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Re-Analysis of the Uncertainty of the 0.895 mm Diameter (NIST SRMRG 1690) and the 0.269 mm Diameter (NIST SRMRG 1691) Sphere Standards.


pdf icon Re-Analysis of the Uncertainty of the 0.895 mm Diameter (NIST SRMRG 1690) and the 0.269 mm Diameter (NIST SRMRG 1691) Sphere Standards. (523 K)
Mulholland, G. W.

Journal of Research of the National Institute of Standards and Technology, Vol. 110, No. 1, 27-30, January/February 2005.

Keywords:

standards; uncertainty; light scattering; Mie Scattering; polystyrene spheres; Standard Reference Materials; transmission electron microscopy

Abstract:

The uncertainties of the mean diameters of the nominal 1.0 mm SRMRG 1690 polystyrene spheres and of the nominal 0.3 mm SRMRG 1691 polystyrene spheres are recomputed using the current NIST Guidelines for computing uncertainty. The revised expanded uncertainty (approximately 95% confidence level) for SRMRG 1690 polystyrene spheres is equal to 0.005 mm compared to previous value of 0.008 mm. The revised expanded uncertainty for SRMRG 1691 is equal to 0.004 mm compared to the previous value of 0.007 mm. The major cause of the reduction in the uncertainty for the 1.0 mm spheres is from a decrease in the recomputed uncertainty of the refractive index of the polystyrene spheres. The 1.0 mm spheres were used in calibrating the electron microscope used to size the 0.3 mm spheres, and the reduction in the uncertainty of 1.0 mm SRMRG uncertainty was the biggest factor in the decrease in the uncertainty of the 0.3 mm spheres.