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![]() For non-spherical particles, this usually results in a wider distribution being output than in image analysis.ĭynamic Light Scattering (DLS) is a method for particle measurement which is particularly suitable for the analysis of nanoparticles. All scattered light data are referred to a spherical model, they are so-called equivalent diameters. Particle measurement by laser diffraction cannot distinguish between length and width. This is done either via the Mie theory, for which the refractive index of the particles must be known, or via the Fraunhofer approximation, which, however, is only usefully applicable for larger particles. It is therefore a superposition of angle-dependent scattered light intensities, from which the contributions of the different particle sizes must be calculated. This means that the measurement signal is generated simultaneously by many particles of different sizes. While in imaging techniques each recorded particle represents a measurement event and is included in the overall result, scattered light or diffraction analysis are so-called ensemble measurement techniques. There are some fundamental differences in particle measurement by laser diffraction compared to image analysis. Depending on the problem, a suitable size definition is used for the particle measurement. Furthermore, the diameter of an equal area circle can be defined as the size of the particle projection. smallest inner diameter, X c min) or Martin diameter (area bisector). Alternatives would be chord dimensions (e.g. The largest distance would be the Feret length (X Fe max), the smallest the Feret width (X Fe min). These are determined as one would with a caliper: by measuring the distance between parallel tangents. Feret diameters, for example, can be specified to describe the various dimensions. By analyzing individual particle images, both shape and size are measured. With the static method, the particles are at rest during the measurement (as with a microscope) with dynamic image analysis, moving particles are analyzed, either in a liquid, in an air stream or in free fall. A distinction is made between particle measurement with Dynamic Image Analysis and Static Image Analysis. Imaging techniques for particle measurement offer a number of advantages. Our experts will be happy to assist finding the right solution for your application. With an extensive understanding of the strengths and weaknesses of each method, Microtrac offers an unrivalled product range of technologies for particle measurement. Since the result of a particle measurement depends on how "size" is defined, there is often confusion in the interpretation of the measurement results. ![]() In all possible measuring directions, the same result is obtained.įor non-spherical particles, however, the result of the particle measurement depends both on the orientation of the particles during the measurement process and on the peculiarities of the method used. ![]() Particle measurement with these different methods leads to different results, because the "size" of particles can be interpreted quite differently: Size is unambiguously defined only for spherical particles (diameter = particle size). ![]() These include laser diffraction, image analysis, dynamic light scattering as well as sieve analysis. Different particle measurement methods for the characterization of particle size distributions in granulates, bulk materials, powders and suspensions exist.
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