Viscometer

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A device known as a viscosimeter is used to measure the viscosity of a fluid. For liquids with varying viscosities that change based on flow conditions, an instrument called a rheometer is utilized. Therefore, a rheometer can be considered a specific type of viscometer. Viscometers only measure under one flow condition. In general, either the fluid remains stationary and an object moves through it, or the object is stationary and the fluid flows past it. The drag caused by the relative motion between the fluid and a surface measures the viscosity. The flow conditions must have a sufficiently small Reynolds number value for laminar flow to occur. At 20 °C, the dynamic viscosity (kinematic viscosity × density) of water is 1.0038 mPa·s, and its kinematic viscosity (product of flow time × factor) is 1.0022 mm²/s. These values are used for calibrating certain types of viscometers.