The principle of Smarter NO3 ion selective method: An ion selective electrode is an indicator electrode that has selectivity for a specific ion. The Smarter NO3 online ion concentration analyzer detects the sample and records the electrode potential. Then, a high-precision diaphragm pump or injection pump is used to add a certain standard solution to the reaction pool and read again. Based on the difference between the two readings, the initial concentration of the sample was calculated, eliminating the influence of other components in the sample. In addition, due to the automatic adjustment of the amount of standard solution added, the measurement range also changes automatically. Within a considerable concentration range, the measurement accuracy can be maintained within 1%.