The NH4 ion selective electrode is a grid film electrode,the material of which mainly uses a special organic ion exchange membrane that dissolves in the organic solution and penetrates with the PVC mesh. The fields it is widely used include: drinking water, fertilizer, and refrigerant. To use the electrode requires the reference electrode, it has good repeatability and faster response time, but its accuracy is no better than the colorimetric method. The outer appearance of the ammonia nitrogen sensor is shown in Figure 12.