The NIM Inertial Mass Measurement Project

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 Termsthe Planck constant, inertial mass measurement, capacitance measurement, mechanical oscillator.

Analysis of balance beam deformation in the inertial mass measurement experiment

“…where J 0 is the rotational inertia of the balance beam, m 0 the mass of the dead weight for each suspension, L the balance beam length, M 0 the mass of the balance beam, δ the distance from the central knife to the mass center of the balance beam. Note that the mechanical loss term caused by the air resistance and mechanical friction is not involved in (1); however, the oscillation period correction due to this mechanical loss term is evaluated based on measurements [9], and an effect of −1.8 × 10 −7 has been considered in determining the Planck constant. Besides, the beam length equality is experimentally ensured at a level of several parts in 10 7 [9].…”

“…Note that the mechanical loss term caused by the air resistance and mechanical friction is not involved in (1); however, the oscillation period correction due to this mechanical loss term is evaluated based on measurements [9], and an effect of −1.8 × 10 −7 has been considered in determining the Planck constant. Besides, the beam length equality is experimentally ensured at a level of several parts in 10 7 [9]. Since ( 1) is a standard oscillation equation, its oscillation period is given as…”

“…In [8], an inertial mass measurement project, i.e. IM-1, is proposed to measure the Planck constant, and its principle has been checked by experimental measurements [9].…”