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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.,...
The UTD is generalized for analyzing the coupling between say, monopole and slot antennas, placed on a locally convex platform, and in a frequency band which is significantly higher than the antenna resonant frequency.
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...
Evaluating association rules is an integral post process in association rule mining. Association rules are examined by measures for their interestingness. Different interestingness measures have been proposed. Given an association rule mining task, measures are assessed and selected against a set of user-specified properties. However, in practice, due to the subjectivity and imperfection in property...
In order to reduce the effects of external magnetic fields on the accuracy of magnetic sensor measurements used for the reconstruction of ac electric currents flowing in massive parallel conductors, we use a spatial circular harmonic expansion of the magnetic scalar potential. Thanks to the linearity of the magnetic field problem with respect to the sources, we can then apply the least squares inversion...
The analogue modulation characteristics, including second order harmonic and third order intermodulation distortion, relative intensity noise (RIN) and spurious free dynamic range (SFDR), of single mode, GaAs-based 1.28 m vertical cavity surface emitting laser (VCSELs) with highly strained InGaAs quantum wells have been investigated. The VCSELs utilise an oxide aperture for current and optical confinement...
This paper presents a novel phase current reconstruction scheme using the information obtained from shunt resistors (in series with low-side switches in a conventional three-phase inverter) for closed-loop current control in low-cost PMSM drives. A state observer is developed for reconstructing phase currents when they cannot be directly measured only in a portion of fundamental period due to the...
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