How does the Viscometer work?

The viscometer allows us to measure the viscosity of liquids and assess their flow properties. This equipment has various applications and can be used in different substances and materials.

The operation of this equipment depends on the type of instrument. There is a wide range of devices that can be classified into the following categories:

  • Capillaries.
  • Rotational.
  • Of vibration.
  • Special purpose.

Due to the different types and modes of operation within each category, in this article we will limit ourselves to describing the general operation of each category, with the exception of special purpose viscometers, where we will mention the operation of three models, due to the diversity existing within the category.

Capillary viscometers

There is a wide variety and they are the simplest equipment available; they are easy to use and are basically laboratory instruments. This category can be divided into three groups, modified Ostwald, suspended level for clear liquids and reverse flow for clear and opaque liquids.

They consist of a U-shaped glass tube with two bulbs, one located on top and one located on the bottom. Usually, fluid passes from the bulb above to below through a capillary. The measurement is the time taken by a known volume of the fluid under test to pass through a length of capillary tube. The driving force of the fluid can come from gravity, or in the case of more sophisticated equipment, of pressurized gas.

Rotational viscometers

The basis of the measurement made by this type of instrument is the value of the torque required when turning a device in a fluid, at a known speed, a value that is used for the calculation of viscosity. These viscometers offer a higher potential measuring range, compared to capillary or Saybolt viscometers. Therefore, they are suitable for measuring very viscous substances.

They can function according to two principles, of Searle and of Couette. In the first, the motor moves the submersible element within the fixed cup. In the second, the engine moves the container or cup, while the submersible remains stationary. Currently, most commercial rotational viscometers incorporate the Searle principle.

In the category of rotational viscometers we find, coaxial cylinders, rotating disk, cone and plate, cone-cylindrical and mixers or pallets. The variation between these devices is found in the design of the submersible element.

Vibration viscometers

They use a vibrating rod that is driven by a motor. The basis of the calculation is the damping of vibration or the rate at which vibration is degraded, caused by the viscosity of the liquid. These devices are popular because of their high sensitivity.

Special purpose viscometers

In this group we have, those of mobile body, such as ball or descending piston, rolling ball, torsion, oscillation, oscillating piston, universal Saybolt, among others.

In the piston or descending ball and rolling ball systems, the basis of the calculation is the terminal speed achieved by a falling piston or ball through the liquid. For measurement, the fluid being tested is placed inside the piston cylinder or ball. The time it takes for the piston or ball to descend, due to the strength of the liquid, is used to determine the viscosity.

The oscillating piston device, also called electromagnetic, consists of a measuring chamber and a magnetically actuated piston. For the calculation of viscosity, the data of the ring space between the piston and the measuring chamber, the force of the electromagnetic field and the travel distance of the piston are used.

In the case of Saybolt viscometers, they consist of a tube or container with a specific diameter and a hole in its lower part, through which the liquid flows, which is collected in a container. The viscosity is determined by timing the time it takes the container to empty and measured in seconds. These equipment are easy to use and are popular in the paint industries.

Kalstein Viscometers

At Kalstein we offer a wide variety of YR series viscometers, with models that you can choose according to the needs of your industry. Kalstein equipment offers stability, accuracy and precision in the measurements made. In addition, they are designed with an LCD screen that facilitates the configuration and display of the parameters of the measurement being made. For more information on Kalstein viscometers, visit the HERE We are manufacturers, so in Kalstein you can make the purchase of viscometers at advantageous prices. For more detailed information, visit HERE