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Instrument calibration is essential for ensuring that instruments produce accurate and consistent results. It is vital in manufacturing, healthcare, testing laboratories, and scientific research. Calibration processes are specific to each instrument and help enhance data accuracy. Each instrument has a unique calibration process tailored to its design and function to improve data accuracy.
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The International System of Units or SI system, by international agreement, has fixed measurement units for seven fundamental properties: length, mass, time, temperature, electric current, amount of substance, and luminosity. These are called the SI base units.
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Recalibration of the U.S. National Prototype Kilogram.

R S Davis1

  • 1National Bureau of Standards, Gaithersburg, MD 20899.

Journal of Research of the National Bureau of Standards (1977)
|September 27, 2021
PubMed
Summary

The U.S. national prototype kilogram (K20) and its check standard (K4) were recalibrated, revealing updated mass values. These recalibrations are crucial for maintaining accurate mass standards and understanding long-term stability.

Keywords:
International System of UnitsSystème International d’Unitéskilogram unitmassnational prototype kilogramsplatinum-iridium kilogramsstainless steel kilogramsstandards of mass

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Area of Science:

  • Metrology
  • Mass Measurement Standards

Background:

  • The U.S. national prototype kilogram (K20) and its check standard (K4), both platinum-iridium alloys, underwent recalibration.
  • K20's last calibration was in 1948, while K4 had never been recalibrated since its 1889 certification.

Purpose of the Study:

  • To establish new, accurate mass values for the U.S. national prototype kilogram (K20) and its check standard (K4).
  • To assess the long-term stability of these critical mass standards.

Main Methods:

  • Recalibration of K20 and K4 at the Bureau International des Poids et Mesures (BIPM).
  • Inclusion of two stainless steel kilograms for comparative calibration.

Main Results:

  • The new mass value for K20 was determined to be 1 kg - 0.022 mg.
  • The new mass value for K4 was determined to be 1 kg - 0.106 mg.

Conclusions:

  • The recalibration provides updated mass values for key U.S. standards.
  • Further analysis is needed to assign realistic uncertainties and assess long-term stability of the standards.