Rheometers measure the characteristics of viscous fluids. The devices test by way of dynamic oscillation, or they measure normal force, stress jump or the effects of shear. The fluids, themselves, that rheometers test are of two types. Many pure oils and solvents keep the same viscosity regardless of the level of shear. However, the properties of some viscous fluids and many mixed fluids change as the shear rate increases.
Each type of rheometer employs a different scientific principle to produce a measurement. Less common types include needle rheometers and positive displacement rheometers, as well as various types of extensional rheometers. Here are the three common types of rheometers:
1. Rotational rheometers measure viscosity as proportional to the torque on a submerged, rotating spindle.
2. Capillary rheometers measure kinematic viscosity based on the time it takes for a liquid to pass through a tiny, controlled aperture. Both capillary diameter and pressure adjust to regulate shear on these rheometers.
3. Falling ball rheometers measure viscosity as proportional to the time it takes for a ball to fall through the tested liquid.
Shop quality rheometer manufacturers and rheometer sellers that have wide selectionsThe bigger the rheometer selection, the higher the chance of finding the right rheometer for your applications.
Find rheometer distributors that sell capillary rheometersCapillary rheometers are sometimes more complex or precise than rotational or falling ball industrial rheometers. When buying capillary rheometers, take a look at a few more websites to make sure you know what you're buying and get the best machine for your needs.
Buy extensional rheometers from rheometer suppliersBesides common shear rheometers, there are also much rarer extensional rheometers. One example is a string rheometer: after placing the liquid between two solid surfaces, one of the surfaces is lifted and the rheometer measures the force of the liquid on the stationary surface.
- Viscometers take similar measurements as rheometers, but they can only measure a single value of viscosity. For applicable viscous fluids, rheometers measure a more complex group of properties called the "rheology."