The Research On Trace Harmful Gas Detection Technology Based On Electrochemical Method

Human production and life are inseparable from the gas environment.With the development and progress of social economy,a variety of harmful gases exist in a wide range of environments,such as atmosphere,production workshops,closed Chambers and so on.The harmful gases in the environment are often difficult to detect and can easily lead to various acute poisoning accidents and chronic poisoning damage.Timely monitoring the change of harmful gases in the environment is of great significance for controlling air pollution,detecting the leakage of harmful gases as early as possible,and protecting people’s lives and health.In this paper,based on the analysis and comparison of various gas detection methods,the electrochemical gas detection method was selected for the detection of harmful gases such as carbon monoxide and nitrogen dioxide at low concentration.The problems of noise,sensor calibration and cross interference in low concentration electrochemical sensor detection are studied.The main work of the paper is as follows:1.Based on a wide searching of the control standards of hazardous gases at home and abroad,the technical indicators of electrochemical gas sensors at home and abroad were investigated,and the sensor selection of detection system was completed.According to the working principle of electrochemical sensor with different structure,the hardware system of electrochemical sensor with different structure and gas can be designed and developed.Hardware system including:general in reducing and oxidizing gas detection of two electrodes,three,four electrode sensor electrode constant voltage driver module,trans-impedance amplifier current detection circuit module,potential adjustment circuit,A/D conversion circuit,the hardware part of the power supply module and microcontroller part of used for data collection.The hardware part can drive the sensor correctly after experimental debugging,and the measured working parameters can meet the relevant design requirements.2.Aiming at the problem of noise affecting measurement results in the detection of high precision electrochemical sensor with low concentration of harmful gas,an electrochemical gas sensor filtering method based on kalman-wavelet filtering was proposed by analyzing the possible causes of noise through experiments.The results of this method are compared with the traditional filtering methods such as mean filtering and median filtering.Experimental results show that kalman-wavelet filter can filter noise better than other filtering methods.3.Aiming at the existing problem of harmful gas in the calibration of sensor,based on the ecological environment was proposed and designed for data center air pollution monitoring data,combined with sensors data fitting of sensor calibration experiment method,used in this paper,the experimental method of sensor calibration,the experiment methods in the complete sensor calibration at the same time,reduced the demand for high precision distribution equipment,at the same time avoid the harmful gas pollution in the process of calibration.Carbon monoxide sensor using the method of calibration of three electrodes measured value and true value of root mean square error in 24 hours of 0.0648mg·m-3,four electrode carbon monoxide sensor measurement value and real value of root mean square error in 24 hours of 0.0860mg·m-3,four electrode NO2 sensors in ozone concentration under the condition of less than 20μg·m-3 measure value and real value root mean square error in 24 hours 9.5963μg·m-3.4.Aiming at the problem of ozone cross interference in NO2 sensor.Based on the analysis of the mechanism of cross interference of electrochemical gas sensor,a compensation method for ozone cross interference of electrochemical gas sensor of nitrogen dioxide based on multi-sensor fusion is proposed.Experiments have proved that this method can effectively compensate the interference of ozone on NO2 sensor.The measured value of NO2 and the real value after compensation have a root mean square error of 18.98μg·m-3 within 24 hours in the presence of ozone interference,which is better than the root mean square error of 68.09μ·m-3 in the uncompensated condition.