Selecting a Viscometer on Amazon.com
A viscometer, sometimes called a viscosimeter, is an instrument used to measure fluid viscosity, which is a measure of the resistance of a fluid to flow freely. Viscosity is usually expressed as units of poise, centipoise, pascal seconds, and millipascal seconds. Viscosity measurements are used in quality and safety inspections in oil and gas, food and beverage, paint and ink, and pharmaceutical and cosmetic industries.
Viscometers have three basic forms: rotational, capillary, and falling ball. A rotational viscometer, sometimes called a paddle or Brookfield viscometer, uses rotational shear to measure viscosity and has a paddle or other stirring mechanism that measures the force required to stir a fluid. Rotational viscometers can be used to test the viscosity of Newtonian and non-Newtonian fluids. A capillary viscometer, sometimes called a U-tube viscometer, uses capillary action to measure the viscosity of Newtonian fluids. Benefits include cost effectiveness, ease of use, portability, and small sample size requirements. The simplest type is the falling ball viscometer, sometimes called a rolling ball or Hoppler viscometer. It uses gravity to measure the time it takes for a ball to fall through a Newtonian fluid. After three measurements are taken, the averaged results are used to calculate viscosity. Newtonian fluids don't change viscosity when subjected to force, whereas non-Newtonian fluids change viscosity when subjected to force or shaking.
Some considerations when selecting a viscometer include the viscosity of fluid being tested; whether the meter is for field or lab use; which standards are being tested; the measurement units and rotational speed (rpm) required; and whether features such as data logging, or analog or digital functionality, are desired. Low viscosity fluids include dairy products, inks, and juices; medium viscosity fluids include asphalt, ceramics, and pulp; and high viscosity fluids include chocolate, epoxies, paste, sealants, and tar. Most viscometers require occasional calibration using a viscometer standard and are designed to test one viscosity range, though some test more. Some viscometers are manufactured to meet industry or governmental standards, including Ingress Protection (IP), National Institute of Standards and Technology (NIST), International Standards Organization (ISO), and ASTM International (formerly American Society for Testing and Materials).