Capacitive level gauge measures the height of the liquid level by measuring the change in capacitance. It is a metal rod inserted into a liquid container, with the metal rod serving as one pole of the capacitor and the container wall serving as the other pole of the capacitor. The medium between the two electrodes is liquid and the gas above it. Due to the difference between the dielectric constant ε 1 of the liquid and the dielectric constant ε 2 on the liquid surface, such as ε 1>ε 2, when the liquid level rises, the total dielectric constant value between the two electrodes of the capacitive level gauge increases, resulting in an increase in capacitance. On the contrary, when the liquid level drops, the value of ε decreases and the capacitance also decreases. So, a capacitive level gauge can measure the level of liquid by the change in capacitance between two electrodes. The sensitivity of a capacitive liquid level gauge mainly depends on the difference between two dielectric constants, and only constant values of ε 1 and ε 2 can ensure accurate liquid level measurement. Due to the conductivity of the measured medium, the metal rod electrode is covered with an insulation layer. Capacitive level gauges have a small volume, are easy to achieve remote transmission and adjustment, and are suitable for measuring liquid levels in corrosive and high-pressure media.