The accurate determination of interdiffusion coefficients is a technologically relevant problem that has implications on the correctness of the predictions when using the existing models of solidification. It is also important in the validation of different theories of atomic diffusion. The experimental determination of these coefficients when there is a liquid phase is difficult due to the unavoidable presence of buoyancy driven convection currents that enhance mass transport and disturb diffusion measurements. To minimize as much as possible these problems, long capillaries are used in order to confine the fluid and reduce the intensity of the convective motions. More recently, these measurements have been done in reduced gravity environments, but the residual gravity is still able to induce buoyancy driven convection motions. The aim of our work is to numerically analyze the impact of low and moderate Rayleigh number environments on the accuracy of the interdiffusion coefficient measurements using long capillaries. In the present study we deal with two liquid systems; photovoltaic silicon and Al-based liquid binary alloys at high temperature. We have numerically simulated in 3D two different experimental techniques used to determine the diffusion coefficients, this extends previous reported 2D calculations. We also consider the effect of rotating the cylindrical cell along their axis as a general stabilization mechanism of the convective motions. Finally, we use typical accelerometric signals from the International Space Station (ISS) in the quasi-steady range of frequencies. The signals concentrate on typical station reboosts because of the accelerometric level of the rest of disturbances -dockings, undockings and Extra Vehicular Activities, EVAs-is considerably lower. Keywords: Diffusion coefficients, Numerical simulation, Microgravity conditions, Melted semiconductors, Liquid metals, Shear Cell, Long Capillaries