From time to time, Sequoia will update the
US and other International Standards known to us, that relate to our products.
We invite visitors to our website to send us information on relevant standards
that need to be included on this page.
ISO-7027 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
http://www.omega.com/techref/ph-6.html.
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.
ISO-13320-1 This standard
describes the laser diffraction method. Click here to go to the standard.
AWWA-2560D The American Water Works Association has proposed a
standard based on laser diffraction technology. Status unknown.
EPA
Drinking Water Standards: go to http://www.epa.gov/OGWDW/mcl.html
OBTAINING STANDARD PARTICLES
For extremely precisely sized polystyrene
spheres, go to http://www.dukescientific.com/
To obtain glass beads for laboratory calibrations, visit http://www.whitehousescientific.com
To obtain natural particle standards (Arizona dust, also called AC
Spark Plug Powder, and also used as a standard by USGS, ISO-12103-1,
contact Powder Technology Inc., Burnsville, MN, Tel: 952-894-8737
To
obtain Turbidity Standards in NTU units, visit http://www.voigtglobal.com/turbidity.htm
|