Sequoia Scientific


Laser Diffraction Standards


ISO standard describing the laser diffraction method.

ASTM B822-10

ASTM standard describing the laser diffraction method.

ASTM D4464

ASTM standard describing the laser diffraction method.

Turbidity Standards


This is a turbidity standard, reporting results in FNU (Formazin Nephelometric Units). It is based on monochromatic light scattering at 90-degrees plus or minus 2.5-degrees. Like the USEPA turbidity standard below, this standard has no relationship to suspended sediment mass or volume. The conversion to suspended sediment concentration changes with changes in sediment grain size, color, ligth wavelength, and particle shape. For more details, we recommend visiting

US EPA 180.1

This is the US version of the ISO standard mentioned above. The results are reported in NTU (Nephelometric Turbidity Units), again with Formazin as the standard. This method, unlike ISO-7027, this standard is more lax (and therefore, even less reliable). The scattering angle can be 90 +/- 20-degrees. The lamp need not be monochromatic, etc. Fundamentally, this method suffers from all the ills of the ISO method.

Drinking Water Standards


Standards Particles

Sequoia provides a 1 g vial of standard particles with each instrument; typically in the 75-90µm size range. Beyong that, Sequoia does not sell or supply standard particles. Please contact the manufacturers below directly if you wish to purchase standards to use with your LISST instrument.
Polystyrene spheres
For extremely precisely sized polystyrene spheres, go to
Glass beads
To obtain Glass Microspheres for laboratory calibrations, visit Sequoia uses the following Whitehouse Glass Microspheres for validation:

 Sieve Fraction (µm)

Catalogue No:

Nominal Weight (g)






















(AZ test dust)
To obtain natural particle standards of Arizona Test Dust, also called AC Spark Plug Powder, contact Powder Technology Inc. These particles are also used as a standard by USGS. Sequoia uses the following Arizona Test Dust Nominal Sizes for validation:

 Nominal Size Range (µm)








ISO 12103-1, A3 Medium Test Dust


ISO Coarse A.T.D. 12103-1, A4

Turbidity Standards  To obtain Turbidity Standards in NTU units, visit