Method and apparatus for measuring the grain-size of fine powders

In a centrifuge suitable for measuring particle size distribution of powder in a liquid dispersion, by sedimentation in the centrifugal field comprising:

• a. a rotatable spindle having a sedimentation vessel fixedly mounted thereon for rotation therewith for holding and centrifuging of a specimen of the dispersion,
• b. a settling plate disposed in the sedimentation vessel for receiving sediment of the powder, a connector for the settling plate, the settling plate being secured to the connector and the connector being mounted on the spindle for radial displacement of the settling plate in dependence on the centrifugal force acting on the settling plate due to accumulation of sediment thereon,
• c. gauge means for measuring said displacement as a measure of said particle size distribution,
• the improvement which comprises:
• d. buoyancy means attached to the connector for movement therewith for generating a force by buoyancy counteracting said centrifugal force and limiting said radial displacement of the connector so that the connector assumes a balanced position in dependence on the amount of sediment accumulated on the settling plate, said gauge means being for measuring the balance position.