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Intro To Rotational Viscometers With HAAKE 550

Updated on February 11, 2012

Many Food Items Have A Viscometer Tailored Viscosity

photo by iwouldstay on Flickr
photo by iwouldstay on Flickr

Rheology With Quality Control Viscometers

Quality control across a broad range of specialty fields relies on rheology and special tools of the trade. Quality control specialists must monitor the product flow in order to determine if it meets rigorous criteria and standards. Of the various tools available for the task, one of the most useful and best return on investment is a digital rotational viscometer. Food rheologists will use a digital rotational viscometer to measure the viscosity of condiments such as gourmet yellow mustard at room temperature in order to insure the end consumer experiences just the right texture as he coats his Pink's hot dog. On the other end of the spectrum, a quality control digital rotational viscometer might be used by a government consulting company to measure shear rate and other various properties of a municipal sewage sludge and coal water slurry blend in order to best manipulate the waste product. Engineers and commercial as well as university laboratories rely on a viscometer such as the HAAKE 550 by Thermo Scientific to do much of their rheology work.

A quality viscometer, such as the HAAKE 550 viscotester model, is a delicate precision machine. It is defined by a step motor which does much of the work. The 550 has 100 predefined speed levels in the range of .5 revolutions per minute (rpm) to 800 rpm. Viscosity measurements can be taken according to well defined DIN53019 or the International Organization for Standardization specification ISO3219. These are detailed specifications for calculating viscosity and their associated flow curves with the assistance of a rotational viscometer with either cone and plate or coaxial cylinder geometries. The Haake 550 model of viscometer is capable of being computer-controlled from a laptop or other system and can make temperature readings. An optional circulator accessory is available to maintain a constant temperature or work a temperature program. Rotational viscometers utilize the physical principle that a sensor turning in a fluid will require a greater angular torque to make rotations at a constant speed as the viscosity of the substance being measured is increased. The 550 is compatible with the cone and plate sensor to measure shear stress and shear rate in order to compute viscosity. Other available sensor types are the coaxial cylinder, immersion sensors, relative sensors and special immersion sensors. The various attachments provide a great level of precision according to the various industry standards: DIN 53018, ISO 3219, DIN 53019, and ISO 2555. There is an RS-232 printer interface for printing the various readings for later perusal. Measurements are made manually, computer-controlled, or programmed in the viscometer and CD-method yield point determination is also an incorporated feature. The rotational viscometer will work at a temperature range of around -20 degrees Celsius to 100 degrees Celsius and usually calculate a viscosity and flow curve within a minute. It is an industry leading device that no quality control lab should be without. No need to settle for the old u-tube viscometers or the falling sphere variety.

Rotational viscometers ("cup and bob") like the Haake 550 are distinguished as either being the Couette or the Searle variety. Searle rotational viscometers utilize a rotating cylinder inside a stationary outer cylinder. The Haake is the latter and preferred Searle variety. Whether running tests and measurements for the food industry, cosmetic industry, pharmaceutical industry, paint and chemical industry, or any other area where reliable viscosity measurements are required, the Haake 550 is the choice of many professionals. Thermo Scientific also has some other de facto industry standard viscometers in their line of products.



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