Gravitational configuration effect upon precision mass measurements

Modern weighing practice consists of making comparisons between the gravitational attractive forces exerted on standard and unknown weights. An effect coupling the gravitational force exerted on a weight to the height of the weight’s center of gravity above its base has been found to be significant when weighings of the highest precision are attempted. This effect will cause systematic errors in mass measurements if not properly accounted for. The effect, called the ’’gravitational configuration effect,’’ arises because the centers of gravity of nominally equal weights above their bases, and hence the weights’ effective distances from the center of the Earth, are affected by the weights’ size and shape. Variations of 1 cm in the separation between the centers of gravity of weights and the center of the Earth produce differences in gravitational attractions of 3.14 parts in 10⁹. Currently, mass comparisons at the 1‐kg level can be carried out with standard deviations as small as 1.5 parts in 10⁹. Thus, the gravitational configuration effect must be considered if weighing accuracies approaching weighing precisions are to be obtained when kilogram weights of significantly different sizes and/or shapes are compared. Corrections for the gravitational configuration effect can readily be combined with corrections for better‐known effects, such as air buoyancy, to generate an overall equation to express the results of mass comparisons.