The falling needle viscometer (FNV) was originally developed to measure the rheological properties of Newtonian and non-Newtonian fluids. However, the FNV is a versatile instrument that can also experimentally determine other physical properties of liquids. In addition to measuring viscosity, it can measure liquid density, zero shear rate viscosity and yield stress, mixture concentration, relative particle settling rates, intrinsic viscosity and molecular weight, and high-pressure (up to 50000psi) and high- temperature (up to 350°C) viscosity. Because of the simplicity of the FNV principle, portable and/or disposable viscometers can be made available for lubricants and greases even under field conditions. These types of viscometers greatly reduce testing time because sample tube cleaning is not required. Examples of measurements of rheological properties as well as the aforementioned topics will be presented and discussed.
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