Method and device for the simultaneous determination of a kinematic viscosity and surface tension of transparent fluids with the aid of the surfaces of light scattering (surface light scattering, sls)

摘要

The determination of viscosity and surface tension of fluids with the aid of the method of surface light scattering is, according to prior art, insufficiently possible. It is possible, for example, to find systematic variations of several per cent in comparison with recognised values when analysing well-known reference fluids with the method of surface light scattering. According to the inventive method, it is possible for the first time to use the surface light scattering method to determine simultaneously the viscosity and surface tension of fluids in a highly accurate manner without having to perform a calibration process. The starting point for the inventive method is a special embodiment of surface light scattering. The scattered light is analysed for transparent fluids in a forwards direction and analysed for non-transparent fluids in a backwards direction. On the basis of high signal intensities, the advantage of the method used for transparent fluids, in comparison with the conventional form of measuring technique used in backscattering, is that it is relatively easy, and requires no additional effort for signal optimisation, to select a sufficiently high scatter vector range in order to avoid instrument-related influences. Detection is carried out in an alternately homodyne or heterodyne manner. According to the inventive method, in order to determine surface tension and viscosity in a highly accurate manner, an exact digital resolution of the dispersion relation of surface waves is performed during the evaluation of data.