The National Institute of Standards and Technology (NIST) is responsible for the dissemination of the unit of mass within the United States of America through the national prototype kilogram K20 and its check standard K4. These platinum-iridium artifacts have been in use since 1889 and are periodically sent to the International Bureau of Weights and Measures (BIPM) for recalibration. The following is a brief description of the roles of the national prototype kilograms in the dissemination of mass in the U.S., and the implications for NIST mass calibration customers of the most recent recalibrations of K20 and K4.
Citation: Journal of Research (NIST JRES) - 119.001Report Number:
NIST Pub Series: Journal of Research (NIST JRES)
Pub Type: NIST Pubs
mass metrology, kilogram, SI unit of mass, dissemination, calibration, national prototypes, mass stability, BIPM calibration, Platinum-Iridium kilograms, national standards, recalibration of US national standard