floating scale 3 in 1

The idea:
for the science challenge I wanted to design something that demonstrates the principle of buoyancy, displacement and density. Density is calculated by dividing mass by volume so both have to be measured. Volume is measured by the displacement of water in a container and mass by means of buoyancy. Additionally I wanted to show the comparison between to objects with different densities but same mass in the way Archimedes did it.

The design:
-measure volume:
A cylinder is filled