Capacitive sensors of all sorts have been an interest of mine. They become interesting when you start to discover the huge variety of applications they are used for. While doing research for the new Control Panel in our airstream, I came across a couple of varieties of what appear to be a capacitive liquid level sensor for tanks. The TechEdge moda sensors appear to be capacitive based if you download there moda sensor manual and have a look.
These sensors incorporate two sheet aluminum plates that when stuck in proximity to one another on the tank form a small capacitor between them. Filling the tank with water changes the dielectric and therefor the capacitance. I decided to conduct a little experiment to see if I could do something similar.