In a preferred embodiment, a capacitive sensor element which includes a metal plate which is flat and smooth and hard-coated with a dielectric material, such as an oxide. The dielectric surface slidingly contacts a smooth metal plate, such as hardened steel, with the capacitance of the sensor element varying with the area of contact of the two plates. Aluminum oxide provides an excellent dielectric surface. The sensor may be constructed in a number of configurations and can be ruggedly constructed for harsh environments. In a further embodiment, a metal member having a hard-coated dielectric material on the surface thereof is partially immersed in a conductive liquid to form a capacitive liquid level sensing element.