Measurement of mass scaling and alternate materials on the NIST electronic kilogram system

A blind test was conducted with mass references of a 0.5 kg silicon and 1 kg each of steel and gold-plated copper, calibrated in vacuum at the NPL and measured with the watt balance at the National Institute of Standards and Technology (NIST). The results were analyzed against a 1 kg PtIr mass calibrated at NIST. The results showed good and consistent agreement between the Si, steel, and PtIr masses. The Au-plated Cu mass was stable while being measured but may have shifted during the transfer.