Abstract
The paper deals with a functional instability of electronic nose (e-nose) units which significantly limits their real-life applications. Here we demonstrate how to approach this issue with example of an e-nose based on a metal oxide sensor array developed at the Karlsruhe Institute of Technology (Germany). We consider the instability of e-nose operation at different time scales ranging from minutes to many years. To test the e-nose we employ open-air and headspace sampling of analyte odors. The multivariate recognition algorithm to process the multisensor array signals is based on the linear discriminant analysis method. Accounting for the received results, we argue that the stability of device operation is mostly affected by accidental changes in the ambient air composition. To overcome instabilities, we introduce the add-training procedure which is found to successfully manage both the temporal changes of ambient and the drift of multisensor array properties, even long-term. The method can be easily implemented in practical applications of e-noses and improve prospects for device marketing.
Highlights
A sufficient time has gone since introduction of the electronic nose concept, which harks to a pioneering paper by Persaud and Dodd [1]
In view of the main topics of the present study, we first summarize that the ambient air variations seem to be the most significant factor to disturb the stability of recognition by the e-nose based on metal-oxide multisensor arrays
This is supported by our data recorded over different time scales of e-nose operation ranging from tens of minutes to several years in an ambient indoor air background
Summary
A sufficient time has gone since introduction of the electronic nose (or e-nose) concept, which harks to a pioneering paper by Persaud and Dodd [1]. The sensitivity and selectivity are very frequently considered as the major topics of research for many labs dealing with e-nose and/or gas sensors in general [3,4,18,19] These issues are abundantly reported to be sufficient for many practical applications where a high discrimination of gases at low concentrations is not necessary [20,21]. In spite of the listed instability factors, we try to show here that the currently available e-noses can work stably even on the long-term scale We approach this critical issue considering primarily the e-nose based on a chemiresistive metal-oxide multisensor array.
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