Search: viscosity measurement

The amount of time required for a special ball to fall while sinking through a glass tube filled with a test fluid between two marks is measured. The precision of this method is increased if the time is measured using a photoelectric beam to an accuracy of 0.01 s, rather than manually with a stop watch.

The measuring principle of the Lovis micro viscometer is based on the Höppler “Falling Ball Viscometer”. A ball of known dimension rolls through a closed capillary, which is inclined at a defined angle. Inductive sensors detect the ball along an exactly defined distance of approximately 100 mm or 25 mm. The rolling time is measured by the instrument and is used for dynamic viscosity calculation. The temperature is precisely regulated by thermoelectric Peltier elements and checked by a Pt-100 temperature sensor. A temperature accuracy of ±0.02 °C and repeatability of ±0.005 °C can be reached.

These devices measure the torque transferred through a cylindrical liquid layer between a stationary and a rotating disc. This method also allows changes in viscosity, which occur through the action of α-amylase on starch, to be automatically recorded by a plotter or PC.

The viscosity of the Congress wort primarily provides information regarding the cytolytic degradation of the malt. A better indicator of this, however, is the viscosity of the isothermal 65 °C mash. The Congress mash method consists of a longer β-glucan rest, the 45 °C rest, after which the mash is immediately heated to 70 °C, and thus excluding an adequate β-glucan solubilase rest. (R-206.00.002 Kongressmaischverfahren). Therefore, the degree of cytolytic degradation in different malts cannot be satisfactorily quantified. The isothermal 65 °C mash serves to reveal these differences more starkly through the high temperature at mashing-in and the intense β-glucan solubilase rest (R-207.00.002 Isotherme 65-°C-Maische). Likewise, it provides a good indication of the expected duration of the lautering process.

The time required for a volumetrically defined amount of fluid (the volume between two marks on the tube of the viscometer) to flow through a capillary of a defined length is measured.

Definition:

1 square meter per second is the kinematic viscosity of a homogenous fluid with a dynamic viscosity of 1 Pa × s and a density 1 kg/m³.

The unit for expressing kinematic viscosity (the relationship of viscosity to density = viscoplasticity) is 1 m²/s = 10⁶ mm²/s

If a beam of light strikes a particle with a diameter larger than the wavelength of the light, the light is scattered. In measuring turbidity during the lautering process, it has been shown that only light scattered in a forward direction should be measured to achieve a meaningful correlation between the concentration of solids and the measurement value. Measurements performed at a 90° angle do not correlate with the amount of solids in wort due to particle size and dependence on color. Measurements performed at a 12° angle not only measure the amount of scattered light, but also the absorption (light transmission). The utilization of dual light beams eliminates disruptive factors, such as color, the age of the lamp and window fouling.

Measuring the turbidity during lautering serves to monitor and control lauter bed cutting operations and recirculation of the turbid wort as well as the quality of milling and mashing processes. There is a direct relationship between the turbidity profile during lautering, the results of the photometric iodine test and the solids content of the lauter wort.