Capacitance Transmitter

Capacitance Transmitter is one kind of sensors. It utilizes the capacitance formed between two probes to calculate the level of the liquid/medium inside the vessel. The capacitance between the two probes increases when a dielectric is introduced between them. 

Thus, if the liquid is a dielectric then corresponding capacitance (between the probes) will be proportional with its height.

In aircraft this types of sensors are mostly used in the fuel tanks to measure the fuel heights. When the tank is empty the capacitance will be the lowest.