kapillärviskosimeter

A capillary viscometer, known in Swedish as a kapillärviskosimeter, is a device used to measure the dynamic viscosity of a fluid. It operates on the principle that the time it takes for a known volume of liquid to flow through a narrow capillary tube under gravity is proportional to its viscosity. The higher the viscosity, the longer the flow time.

The most common type is the Ostwald viscometer, which consists of a U-shaped glass tube with two bulbs and a capillary section. The fluid is introduced into the larger bulb, and by tilting the viscometer, the liquid is drawn up into the upper bulb above a calibration mark. When the viscometer is returned to a vertical position, the liquid flows down through the capillary. The time taken for the liquid level to pass between two etched marks on the tube is measured.

Another variation is the Ubbelohde viscometer, which features a third arm that allows for measurements independent of the total volume of liquid. This design is advantageous as it minimizes errors due to capillary end effects.

The kinematic viscosity of the fluid can be calculated from the measured flow time and the viscometer's calibration constant. To determine dynamic viscosity, the kinematic viscosity is multiplied by the fluid's density. Capillary viscometers are widely used in various industries, including chemistry, pharmaceuticals, and food processing, for quality control and research purposes. They are relatively simple, inexpensive, and offer good accuracy for many applications, particularly for Newtonian fluids. Temperature control is crucial as viscosity is highly dependent on temperature.