Viscometers measure viscosity, the resistance of fluids to flow or stress. In common terms, viscosity is related to a fluid’s “thickness”—a physical property of great interest to manufacturers of liquids, slurries, and pastes. Viscosity is a critical characteristic of foods (e.g., dairy, honey, syrup, soft drinks), paints, cleaners, adhesives, polymers, fuel oils, and pharmaceuticals. Many industries use viscosity as an endpoint in the manufacture of liquid-formulated products.
Top 6 Questions You Should Ask When Buying a Viscometer
1. What kind of temperature control and spindle rotational speed control does the instrument offer? Temperature is critical, since viscosity generally rises as a fluid cools. Spindle rotation may also affect viscosity.
2. What range of accessories (ex. sample holders) does the company offer for the instrument?
3. How easy to use is the viscometer? Since most users nowadays aren’t experts, an easy-to-use instrument is probably the best fit for most labs.
4. What are the sizes of the samples you’ll be working with? This may be an issue when analyzing very expensive materials such as drugs or proteins and cost of ownership is also important for high-volume applications.
5. What is the instrument’s measurement range? If you’re analyzing petroleum, from crude oil to gasoline, do you want to change out the capillary for each measurement, or use something that works all the way through?
6. What kind of service and support does the company provide?
Fast Facts on Viscometers
• Viscometers range in cost from about $100 for simple mechanical viscometers to $15,000 automated instruments. Rheometers, which measure viscosity and related properties, may cost as much as $200,000.
• Viscometry is an old technique, as illustrated by the persistence of mechanical viscometers. But while manufacturers continue to fine-tune more-sophisticated electromechanical rotational viscometers, the underlying technology hasn’t changed much.
• Twenty years ago, most viscometers users had an academic specialization in viscometry or rheology. Today the specialists are gone and users tend to be generalists.
• Viscosity measurements are usually conducted on dilute solutions and at varying concentrations. Measurement of the viscosity of polymer solutions at different strengths, for example, provides estimates of secondary properties such as intrinsic viscosity, molecular weight, and chain length.
• Rheometers are closely related to viscometers in that they measure viscosity and yield stress. Where viscometers determine a fluid’s “thickness” under native conditions, rheometers measure it as a function of applied shear or stress.
Recently Released Viscometers
Lovis 2000 M/ME
• Measures the rolling time of a ball through transparent and opaque liquids according to Hoeppler’s falling ball principle
• Measurement requires only 400 μL sample volume
• Compact and economical, and saves space in the lab
• Results are given as relative, kinematic or dynamic viscosity
• Provides first results after only 30 seconds
• Combines traditional Brookfield accuracy, reliability and versatility with the advantages of continuous sensing, temperature measurement and data output to PC or printer
• When controlled by PC, the DV-II+ PRO becomes a Rheometer with variable speed capability from 0.01 to 200 rpm
• Continuous display of: Viscosity (cP or mPa·s), Temperature (°C or °F), Shear Rate
E chip for m-VROC Viscometer
• Expands the range of viscosity measurements with significantly greater shear rates
• Mounted on the m-VROC viscometer, attains 2,000,000 1/s measurements of water-like viscosity or 1,000,000 1/s for various injket inks (~ 4 mPas)
• Eliminates the onset of early turbulence • Maintains the laminar flow at high shear rates, producing accurate measurements
• Directly measures the relative viscosity of dilute polymer solutions using advanced pressure sensing technology
• Fast, accurate and precise as well as self-calibrating and self-cleaning
• Several automation and sample preparation options give flexibility for system configuration to meet application or budgetary requirements
• Features robust construction and reliability