Research On Drift Problem Of Limit Current Oxygen Sensor

As a kind of solid electrolyte sensor,limit current oxygen sensor has been widely valued for its high accuracy,fast response and long service life.It is the core component of oxygen concentration measurement instrument.Oxygen sensor is mainly used to detect the concentration of oxygen in gas.It has been widely used in all walks of life.However,the inevitable drift will occur in the actual use of oxygen concentration sensor.The drift characteristic is highly non-linear,which results in the reliability of the whole measurement system and the output accuracy deterioration.Therefore,it is of great significance to analyze,predict and compensate various factors affecting drift.Firstly,aiming at the drift problem of oxygen sensor,the conductive mechanism of zirconia solid electrolyte,reaction mechanism of oxygen pump in solid electrolyte,gas diffusion,heating process of solid electrolyte and theoretical calculation formula of limit current were studied.The difference method is used to quantitatively describe the drift of the oxygen sensor,and a modified formula for calculating the oxygen concentration considering the drift characteristics of the oxygen sensor is given in differential form.The mechanism of oxygen sensor gas sensing drift is analyzed and discussed in terms of chemical reaction activation energy,gas diffusion and aging of electrolyte materials.Three macro factors affecting oxygen concentration drift characteristics are concluded as external temperature of oxygen sensor,environmental oxygen concentration of test and time factor.Secondly,based on the data provided by the oxygen sensor drift characteristic test,the algorithm of machine learning and intelligent optimization is introduced to study the drift prediction of oxygen concentration sensor,and a compensation method based on prediction network is proposed.The test environment temperature,the spatial oxygen concentration,the sensor working time are used as the input parameters of the sensor drift prediction model,the output parameter is the sensor drift,the BP neural network prediction model is constructed,and the constructed BP is optimized by GA.The synchronization optimization of its weight and threshold improves the calculation accuracy.The SVR prediction model of oxygen concentration sensor is constructed,and the PSO is used to optimize the kernel function parameters and penalty factors of the prediction model,which improves the prediction performance of the SVR algorithm.Thirdly,based on the working mechanism of the limiting current type oxygen sensor,the FLUENT fluid analysis software is used to analyze the electrochemical process of the oxygen sensor fluid through numerical simulation,and an electrochemical simulation model is constructed.The electrochemical simulation model of the oxygen sensor was verified.The oxygen mass fraction distribution profile,the sensor current density distribution profile,and the electrolyte layer current density distribution cloud map were simulated.The particle size and porosity of the solid electrolyte microstructure parameters were taken as the main research objects.The influence of the microstructure change of the solid electrolyte on the electrochemical performance of the oxygen sensor was discussed in detail.Finally,the solid electrolyte performance characterization test,TGA test,and the factors affecting the drift of the oxygen sensor were discussed.Scanning electron microscopy and energy spectrum analysis were used to analyze and compare the microscopic morphology of the sensor core with drift over fault and the sensitive core of the normal working sensor,indicating that the oxygen sensor has drift fault and solid electrolyte crystal.There is a clear relationship between changes in microstructure,and changes in the porosity and grain size of the solid electrolyte layer lead to degradation of oxygen sensor performance.The thermogravimetric test was carried out on the solid electrolyte material by TG.The test results confirmed that the zirconia solid electrolyte has good thermal stability.In this paper,the oxygen sensor drift compensation algorithm verification test is used to further verify the rationality of the drift compensation algorithm,which provides an effective solution for the drift compensation problem of gas sensors.