| Autor: |
Abbott, Patrick J., Benck, Eric C., Mulhern, Edward, Stambaugh, Corey, Kubarych, Zeina J. |
| Zdroj: |
NCSLI Measure; October 2016, Vol. 11 Issue: 3-4 p45-50, 6p |
| Abstrakt: |
Abstract:The International System of Units (SI) will be redefined in 2018 so that the present seven SI base units are realized by a set of defining constants having exact values. For the unit of mass, the kilogram, this means a change in realization from a physical artifact, the International Prototype Kilogram (IPK) to an experiment that uses the Planck constant to measure mass with an uncertainty. Although traditional artifact-based mass metrology will not change, National Measurement Institutes (NMIs) will change the way that they realize the unit of mass and disseminate it to working standards. Much of this change is due to the necessary vacuum environment of the experiments (Kibble balance and x-ray crystal density (XRCD)) that will use the Planck constant to measure mass. At the National Institute of Standards and Technology (NIST), mass measurements, artifact transfers, and storage of standard artifacts will be done in both vacuum and atmospheric pressure environments to produce and maintain SI-traceable mass standards. This process of realization and dissemination is known as a mise en Pratiqueand consists of four main components, each of which is described. |
| Databáze: |
Supplemental Index |
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