共查询到17条相似文献,搜索用时 62 毫秒
1.
2.
3.
1988年10月举行的国际计量委员会(CIPM)第77次会议决定,从1990年1月1日起在世界范围内启用量子化霍尔电阻标准。中国计量科学研究院从1987年起也开始了建立量子化霍尔电阻标准的研究课题,该项标准现已建成,用量子化霍尔效应复现的10kΩ和1kΩ电阻量值的不确定度为2.2×10~(-8)。 相似文献
5.
6.
7.
2007年1月19日,受科技部委托,由国家质检总局在中国计量科学研究院主持召开了科技部基础性工作专项《国家现代电学计量标准和检测体系的建立和完善》子课题“交流电阻计量标准”的课题验收会。 相似文献
8.
<正>作为我国最高的计量科研机构,中国计量科学研究院走过了60年的历程。60年的发展,我们的计量科技工作从艰难起步、努力追赶到迅速腾飞,为我国计量事业发展打下雄厚基础,为国民经济发展、科技进步、国防建设等的发展起到积极的促进作用。在此,我向关心和支持计量科技工作发展的各级领导,以及为中国计量科学研究院60年发展作出贡献的单位和个人表示感谢!值此新年之际,也向全国计量工作者致以崇高的敬意!60年,我们计量科技工作的脚步从未停歇。科技工作者满怀热情,发扬自力更生、艰苦奋斗、自 相似文献
9.
10.
11.
12.
J. Matthews M. E. Cage 《Journal of research of the National Institute of Standards and Technology》2005,110(5):497-510
We present detailed measurements of the temperature dependence of the Hall and longitudinal resistances on a quantum Hall device [(GaAs(7)] which has been used as a resistance standard at NIST. We find a simple power law relationship between the change in Hall resistance and the longitudinal resistance as the temperature is varied between 1.4 K and 36 K. This power law holds over seven orders of magnitude change in the Hall resistance. We fit the temperature dependence above about 4 K to thermal activation, and extract the energy gap and the effective g-factor. 相似文献
13.
14.
15.
16.
M. E. Cage A. Jeffery R. E. Elmquist K. C. Lee 《Journal of research of the National Institute of Standards and Technology》1998,103(6):561-592
Many ac quantized Hall resistance experiments have measured significant values of ac longitudinal resistances under temperature and magnetic field conditions in which the dc longitudinal resistance values were negligible. We investigate the effect of non-vanishing ac longitudinal resistances on measurements of the quantized Hall resistances by analyzing equivalent circuits of quantized Hall effect resistors. These circuits are based on ones reported previously for dc quantized Hall resistors, but use additional resistors to represent longitudinal resistances. For simplification, no capacitances or inductances are included in the circuits. The analysis is performed for many combinations of multi-series connections to quantum Hall effect devices. The exact algebraic solutions for the quantized Hall resistances under these conditions of finite ac longitudinal resistances provide corrections to the measured quantized Hall resistances, but these corrections do not account for the frequency dependences of the ac quantized Hall resistances reported in the literature. 相似文献
17.
《IEEE transactions on instrumentation and measurement》1983,32(3):446-447
A major step in the precise determination of the quantized Hall resistance is the comparison of a resistor of value nominally 6453.2 ? with a 1-? standard. For this purpose the National Measurement Laboratory will use a build-up resistor comprising 83 resistors each of 80? ?, giving a ratio of 64534/9. An accuracy of better than 1 in 108 is expected. 相似文献