![]() Most instruments are used to measure the particle size distribution, implying an interest in the width or breadth of the distribution. The mean value is flanked by 1 and 2 standard deviation points. For the denominator take the geometric D i to the third power multiplied by the percent in that channel, summed over all channels.įigure 3: A normal distribution. For the numerator take the geometric D i to the fourth power multiplied by the percent in that channel, summed over all channels. The D i value for each channel is the geometric mean, the square root of upper x lower diameters. The best way to think about this calculation is to think of a histogram table showing the upper and lower limits of n size channels along with the percent within this channel. The equation for defining the volume mean is shown below. Laser diffraction results are reported on a volume basis, so the volume mean can be used to define the central point although the median is more frequently used than the mean when using this technique. 3) for an explanation of number, surface, and volume distributions. There are multiple definitions for mean because the mean value is associated with the basis of the distribution calculation (number, surface, volume). The various mean calculations are defined in several standard documents (ref.1,2). Mean is a calculated value similar to the concept of average. If you would like any more information about our particle size analysis instrumentation, please do not hesitate to contact us.Figure 1: Symmetric distribution where mean=median=mode Laser Diffraction Particle Size Analysis from Meritics Meritics is a leading supplier of particle analysis equipment for numerous fields of research, with a detailed understanding of new and emerging equipment for materials characterization on both micro- and macro-scales. Laser diffraction particle size analyzers, such as the LS 13 320 XR, are equipped to perform particle analysis for a broad range of sectors and disciplines, including: The LS 13 320 XR laser diffraction particle analyzer, for example, is equipped with enhanced polarization intensity differential scattering (PIDS) technology to improve scattered light detection for submicron particles, enabling an enhanced dynamic range of 10nm – 3,000μm. Diffraction pattern imagery is then generated by the particle size analyzer, with additional functionalities available for high-end laser diffraction instruments. These are directed into a sample towards a highly-sensitive detector fitted with robust bandpass filters capable of discriminating between the incident light source and diffracted light. The wavelengths of the incident light can vary from blue light at a wavelength of 475 nm, to near infrared at a wavelength of 900 nm. This theoretical foundation supports the intuitive hardware of a laser diffraction particle analyzer, which operates using an incident laser beam generated by a diode or tungsten lamps fitted with robust bandpass filters. Conventionally, laser diffraction particle size analysis relied on either generalized Fraunhofer diffraction or predefined Mie scattering information, but particle analyzers are increasingly enabled for full implementation of both theories to provide a more dynamic sampling range. Mie theory refers to a series of mathematical computations, but is generally applied to analyze submicron-sized particles that are smaller than the wavelengths of the incident light. In basic terminology, Fraunhofer diffraction suggests that the angle and intensity of light scattered from a particle is proportional to its geometric parameters. These can be used to approximate the intensity of scattered light, the scattering angle, and thus the particle’s geometric parameters. These calculations are used to determine the diffraction patterns of different particle sizes prior to performing actual measurements. This article will explore laser diffraction particle size analysis in more detail: Laser Diffraction Working Principle Laser diffraction particle size analysis operates on two primary optical theories: Fraunhofer diffraction and Mie scattering. This process can be used to measure solid and liquid particles, including solids dispersed or dissolved in a solution. Laser diffraction particle size analysis is a common technique applied to measure particles ranging from nanometer (nm) to millimeter dimensions, informing the geometrical characterization of particles in a sample. ![]() These methodologies include dynamic light scattering (DLS), permeability measurements, and laser diffraction particle size analysis. ![]() Outlining Laser Diffraction Particle Size Analysis Multiple technologies and methods exist for performing particle size analysis with the intention of testing the mechanical, chemical, or biophysical properties of a sample. ![]()
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