We report on the first-ever use of a quantum ac source to calibrate a thermal transfer standard as part of the NIST calibration service for such devices, with reductions in calibration uncertainty of as much as an order of magnitude over traditional ac-dc transfer methods. We briefly describe the basic quantum ac calibration system, its operation and measurement results. An analysis of the uncertainties for the measurements is presented and plans for further development are described.

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Abstract-NIST recently reported the first application of a quantum ac Josephson Voltage Standard for calibration of thermal transfer standards in the 1 kHz to 10 kHz frequency range. This paper describes preliminary work on extending its frequency calibration range up to 100 kHz by correcting systematic errors due to voltage leads. A ground loop created by the dc blocks, a previously unaccounted for source of high frequency systematic error, has been identified and its effects partially mitigated.

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This paper describes some of the major contributions to metrology and physics 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 industrial, scientific, and research organizations, and conducts research on topics related to electrical metrology and fundamental constants. The early work of the Electricity Division staff included the development of precision standards, such as Rosa and Thomas standard resistors and the ac-dc thermal converter. Research contributions helped define the early international system of measurement units and bring about the transition to absolute units 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 measurements are described in detail. Several other areas of current research at NIST are described, including the use of the Internet for international compatibility in metrology, determination of the fine-structure and Planck constants, and construction of the electronic kilogram.