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Recording the power input required to keep the apparatus vibrating at a constant amplitude.The resonator generally oscillates either torsionally or transversely and the damping may be determined by: Vibrational viscometers operate by immersing an oscillating electromechanical resonator in the test fluid and measuring the degree of damping the fluid offers. The values a viscosity cup provides is an absolute value and does not include the allowed tolerances-as these differ considerably between each of the standards. Each cup design is unique thus care must be taken when comparing viscosity values between different cup types. A table is then used to convert efflux time (in seconds) to viscosity in centistokes (cSt).įord and Zahn cups are some of the most commonly used viscosity cup varieties. Viscosity cups are typically used for measuring the consistency of paints, varnishes and similar products. The time it takes for the fluid to pass through the opening is measured and correlated to viscosity through the use of charts supplied for the given cup. The fluid is allowed to flow through the opening in a precise amount. This relatively simple test involves placing the fluid in a container with a small opening at the bottom. (For more on this topic, see: Understanding Aluminum Corrosion.

Viscosity cups are used to determine a fluid’s kinematic viscosity and are typically made of anodized aluminium with a stainless steel orifice. Some of the most common methods are as follows: 1. There are several different methods to measure both dynamic and kinematic viscosity. In the centistoke, one cSt equals 10 -6 m 2/s = 1 mm 2/s. Where the viscosity value in Stoke is too large, the smaller unit centistoke (cSt) is often used in its place. Another unit of measurement for this property is Stoke (St), where one St equals 10 -4 m 2/s equals 1 cm 2/s. The SI unit for dynamic viscosity is m 2/s. μ = absolute or dynamic viscosity (N s/m 2).Mathematically, kinematic viscosity can be expressed as: This viscosity is especially useful in describing Newtonian fluids. It reflects a fluid’s resistance to shear flow under the influence of gravity, i.e., shear flow due to the fluid’s own weight. Kinematic viscosity is simply the ratio of the dynamic viscosity to the fluid's density. In the centipoise unit, one cP equals 0.01P, 0.001 N s/m 2 or 0.001 Pa s. For this reason, centipoise (cP) unit is often used in its place. The poise unit can sometimes be too large for practical purposes. Another unit of measurement for dynamic viscosity is poise (p), where one poise equals one-teneth N s/m 2 or 1/10 Pa s. The SI unit for dynamic viscosity is N s/m 2 or the Pascal-second (Pa s). μ = dynamic viscosity of fluid (N s/m 2).Mathematically, dynamic viscosity can be expressed as: Dynamic viscosity is especially useful when describing non-Newtonian fluids.