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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.,...
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...
The load effect of the resistor should be paid great attention for the precise measurement. Here a high accurate resistance voltage divider (RVD) used to precisely measure the load effect of the resistor is provided. A self-calibrated standard resistor at 100Ω with zero load effect is employed as one arm of the bridge, and several stable resistors with the same temperature coefficient and structure...
A simple differential eddy current sensor for measuring small rotation angle is presented and experimentally investigated. The output signal is obtained from changing active areas of a rotatable copper plate with two legs inserted into gaps of a magnetic circuit. Test results show this kind of sensor has a resolution of 8µrad over the effective measurement range of ±7000µrad.
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...
The recent experimental results of a Ka-band second harmonic gyroklystron amplifier are presented. The peak output power of 212kW at 35GHz has been measured with a 3dB bandwidth of 155MHz. The tube is operated at electron beam voltage and current of 58 kV and 23 A, respectively. The efficiency is approximately 16% and the gain is about 24 dB.
This paper describes a single-phase active power filter based on newly developed digital controller. The developed controller utilizes FFT algorithm to extract the reference signal from the load current, considering the phase-angle delay of each harmonic component. Optimizing technique was applied for whole control algorithm to implement the real-time operation of developed controller. The performance...
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