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Permanent magnets with yokes are widely used in the watt and joule balances to measure the Planck constant for the forthcoming redefinition of the unit of mass, the kilogram. Recently, a permanent magnet system has been in consideration for a further practice of the generalized joule balance. In this paper, an analytical model to design the permanent magnet system is presented. The presented model...
The Joule balance method is one of the several approaches to measure the Planck constant for the redefinition kilogram. The first prototype has been built to check the feasibility of the principle and the relative uncertainty is 2.6×10−6. To get better result and make contribution for the redefinition, since 2013, a new Joule balance has been designed with several new approaches to decrease the main...
In the Joule Balance at the National Institute of Metrology (NIM), the dynamic measurement during the coil movement is avoided. But for this method a rather large current in the primary coil is needed to generate the necessary magnetic field in the force weighing phase. Thus the coil heating becomes an obvious uncertainty contribution. To solve this problem, a new coil system, in which the ferromagnetic...
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 is one of the several promising methods for the precise measurement of the Planck constant h to redefine the kilogram. Compared with the Watt Balance, it benefits from its all static measurements. For the new generation of the Joule balance, a magnet system with high-permeability material is designed to reduce the problem of coil heating. Simulations are carried out to demonstrate...
This paper presents a special portable apparatus for workpiece magnetism determination of joule balance at NIM. It could be used to evaluate easily the magnetic variation of mechanical parts before and after processing, quickly measuring weak magnetic properties of materials. The measuring process is simple without a customized sample. From the variation of a mutual inductance value in two different...
For application in the magnetic field of joule balance at NIM, a dc-current source with 250mA for magnetic system, based on series compensation type, has been developed. Through designing the extraordinary sampling resistor, selecting stable voltage reference and operational amplifier with outstanding properties, the stability of this customized constant current source approached to 4.5×10−6/30min,...
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...
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