Toward Sensor to Reproduce Human Sense - The Electronic Nose Artificial Olfaction Technology - page 122

5.5 Applications
• Biomedical and biotechnology applications: Urine analysis, Herbal analysis,
drug analysis.
• Food analysis: wine evaluation for taste and flavor, Alcohols in beverages,
freshness of milk, coffee brand analysis; analyze enhanced flavored level i.e., in
flavored milk, fruit juice.
• Pharmaceuticals industries: taste quantifying tablets, syrups, powders, capsules.
• Environment monitoring
• Safety
• Chemical industry
5.6 Machine Olfaction
Smell is still anonymous to scientists in somehow, which cannot be studied with
straightforwardness in vertebrates. Another problem is that the sense of smell is
poorly developed in human beings in comparison with the same in many verte-
brates [ 13 ]. This makes realization of an artificial olfactory system a challenging
task. An artificial olfactory system (commonly known as E-nose) provides a low
cost alternative to identification, quantification and characterization of odors.
The inspiration behind the mechanisms of machine olfaction is human olfac-
tion. So to understand the operation of an E-nose it is important to first understand
the biological act of smelling. With the human olfactory system that enables us to
characterize an odor. Therefore, a description of the human olfactory system and
the properties of odorous molecules are discussed in Chaps. 3 and 4 before dis-
cussing the so-called method of machine olfaction.
The Artificial nose (Machine olfaction) is a system consisting of three func-
tional components that operate in sequence on an odorant sample- a sample
handler, an array of gas sensors, and a signal-processing system. Odorant
uniqueness is the output of the E-nose and an estimate of the concentration of the
odorant, or the characteristic properties of the odor as might be perceived by a
human. The olfactory system detects small differences in the composition of
natural odorants, made up of hundreds of molecules. Odorous quality is theoret-
ically represented by a combinatorial code: activation of distinct but overlapping
subsets of olfactory receptors resulting in activation of a distinct subset of
glomeruli in the main olfactory bulb.
Fundamental to the artificial nose is the idea that each sensor in the array has
different sensitivity. For example, odorant No. 1 may produce a high response in
one sensor and lower responses in others, whereas odorant No. 2 might produce
high readings for sensors other than the one that ''took'' to odorant No. 1. Human
olfaction and machine olfaction have different mechanisms to sense smell, and
thus the quantitative description of an odorant can also be very different for human