Volume 106, Number 1, January–February 2001 Journal of Research of the National Institute of Standards and Technology [J. Res. Natl. Inst. Stand. Technol. 106, 25–46 (2001)] The Kilogram and Measurements of Mass and Force Volume 106 Number 1 January–February 2001 Z. J. Jabbour and S. L. Yaniv This paper describes the facilities, measure- redefinition of the unit of mass based on ment capabilities, and ongoing research fundamental principles is included. The National Institute of Standards and activities in the areas of mass and force second part of this paper focuses on the Technology, at the National Institute of Standards and unit of force and describes the realization Gaithersburg, MD 20899-0001 Technology (NIST). The first section of the of the unit, measurement procedures, paper is devoted to mass metrology and uncertainty in the realized force, facilities,
[email protected] starts with a brief historical perspective and current efforts aimed at the on the developments that led to the realization of small forces. current definition of the kilogram. An overview of mass measurement procedures is given with a brief discussion Key words: force; kilogram; mass; uncer- of current research on alternative materi- tainty. als for mass standards and surface profiles of the U.S. national prototype kilograms. A brief outlook into the future possible Available online: http://www.nist.gov/jres 1. The Kilogram and Mass Measurements 1.1 The Unit of Mass From the early history of humankind to modern times, mass plays a crucial and vital role. In addition to the mass measurements have formed the corner stone for direct impact on trade and commerce, mass measure- trade and commerce.