Research On Portable Electrochemical NO₂ And O₃ Detection System

As common near-ground air pollutants,Atmospheric NO2 and O3 would seriously affect the oxidation of the atmosphere and hinder the construction of ecological civilization and the development of the national economy.Therefore,it is very meaningful and necessary to realize the accurate measurement of atmospheric NO2 and O3 concentration and to find out the pollution source.With the increasing complexity of atmospheric monitoring environment,the detection limit and resolution of gas monitoring equipment have been put forward higher,but traditional electrochemical sensing and detection equipments generally are costly,which fail to uncompensate sensor temperature and humidity drift.For this purpose,portable electrochemical NO2 and O3 detection systems are designed.Foue-electrode electrochemical sensor is selected as the concentration sensing carrier of the detection system,low noise circuit was selected to complete signal conversion,and data calibration model with temperature and humidity compensation and zero point correction functions was built to complete data calibration.Collection and processing of data was based on STM32 and ADS1115,then these data were transmited to the IOT platform through the WiFi module,realizing the remote online monitoring and storage of atmospheric NO2 and O3 concentrations.In order to ascertain the working performance of the electrochemical sensor,a sensor characteristic test experiment was carried out,which confirmed that the electrochemical sensor has a good linear response characteristic to the target gas of the ppbv level,and the cross sensitivity of the O3 sensor to NO2 gas is about 1.20,The sensor response time to 100ppbv calibration gas is<40s when the environmental temperature was at 10～40℃,but it increases to about 49s and 60s at 0℃ and-10℃.As a result,low temperature environment will impact the sensor’s time resolution.In order to clarify the detection accuracy of the detection system,the detection system and the gas analyzer Thermo were placed in the same conditions to carriy out the field contrast experiment.The parameter values of temperature and humidity compensation algorithm are determined by using the linear fitting method of multiple functions,alse confirmed that the carbon filtration can obtain pure background gas and achieve the zero correction.The concentration of NO2 and O3 ware at 0～30 ppbv and 0～100 ppbv during the experiment,and NO2 and O3 mean absolute error reduce about 1.5 ppbv and 6.8 ppbv after zero correction.To verify the accuracy,the correlation of NO2 data sets and O3 data sets obtained by data calibration and fitting reached 0.8278 and 0.9031 respectively during the measurements.The results show that the detection system provides a portable and low cost measure for remote on-line accurate measurement of atmospheric NO2 and O3.Figure[55]table[10]reference[70]...