The article discusses the transition to a new definition of the kilogram based on a fundamental constant of nature, rather than a physical artifact. This change requires developing methods to disseminate the new standard to laboratories and industries. The International Bureau of Weights and Measures (BIPM) has conducted a pilot study with several national metrology institutes (NMIs) to test their proposed methods.
NIST completed its dry run using a watt balance to calibrate a platinum-iridium mass in vacuum. The challenge is accounting for the mass difference when moving from vacuum to air due to adsorbed water and impurities. NIST is developing two methods: a room-sized magnetic suspension mass comparator and smaller balances that compare masses in air or vacuum.
The BIPM expects to share results from the pilot study by early 2024. Participating NMIs include NIST, NRC Canada, LNE France, PTB Germany, and NMIJ Japan, each using either watt balances or silicon spheres for their primary realizations of the kilogram.
Source: https://www.nist.gov/news-events/news/2016/11/disseminating-new-kilogram-international-dry-run
Keywords: metrology, measurement, precision
