Certification of NIST SRM 1962: 3 μm 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 (μm polystyrene spheres. Two calibration techniques were used: optical microscopy and electron microscopy. The first one gave a mean diameter of [Formula: see text] μm and a standard deviation of the size distribution σ = 0.020 μm, based on measurement of 4600 spheres. The second technique gave [Formula: see text] μm, based on measurement of 120 spheres. The reported value covering the two results is [Formula: see text] μm with a maximum uncertainly of 0.016 μm, with σ =0.020 μm.