20473653 Electronic Nose

8/2/2019 20473653 Electronic Nose

1/28

CHAPTER 1

1. INTRODUCTION

1.1 What is an electronic nose?

Electronic Nose is a smart instrument that is designed to detect and discriminate among

complex odours using an array of sensors. The array of sensors consists of a number of

broadly tuned (non-specific) sensors that are treated with a variety of odour-sensitive

biological or chemical materials. An odour stimulus generates a characteristic fingerprint

from this array of sensors. Patterns or fingerprints from known odours are used to construct a

database and train a pattern recognition system so that unknown odours can Neural Network

based Soft Computing Techniques are used to tune near accurate co-relation smell print of

multi-sensor array with that of Tea Tasters scores. The software framework has been

designed with adequate flexibility and openness so that tea planters themselves may train the

system with their own system of scoring so that the instrument will, then on, reliably predict

such smell print scores.subsequently be classified and/or identified.

Electronic nose is a device that identifies the specific Components of an odour and

analyzes its chemical makeup to Identify it. An electronic nose consists of mechanism for identification of chemical detection such as

an array of electronic sensors and a mechanism for pattern recognition.

An electronic nose is such an array of non-specific chemical sensors, controlled and

analyzed electronically, which mimics the action of the mammalian nose by recognizing patterns

of response to vapors. The sensors used in the device discussed here are conductometric

chemical sensors which change resistance when the composition of its environment changes. The

sensors are not specific to any one vapor; it is in the use of an array of sensors, each of whichresponds differently, that gases and gas mixtures can be identified by the pattern of response of

the array. Electronic Noses have been discussed by several authors, and may be applied to

environmental monitoring as well as to quality control in such wide fields as food processing and

industrial environmental monitoring.


2/28

In the device designed and built for crew habitat air monitoring, a baseline of clean air is

established, and deviations from that baseline are recorded as changes in resistance of the

sensors. The pattern of distributed response of the sensors is deconvoluted, and contaminants

identified and quantified by using a set of software analysis routines developed for this

purpose. The overall goal of the program at JPL/Caltech has been the development of a

miniature sensor which may be used to monitor the breathing air in the International Space

Station, and which may be coordinated with the environmental control system to solve air

quality problems without crew intervention.

Figure 1.1 Electronic NoseElectronic Nose developed in the early 1980s, the operating principle consists of

an array of chemical sensors that are coupled to an appropriate pattern recognition

program that emulates the human olfactory system. The individual sensors consist of

conductive polymers which have defined adsorptive surfaces that, when interacting with

volatile chemicals, display a change of electrical resistance that can be recorded.Even


3/28

though each individual sensor responds more selectively to a certain group of chemicals,

they all show an overlapping response (this is called cross-selectivity ).How the

electronic nose actually works is that, for each complex aroma, the array of sensors

produces a unique response pattern -called a fingerprint- which reflects the aroma

complexity of that sample. An electronic nose, therefore, acts more like a human nose in

that it does not measure the amount of an individual aroma compound, but rather, gives a

global and qualitative idea of the whole aroma profile. The electronic nose consists of

two components, (1) an array of chemical sensors (usually gas sensors) and (2) a pattern-

recognition algorithm. The sensor array "sniffs" the vapors from a sample and provides a

set of measurements; the pattern-recognizer compares the pattern of the measurements to

stored patterns for known materials. Gas sensors tend to have very broad selectivity,

responding to many different substances. This is a disadvantage in most applications, but

in the electronic nose, it is a definite advantage. Although every sensor in an array may

respond to a given chemical, these responses will usually be different. Figure 1.2 shows

sets of responses of a typical sensor array to different pure chemicals:

Acetone Benzene Chloroform

Figure 1.2 Responses of a typical sensor array to different pure chemicals


4/28

1.2 What is an odour?

An odour 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. An odor or odour (see spelling differences) is a

volatilized chemical compound, generally at a very low concentration, that humans or other

animals perceive by the sense ofolfaction. Odors are also called smells, which can refer to both

pleasant and unpleasant odors. The terms fragrance, scent, and aroma are used primarily by the

food and cosmetic industry to describe a pleasant odor, and are sometimes used to refer to

perfumes. In contrast, malodorous, stench, reek, and stink are used specifically to describe

unpleasant odors. The study of odors is a growing field but is a complex and difficult one. The

human olfactory system can detect many thousands of scents based on only very minute airborne

concentrations of a chemical. The sense of smell of many animals is even better. Some fragrant

flowers give off odor plumes that move downwind and are detectable by bees more than a

kilometer away.

The study of odors can also get complicated because of the complex chemistry taking

place at the moment of a smell sensation. For example iron metal objects are perceived to have

an odor when touched although iron vapor pressure is negligible. According to a 2006 study this

smell is the result ofaldehydes and ketones released from the human skin on contact with ferrous

ions that are formed in the sweat-mediated corrosion of iron. The same chemicals are also

associated with the smell of blood as ferrous iron in blood on skin produces the same reaction.

odour in a substance is due to volatile Organic compounds which evaporate and get

carried Away by air.

1.3 Recepters

In biochemistry, a receptor is a protein molecule, embedded in either the plasma

membrane orcytoplasm of a cell, to which a mobile signaling (or "signal") molecule may attach.

A molecule which binds to a receptor is called a " ligand," and may be a peptide (such as a

neurotransmitter), a hormone, a pharmaceutical drug, or a toxin, and when such binding occurs,
http://en.wikipedia.org/wiki/American_and_British_English_spelling_differenceshttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Sensehttp://en.wikipedia.org/wiki/Olfactionhttp://en.wikipedia.org/wiki/Smellhttp://en.wikipedia.org/wiki/Perfumehttp://en.wikipedia.org/wiki/Olfactory_systemhttp://en.wikipedia.org/wiki/Bee_learning_and_communicationhttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ferroushttp://en.wikipedia.org/wiki/Biochemistryhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Ligand_(biochemistry)http://en.wikipedia.org/wiki/Neurotransmitterhttp://en.wikipedia.org/wiki/Hormonehttp://en.wikipedia.org/wiki/American_and_British_English_spelling_differenceshttp://en.wikipedia.org/wiki/Chemical_compoundhttp://en.wikipedia.org/wiki/Sensehttp://en.wikipedia.org/wiki/Olfactionhttp://en.wikipedia.org/wiki/Smellhttp://en.wikipedia.org/wiki/Perfumehttp://en.wikipedia.org/wiki/Olfactory_systemhttp://en.wikipedia.org/wiki/Bee_learning_and_communicationhttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Aldehydehttp://en.wikipedia.org/wiki/Ketonehttp://en.wikipedia.org/wiki/Ferroushttp://en.wikipedia.org/wiki/Biochemistryhttp://en.wikipedia.org/wiki/Proteinhttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Ligand_(biochemistry)http://en.wikipedia.org/wiki/Neurotransmitterhttp://en.wikipedia.org/wiki/Hormone


5/28

the receptor undergoes a conformational change which ordinarily initiates a cellular response.

However, some ligands merely block receptors without inducing any response (e.g.. Ligand-

induced changes in receptors result in physiological changes which constitute the biological

activity of the ligands.

1.4 What is recognition?

receptors in human nose act as binding sites for volatile organic compound these are

volatile organic compound then processed by brain and We recognise the smell.

1.5 What is volatile organic compound?

There is no clear and widely supported definition of a volatile organic compounds. From

a chemistry viewpoint "Volatile Organic Compound" can mean any organic compound (all

chemical compounds containing carbon with exceptions) that is volatile (evaporating or

vaporizing readily under normal conditions). This is a very broad set of chemicals. Definitions

vary depending on the particular context. There are many other widely used terms that are a

subclass of volatile organic compounds. Laws or regulations are often responsible for creation of

legal definitions of volatile organic compounds or definitions of subclasses of volatile organic

compounds.Volatile organic compounds are organic chemical compounds that have high enough

vapour pressures under normal conditions to significantly vaporize and enter the

atmosphere.Volatile organic compounds are numerous and varied. Although ubiquitous in nature

and modern industrial society, they may also be harmful or toxic. volatile organic compounds, or

subsets of the , volatile organic compounds are often regulated.
http://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Volatilehttp://en.wikipedia.org/wiki/Organic_chemicalshttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vaporizehttp://en.wikipedia.org/wiki/Regulation_of_chemicalshttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Volatilehttp://en.wikipedia.org/wiki/Organic_chemicalshttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vaporizehttp://en.wikipedia.org/wiki/Regulation_of_chemicals


6/28

CHAPTER 2

2. COMPONENTS

2.1 Main components of electronic nose

Sensing System

Pattern Recognition System

2.1 Sub components of electronic nose

Sample Delivery System

Detection System

Computing System

2.3Working principle of electronic nose

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 models. 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 one example of a growing research area

called biomimetics, or biomimicry, which involves human-made applications patterned on

natural phenomena.


7/28

Figure 2.1 Block Diagram of Electronic Nose

In a typical e-nose, an air sample is pulled by a vacuum pump through a tube into a small

chamber housing the electronic sensor array.The tube may be of plastic or stainless steel.

A sample-handling unit exposes the sensors to the odorant, producing a transient

response as the volatile organic compounds interact with the active material.

The sensor response is recorded and delivered to the Signal-processing unit.

Then a washing gas such as alcohol is applied to the array for a few seconds or a

minute,so as to remove the odorant mixture from the active material.

The more commonly used sensors include metal oxide semiconductors, conducting

polymers, quartz crystal microbalance, surface acoustic wave, and field effect transistors.

In recent years, other types of electronic noses have been developed that utilize mass

spectrometry or ultra fast gas chromatography as a detection system.

The computing system works to combine the responses of all of the sensors, which

represents the input for the data treatment. This part of the instrument performs global

fingerprint analysis and provides results and representations that can be easily interpreted.

Moreover, the electronic nose results can be correlated to those obtained from other

techniques.


8/28

Figure 2.2 Schematic Diagram Of Electronic Nose

An electronic nose system primarily consists of four functional blocks, viz., Odour

Handling and Delivery System, Sensors and Interface Electronics, Signal Processing and

Intelligent Pattern Analysis and Recognition. The array of sensors is exposed to volatile odour

vapour through suitable odour handling and delivery system that ensures constant exposure rate

to each of the sensors. The response signals of sensor array are conditioned and processed

through suitable circuitry and fed to an intelligent pattern recognition engine for classification,

analysis and declaration.

The most complicated parts of electronic olfaction process are odour capture andassociated sensor technology. Any sensor that responds reversibly to chemicals in gas or vapour

phase, has the potential to be participate in an array of sensor in an electronic nose. For black

manufactured tea, an array of Metal Oxide Semiconductor sensors have been used for assessment

of volatiles.


9/28

Figure 2.3 specified block diagram of electronic nose

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 intoelectrical signals, followed by appropriate signal conditioning and processing to classify known

odours or identify unknown odours, see 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 thousand times

better than the currently available electronic nose. The receptors, which will be housed within an

artificial membrane, remain in a closed steady state until approached by smell molecules, when

they will open and transmit an electrical signal which will indicate the nature ofthe odour.


10/28

Figure 2.4 Electronic Nose Scheme

Electronic Nose uses a collection of 16 different polymer films. These films are specially

designed to conduct electricity. When a substance -- such as the stray molecules from a glass of

soda -- is absorbed into these films, the films expand slightly, and that changes how much

electricity they conduct. Because each film is made of a different polymer, each one reacts toeach substance, or analyte, in a slightly different way. And, while the changes in conductivity in

a single polymer film wouldn't be enough to identify an analyte, the varied changes in 16 films

produce a distinctive, identifiable pattern.


11/28

CHAPTER 3

3. Analogy between the biological nose and electronic 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 enhance taste but also to warn us of dangerous situations. We can easily

detect just a few parts per billion of the toxic gas hydrogen sulfide in sewer gas, an ability that

can save our life. Olfaction is closely related to the limbic or primitive brain, and odors can elicit

basic emotions like love, sadness, or fear The term,"electronic 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.There are striking analogies between the artificial noses of man and the

"Biological-nose" constructed by illustrates a biological nose and points out the important

features of this "instrument". electronic nose. Comparing the two is instructive.

Figure 3.1 Human Nose


12/28

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 to act as filters and

concentrators, while the E-nose has an inlet sampling system that provides sample filtration and

conditioning to protect the sensors and enhance selectivity. The human epithelium contains the

olfactory epithelium, which contains millions of sensing cells, selected from 100-200 different

genotypes that interact with the odorous molecules in unique ways. The E-nose has a variety of

sensors that interact differently with the sample. The human receptors convert the chemical

responses to electronic nerve impulses. The unique patterns of nerve impulses are propagated by

neurons through a complex network before reaching the higher brain for interpretation.

Similarly, the chemical sensors in the E-nose react 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 instrumentation and

software! The Bionose can perform tasks still out of reach for the electronic-nose, but the reverse

is also true.

Figure 3.2 An Electronic Nose Mimicking The Human Nose


13/28

Onboard the space station, astronauts are surrounded by ammonia. It flows through pipes,

carrying heat generated inside the station (by people and electronics) outside to space. Ammonia

helps keep the station habitable. But it's also a poison. And if it leaks, the astronauts will need to

know quickly. Ammonia becomes dangerous at a concentration of a few parts per million.

Humans, though, can't sense it until it reaches about 50ppm and then there's fire. Before an

electrical fire breaks out, increasing heat releases a variety of signature molecules. Humans can't

sense them either until concentrations become high. Astronauts need better noses.That's why

NASA is developing the Electronic Nose, for short. It's a device that can learn to recognize

almost any compound or combination of compounds. It can even be trained to distinguish

between Pepsi and Coke. Like a human nose, the ENose is amazingly versatile, yet it's much

more sensitive .

Figure 1.1 EleINTRODUCTION TO SENSORS

A sensor is a device which can respond to some

properties of the environment and

transform the response into an electric signal. The

general working mechanism of a

sensor is illustrated by the following scheme :

In the field of sensors, the correct definition of

parameters is of paramount importance

because of these parameters:

~allow the diffusion of more reliable

informationamong researchers or sensor operators,

Figure 3.3 Comparison of human nose and electronic nose


14/28

CHAPTER 4

4. INTRODUCTION TO SENSORS

4.1 Definition

A sensor is a device which can respond to some properties of the environment and

transform the response into an electric signal.

Figure 4.1 sensor array

4.2 working mechanism

The general working mechanism of a sensor is illustrated by the following

scheme:

In the field of sensors, the correct definition of parameters is of paramount

importance because of these parameters:

allow the diffusion of more reliable information among researchers or sensor operators,

allow a better comprehension of the intrinsic behavior of the sensors help to propose


15/28

new standards, give fundamental criteria for a sound evaluation of different sensor

performances. The output signal is the response of the sensor when the sensitive material

undergoes modification

Figure 4.2 working mechanism of a sensor

The sensors in the electronic nose are polymer films which have been loaded with a

conductive medium, in this case carbon black. A baseline resistance of each film is established;

as the constituents in the air change, the films swell or contract in response to the newcomposition of the air, and the resistance changes. In the electronic nose, sensing films were

deposited on co-fired ceramic substrates which were provided with eight Au-Pd electrode sets.

Figure 4.3 Sketch of the ceramic substrate chip containing

eight sensors


16/28

4.3 Piezoelectric sensor

4.3.1Definition

A piezoelectric sensor is a device that uses the piezoelectric effect to measure

pressure, acceleration, strain orforceby converting them to an electrical signal.

Figure 4.4 A piezoelectric disk generates a voltage when deformed

Piezoelectric sensors have proven to be versatile tools for the measurement of various

processes. They are used forquality assurance,process control and for research and development

in many different industries.From the Curies initial discovery in 1880, it took until the 1950s

before the piezoelectric effect was used for industrial sensing applications. Since then, the

utilization of this measuring principle has experienced a constant growth and can be regarded as

a mature technology with an outstanding inherent reliability. It has been successfully used in

various applications as for example in medical, aerospace, nuclear instrumentation and in

mobile's touch key pad as pressure sensor.In the automotive industry piezoelectric elements are

used as the standard devices for engine indicating in developing internal combustion engines.

The combustion processes are measured with piezoelectric sensors. The sensors are either

directly mounted into additional holes into the cylinder head or the spark/glow plug is equipped

with a built in miniature piezoelectric sensor[1].The rise of piezoelectric technology is directly

related to a set of inherent advantages. The high modulus of elasticity of many piezoelectric

materials is comparable to that of many metals and goes up to 105 N/m. Even though
http://en.wikipedia.org/wiki/Piezoelectric_effecthttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Accelerationhttp://en.wikipedia.org/wiki/Strain_(materials_science)http://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Quality_assurancehttp://en.wikipedia.org/wiki/Process_controlhttp://en.wikipedia.org/wiki/Pierre_Curiehttp://en.wikipedia.org/wiki/Medicalhttp://en.wikipedia.org/wiki/Medicalhttp://en.wikipedia.org/wiki/Aerospacehttp://en.wikipedia.org/wiki/Nuclear_engineeringhttp://en.wikipedia.org/wiki/Nuclear_engineeringhttp://en.wikipedia.org/wiki/Automotive_industryhttp://en.wikipedia.org/wiki/Internal_combustion_engineshttp://en.wikipedia.org/wiki/Internal_combustion_engineshttp://www.avl.com/wo/webobsession.servlet.go/encoded/YXBwPWJjbXMmcGFnZT12aWV3JiZub2RlaWQ9NDAwMDU1MjUy.htmlhttp://en.wikipedia.org/wiki/Modulus_of_elasticityhttp://en.wikipedia.org/wiki/Modulus_of_elasticityhttp://en.wikipedia.org/wiki/Piezoelectric_effecthttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Accelerationhttp://en.wikipedia.org/wiki/Strain_(materials_science)http://en.wikipedia.org/wiki/Forcehttp://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/Quality_assurancehttp://en.wikipedia.org/wiki/Process_controlhttp://en.wikipedia.org/wiki/Pierre_Curiehttp://en.wikipedia.org/wiki/Medicalhttp://en.wikipedia.org/wiki/Aerospacehttp://en.wikipedia.org/wiki/Nuclear_engineeringhttp://en.wikipedia.org/wiki/Automotive_industryhttp://en.wikipedia.org/wiki/Internal_combustion_engineshttp://www.avl.com/wo/webobsession.servlet.go/encoded/YXBwPWJjbXMmcGFnZT12aWV3JiZub2RlaWQ9NDAwMDU1MjUy.htmlhttp://en.wikipedia.org/wiki/Modulus_of_elasticity


17/28

piezoelectric sensors are electromechanical systems that react on compression, the sensing

elements show almost zero deflection. This is the reason why piezoelectric sensors are so rugged,

have an extremely high natural frequency and an excellent linearity over a wide amplituderange.

Additionally, piezoelectric technology is insensitive to electromagnetic fields and radiation,

enabling measurements under harsh conditions. Some materials used (especially gallium

phosphate[2] ortourmaline) have an extreme stability over temperature enabling sensors to have

a working range of upto 1000C.Tourmaline shows pyroelectricity in addition to the

piezoelectric effect; this is the ability to generate an electrical signal when the temperature of the

crystal changes. This effect is also common topiezoceramic materials.

4.3.2 Principle of operation

Depending on how a piezoelectric material is cut, three main modes of operation

can be distinguished: transverse, longitudinal, and shear.

Transverse effect

A force is applied along a neutral axis (y) and the charges are generated along the

(x) direction, perpendicular to the line of force. The amount of charge depends on the

geometrical dimensions of the respective piezoelectric element. When dimensions a, b, capply,

Cx = dxyFyb / a,

where a is the dimension in line with the neutral axis, b is in line with the charge

generating axis and dis the corresponding piezoelectric coefficient.

Longitudinal effect

The amount of charge produced is strictly proportional to the applied force and is

independent of size and shape of the piezoelectric element. Using several elements that

are mechanically in series and electrically in parallel is the only way to increase the

charge output. The resulting charge is

Cx = dxxFxn,
http://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Electromagnetic_fieldhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Gallium_phosphatehttp://en.wikipedia.org/wiki/Gallium_phosphatehttp://www.piezocryst.com/http://en.wikipedia.org/wiki/Tourmalinehttp://en.wikipedia.org/wiki/Pyroelectricityhttp://en.wikipedia.org/w/index.php?title=Piezoceramic&action=edit&redlink=1http://en.wikipedia.org/wiki/Series_and_parallel_circuitshttp://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Amplitudehttp://en.wikipedia.org/wiki/Electromagnetic_fieldhttp://en.wikipedia.org/wiki/Radiationhttp://en.wikipedia.org/wiki/Gallium_phosphatehttp://en.wikipedia.org/wiki/Gallium_phosphatehttp://www.piezocryst.com/http://en.wikipedia.org/wiki/Tourmalinehttp://en.wikipedia.org/wiki/Pyroelectricityhttp://en.wikipedia.org/w/index.php?title=Piezoceramic&action=edit&redlink=1http://en.wikipedia.org/wiki/Series_and_parallel_circuits


18/28

where dxx is the piezoelectric coefficient for a charge in x-direction released by forces

applied along x-direction. FX is the applied Force in x-direction [N] and n corresponds to

the number of stacked elements.

Shear effect

Again, the charges produced are strictly proportional to the applied forces and are

independent of the elements size and shape. Forn elements mechanically in series and

electrically in parallel the charge is

Cx = 2dxxFxn.

In contrast to the longitudinal and shear effects, the transverse effect opens the possibility

to fine-tune sensitivity on the force applied and the element dimension.

CHAPTER 5


19/28

5.Range of applications

5.1 Electronic nose for enviromental monitoring

Enormous amounts of hazardous waste (nuclear, chemical, and mixed wastes) were

generated by more than 40 years of weapons production in the U.S. Department of Energies

weapons complex. The Pacific Northwest National Laboratory is exploring the technologies

required to perform environmental restoration and waste management in a cost effective manner.

This effort includes the development of portable, inexpensive systems capable of real-time

identification of contaminants in the field. Electronic noses fit this category . 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.

5.2 Electronic nose used in detection of bombs

The tragic bombings in London on the 7 July 2005 have caused many to call for bagsearching 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 chemical makeup to identify it. One

mechanism would be an array of electronic sensors would sniff out the odours while a second

mechanism would see if it could recognize the pattern.

5.3 World record for detecting explosive


20/28

Aside from identifying people from their skin vapours, another of the important

applications of the newsystem is that it is able to detect tiny amounts of explosives. The system

can "smell" levels below a few parts per trillion, and has been able to set a world sensitivity

record at "2x10-14

atmospheres of partial pressure of trinitrotoluene. The "father" of ionisation using the

mass spectrometry electrospray is Professor John B. Fenn, who is currently a researcher at the

University of Virginia (United States), and in 2002 won the Nobel Prize in Chemistry for using

this technique in the analysis of proteins.

5.4 Electronic nose for multimedia Aaplication

Multimedia systems are widely used in consumer electronics environments today, where

humans can work and communicate through multi-sensory interfaces. Unfortunately smell

detection and generation systems are not part of today's multimedia systems. Hence we can use

electronic nose in multimedia environment.

5.5Electronic nose for medicine

Because the sense of smell is an important sense to the physician, an electronic nose hasapplicability 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 tissues emit distinctive odors that can be 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.

5.6Electronic nose for the food industry

An electronic nose has been found to be a useful tool in controlling the quality of food

packaging board. The nose identifies paperboard from which off-flavor transfers into the

packaged food. Usually, off-flavor is evaluated by a sensory panel, which consists of 8 - 10

people trained to make a sensory evaluation. Before the evaluation, the sample to be examined is


21/28

kept for 48 hours in the same container with a reference foodstuff, usually chocolate. The

members of the panel then taste the chocolate and determine whether any off-flavor has been

transferred to the chocolate from the paperboard being examined. Sensory evaluation of samples

is very time-consuming and requires numerous trained people for the panel. For this reason,

some other method to replace sensory evaluation has been sought.

Currently, the biggest market for electronic noses is the food industry. Applications of

electronic noses in the food industry include quality assessment in food production, inspection of

food quality by odor, control of food cooking processes, inspection of fish, monitoring the

fermentation process, verifying if orange juice is natural, monitoring food and beverage odors,

grading whiskey, inspection of beverage 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 production especially

when qualitative results will do.

5.7 Electronic nose created to detect skin vapours

A team of researchers from the Yale University (United States) and a Spanish

company have developed a system to detect the vapours emitted by human skin in real

time. The scientists think that these substances, essentially made up of fatty acids, are what

attract mosquitoes and enable dogs to identify their owners.

"The spectrum of the vapours emitted by human skin is dominated by fatty acids. These

substances are not very volatile, but we have developed an electronic nose' able to detect them",

Juan Fernndez de la Mora, of the Department of Mechanical Engineering at Yale

University (United Status) and co-author of a study recently published in the Journal of the

American Society for Mass Spectrometry, tells SINC. The system, created at the Boecillo

Technology Park in Valladolid, works by ionising the vapours with an electrospray (a cloud of

electrically-charged drops), and later analysing these using mass spectrometry. This technique

can be used to identify many of the vapour compounds emitted by a hand, for example. "The

great novelty of this study is that, despite the almost non-existent volatility of fatty acids, which

have chains of up to 18 carbon atoms, the electronic nose is so sensitive that it can detect them


22/28

instantaneously", says Fernndez de la Mora. The results show that the volatile

compounds given off by the skin are primarily fatty acids, although there are also others such as

lactic acid and pyretic acid. The researcher stresses that the great chemical wealth of fatty acids,

made up of hundreds of different molecules, "is well known, and seems to prove the hypothesis

that these are the key substances that enable dogs to identify people". The enormous range of

vapours emitted by human skin and breath may not only enable dogs to recognise their owners,

but also help mosquitoes to locate their hosts, according to several studies.

5.8 In resources and development laboratories

Formulation or reformulation of products

Benchmarking with competitive products

Shelf life and stability studies

Selection of raw materials

Packaging interaction effects

Simplification of consumer preference test

Figure 5.1 Testing of Electronic Nose


23/28

5.9 In quality control laboratories

Batch to batch consistency

Conformity of raw materials, intermediate and final products

Detection of contamination, spoilage, adulteration

Origin or vendor selection

Monitoring of storage conditions.

Figure 5.2 Conformity of raw materials through electronic nose


24/28

CHAPTER 6

6. ADVANTAGE

6.1Problems Where the E-Nose Can Help

The electronic nose is best suited for matching complex samples with subjective

endpoints such as odor or flavor. For example, when has milk turned sour? Or, when is a batch

of coffee beans optimally roasted? The electronic nose can match a set of sensor responses to a

calibration set produced by the human taste panel or olfactory panel routinely used in food

science. The electronic nose is especially useful where consistent product quality has to be

maintained over long periods of time, or where repeated exposure to a sample poses a health risk

to the human olfactory panel. Although the electronicose is also effective for pure chemicals,

conventional methods are often more practical.

6.2 Problems That the E-Nose Does Best

Identification of spilled chemicals in commerce (for U.S. Coast Guard).

Quality classification of stored grain.

Water and wastewater analysis.Identification of source and quality of coffee. Monitoring of roasting process.

Rancidity measurements of olive oil (due to accumulation of short-chain aldehydes).

Detection and diagnosis of pulmonary infections.Diagnosis of ulcers by breath tests.

Freshness of fish.

Process control of cheese, sausage, beer, and bread manufacture.

Bacterial growth on foods such as meat and fresh vegetables.

6.3 Advantage


25/28

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

6.4. Next generation products

Figure 6.1 Next Generation Products

CHAPTER 7


26/28

CONCLUSION

Humans are not well suited for repetitive or boring tasks that are better left to machines.

No wonder the electronic 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.

In my view the electronic nose is a very useful instrument now a days.


27/28

REFERENCES

REFERENCES

[1]. Alfredo Vzquez Carazo (January 2000). Novel Piezoelectric Transducers for High

Voltage Measurements. Universitat Politcnica de Catalunya. pp. 242.

[2]. Karki, James (September 2000). "Signal Conditioning Piezoelectric Sensors" (PDF).

Texas Instruments. http://focus.ti.com/lit/an/sloa033a/sloa033a.pdf. Retrieved 2007-12-

02.

[3]. Ludlow, Chris (May 2008). "Energy Harvesting with Piezoelectric Sensors" (PDF). Mide

Technology http://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf.

Retrieved 2008-05-21.

[4]. Pablo Martnez Lozano y Juan Fernndez de la Mora. On-line Detection

of Human Skin Vapors. Journal of the American Society for Mass Spectrometry 20 (6):

1060-1063, 2009.

[5]. Pablo Martnez Lozano, Juan Rus, Gonzalo Fernndez de la Mora,

MartaHernndez, y Juan Fernndez de la Mora. Secondary Electrospray

Ionization (SESI) of Ambient Vapors for Explosive Detection at Concentrations Below

Parts Per Trillion. Journal of the American Society for Mass Spectrometry 20 (2): 287-

294, 2009

[6]. M.G. Buehler and M.A. Ryan. Proc. SPIE Conf. on Electro-Optical Tech. for Chemical

Detection, (April, 1997).

[7]. J.W. Gardner, T.C. Pearce, S. Friel, P.N. Bartlett and N. Blair, Sensors and Actuators,

B18-19, 240, (1994).

[8]. Agarwal A, Balasubramanian N, Ranganathan N and Kumar R 2005 ICMAT 2005 &

IUMRSICAM 2005

[9]. Alocilja, E.C. Ritchie, N.L.Grooms, D.L. Dept.of Biosystems Eng., Michigan State

Univ., East Lansing, MI, USA; Sensors Journal, IEEE Dec.2007 Digital ObjectI

dentifier: 10.1109/JSEN.2003.820326 Current Version Published: 2004-02-19
http://focus.ti.com/lit/an/sloa033a/sloa033a.pdfhttp://focus.ti.com/lit/an/sloa033a/sloa033a.pdfhttp://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdfhttp://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf.%20Retrieved%202008-05-21http://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf.%20Retrieved%202008-05-21http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=7361http://focus.ti.com/lit/an/sloa033a/sloa033a.pdfhttp://focus.ti.com/lit/an/sloa033a/sloa033a.pdfhttp://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdfhttp://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf.%20Retrieved%202008-05-21http://www.mide.com/pdfs/vibration_harvesting_conference_2008.pdf.%20Retrieved%202008-05-21http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=7361


28/28

20473653 Electronic Nose

Documents

Transcript of 20473653 Electronic Nose