Model HTD13145 rotational viscometers are direct-reading instruments which are available in six-speed and twelve-speed designs for use on either 50Hz or 60Hz electrical power. The power source is 100～240V. All models are fitted with a standard transformer.

   Model HTD13145 rotational viscometers are coaxial cylinder rotational viscometer. In this viscometer, the test fluid is contained in the annular space (shear gap) between an outer cylinder and the bob (inner cylinder).

    Viscosity measurements are made when the outer cylinder, rotating at a known velocity, causes a viscous drag exerted by the fluid. This drag creates a torque on the bob, which is transmitted to a precision spring where its deflection is measured. Compare measurements with test conditions and instrument constants. Model HTD13145/13185 rotational viscometers are used in research and production. These viscometers are used for evaluating the rheological properties of fluids.

    Viscosity measured by a coaxial cylinder rotational viscometer. Model HTD13145, is a measure of the shear stress caused by a given shear rate. This relationship is a linear function for Newtonian fluids (i.e., a plot of shear stress vs. shear stress vs. shear rate is a straight line).

    The instrument is designed so that the viscosity in centipoise (or millipascal second) of a Newtonian fluid is indicated on the dial with the standard rotor, bob, and torsion spring operating at 300 rpm. Viscosities at other test speeds may be measured by using multipliers of the dial reading. A simple calculation that closely approximates the viscosity of a pseudo-plastic fluid, such as a drilling fluid.

   The shear rate may be changed by changing the rotor speed and rotor-bob combination. Various torsion springs are available and are easily interchanged in order to broaden shear stress ranges and allow viscosity measurements in a variety of fluids.