It is a metal rod inserted into a liquid container, the metal rod acts as a pole of the capacitor, and the wall of the container acts as the other pole of the capacitor. The medium between the two electrodes is the liquid and the gas above it. Since the dielectric constant ε1 of the liquid and the dielectric constant ε2 on the liquid surface are different, for example, ε1>ε2, when the liquid level rises, the total dielectric constant value between the two electrodes increases and the capacitance increases. . Conversely, as the liquid level drops, the ε value decreases and the capacitance decreases. Therefore, the level of the liquid level can be measured by the change in capacitance between the two electrodes. The sensitivity of the capacitor depends mainly on the difference between the two dielectric constants. Moreover, only the constant ε1 and ε2 can ensure the accurate measurement of the liquid level. Because the measured medium has conductivity, the metal rod electrode has an insulating layer covering. Small capacitance, easy to achieve remote transmission and adjustment, suitable for liquid level measurement of corrosive and high pressure media