The New Kilogram Definition and its Implications for High-Precision Mass Tolerance Classes.

Area of Science:

• Metrology and Measurement Science
• Physical Constants
• International System of Units (SI)

Background:

• The kilogram is the last SI unit defined by a physical artifact, the International Prototype Kilogram (IPK).
• Upcoming redefinition of the kilogram based on the Planck constant is nearing completion.
• Current IPK-based realization introduces limitations in mass metrology.

Purpose of the Study:

• To compare legal metrology requirements for mass calibration laboratories post-kilogram redefinition.
• To assess the impact of the redefinition on reference standards used by secondary calibration laboratories.
• To evaluate the transition from artifact-based to constant-based mass unit realization.

Main Methods:

• Analysis of current legal metrology standards for precision mass calibration.
• Review of recommendations from the Consultative Committee for Mass and Related Quantities (CCM).
• Comparative study of mass calibration capabilities before and after the kilogram redefinition.

Main Results:

• The redefinition may lead to increased uncertainties passed from National Metrology Institutes (NMIs) to customers.
• Potential impact on reference standards in secondary calibration laboratories is identified.
• The shift to a Planck constant-based definition necessitates adjustments in metrological practices.

Conclusions:

• The redefinition of the kilogram is a significant shift in fundamental metrology.
• Calibration laboratories must adapt to potentially revised uncertainty budgets.
• Ensuring seamless transition and maintaining measurement traceability are critical.