A viscometer is a device that measures the viscosity of any fluid. Viscosity measurement is used to determine the quality of products.

Types of fluids:

Fluids either have constant viscosity, which are known as Newtonian fluids, or they do not have constant viscosity, which are called non-Newtonian fluids. In Newtonian fluids, the relationship between stress changes and strain rate is linear, while in non-Newtonian fluids, this linear relationship has no meaning. In Newtonian fluids, their viscosity changes with flow, so a special type of viscometer called a rheometer is used to measure the viscosity of these fluids.

Viscometers usually work in two different ways:

1- The instrument for measuring viscosity is stationary and the viscous liquid moves.

2- The viscous liquid is stationary and the viscosity measuring instrument moves inside it.

Usually, the simplest method to measure viscosity is to flow liquids in a capillary tube and measure the transit time and volume of the desired liquid.

TYPES OF VISCOMETERS:

1. U-shaped viscometers

This type of viscometer, in honor of William Ostwald, is better known as the Ostwald viscometer, which is also known as the capillary glass viscometer. These viscometers are divided into direct or reverse flow viscometers. Direct flow viscometers have a tank below the indicators, while in reverse flow viscometers, this tank is above the indicators.

There is another type of viscometer, which is a combination of these two types of viscometer, i.e. direct flow viscometer and reverse flow viscometer.

In Estwald viscometers, due to the fact that it is not an easy task to accurately measure viscosity from a scientific point of view, viscosity is usually measured relatively, which usually means that a liquid is selected as a reference liquid against which other liquids are measured. they take. It should be noted that the reference liquid is a liquid whose viscosity has been accurately measured at different temperatures.

2. Vibrating viscometers:

The working basis of this type of viscometers is based on measuring the amount of reduction of vibrating electromagnetic oscillations during vibration inside the tested fluid.

3. Falling viscometers:

Stokes’ law forms the basis of the work of falling viscometers.

Stokes’ law tells us that the speed of a particle settling inside a fluid is directly related to the force of gravity, the difference between water density and particle density, and the second power of the particle’s radius. The settling speed is inversely related to gravity. It is the fluid or the viscosity of the liquid.

4. Rotational viscometers:

This type of viscometer is based on measuring the amount of torque required to rotate an external object in the fluid, which can be a way to measure the viscosity of the fluid. Among the types of rotary viscometers, we can mention Brookfield viscometers and viscometers made by Chinese companies.