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The Joule balance method to measure the Planck constant and redefine the Kilogram ultimately has been going on at the National Institute of Metrology of China (NIM) since 2007. The first prototype has been built to check the feasibility of the principle. In 2012, the relative uncertainty of the plank constant measurement result is at 10−5 level. Self-heating of the coils, swing of the coil, etc.,...
The Joule Balance method, for the same purpose but different from the Watt Balance method, is going on at NIM for several years. The first measurement result of the Planck constant h is 6.6261(5)×10−34Js with a measurement uncertainty of 7.7 × 10−5. The further plan for improvement is discussed.
In the weighing phase of the Joule Balance, to get a high enough magnetic field and avoid the heating from the coil wound with normal enameled copper wire, a superconducting magnet is used as the fixed coil. The mutual inductance measurement between this superconducting coil and the movable coil of enamel copper wire should be measured precisely. A standard square-wave compensation method has been...
A new Joule balance project has been in progress for three years in NIM, China. In this paper, the general configuration and the main parts of the magnetic system currently in development are presented. The spatial distribution of magnetic field of Joule balance was measured, which verified the existence of annular homogeneous magnetic field. The measured value matched to theoretical calculation value,...
The precise measurement of Planck Constant h to establish a kind of quantum mass standard is an important but very difficult work. The Joule Balance method, for the same purpose but different from Watt Balance method, is going on in NIM for three years. The principle and progress are described.
Traditionally, the most precise way to get the mutual inductance value is by a calculable mutual inductor. Here a new approach of measuring the mutual inductance at low frequency with compensation method is described. The mutual inductance is traced to the value of the frequency and resistance directly. The measurement uncertainty is 0.1 ppm and could be improved further.
DDS sources were developed in NIM for impedance measurements. Stable and accurate phase difference can be obtained easily by this technique. It has been used for mutual inductance measurements and an uncertainty of 1×10-7 has been obtained.
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