Abstract: The instrument includes a cylindrical chamber with two parallel end walls. At least one of the end walls is plated with two semicircular condenser plates forming a gap between them. The chamber is filled half and half with two non-intermixing liquids of different specific gravity. In one embodiment the other end wall is plated with a third condenser plate and the two liquids are non-conductive and have different dielectric properties. In another embodiment, the two condenser plates on the one end wall are plated with a dielectric layer and at least one of the two liquids is an electrolyte. The instrument has a high measuring range and high accuracy and resolution.