Digital Image Processing
In many applications particle size and shape information provides an important process and quality indicator. Based on digital image processing the CAMSIZER / CAMSIZER XT is immediately able to analyze the particle shape of the sample material in a detailed and representative manner. The advantages of the full-frame cameras used in the CAMSIZER / CAMSIZER XT for the distortion-free recording of all the particle projections is particularly obvious when measuring the particle shape and size.
The patented measuring setup – two digital cameras as an adaptive measuring unit – improves and optimizes particle analysis by digital image processing. Thus, it is possible to measure a wide range of particles from 1 µm to 30 mm extremely accurately, without having to switch measuring ranges or make adjustments.
The sample is fed in from the feed channel so that all particles fall through the measurement field. During the measurement procedure the two digital cameras (CCD) perform different tasks. The basic camera (CAM-B) records large particles, the zoom camera (CAM-Z) records the small ones. The contact-free optical measurement is carried out in real time and simultaneously obtains all the required information about particle size and particle shape.
Particle shape analysis and its applications
As a result of the high information content obtained from the digital images made during the measurement procedure, the particle projections can be evaluated in many different ways. Depending on the application, the CAMSIZER / CAMSIZER XT measures the particle projections according to various areas, circumferences and lengths by making a high-resolution scan of each individual particle in 64 directions. The results obtained can be, for example:
- chord length
- width/length aspect ratio
- Martin diameter
- Feret diameter
- straight length
Examples of particle shape analysis applications are:
- determination of fractions of mixture components (see graph)
e.g. of ion exchangers and active charcoal for water filters as well as glass beads and corundum in colors used for road markings
- determination of edge-holding property (angularity)
e.g. quality assessment of abrasives as a preliminary to further processing
- analysis of the broken fraction of granules
e.g. as a replacement for time-consuming breakage studies on the rolling properties of granules
- determination of width/length distribution of extrudates (“rods”)
e.g. determining the volumetric density of catalysts in reactor containers
- prediction of flow and compacting behavior
e.g. press-molding powders and granules to form tablets
Wide dynamic measuring range
Thanks to the patented two-camera-principle the CAMSIZER XT offers both excellent resolution and reliable detection of oversized particles with exceedingly good statistics. The example above compares two differently ground coffee samples with similar d50 values. The red curve represents a more homogenous sample with a narrow size distribution, whereas the green curve shows both more fines and more oversized particles.
The large field of view of the patented 2 camera system ensures that the full width of the particle beam is analyzed. This results in an excellent repeatability, even with very small amounts of sample. The graphic above shows five repeated measurements of a trimodal mixture of glass beads in the size range from 50 μm to 1.5 mm. Each measurement took approximately 2.5 minutes, with more than 5.000.000 detected particles.