Patent ID: 7396452

Claim:
An apparatus comprising: a processing chamber adapted for rotation about an axis; an inlet to convey a first fluid into the chamber, the first fluid comprising first and second components having generally different densities such that an interface forms between at least portions of the first and second components at a first location during rotation of the chamber; at least one outlet to remove at least one of the first and second components of the first fluid from the chamber; a controller adapted to introduce the first fluid to the chamber through the inlet at a rate of introduction and to remove at least one of the first and second components through the outlet at a rate of removal, the controller being operable to control the rates of introduction and/or removal to move the interface from the first location to a second location and to move the interface from the second location in a direction toward the first location and to return the interface to the second location, the controller being operable to determine a flow rate of the first or second component within the first fluid in the chamber, such determination being based, at least in part, on a time interval between when the interface moves between the second location to the first location and returns to the second location; and at least one sensing assembly adapted to sense when the interface is at the first and second locations.