Question

In a DVE Viscometer experiment, what does the Torque percentage shown on the screen signify?

Course: Fluid Power Technology

Answer 1

Viscosity is a measure of a fluid’s resistance to flow. The DVE Viscometer measures fluid viscosity at given shear rates. The principle of operation of the DVE is to rotate a spindle (which is immersed in the test fluid through a calibrated spring. The viscous drag of the fluid against the spindle is measured by the spring deflection. Spring deflection is measured with a rotary transducer which provides a torque signal. The measurement range of a DVE (in centipoise or milliPascal seconds) is determined by the rotational speed of the spindle, the size, and shape of the spindle, the container in which the spindle is rotating, and the full-scale torque of the calibrated spring.

In taking viscosity measurements with the Dial Viscometer there is a consideration which pertains to the low viscosity limit of effective measurement.

1). Viscosity measurements should be accepted within the equivalent % Torque Range from 10% to 100% for any combination of spindle/speed rotation.

The above consideration has to do with the precision of the instrument. All Dial Viscometers have a full-scale range precision of ± 1% for any spindle/speed combination. We always discourage taking readings below 10% of range because the potential viscosity error of ± 1% is a relatively high number compared to the instrument reading.

In addition to that, one of the important thing about torque % reading is that, If your first reading is over 100% try a lower speed or a smaller spindle as the DVE gives indications for out of specification or out of range operation when torque % readings exceed 100.0% (over range). Similarly, if your reading is under 10% try a higher speed or a larger spindle.