Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Construction and Performance of the NIST-4 Magnet System



Frank C. Seifert, Alireza R. Panna, Leon S. Chao, Yusi A. Cao, Darine El Haddad, Shisong Li, Stephan Schlamminger, Jon R. Pratt, Heeju Choi, Lori Haley


A watt balance is a promising instrument to realize the unit of mass at the kilogram level. The magnet system is one of the key elements of such an instrument. For the new watt balance currently under construction at the National Institute of Standards and Technology, a permanent magnet system was chosen. We describe the construction of the magnet system, first measurements of the field profile, and techniques that were used to achieve a flat field profile.
Proceedings Title
Conference on Precision Electromagnetic Measurements (CPEM) 2014
Conference Dates
August 24-29, 2014
Conference Location
Rio de Janeiro
Conference Title
CPEM 2014 Digest


permanent magnet, mass, Planck constant, watt balance, mass metrology


Seifert, F. , Panna, A. , Chao, L. , Cao, Y. , El, D. , Li, S. , Schlamminger, S. , Pratt, J. , Choi, H. and Haley, L. (2014), Construction and Performance of the NIST-4 Magnet System, Conference on Precision Electromagnetic Measurements (CPEM) 2014 , Rio de Janeiro, -1, [online], (Accessed May 29, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 24, 2014, Updated November 29, 2019