Gravity Measurement for the KRISS Watt Balance

Abstract

Gravity was investigated to obtain the local acceleration due to gravity at the center of the test mass in the KRISS watt balance system. Three gravity terms were considered in order to determine the local acceleration due to gravity. Before installing the system, the absolute gravity was measured by a free-fall type gravimeter, after which, the gravity was transferred to the center of the test mass by a vertical gravity gradient. The gravity change due to self-attraction after installing the system was calculated using an analog of gravity to the electrostatic force. The mean gravity value at the center of the test mass in the KRISS watt balance is (979 832 568.9 ± 5.0) $\mu $ Gal ( $k =2$ , $1~\mu $ Gal $= 1 \times 10^{{\mathbf {-8}}}$ m/ $\text{s}^{{\mathbf {2}}}$ ). The relative and absolute gravity measurement results in this paper were verified indirectly by comparing the gravity difference between two absolute gravity points. The gravity study will contribute to the KRISS watt balance experiment as preparation for the forthcoming kilogram redefinition.