Holmarc's Apparatus for Determination of Particle size (Model No: HOED-D-05) is a simple equipment. When laser light passes through the particles, diffraction occurs and pattern is observed on a screen or wall at a distance. Kinematic adjustment of the laser head can be used to direct laser beam to the required spot on the glass slide with particle.
The device consists of a diode laser held on a kinematic mount and a glass slide fixed on the slide holder. The particles, of which diameters are to be determined are sprinkled on the glass slide.
Both the laser and slide holder are fixed on rail carriers which are held on a graduated solid aluminum rail. Particle size influences many properties of particulate materials and is a valuable indicator of quality and performance. The size and shape of powders influences it’s diffraction characteristics. The diffraction pattern of larger particles will have less distance between the first dark ring and the central maximum than that of smaller ones. There are several industrial and research applications where measurement of particle size is important.
The laser diffraction technique is based on the fact that the spatial distribution of scattered light is a function of the particle size of the sample
The diffraction equation is,
D = 1.22 l λ / Sin θ
Where D is the size of the particle, l is the distance between the particle and the screen, λ is the wavelength of light used and θ is the angle of diffraction.
|Classification of Powders||Particle Size (μm)|
|Very Coarse||> 1000|
|Coarse||355 - 1000|
|Moderately Fine||180 - 355|
|Fine||125 - 180|
|Very Fine||90 - 125|