Online conductivity sensor work by measuring the electrical conductivity of ions in a liquid to determine the conductivity of the liquid. A four-electrode type conductivity sensor consists of two pairs of electrodes, one pair for transmitting current and the other pair for measuring voltage. This design eliminates the effects of contact resistance and improves the accuracy and stability of the measurement, making it particularly suitable for monitoring highly concentrated solutions or frequently changing processes. Conductivity sensors have a wide range of applications in many fields, such as chemistry, environmental monitoring, water treatment, agriculture and industrial production. In these fields, conductivity sensors provide important data support for production and life through the measurement of solution conductivity.