the moving piston and the swelling ratio. Preliminary tests conducted on power-law liquids demonstrate reproducibility of rheological parameters even for very high viscosity liquids. A new correction to inlet effects is also derived as a function of Reynolds number.