Analysis of balance beam deformation in the inertial mass measurement experiment

This paper provides an analysis of mechanical balance beam deformation in the inertial mass measurement experiment since 2012. The relation between the applied test masses and three types of mechanical elastic deformation of the balance beam, i.e. the changes of rotational inertia, beam length and mass center, are discussed. It is found that changes in the rotational inertia and beam length are high order small quantities of the test mass, and a mechanically optimized balance beam which has good mechanical strength and a light structure is adopted to decrease the influence of the two types of deformation. The mass center change, being proportional to the test mass, has the most impact and can be compensated by a novel mass center compensation approach. Simulations and experiments confirm the effectiveness of the new balance beam and the mass center compensation method. It is emphasized that the analysis of the beam deformation in this paper can also be applied in other experiments where mechanical deformation of the balance beam needs to be considered. (paper)