CERTIFICATION OF NIST SRM 1962 - 3 MU-M DIAMETER POLYSTYRENE SPHERES

This report describes the certification of SRM 1962, a NIST Standard Reference Material for particle diameter. It consists of an aqueous suspension of monosize 3-mu-m polystyrene spheres. Two calibration techniques were used: optical microscopy and electron microscopy. The first one gave a mean diameter of DBAR = 2.977 +/- 0.011-mu-m and a standard deviation of the size distribution sigma(D) = 0.020-mu-m, based on measurement of 4600 spheres. The second technique gave DBAR = 2.990 +/- 0.009-mu-m, based on measurement of 120 spheres. The reported value covering the two results is DBAR = 2.983-mu-m with a maximum uncertainty of 0.016-mu-m, with sigma(D) = 0.020-mu-m.