Microtrac S3500 Technology |
Tri-Laser Diffraction Technolology The TRI-LASER Diffraction System developed by MICROTRAC allows light scattering measurements to be made from the forward low angle region to almost the entire angular spectrum (approximately zero to 160 degrees). It does so by a combination of three lasers and two detector arrays, all in fixed positions. The primary laser (onaxis) produces scatter from nearly on-axis to about 60 degrees, detected by a forward array and a high-angle array, both of which have logarithmic spacing of the detector segments. The second laser (off-axis) is positioned to produce scatter beyond the 60 degree level which is detected using the same detector arrays. The third laser (off-axis) is positioned to produce backscatter, again using the same detector arrays. This technique effectively multiplies the number of sensors that are available for detection of scattered light. During a measurement cycle, Laser 1 is switched on while Lasers 2 and 3 remain inactivated. The sample to be measured scatters light in an angular pattern depending on the material size. The scattered light from Laser 1 is detected by the on axis, forward detector and the off axis, high angle detector. Laser 1 is then switched off and Laser 2 is activated. Laser 2 is directed at the sample at a different angle of incidence providing a different optical axis. Light scattered by the sample is detected by the same fixed detectors. Laser 2 is then switched off and Laser 3 is activated. Again the angle of incidence and optical axis is different. In this case the fixed detectors detect light that is back–scattered by the sample. The resultant scattered light information from all three lasers is combined to generate particle size distributions with unsurpassed resolution. Tri laser diffraction technology is proprietary and is patented by Microtrac. Turbotrac: How it works This combination provides unparalleled dispersion of dry powders for use in the pharmaceutical, biotech, food and beverage, ceramics, cement, metal powders and oxides,abrasives and general materials processing industries. Turbotrac: Wet-Dry Data Comparison The Turbotrac eductor system provides superb dispersion of dry powders through its unique Turbojet feature. Four different Aluminium Oxide samples were run in the Microtrac S3500 Particle Size Analyser. The samples were run wet in the Sample Dispersion Controller (SDC) and dry in the Turbotrac Dry Powder Dispersion System. The samples had mean volume particle sizes of 5, 10, 18 and 65 microns respectively. As shown in the graphic, the dry Turbotrac data shows excellent agreement with the corresponding wet analyses. mie theory and fraunhofer apptoximation |
A compressed air stream is used both as a carrier and a dispersing agent for the dry powder. The air stream is connected to the eductor block. The Turbotrac eductor nozzle incorporates a series of TURBOJETS set at multiple angles to the sample flow. This arrangement creates a number of mini-vortices within the sample flow which disperse the material. The eductor gap can be adjusted by raising or lowering the eductor nozzle resulting in increased or decreased sample dispersion. Air pressure settings and eductor gap settings are determined on the basis of the degree of dispersion required and the friability of the material being measured. The measured material is then collected by a vacuum system.
