The ampere and electrical standards

This paper describes some of the major contributions to metrology and physi cs made by the NIST Electricity Division, which has existed since 1901. It was one of the six original divisions of the National Bureau of Standards. The Electricity Division provides dc and low-frequency calibrations for ind ustrial, scientific, and research organizations, and conducts research on t opics related to electrical metrology and fundamental constants. The early work of the Electricity Division staff included the development of precisio n standards, such as Rosa and Thomas standard resistors and the ac-dc therm al converter. Research contributions helped define the early international system of measurement units and bring about the transition to absolute unit s based on fundamental principles and physical and dimensional measurements . NIST research has helped to develop and refine electrical standards using the quantum Hall effect and the Josephson effect, which are both based on quantum physics. Four projects covering a number of voltage and impedance m easurements are described in detail. Several other areas of current researc h at NIST are described, including the use of the Internet for internationa l compatibility in metrology, determination of the fine-structure and Planc k constants, and construction of the electronic kilogram.