What statement is true concerning the operating principle of a liquid level sensing and transmitting system of the capacitance type?

Correct Answer: Option A — The capacitance method is generally used with non-conductive liquids and works on the principle of the substantial difference between the dielectric constant of air and that of the liquid in the tank.

Capacitance level sensors function as a capacitor where the liquid acts as the dielectric. Since non-conductive liquids have a dielectric constant significantly different from air, the change in capacitance as the liquid level rises between the probe and tank wall provides a reliable, continuous measurement of level.