Volt Maintenance at NBS via 2e/h: A New Definition of the NBS Volt
Volt Maintenance at NBS via 2e/h: A New Definition of the NBS Volt
复制标题
NBS 通过 2e/h 进行电压维护：NBS 电压的新定义
DOI：
10.1088/0026-1394/9/4/003
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发表时间：
1973
期刊：
影响因子：
2.4
通讯作者：
J. Toots
中科院分区：
文献类型：
--
作者：
B. Field;T. Finnegan;J. Toots
本文详细描述了通过交流约瑟夫森效应建立美国法律电压新定义的程序、方法和测量方法。这一新定义是通过使用薄膜隧道结(能够产生10 mV输出)和高精度电压比较器来实现的。约瑟夫森结被用作转换系数等于2e/h的精密频率-电压转换器。一系列2e/h的测量已经在NBS进行，参考基于一大组标准电池的维持的电动势单位。在一年的时间里(1971-1972)定期进行的测量表明，这组标准电池的平均电动势在107年下降了约4%。主要是为了消除这种漂移的影响，1972年7月1日，通过选择与现有电动势单位一致的2e/h值，定义了一个新的维持单位。采用的2e/h为483593.420 GHz/vnbs。用本技术和装置可以保持新的电动势单位的精度(一个标准差)约为2/108。本系统的精度估计为1/108的4份。由于与标准电池的物理转移有关的不确定性，不同国家实验室对2e/h系统的比较一直受到限制。为了确定精度优于1/2的各种2e/h系统的相对一致性，似乎希望通过传输其中一个系统来直接比较2e/h系统。
This paper describes in detail the procedures, methods and measurements used to establish a new definition of the U.S. legal volt via the ac Josephson effect. This new definition has been made possible by the use of thin film tunnel junctions (capable of producing 10 mV outputs) and high accuracy voltage comparators. The Josephson junction is used as a precise frequency-to-voltage converter with a conversion factor equal to 2e/h. A series of measurements of 2e/h has been carried out at NBS referenced to the as-maintained unit of emf based on a large group of standard cells. Measurements made at regular intervals over a one year period (1971 to 1972) indicate that the mean emf of this group of standard cells has decreased about 4 parts in 107. Primarily to remove the effects of this drift, on July 1, 1972 a new as-maintained unit was defined by choosing a value of 2e/h consistent with the existing unit of emf. The adopted value of 2e/h is 483593.420 GHz/VNBS. The precision (one standard deviation) with which the new unit of emf can be maintained with the present techniques and apparatus is about 2 parts in 108. The accuracy of the present system is estimated to be 4 parts in 108. Comparisons of 2e/h systems at different national laboratories have been limited by uncertainties associated with the physical transfer of standard cells. In order to determine the relative agreement of the various 2e/h systems with precision better than 1 or 2 parts in 107, it appears desirable to compare 2e/h systems directly by transporting one of them.