Ammonia nitrogen sensors use the ion-selective electrode principle. An ion-selective electrode is an electrode that responds selectively to specific ions. In ammonia nitrogen sensors, ammonia gas-sensitive electrodes or ammonium ion-selective electrodes are commonly used. The membrane material of these electrodes is selectively permeable to ammonia or ammonium ions, and when the electrode is in contact with a water sample, a potential difference is generated on both sides of the membrane, which is proportional to the concentration of ammonia and nitrogen in the water. By measuring the potential difference between the indicator electrode and the reference electrode, the concentration of ammonia nitrogen in water can be calculated. Ammonia nitrogen sensor is widely used in various natural water bodies such as rivers, lakes, groundwater, etc. as well as sewage outfalls, sewage treatment plants, etc. for ammonia nitrogen monitoring, providing real-time, continuous and accurate data support for environmental management departments.