ELECTRONIC NOSE BY
Sree sailaja Suravarapu (y5ec089) Email-id:
[email protected] Vijaya Kolli (y5ec116) Email-id:
[email protected]
ABSTRACT The term "electronic nose" was first used in a jocular sense during our early work with sensor arrays in the 1980's. An electronic nose (e-nose) is a device that identifies the specific components of an odor and analyzes its chemical makeup to identify it. Of all the five senses, olfaction uses the largest part of the brain and is an essential part of our daily lives. Our human nose is elegant, sensitive, and self-repairing, but the E-nose sensors do not fatigue or get the "flu". Further, the E-nose can be sent to detect toxic and otherwise hazardous situations that humans may wish to avoid. An electronic nose can be regarded as a modular system comprising a set of active materials which detect the odour, associated sensors which transduce the chemical quantity into electrical signals, followed by appropriate signal conditioning and processing to classify known odours or identify unknown odours. The signals generated by an array of odour sensors need to be processed in a sophisticated manner. An odor is composed of molecules, each of which has a specific size and shape. Each of these molecules has a correspondingly sized and shaped receptor in the human nose. When a specific receptor receives a molecule, it sends a signal to the brain and the brain identifies the smell associated with that particular molecule. Electronic noses based on the biological model work in a similar manner, albeit substituting sensors for the receptors, and transmitting the signal to a program for processing, rather than to the brain. Electronic noses are useful in various fields. Currently, the biggest market for electronic noses is the food industry. Environmental applications of electronic noses include analysis of fuel mixtures, detection of oil leaks, testing ground water for odors, and identification of household odors. Potential applications include identification of toxic wastes, air quality monitoring, and monitoring factory emissions. Sensors can detect toxic CO, which is odorless to humans. An electronic nose has applicability as a diagnostic tool. The tragic bombings in London on the 7 July 2005 have caused many to call for bag
searching at the ticket barriers on the Underground. This would cause huge delays, apart from finding the manpower to do it. A possible alternative is using an “electronic nose” to sniff out possible explosives so that only selected bags need to be searched by staff.
1.0 INTRODUCTION:
An electronic nose can be regarded as a
Scientists have endowed computers with
modular system comprising a set of
eyes to see, thanks to digital cameras,
active materials which detect the odour,
and ears to hear, via microphones and
associated sensors which transduce the
sophisticated recognition software. Now
chemical quantity into electrical signals,
they're taking computers further into the
followed
realm
the
conditioning and processing to classify
development of an artificial nose. The
known odours or identify unknown
term "electronic nose" was first used in a
odours. The "electronic nose" is a
jocular sense during our early work with
relatively new tool that may be used for
sensor arrays in the 1980's. As the
safety, quality, or process monitoring,
technology
accomplishing
of
the
senses
developed,
with
it
became
by
appropriate
in
a
few
signal
minutes
apparent that the animal and human
procedures that may presently require
olfactory systems operate on the same
days to complete. The two main
principle: A relatively small number of
components of an electronic nose are the
nonselective
sensing
receptors
allow
the
system
which
consists
of
discrimination of thousands of different
chemical sensors and the automated
odors. Electronic/artificial noses are
pattern recognition system. The sensing
being developed as systems for the
system can be an array of several
automated detection and classification of
different
odors, vapors, and gases. An electronic
chemical sensors), where each element
nose (e-nose) is a device that identifies
measures a different property of the
the specific components of an odor and
sensed chemical, or it can be a single
analyzes its chemical makeup to identify
sensing device (e.g., spectrometer) that
it.
produces an array of measurements for
2.0
WHAT
IS
ELECTRONIC NOSE?
AN
each
sensing
chemical,
combination.
or The
elements
it
can
quantity
(e.g.,
be
a and
complexity of the data collected by
comprising a set of active materials
sensors array can make conventional
which detect the odour, associated
chemical
an
sensors which transduce the chemical
automated fashion difficult. Gas sensors
quantity into electrical signals, followed
tend to have very broad selectivity,
by appropriate signal conditioning and
responding to many different substances.
processing to classify known odours or
This
identify unknown odours, see Figure 4
is
analysis
a
of
data
disadvantage
in
in
most
applications, but in the electronic nose, it is a definite advantage. ENose can detect an electronic change of 1 part per million. Although every sensor in an array may respond to a given chemical, these responses will usually be different. Figure 1 shows sets of responses of a typical sensor array to different pure chemicals:
FIGURE-2 ELECTRONIC NOSE SCHEME
Using variants of molecules found in biology it is possible to create 'senses' from electrical charges caused by the binding of the molecules to mimic the human nose. With this approach, the sensitivity of the device can be a
3.0
ELECTRONIC
NOSE
SCHEME:
as
available electronic nose. The receptors, which will be
An electronic nose can be regarded
thousand times better than the currently
a
modular
system
housed within an artificial membrane, remain in a closed steady state until
approached by smell molecules, when they will open and transmit an electrical
4.0 DATA PROCESSING
signal which will indicate the nature of
METHODS:
the odour
The signals generated by an array of odour sensors need to be processed in a sophisticated manner. The electronic nose
research
group
has
obtained
considerable experience in the use of various parametric and non-parametric pattern
analysis
techniques.
These
include the use of linear and non-linear techniques, such as discriminant function analysis,
cluster
analysis,
genetic
algorithms, fuzzy logic, and adaptive
FIGURE-3 CHEMICAL SENSOR
models. An odor is composed of ENose uses a collection of 16 different
molecules, each of which has a specific
polymer films. These films are specially
size and shape. Each of these molecules
designed to conduct electricity. When a
has a correspondingly sized and shaped
substance -- such as the stray molecules
receptor in the human nose. When a
from a glass of soda -- is absorbed into
specific receptor receives a molecule, it
these films, the films expand slightly,
sends a signal to the brain and the brain
and that changes how much electricity
identifies the smell associated with that
they conduct. Because each film is made
particular molecule. Electronic noses
of a different polymer, each one reacts to
based on the biological model work in a
each substance, or analyte, in a slightly
similar
different way. And, while the changes in
sensors
conductivity in a single polymer film
transmitting the signal to a program for
wouldn't be enough to identify an
processing, rather than to the brain.
analyte, the varied changes in 16 films
Electronic noses are one example of a
produce
growing
pattern.
a
distinctive,
identifiable
manner, for
biomimetics,
albeit
the
research or
substituting
receptors,
area
biomimicry,
and
called which
involves
human-made
applications
patterned on natural phenomena.
or primitive brain, and odors can elicit basic emotions like love, sadness, or fear The term, "electronic nose" or "E-nose" has come into common usage as a generic term for an array
of
chemical
gas
sensors
incorporated into an artificial olfaction device, after its introduction in the title of a landmark conference on this subject in Iceland in 1991. The term E-nose is not
pejorative.
There
are
striking
analogies between the artificial noses of man and the "Bio-nose" constructed by Figure-4 electronic nose
Nature. Figure 2 illustrates a biological
5.0 ANALOGY BETWEEN
nose and points out the important
THE BIOLOGICAL NOSE
features
of
this
"instrument".
AND E-NOSE: Of all the five senses, olfaction uses the largest part of the brain and is an essential part of our daily lives. Indeed, the appeal of most flavors is more related to the odor arising from volatiles than to the reaction of the taste buds
to dissolved
substances.
Our
olfactory system has evolved not only to
Fig-5 the "Biological Nose" (by Mother Nature)
enhance taste but also to warn us of dangerous situations. We can easily
Figure
detect just a few parts per billion of the
electronic nose. Comparing the two is
toxic gas hydrogen sulfide in sewer gas,
instructive.
an ability that can save our life. Olfaction is closely related to the limbic
3
illustrates
the
artificial
with the sample and produce electrical signals. A computer reads the unique pattern of signals, and interprets them with some form of intelligent pattern classification algorithm. From these similarities we can easily understand the nomenclature. However, there are still fundamental differences in both the Fig-6 Artificial Electronic Nose
The human nose uses the lungs to bring the odor to the epithelium layer; the electronic nose has a pump. The human nose has mucous, hairs, and membranes
instrumentation and software! The Bionose can perform tasks still out of reach for the E-nose, but the reverse is also true
to act as filters and concentrators, while
October 6, 2004: Onboard the space
the E-nose has an inlet sampling system
station, astronauts are surrounded by
that provides sample filtration and
ammonia. It flows through pipes,
conditioning to protect the sensors and
carrying heat generated inside the station
enhance
(by people and electronics) outside to
epithelium
selectivity. contains
The the
human olfactory
epithelium, which contains millions of
space. Ammonia helps keep the station habitable.
sensing cells, selected from 100-200 different genotypes that interact with the
But it's also a poison. And if it leaks, the
odorous molecules in unique ways. The
astronauts will need to know quickly.
E-nose has a variety of sensors that
Ammonia becomes dangerous at a
interact differently with the sample. The
concentration of a few parts per million
human receptors convert the chemical
(ppm). Humans, though, can't sense it
responses to electronic nerve impulses.
until it reaches about 50 ppmAnd then
The unique patterns of nerve impulses
there's fire. Before an electrical fire
are propagated by neurons through a
breaks out, increasing heat releases a
complex network before reaching the
variety of signature molecules. Humans
higher brain for interpretation. Similarly,
can't
the chemical sensors in the E-nose react
concentrations become high. Astronauts
sense
them
either
until
need better noses!That's why NASA is
Northwest
National
developing the Electronic Nose, or
exploring the technologies required to
ENose for short. It's a device that can
perform environmental restoration and
learn to recognize almost any compound
waste management in a cost effective
or combination of compounds. It can
manner.
even be trained to distinguish between
development of portable, inexpensive
Pepsi and Coke. Like a human nose, the
systems
ENose is amazingly versatile, yet it's
identification of contaminants in the
much more sensitive
field. Electronic noses fit this category.
This
Laboratory
effort
capable
includes of
is
the
real-time
Environmental applications of electronic noses include analysis of fuel mixtures, detection of oil leaks, testing ground water for odors, and identification of household odors. Potential applications
figure-7 working process
include identification of toxic wastes, air
6.0 ADVANTAGES OF E-NOSE:
quality
Our human nose is elegant, sensitive,
factory emissions. Sensors can detect
and
toxic CO, which is odorless to humans.
self-repairing,
but
the
E-nose
sensors do not fatigue or get the "flu". Further, the E-nose can be sent to detect toxic and otherwise hazardous situations that
humans may
6.1
ELECTRONIC
wish
monitoring
NOSES
FOR
MEDICINE:
avoid.
Because the sense of
NOSE
FOR
smell is an important sense to the
Enormous amounts of hazardous waste (nuclear, chemical, and mixed wastes) were generated by more than 40 years of weaponsÕ production in the U.S. Department of EnergyÕs complex.
ELECTRONIC
and
to
ENVIRONMENTAL MONITORING:
weaponsÕ
6.2
monitoring,
The
Pacific
physician,
an
electronic
nose
has
applicability as a diagnostic tool. An electronic nose can examine odors from the body (e.g., breath, wounds, body fluids,
etc.)
and
identify
possible
problems. Odors in the breath can be indicative of gastrointestinal problems, sinus problems, infections, diabetes, and
liver problems. Infected wounds and
production especially when qualitative
tissues emit distinctive odors that can be
results will do.
detected by an electronic nose. Odors coming from body fluids can indicate liver and bladder problems. A more futuristic application of electronic noses has
been
recently
proposed
for
telesurgery
6.4
ELECTRONIC
NOSE
FOR
MULTIMEDIA APPLICATIONS: Multimedia systems are widely used in consumer
electronics
environments
today, where humans can work and
6.3 ELECTRONICS NOSE FOR THE
communicate
through
multi-sensory
interfaces. Unfortunately smell detection
FOOD INDUSTRY:
and generation systems are not part of Currently, the biggest
today's multimedia systems. Hence we
market for electronic noses is the food
can use electronic nose in multimedia
industry. Applications of electronic noses
environment.
in the food industry include quality assessment
in
food
production,
inspection of food quality by odor,
6.5 ELECTRONIC NOSE USED IN DETECTION OF BOMBS:
control of food cooking processes, inspection
of
fish,
monitoring
the
fermentation process, verifying if orange juice is natural, monitoring food and beverage inspection
odors, of
grading
beverage
whiskey, containers,
checking plastic wrap for containment of onion odor, and automated flavor control to name a few. In some instances electronic noses can be used to augment or replace panels of human experts. In other cases, electronic noses can be used to reduce the amount of analytical chemistry that is performed in food
The tragic bombings in London on the 7 July 2005 have caused many to call for bag searching at the ticket barriers on the Underground. This would cause huge delays, apart from finding the manpower to do it. A possible
alternative
is
using
an
“electronic nose” to sniff out possible explosives so that only selected bags need to be searched by staff. The concept has been around for a long time, and was initially ridiculed. The basic idea is a device
that
identifies
the
specific
components of an odour and analyzes its
2.
chemical makeup to identify it. One
encyclopedia
mechanism would be an array of
nose.mht
E:\enose\Electrochemistry ---
Electrochemical
electronic sensors would sniff out the odours while a second mechanism would see if it could recognize the pattern.
3. http://science.nasa.gov/headlines/y2004/ 06oct_enose.htm
6.6 OTHER APPLICATIONS: 4. E:\enose\The Electronic Nose.mht Electronic nose can be used for early fire detection. E-nose offers an opportunity to develop an instrumental approach for the human analytical endpoints like odor, flavor, hazardous, contaminated, spoiled, and the like.
7.0 CONCLUSION: Humans are not well suited for repetitive or boring tasks that are better left to machines. No wonder the E-nose is sometimes referred to as a "sniffer". The E-nose has the interesting ability to address analytical problems that have been refractory to traditional analytical approaches. GOSPEL is a European network of excellence in Artificial Olfaction.
8.0 REFERENCE: 1. Electronics for u August 2006 edition.
5. E:\enose\12.mht 6. E:\enose\Artificial Noses ___ and Taste.mht