Electronic Aroma-sensing Systems

RESONANT FREQUENCY OF A SAW DELAY LINE OSCILLATOR RESONDS TO THE MASS CHANGE OF A SELECTIVE COATING EXPOSED TO VAPORS 

The instruments have been compared to a musician with a manuscript. If we see the musical score of, say, Sibelius s Finlandia, it might be difficult to imagine the associated sound unless we are musicians. Electronic odour sensing seeks to transcribe, as it were, a sensory stimulus for one sense (olfactory) to another (visual). In addition, this transcription is required to be measurable and sufficiently reproducible to allow comparison. The analogy with music continues. Just as with a musical score, the transcription cannot reproduce all of the attributes for example, the precise speed of performance, the balance of the instruments and so on only artificial reproduction in the form of a recording can do that. In the same way, electronic odour sensing can only depict some of the attributes of a fragrance. 

The artificial intelligence systems to which sensor arrays are coupled supply the closest likeness to the human olfactory system. Some of the recent theories on olfaction require that the human nose has only relatively few types of receptor, each with low specificity. The activation of differing patterns of these receptors supplies the brain with sufficient information for an odour to be described, if not recognized. As a consequence of this belief, the volatile chemical-sensing systems commercially available only contain from 6 to 32 sensors, each having relatively low specificity. Statistical methods such as principal component analysis, canonical discriminant analysis and Euclidian distances are used for mapping or linked to artificial neural nets as an aid to classification of the odour fingerprints . 

Apart from the use as a Quality Control device, other areas in which an artificial odour-sensing system could be utilized include all those in which classification of odour is required for example, human body odour, malodours and malodour counteractancy. Another area in which the new instrumentation could be utilized to advantage includes perfume substantivity, or diffusion from a substrate. For example, it could be used to measure levels of perfume in the air from a hard surface cleaner when used on a ceramic tile, or odour from human skin after spraying with a cologne, and so on. 

Amoore, The Stereochemical Theory of Olfaction, Proc. Sci. Sec. Toilet Goods Assn., 1962,37, Parts 1 2 (1-23, special supplement). 

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S Rocha, I Delgadillo, AJ Ferrer Correia, A Barros, P Wells. Application of an electronic aroma sensing system to cork stopper quality control. J Agric Food Chem 46 145-151, 1998. 

One scientific area in which neural networks have gained popularity is that of the development of systems inspired on olfactory and taste senses. The electronic nose (Gardner and Bartlett 1999), firstly conceived and applied, has gained recognition in fields like food, aroma or medical diagnosis. The electronic tongue (Vlasov and Legin... 

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