Li Shisong

The joule balance in NIM of China

The advantage of the joule balance over the classic watt balance is that the dynamic measurement in the watt balance is replaced by a static measurement, which makes the whole measurement procedure easier. The main problems in the joule balance are the precise measurement of mutual inductance and coil heating. These problems and recent progress in the development of the joule balance are described and discussed in this paper. The whole system is at the stage of being adjusted and improved. The principle of the joule balance has been demonstrated by a measurement of the Planck constant, h = 6.626 104(59) × 10−34 J s with an 8.9 ppm measurement uncertainty.

Progress on accurate measurement of the Planck constant: Watt balance and counting atoms *

The Planck constant h is one of the most significant constants in quantum physics. Recently, the precision measurement of the numeral value of h has been a hot issue due to its important role in establishment for both a new SI and a revised fundamen tal physical constant system. Up to date, two approaches, the watt balance and counting atoms, h ave been employed to determine the Planck constant at a level of several parts in 10. In this paper, the principle and progress on precision measurement of the Planck constant using watt balance and co unting atoms at national metrology institutes are reviewed. Further improvements for the Plan ck constant determination and possible developments of a revised physical constant system in futur e are discussed. PACS numbers: 06.20.-f, 06.20.Jr, 07.05.Fb, 07.10.Pz Submitted to:Chinese Physics BThe Planck constant h is one of the most significant constants in quantum physics. Recently, the precision measurement of the value of h has been a hot issue due to its important role for the establishment of both a new SI and a revised fundamental physical constant system. Up to date, two approaches, the watt balance and counting atoms, have been employed to determine the Planck constant at a level of several parts in 108. In this paper, the principle and progress on precision measurement of the Planck constant using watt balance and counting atoms at national metrology institutes are reviewed. Further improvement in determining the Planck constant and possible developments of a revised physical constant system in future are discussed.

Nonlinearity and periodic solution of a standard-beam balance oscillation system

We present the motion equation of the standard-beam balance oscillation system, whose beam and suspensions, compared with the compound pendulum, are connected flexibly and vertically. The nonlinearity and the periodic solution of the equation are discussed by the phase-plane analysis. We find that this kind of oscillation can be equivalent to a standard-beam compound pendulum without suspensions; however, the equivalent mass centre of the standard beam is extended. The derived periodic solution shows that the oscillation period is tightly related to the initial pivot energy and several systemic parameters: beam length, masses of the beam, and suspensions, and the beam mass centre. A numerical example is calculated.