The principle of capacitive level measurement is based on the capacitance change of a capacitor. The probe and the tank wall form a capacitor whose capacitance is dependent on the amount of product in the tank: An empty tank has a lower, a filled tank a higher capacitance.

Capacitance type level switch is based on RF capacitance principle. Capacitance is formed between the level sensing probe and metallic wall of the vessel which act as two electrodes, and the application media acts as a dielectric medium when the sensor is introduced into the vessel. These electrodes are separated by an insulator by suitable media known as a dielectric medium. When the level of process material rises, the value of dielectric changes which results in change in the value of capacitance between the level sensing probe and the vessel wall. This change can be detected and measured by the Radio Frequency technique.