Principle of Measurement

Principle of High-Concentration Sample Measurement by the Laser Diffraction/Scattering Method

  • The laser diffraction/scattering method is the mainstream means used for measuring particle size distribution.
  • The basic approach to this method is exactly the same as measurement using a regular flow cell and batch cell.
  • The sample is held between two thin sheets of glass (glass slides), and laser light is irradiated on the sample to measure its particle size distribution.

Principle of Measurement

If a standard flow cell or batch cell is used to measure a sample at a high concentration, the long light path results in multiple scattering and this makes it impossible to obtain accurate measurements.

Measurement is possible by simply holding the high-concentration sample particles to be measured between two glass slides. This significantly shortens the length of the light path, avoids the negative effects of multiple scattering and makes accurate measurement possible. 

Shortening the light path to avoid multiple scattering

Measurement with a Standard Flow Cell

Measurement with a Standard Flow Cell or Batch Cell

Sample Held between

Sample Held between Two Glass Slides

Detection of side scattered light

Also, placing the sample so that it is diagonal to the optical axis makes it possible to detect side scattered light. 

Applying particle size calculations to this and also to forward and back scattered light enables measurement of high-concentration samples in sub-micron region. (Side and back sensors are not available for the SALD-300V and SALD-200V ER.) 

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