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| The Progress of Joule Balance |
| ZHANG Zhong-hua1, LI Chen2, HE Qing1, LI Zheng-kun1, HAN Bing1, LU Yun-feng1,LAN Jiang3, LI Shi-song2, FU Ya-qiong4, WANG Gang5 |
1. National Institute of Metrology, Beijing 100029, China;
2.Tsinghua University, Beijing 100084, China;
3. Yichang Institute of Metrology, Yichang, Hubei 430003, China;
4. Beihang University, Beijing 100109, China;
5. China Jiliang University, Hangzhou, Zhejiang 310018, China |
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Abstract The National Institute of Metrology (NIM) has been studying the Joule Balance method (which is used for the same purpose as the Watt Balance method but operated differently), for several years to establish a kind of quantum mass standard by means of measuring the Planck constant. Since 2010, some progress has been achieved. A new standard square wave compensation method has been developed to measure the DC mutual inductance with an uncertainty of several parts in 10-7 (k=1) An eddy current sensor for positioning has been designed and implemented to obtain a more accurate position of the movable coil The alignment technique for the coil system has also been placed under consideration Specifically, a newly developed oil damping device reduces the small swing of the coil set which occurs because of a combination of the weak vibration of the balance base and the hot ascending warm air from the current heating of coils. As a result, the measurement uncertainty of the coil position and mutual inductance is improved.The recent measurement result of the Planck constant h is 6626104(59)×10-34J·s with an uncertainty of 8.9×10-6 (k=1) Further improvements and difficulties are also discussed.
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2014, Vol. 35 
