The online nitrite ion sensor adopts PVC membrane ion selective electrode method, designed specifically for online monitoring of nitrite concentration in water quality. The measurement range is 0~2.000 mg/L, with an accuracy of ± 5%, and built-in Pt1000 automatic temperature compensation. Output RS485 (Modbus RTU) signals, which can be easily connected to PLC, DCS, and industrial control systems. The shell is made of 316L stainless steel, with a protection level of IP68, and supports 3/4NPT threaded immersion installation. The sensor has undergone two-point calibration before leaving the factory and has long-term stability, suitable for various working conditions such as pipelines and water tanks.