Viscometers

An Ubbelohde viscometer uses a suspended level. The result does not depend on how much sample you fill in, and you can dilute in the tube. That makes it the usual choice for standard methods, for example the calibrated Ubbelohde viscometer, 5–50 mm²/s. A Cannon-Fenske is compact and robust for routine work. Its reverse-flow version keeps the meniscus visible in dark or opaque liquids such as used oils, as with the calibrated reverse-flow Cannon-Fenske viscometer, 3–15 mm²/s. A micro-Ostwald needs only a small sample volume, such as the micro-Ostwald viscometer for automatic measurement.

The capillary number sets the measuring range in mm²/s. A narrow capillary suits thin liquids such as solvents, and a wide one suits oils and more viscous samples. Pick the number whose range covers your expected viscosity, ideally in the middle of the range, so the flow time is long enough to time accurately. Each product page states the range and constant, for example the Ubbelohde viscometer for 5–50 mm²/s. Your test method may also prescribe a minimum flow time. Unsure? Send us your sample type at sales@luminixhealth.com.

A calibrated viscometer comes with its own measured constant. You multiply the flow time by that constant and get the kinematic viscosity directly, which is what accredited methods and audits expect. One example is the calibrated Ubbelohde viscometer, which has its constant printed on the body. A non-calibrated version, such as the Ubbelohde viscometer, 5–50 mm²/s, not calibrated, only has a nominal constant. You then have to calibrate it yourself against a reference oil. That works well for comparative measurements and teaching. If you need documented traceability, you can also order a calibration certificate for viscometers at 25 °C.

Use a glass capillary viscometer for Newtonian liquids, whose viscosity does not change with flow rate. Examples are oils, solvents and dilute solutions. It gives you the kinematic viscosity with high precision, often as required by standard methods. Pastes, gels, creams, paints and suspensions are usually non-Newtonian, so their viscosity depends on shear. For those, a rotational viscometer measures the dynamic viscosity at a defined speed and temperature, for example the rotational viscometer package with heating and cooling. For more instruments and accessories, see density and viscosity measurement. Not sure which your sample needs? Write to sales@luminixhealth.com.

A capillary viscometer times the flow of a liquid through a tube. A rotational viscometer twists a spindle in the liquid. Both need a stated temperature. Kinematic and dynamic viscosity are different numbers. The capillary size has to put the flow time in the range the method allows.

Density is mass divided by volume. A hydrometer floats at a depth that depends on the density of the liquid. A pycnometer is a vessel of known volume that is weighed full. Viscosity is the resistance to flow. A capillary viscometer times how long a volume takes to fall through a tube. Both measurements need a stated temperature, because liquids change density and viscosity as they warm. The units trace to the BIPM and to NIST.

This shelf belongs to Density & viscosity measurement, inside Lab instruments. Luminix Health distributes this range for laboratory use.

The neighbouring shelves are Hydrometers and Density meters & pycnometers. The category above this shelf is Density & viscosity measurement.

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