MicroSet series CLT-12 are capacitance type level transmitters. vessel wall & probe forms two electrodes. If vessel is of non conductive material, the probe will be double rod type. The distance between electrode & surface area of electrodes remain unchanged. The variable is the depth of the material being measured which represents the dielectric constant between two electrodes. Air & vacuum have relative dielectric constant as 1& that of liquids, it is greater then. 1. The capacitance of the capacitor therefore depends on how much material lies between the probe & vessel wall.