How does capacitance-based level measurement work?

Capacitance level sensors measure level changes based on the dielectric properties of the process medium. A probe forms one plate of a capacitor with the tank wall as the other plate. As level rises, the dielectric constant between plates changes (air has dielectric constant ~1, water ~80), changing capacitance proportionally. These sensors work for liquids and solids, are suitable for high pressure/temperature, and have no moving parts.