We normally start with the size range of interest and samples or materials you want to measure the size of. If your sample is in the micron to mm size range (e.g. 1 um to 1000 um or more) we would normally look at laser diffraction as the measurement technology.
Examples of such systems are the Malvern Mastersizer 3000E or 3000. Laser diffraction is the widest used modern sizing technique today. It is used for everyday materials like cement and paint to chocolate and milk and many other materials.
If you sample is sub-micron in size or in the nanometer range (say 0.3 nm to 6 -9 um) there is several technologies that might be suitable. One of the most popular systems the Zetasizer Nano uses a technique called dynamic light scattering to determine the particle size of anything from nano particles, colloids , proteins to polymers.
Other techniques that might also be appropriate are nanoparticle tracking analysis (NTA) as used in the Nanosight NS300. It offers specific advantages for samples at low concentration as the technique track individual particles. Malvern Instruments recently released an application eBook with over a 1000 applications.
For the ultimate in sub-micron resolution and the ability to distinguish between proteinaceous material and contaminants such as silicone resonant mass measurement is the answer. The Archimedes Particle Metrology system uses this technique.
Contact us if you need any assistance to decide which technology is best suited to your samples and applications.