Leeds and Northrup Microtrac

Leeds and Northrup Microtrac Ultrafme Particle Analyzer (VPA) uses the controlled reference method, using a sapphire tipped waveguide that collects back-scattered light within 100 pm of probe tip, to cover the size range 0.003 to 6.5 pm. 

Leeds and Northrup Microtrac Series 9200 Ultrafme Particle Analyzer Model 9230 operates in the 0.003 pm to 6 pm size range (Figure 10.19) and gives reproducible results in the concentration range 2 to 2000 ppm... 

The first of the modem diffraction based instruments for particle size analysis is probably that produced by CILAS (France). This is described by Comillautf and used a moveable mask to detect light scattered at different angles. The Leeds and Northrup Microtrac dates from 1976, this was described by Wiess and Frock . 

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