The instruments are used for level detection in conductive liquids. When the electrode is immersed, a low alternating current flows which is detetcted by the VEGATOR signal conditioning instrument and converted into a respective switching signal. The switching signal is determined via the mounting position or the length of the respective probe. The easy and robust construction of the sensors offers a maintenance free and reliable level detection in all areas of industrial measurement technique. Typical applications are e.g. overfill protection, pump control or dry run protection.