Liquid density measurements using the falling needle viscometer

Abstract

The falling needle density meter/viscometer (FNDV) consists of a vertical cylinder which is filled with the test sample. Using a needle launcher at the top of the cylinder, the first needle having a known density is allowed to fall through the liquid in the cylinder. The time that the needle falls between two marks, or transducers, spaced on the cylinder with a known distance apart is measured and the velocity of the needle through the liquid is calculated. Then a second needle having the same dimensions as the first and a known density different from that of the first needle is allowed to fall through the liquid. The time that the second needle falls between the two marks on the cylinder or transducers is measured and the velocity of the second needle through the liquid is calculated. Using the densities of the two needles and the velocities through the Newtonian liquid the density and viscosity of the liquid can be determined simultaneously. Two Newtonian fluids were used for density and/or viscosity measurements. In addition, density and apparent viscosity measurements were made using a power law non-Newtonian fluid for which three needles must be dropped. Results are presented showing that the Newtonian density measurements agreed within 0.27% with the standard values and the non-Newtonian fluid within 0.44% of independent density measurements.