DDG-GY The advantage of the common electrode type is the price, but the defect of its "polarization" is too obvious. When a current passes through the electrode, an oxidation or reduction reaction occurs, thereby changing the composition of the solution near the electrode, causing a "polarization" phenomenon, resulting in crystallized scale on the surface of the electrode. If not cleaned in time, it will cause serious errors in conductance measurement, even Damaged, the service life is not satisfactory. Even with the high-frequency alternating current measurement, it only reduces the above-mentioned polarization phenomenon. In order to maintain measurement accuracy, it must be cleaned and calibrated regularly. Every time the sensor is cleaned or replaced, it must be shut down and interrupted, which affects efficiency. Therefore, most foreign equipment uses stepless sensors.