Test method A: Determination of the apparent viscosity at 25 ☌ at a certain speed. In the next chapters, you will learn how to measure the viscosity of different chemical samples with such a spring-type viscometer. In case of low-viscous substances, the spring needs to be sufficiently sensitive, whereas for samples in the high viscosity range, a more robust spring is required. Different spring-types of rotational viscometers allow measuring substances from low to high viscosity. Optical sensors detect the deflection and, as a result, we get the viscosity of the sample. The rotation (torque) of the spindle deflects the spring.
A spring connects the motor of the viscometer and the spindle. The sample in the cup follows this movement and in further consequence the torque (force) required for turning the spindle against the fluid’s viscous forces is measured. The speed on the viscometer is preset and the spindle starts to rotate. A typical rotational viscometer used for quality control measures the viscosity according to the “ Searle principle”.Ī cup is matched with a so-called spindle that is placed in the sample. The system makes use of a distinctive single position auto-sampling that offers integrated sample heating of up to 200 ✬ and utilizes a preheated solvent to efficiently clean the viscometer tube.Before we get started with how to measure viscous materials, let’s have a quick look at how a rotational viscometer works.
Measurements are conducted with excellent accuracy and within acceptable temperature stability with the help of sophisticated temperature control. Fully opaque fluids without any challenges or limitations can be detected using these tubes, and the need to use reverse-flow tubes is eliminated, thanks to specially designed thermal sensors. The well-known and tested Ubbelohde design serves as the foundation for viscometer tubes. The BitUVisc is a member of the U-Visc family of completely automatic viscometer systems from Omnitek. This automatic kinematic viscometer model fully complies with ASTM D445 and D2170 and was specifically designed to address sample types that pose a great threat to automatic sampling, measurement, and cleaning as a result of their viscosity and high pour point. With Omnitek BitUVisc it is possible to test samples with high viscosities what is considered "extreme samples" for the kinematic viscometer market. Testing highly viscous samples with an automatic ASTM D445 viscometer
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