The determination of gravitational acceleration in the joule balance at NIM

摘要

The determination of the local acceleration of gravity at the mass position is an important aspect of the joule balance. Since a simultaneous measurement of the absolute gravity at the mass position with the joule balance in place is impossible, seven gravity reference sites are chosen in the joule balance laboratory. Absolute and relative gravity measurements at the reference sites were performed between 2015 and 2019, and varioust transfer methods were used to obtain an absolute gravity value at the mass position. The self-attraction effects of joule balance apparatus are corrected by FEA simulation, and calculation accuracy is also verified by experiment. To obtain real-time local gravitational acceleration values during the joule balance experiment, geophysical effects, such as atmospheric pressure, Earth tides, and polar motion are considered. The absolute gravity results exhibit good stability from 2015 to 2019, and the final gravitational uncertainty contribution in the joule balance is 6.1 mu Gal.