Relative humidity: An interfering parameter for the characterization of a TGS sensor array

In air conditioned atmospheres, relative humidity (RH) is generally fixed in the 30%-60% RH range to be comfortable. But tin oxide gas sensors, which are generally used in electronic nose applications, are sensitive to the humidity. So, we have studied the influence of the relative humidity rate variation on the response of a Tagushi type sensor array used in an environmental electronic nose application. In this paper, we first summarize the sensor response distribution in terms of conductance dynamic slope or steady-state conductance values. Afterwards, two pattern recognition methods, Principal Component Analysis and Discriminant Factorial Analysis, are successively applied. We show that we are able to identify the target gas, a refrigerant gas Forane R134a, and also to well discriminate an unknown case by using only the conductance dynamic slope even if the relative humidity rate varies.