Study On The Effect Of Gas Humidity And Flow Rate To Response Characteristics Of Electronic Nose

In recent years,the research of electronic nose technology has received extensive attention,how to reduce the influence caused by gas humidity and flowrate and reduce the measuring error is the key issue in the field of electronic nose technology research.In this thesis the author chosed CH₄ and C₂H₄ as test gases,and studied the influence of gas humidity and flow rate on the electronic nose measurement,and puts forward different methods to reduce the measuring error.The main work and research results of this thesis can be list as follows:?1?In this thesis,the author designed a set of electronic nose system based on MP-4,TGS-816,TGS-2611 and TGS-2620 these four kinds of semiconductor gas sensors.The author designed and implemented the signal acquisition and processing module,algorithm identification module and display module.?2?By experiment,this thesis studied on the nonlinear relationship between the response voltage of the electronic nose sensors array and the gas humidity.In view of the measuring error caused by humidity to the electronic nose,the author used radial basis function neural network and BP neural network to compensate the measuring error.Test results showed that the measurement error of the electronic nose is reduced by more than 80%after the introduction of the humidity compensation algorithm,and the compensation effect of the radial basis function neural network algorithm is better than that of the BP neural network algorithm.?3?The author test with gas sensors in the electronic nose at different flowrate,and found that,when the gas flowrate increased,the reference voltage and steady-state voltage of the sensors would significantly reduced,the response time would greatly shortened,and the sensitivity would significantly improved.When the gas flowrate is lower than 200sccm,the characteristic parameters of the sensors would be greatly influenced by the gas flowrate;when the gas flow rate is higher than500sccm,the characteristic parameters of the sensors would be less affected by the gas flowrate.To reduce the measurement error caused by the change of gas flowrate,the author suggest that,in the electronic nose,a constant current pumping device could make the gas sensor working in the stable airflow to reduce the measuring error of the electronic nose.