Patent ID: 7869728

Claim:
A density detection device, comprising: a casing including an internal space to allow liquid to pass therethrough; an inflow path, the liquid passing therethrough, the inflow path being communicated with the internal space through an inlet, the inlet facing the internal space; an outflow path, the liquid passing therethrough, the outflow path being communicated with the internal space through an outlet, the outlet facing the internal space; a base being provided in the internal space to block the liquid flowing from the inlet, the base having a top side positioned above the inlet; a movable member having a bottom side opposed to the top side of the base, the movable member being configured to move to cause the bottom side to move toward and away from the top side of the base; and a density detection section being configured to detect density of a liquid layer formed between the bottom side of the movable member and the top side of the base while the bottom side of the movable member is closely positioned a predetermined distance relative to the top side of the base.