This calculation of viscosity is based on the Hagen-Poiseuille equation and is expressed as absolute viscosity. The viscosity of the flowing medium is directly proportional to the ratio of pressure drop and volumetric flow rate. Viscosity is measured by determining the pressure drop through the mass flowmeter. Water or gasoline are "thinner" and have much lower viscosities.Ī DP meter can be installed around the mass flowmeter with taps upstream and downstream. Tar or syrup cannot be poured easily and have high viscosities. Certain types of fluids offer greater resistance to velocity than others.
Viscosity is the measure of a fluid's internal or intermolecular resistance to shear stress.
Most of these meters also include temperature measurement and are thus true multivariable instruments.Ī traditional method for measuring viscosity with mass flowmeters is to add a differential pressure (DP) meter. Since the 1970s, instrument designers have used the principle of Coriolis force to measure mass flow and density with Coriolis flowmeters. This apparent bending force is known as the Coriolis force, and is named after the French mathematician Gustave Gaspard Coriolis (1792-1843). The Earth rotates, so any movement in the Northern hemisphere is diverted to the right and any movement in the Southern hemisphere is bent to the left. Dan Hebert is senior technical editor for Control, Control Design and Industrial Networking.
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