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Characteristics of precision 1 Ω} standard resistors influencing transport behavior and the uncertainty of key comparisons



George R. Jones Jr., Brian J. Pritchard, Randolph Elmquist


National Measurement Institutes (NMIs) participate in international key comparisons organized by the BIPM, the Regional Metrology Organizations (RMOs), or the Consultative Committees of the Comite International des Poids et Mesures (CIPM) in order to provide evidence of equivalent national reference standards and measurement capabilities. The U.S. National Institute of Standards and Technology (NIST) and the National Measurement Institute of Australia (NMIA) have recently examined power loading and several other effects in precision transportable 1 Ω} resistors that can increase the uncertainty of key comparisons. We have studied the effects of temperature, barometric pressure, humidity, power loading, and heat dissipation in oil on transportable wire-wound 1 Ω} resistance standards that are based on different alloys and construction principles. This work focuses on standards manufactured from 1970 through 2000 by the NML, and on Thomas-type resistors designed in the 1930s and made of Manganin alloy. We describe the characterization process and relate the effects to the mechanical and physical design, construction, and condition of the standards.


electrical resistance standard, key comparison, temperature coefficient, power loading


Jones Jr., G. , Pritchard, B. and Elmquist, R. (2009), Characteristics of precision 1 {Ω} standard resistors influencing transport behavior and the uncertainty of key comparisons, Metrologia (Accessed June 15, 2024)


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Created July 30, 2009, Updated October 12, 2021