Magnetic needle rheometer

Abstract
A magnetic needle rheometer has been developed. Its principle of operation is identical to the one of a magnetic sphere rheometer, except that the magnetic sphere is replaced by a magnetic needle. Important advantages result from this modification: (i) The lower limit of measurableviscosities (≂0.3 cP) becomes several orders of magnitude lower; (ii) analytic expressions for shear rate and shear stress have been derived; (iii) the needle can be covered by using a quartz capillary tubing, which is chemically much more inert than any magnetic material; (iv) precise determinations (±0.1%) of fluid densities, especially at high temperatures, are possible; and (v) the cost of manufacturing magnetic needles is much lower than for magnetic spheres. The device has been tested with viscosity standards.

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