Discrimination of a refrigerant gas in a humidity controlled atmosphere byusing modelling parameters

For real life conditions of use, the application based on tin oxide gas sen sors must be humidity controlled, because humidity is a very influent param eter which may cause false gas detection. In our application, we want to di stinguish a refrigerant gas (Forane R134a) in an air conditioned atmosphere using a TGS gas sensor array. At first, this paper presents a summary of t he sensor array time-dependent response in a Forane R134a gas concentration (0-1000 ppm) for a humid air atmosphere (0-85%). We show that these respon ses can be well fitted by a double exponential model for which we extract f ive modelling parameters. These variables are coupled or not with two exper imental parameters, the steady-state conductance and the conductance dynami c slope, and then arranged in data bases. Afterwards, these data bases are treated by using two complementary pattern recognition methods: the princip al component analysis (PCA) followed by the discriminant factorial analysis (DFA). We show the ability to discriminate the target gas, whatever the hu midity rate, when the modelling parameters are coupled or not with the expe rimental parameters. Finally, the identification of unknown cases is descri bed. (C) 2000 Elsevier Science S.A. All rights reserved.