Qing He

Harbin Institute of Technology, Charbin, Heilongjiang Sheng, China

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Publications (14)16.69 Total impact

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    ABSTRACT: A new type of calculable capacitor was initially built at the National Institute of Metrology, China, in cooperation with the National Measurement Institute, Australia. The capacitor realized the SI unit of capacitance at 1 pF, with an uncertainty of 20 parts in $10^{9}$ . A simplified operational approach was used that avoids the complex substitution measuring process with small-value capacitors. The details of novel aspects of the installation and adjustment processes are presented, together with the experimental results and an initial uncertainty estimation.
    IEEE Transactions on Instrumentation and Measurement 01/2015; 64(6):1-1. DOI:10.1109/TIM.2015.2399012 · 1.71 Impact Factor
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    ABSTRACT: The principle, design, and measurement of a 10-A highly stable dc current source is described. Based on a modified low-frequency equivalent model of the MOSFET, we obtain the strict current equation of the MOSFET-based voltage-controlled current source. Factors determining the current stability are investigated and reasonable selection criteria for the key components are discussed. Reasons for oscillation due to the high parasitic capacitance of the paralleled MOSFETs with low set of drain–source voltage are explained and a combined noise gain and lead compensation method is proposed. The best measurement results show that the relative standard deviation and relative drift of the current in 1 h are, respectively, $7.5 times 10^{-8}$ and $2.2 times 10^{-8}$ . The current source has been used in our high-current meter stability evaluation experiments and can be used for other cases with appropriate improvement, such as the Joule Balance Project to redefine the kilogram at National Institute of Metrology.
    IEEE Transactions on Instrumentation and Measurement 01/2015; 64(6):1324-1330. DOI:10.1109/TIM.2014.2376114 · 1.71 Impact Factor
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    ABSTRACT: The development of the joule balance method to measure the Planck constant, in support of the redefinition of the kilogram, 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 2011, the relative uncertainty of the Planck constant measurement at NIM is 7.7×10 -5 . Self-heating of the coils, swing of the coil, are the main uncertainty contributions. Since 2012, some improvements have been made to reduce these uncertainties. The relative uncertainty of the joule balance is reduced to 7.2×10 -6 at present. The Planck constant measured with the joule balance is h=6.6261041(470)×10 -34 Js. The relative difference between the determined h and the CODATA2010 recommendation value is 5×10 -6 . Further improvements are still being carried out on the NIM-1 apparatus. At the same time, the design and construction of a brand new and compact joule balance NIM-2 are also in progress and presented here.
    IEEE Transactions on Instrumentation and Measurement 01/2015; 64(6). DOI:10.1109/TIM.2015.2395552 · 1.71 Impact Factor
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    ABSTRACT: An inertial mass measurement project, which is expected to precisely measure the Planck constant, h, for possible comparisons with known gravitational mass measurement projects, e.g., the watt balance and the Avogadro project, is being carried out at the National Institute of Metrology, China. The principle, apparatus, and experimental investigations of the inertial mass measurement are presented. The prototype of the experiment and the Planck constant with relative uncertainty of several parts in 10 4 have been achieved for principle testing. Index Terms the Planck constant, inertial mass measurement, capacitance measurement, mechanical oscillator.
    IEEE Transactions on Instrumentation and Measurement 10/2014; 64(6). DOI:10.1109/TIM.2014.2375691 · 1.71 Impact Factor
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    CPEM2014; 08/2014
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    ABSTRACT: A system based on laser heterodyne interferometer is proposed in this paper to measure and control the movable coil position of a joule balance. A damping system is used to suppress the movement of the movable coil in the horizontal direction while a piezoelectric ceramic control unit with PID controller is used to inhibit the vibration and long term drift of the movable coil in the vertical direction. The effectiveness of the proposed method in measuring and controlling the movable coil position of a joule balance is proved through experiments. Experimental results indicate that the displacement of the movable coil in the vertical direction can be reduced from 400 to 50 nm while its drift is successfully inhibited.
    Measurement Science and Technology 04/2014; 25(6):064003. DOI:10.1088/0957-0233/25/6/064003 · 1.35 Impact Factor
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    ABSTRACT: The joule balance, an approach for precisely mea-suring the Planck constant at the National Institute of Metrology (NIM), China, is currently limited by the self-heating of the coil when the measuring current flows. To solve this heating problem, a superconducting coil has been built to replace the existing fixed coil wound with enameled copper wire. The movable coil set is formed by two enameled coils connected oppositely for easy alignment in air. However, the large self-inductance of the superconducting coil brings new challenges for the a mutual inductance measurement. Mutual inductance measurement of superconducting coil based on standard square wave compensation method is presented and discussed in this paper.
    IEEE Transactions on Instrumentation and Measurement 06/2013; 62(6). DOI:10.1109/TIM.2013.2256712 · 1.71 Impact Factor
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    ABSTRACT: A quasi-elastic electrostatic oscillation method is proposed for the absolute determination of inertial mass, which is distinguished from the gravitational mass measurement in the watt balance experiment. The value of the kilogram is determined by comparing oscillation periods of the quasi-elastic electrostatic oscillator with different test masses and applying different dc voltages on a symmetrical twin-Kelvin-capacitor system. The required measuring quantities for this method include the capacitance, voltage, vertical distance and oscillation periods, which in principle can be measured with high accuracy. In addition, this experiment is insensitive to the air buoyancy and the heating problem, and it can be operated in air. Both the theory and experimental verifications are presented. (Some figures may appear in colour only in the online journal)
    Metrologia 02/2013; 50(1):9-14. DOI:10.1088/0026-1394/50/1/9 · 1.65 Impact Factor
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    ABSTRACT: The precise dc-based measurement of the mutual inductance is one of the key issues in the Joule Balance method used to determine Planck's constant h. Here, a new compensation method with a standard square wave is provided. The dc value of the mutual inductance is obtained by measuring the integral area of the induced voltage. To increase the accuracy of this integral method, we just accurately measure the residual area observed between the induced voltage of the mutual inductor and a synchronously generated standard square wave. Experimental results indicate that this approach is consistent with the previous frequency extrapolation method within 1 ppm. The measurement uncertainty is estimated to be about 0.22 μH/H for the 340-mH mutual inductor at room temperature. A better result of 0.1 ppm could be obtained when the superconducting coil is used.
    IEEE Transactions on Instrumentation and Measurement 09/2012; 61(9):2524-2532. DOI:10.1109/TIM.2012.2190335 · 1.71 Impact Factor
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    ABSTRACT: Traditionally, the most precise way to get the mutual inductance value is by a Campbell calculable mutual inductor. Here, an approach of measuring the mutual inductance at low frequency with compensation method is described. A multi-channel direct digital frequency synthesis source is developed to provide stable and precise phase. The mutual inductance is traced to the value of the frequency and resistance directly. The measurement uncertainty is 0.43 ppm at present and could be improved further.
    IEEE Transactions on Instrumentation and Measurement 08/2011; DOI:10.1109/TIM.2010.2099270 · 1.71 Impact Factor
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    ABSTRACT: The precise measurement of Planck constanthto 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, has been going on at the National Institute of Metrology for three years. All the measurements were carried out in the atmosphere of an air-conditioned room. The uncertainty is several parts in104 (k=1) and expected to be improved when superconducting coils and other approaches are used further. The principle and progress are described here.
    IEEE Transactions on Instrumentation and Measurement 07/2011; 60(7):2533-2538. DOI:10.1109/TIM.2011.2113930 · 1.71 Impact Factor
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    ABSTRACT: The uncertainty source in measurement with CCC apparatus is discussed. Experiment shows that the uncertainty in operation of CCC is mainly from the pressure fluctuation of helium gas in cryostat. Some approaches of decreasing the uncertainty are proposed. In addition, increasing the turn number of the CCC windings can improve the S/N ratio in measurement and is also effective for decreasing the measurement uncertainty
    Precision Electromagnetic Measurements Digest, 2004 Conference on; 07/2004
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    ABSTRACT: This paper analyses the sources of uncertainty and evaluates the magnetic density in geometrical center of magnetic system, based on special structure of coil system of energy balance. It proved that the uncertainty u(I) of current existing in the coil of magnetic system would affect combined uncertainty of magnetic field uc(H0) to the greatest extent. Therefore the high-precision constant-current source was recommended to diminish uncertainty of magnetic field of Energy Balance.