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ensors an ens ng ys ems orMachine Olfaction Electronic

Nose and Electronic Tongue

Dr. Nabarun Bhattachar a

C-DAC, Kolkata

. .

October 29, 2009

Presentation StructureHuman OlfactionMachine Olfaction

Electronic NoseDesign Details and Results

Electronic Tongue

Desi n Details and ResultsRoadmap for Research in MachineOlfaction

Conclusion


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Human OlfactionThe olfactory region is locatedin the roof of the two nasalcavities

when compounds (called

odorants) that are carried byinhaled air stimulate receptorslocated in the olfactoryepithelium.

The mucous lipid, which ispro uce n e o ac oryepithelium, assists intransporting the odorantmolecules.

Only volatile materials that aresoluble in the mucous can

interact with the olfactoryrecep ors an pro uces esignals that our brain interpretsas odor.

Machine Olfaction

Attempts to mimic human senses of smelland taste by electronic means are calledmachine Olfaction.

Sensors are the most crucial components in amachine olfaction system.

Signal conditioning, data acquisition, data,data processing and pattern recognition arethe crucial modules of an olfactory sensing

.


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Machine Olfaction System

Human Perception Machine Sensing

Eye: VISION VISION:Camera

ar:

Skin: TACTILE

: crop one

TOUCH: Tactile

SENSES Devices

-

Tongue:TASTE TASTE: E-Tongue


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About Electronic Nose

9Electronic Nose senses complex odours using an Arrayof Sensors (called sensor array): each tuned foro our o a am y o vo at e compoun s.

9Odour stimulus imprints a characteristic electronic.

9This smell print is statistically classified and resolvedwith suitable attern reco nition en ine as ameasurement of odour of the sample.

In short, Electronic Nose is

A scientific, reliable, repeatable, physical, non-invasive,

affordable real-time techniques for various applicationslike food quality assessment, environmental polution

detection, medical applications, explosive detection etc.

Basic Block Diagram

Odour Delivery Sensor Array Signal

System Conditioning

DataClassificationAcquisition

ent cat on


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our an ng e very

Headspace Sampling

Autosampling Stage

Air

Mass FlowController

S1

S2 S3Solenoid Valves

Sensor Cell

MeasurementCircuit

Bubbler System

TemperatureControlled

Bath

Syringe

NeedlesLiquid Sample


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ensors

Desirable Properties of

Selectivity : Must respond to a range of chemicalspecies.

Sensitivity : Should be sensitive to detect vapour.

Speed of Response : Response time should be in

.Reproducibility : Sensors response characteristicsshould be reproducible.

Reversibility : Should be able to recover immediatelyafter exposure to gas.

Portability : Should be small so that less samplevolume may be used.


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Sensors for Electronic Nose

Conductometricor Resistive

Conductance/Resistance

MOS, CP

Capacitive Capacitance PEUT Coated

Electrodes

Potentiometric EMF/Voltage MOSFET

Gravimetric Mass/Pizeoelec SAW / QCMtricity

Calorimetric Temperature Pellisters,Thermopile

Optical RI/Wavelength Surfacentens ty o

Radiationasma

Sensor

Sensors for Electronic Nose

Amperometric Current MicrofuelCellsPolarographicSensors

Flourescent

Type

Optical

intensity,

Optical fibres

deposited withflorescenceetc.

flourescentindicator dye.


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Sensors

Conducting polymer micro-

-

Conductance is altered si nificantl binteraction with vapour species.

Sensors are fabricated by electro-polymerization in controlled manner

Different polymers show non-overlappingselectivity to different chemicals.

Fast response time with excellent reversibility


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Conducting polymer micro--

Excellent reproducibility

Wide selectivity

Wide range of applications

a e

Low power

Operate at ambient temperature

Metal Oxide Sensors -

MOS are semiconducting sensing elements, . .,

MOS operate in the range from 300 oC too

The sensors require O2 to function

Volatiles under o redox reactions at thesensor surface, resulting in a change of conductivity across the sensor

e ect v ty can e mo e y op ng t emetal oxide (e.g with Pd, Pt) or modifying the


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Metal Oxide Sensors -

Lon evit

Sensitivity

Wide range of applications

Large response and good discriminatingpower

Bulk Acoustic Wave

range of different selective coating films

On adsorbin anal tes the additional mass ofthe film results in a change in the frequency

of oscillation of the sensorA typical sensor has an operating frequencyof about 10 MHz


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Bulk Acoustic Wave

High selectivity

-

Able to measure both polar and non-polar

speciesStable over a wide temperature range

Low power (low mW)

Low sensitivity to humidity

High stability

Good reproducibility

Well characterised coating chemistry

Intelligent Pattern Analysis

Statistical

Methods

Quantitative Supervised MLR, PLS

,

Supervised DFA, PCR

Biologically

inspired

methods

ANN Unsupervised SOM

Su ervised MLP PNN RBFLVQ

Fuzzy Methods Supervised FIS, FNN, FCM

Self-supervised ART, Fuzzy

ARTMAP

Others Self-supervised GA

Supervised NFS, Wavelets


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Intelligent Pattern

PCA Principal Component Analysis

PLS Partial Least Square

MLR Multiple Linear Regression

DFA Discriminant Function Analysis

LDA Linear Discriminant Analysis

ANN Artificial Neural Network

SOM Self Organizing Map

ene c gor m

ART Adaptive Resonance Theory

RBF Radial Basis Function

NFS Neuro Fuzzy System

Applications of Electronic

Environmental monitoringo Monitoring of air, water and land.

Medical Dia nostics andHealth Monitoring

o Breath Monitorino Eye Infection

o Leg Ulcers

o


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Electronic Noseapp ca ons

Food and Beverage Applications, ,

meat, fish, brewery, coffee etc. through electronic nosehas been reported.

utomot ve an erospace pp cat onso Detection of hazardous gas within automobiles,

s acecrafts.

Narcotic Detection.

A lication in Cosmetics and Fra ranceIndustry

Detection of ExplosivesMiscellaneous upcoming Applications.

- ose or ea


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Sensor Selection

MOS sensors only havebeen considered.

Procurement ofCommercially AvailableMOS Sensors.

Procurement of majoraroma determiningcompounds of tea.

Experimenta Tria s

Finalization of SensorArray

MOS Sensors Considered ropane an

Butane ese

Exhaust

Solvents

,TGS 203

Monoxide

Gases

,TGS 822

,Toluene, Xylene

R-21, R-22

Contaminants

Sulphide

GS 2180 Water Va or GS 826 Ammoniafrom Food


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Aroma Determinants in Tea

Overall aroma of tea is a

complex interplay of aMajor Aroma Determinants of Tea

-

2 Benzaldehyde

flavoury compounds

(VFC).

3 - ionone

4 Geraniol

TRA reports more than

700 biochemical volatiles

5 Linaloolcon r u e pos ve y or

negatively to tea aroma

7 Terpeniol

. .

identified 112 aroma

compounds in Darjeelingtea by GC - MS

Sensor Response to Individual Chemicals

0.92-phenyl-ethanol

Benzaldehyde

B-ionone

Sensor1-TGS 2610

Sensor2-TGS 2620

Sensor3-TGS 2611

Sensor4-TGS 2600

0.7

0.8Linalool

Linalool oxide

Terpeniol

Sensor5-TGS 816

Sensor6-TGS 831

Sensor7-TGS 832

Sensor8-TGS 823

0.5

0.6

so

rResponse

0.3

0.4Se

0.1

0.2

1 2 3 4 5 6 7 80

Sensor Serial Number


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Sensor Response to Smell of Tea

Finalization of Sensor Arrayna ze array o sensors cons s s o

EIGHT Figaro sensors: TGS 816, TGS, , , ,

2610, TGS 2611 and TGS 2620


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Interface Circuit Diagram

Each sesnsor is a MOSsensor made from a

Vc V RL

metal oxide film, e.g.,

Tin Oxide Volatiles under o redox R L

reactions at the sensorsurface, resulting in achan e of conductivit

V H

across the sensor

Each sensor is reversible.GND

Measurement Circuit with MOS Sensor

within TTL range.

Signal ConditioningThe output of the sensors is analogue voltage.

stages,namely,buffering,amplification,filtering,co

the USB card used in the system for data

acquisition.No additional electronics has been used for thispurpose


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Data Acquisition

Circuit USB 6009 card from the NationalInstruments has been used.

DAQ system consists of sample and-,to digital conversion module.

Sample rate :250 Ksamples/second

Signal Pre-processingSteps of Signal Pre-processing:

Baseline identification and mani ulation

Compression


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Baseline Handling

Baseline refers to sensor response in noexposure condition

Fractional techni ue of baselinemanipulation is used for compensationa ainst drift and contrast enhancement.

0xtx

0

sss

x

ty =

Compression TechniqueCompression is a preprocessing stagewhere the response of sensor array isuti ize as a eature vector or afingerprint by reducing the number ofescriptors.

The maximum value vector from thesensor output data has only beenconsidered for data analysis.

= [ ]max8max1 .............. ii SS


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Characteristic Sensors Response

2.5

3

3.5

4

4.5

(V)

Purging

RegionSaturation

Region

0

0.5

1

1.5

2

Voltage

Transient

Region

0 100 200 300 400 500 600 700 800 900-0.5

Time (Values have no significance)

Odour Handling & DeliveryA mini air compressoris used to developrequisite airflow (5 ml.

PATTERNRECOGNITION IN

COMPUTER

Per sec.)

Three solenoid valvesSOLINOID

VALVE-III

SENSOR ARRAY

SUCTION BLOWER

airflow to the sample

holder and the sensorAMBIENT

AIR

(V3)

PURGINGAMBIENTAIR

array.

A blower is used to

ODOURMOLECULES

AIR PUMP

VALVE-I(V1)

VALVE-II(V2)

AIR

evacuation duringpurging.

SAMPLEVESSEL


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Illumination Based Heating

The tea sample isheated for 65

PTFE FIXTUREPTFE FIXTURECOMPUTER WITH OLFACTION

SOFTWARE

Temperature ofthe sample

ELECTRONIC

INTERFACE FORLAMP

ELECTRONIC

INTERFACE FORLAMP

HALOGEN LAMP

FAN AGITATOR

reac es o -30C

35 W miniatureSAMPLE

HOLDER

RTD

halogen lamp isused

Heatin im roves

DC MOTOR &

INTERFACE

ANALOGUEDIGITAL DIGITAL

DC MOTOR &

INTERFACE

sensitivity of the

system indirectly

USB DATA ACQUISITION CARDUSB DATA ACQUISITION CARD

INPUTOUTPUT OUTPUT

A Typical Sniffing CycleA Typical Sniffing Cycle

sample

volatiles released by tea within the sample holder by blowingregulated flow of air on the sample

Sampling: During sampling; the sensor array is exposed to aconstant flow of volatiles through pipelines.

Purging: During purging operation, sensor heads are cleared withblow of fresh air so that the sensors go back to their baseline

Dormancy: The system is kept in suspended animation till the.


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A Typical Sniffing Cycle

TIME

HEADSPACE

GENERATION TIME

NVOLTS

4.0SAMPLING TIME

PURGING TIME

RESPONSEI

3.0

SENSO

1.0

.

0 40 80 120 160 200 240 280 320

E-Nose Prototype Developed

Sample container with

bayonet fitting


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Nose

Olfaction Software

Software features:

-Programmable Sequence Control

-Dynamic Fermentation Profile Display

-Data Logging

-Alarm Annunciation

- ex y o perm ea p an ers emse ves o ra n an cus om ze

the system as per their requirements.


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a a na ys s

About Sensor Array OutputSensor responses

during headspace

generation

282221

......

...

...

bbb

=181211

821

...

...

......

......

hhh

SSS

bbbA

282221

......

......

...

...

SSS

Sensor responses when

exposed to tea odour

during sampling

821 ...

......

mmm SSS

Data is 8-dimensional

Headspace Duration : 30 Seconds and Sampling Duration : 50 seconds

10 rea ings are scanne per secon

Approximately 800 rows are there in any sniffing data matrix


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Data Analysis StrategyMULTIVARIATE DATA

DATA EXPLORATION DATA

QUANTIFICATION

DATA CO-RELATION

PRINCIPAL

COMPONENT

AROMA SCORE

CALCULATION BY 2-

AROMA SCORE

CALCULATION BYANALYSIS (PCA) NORM METHOD MAHALANOBIS

DISTANCE METHOD

BACK ARTIFICIAL NEURAL

PROPAGATION NETWORK

RADIAL BASIS

FUNCTION

PROBALISTIC

NEURAL NETWORK

Results Different Clones

Well-defined clusters are found in PCA.

100% classification accurac observedin BP-MLP


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Results Different flavoursPCA ex i its istinctaroma clusters for 0.15

0.2

taster scores. 00.05

.

3.6004%

)

exhibit varyingclassification abilit -0.15

-0.1

-0.05

PCA2(

Taster score 8

as follows:BP-MLP: 81% 85% -1 -0.5 0 0.5 1 1.5

-0.25

-0.2

PCA1 (96.3448%)

Taster score 5

Taster score 7

Taster score 6

RBF: 86% - 91%

PNN: 91% - 94%

E-Nose for Tea Fermentation

9Oxidation process

9Fermentation Process Starts as soon as Tea Leaves

cells are broken during CTC or Rolling Process

9Fermentation duration is very crucial in determining

na ua y o ea.

9E-Nose can Monitor Volatile Emission Pattern during

Fermentation for automatically determining and

announcing the completion of useful fermentation


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Sample fermentation profiles by Colorimeter

Results of PCA


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Sample fermentation profiles by E-Nose

Fermentation Aroma Profile

Mahalanobis Aroma Score

2-Norm Aroma Score

1.2 5

0.6

0.8

1

-Norm

m

aScore

2

3

4

alanobis

m

aScore

0

0.2

.

0 8 16 24 32 40 48 56 64 72 80 88 96 104 112 120

Aro

0

1Ma

Aro

Time in Minutes

Detection of Fermentation Peak


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Results

Colorimeter testColorimeter test

No of Fermentation run 81

Accurac of detection of Fermentation 95%Summary of Results:

Completion time by E-Nose vis--visColorimeter test

Accuracy of detection of Fermentation

Completion time by E-Nose vis--vis Human

96%

Eva uation

Electronic Tongue : Definition

AnAn ElectronicElectronic TongueTongue is an instrument which comprises ofis an instrument which comprises of

electrochemical cell, sensor array and appropriate patternelectrochemical cell, sensor array and appropriate pattern

recogn on sys em, capa e o recogn z ng s mp e or recogn on sys em, capa e o recogn z ng s mp e or

complex soluble noncomplex soluble non--volatile molecules which forms a tastevolatile molecules which forms a taste

of a sample.of a sample.

The sensor array consists of broadly tuned (nonThe sensor array consists of broadly tuned (non--specific)specific)

variety of common anion of a salt in solutionvariety of common anion of a salt in solution chemicalchemical

materials.materials.


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Cont

The Electronic Tongue is consisting of working electrode,

reference electrode and counter electrode. Basically, an

transferred. A potential is applied consecutively to each

electrode and transient current responses are collected from

e ec ro e roug a a acqu s on car .

In voltammetric method, a voltage is applied over the

working electrode and reference electrode. A current is

measured between working electrode and counter

electrode.

Cont..

Working Electrode: The working electrode is an innert materialsuc as o , at num, or assy ar on, etc. n t ese case, t e

working electrode serve as a surface on which the

electrochemical takes place. It places where redox reaction occur.

Surface area should very less (few mm2) to limit current flow

Reference Electrode: The reference electrode is used in

measuring the working electrode potential. A reference electrode

should have a constant electrochemical potential as long as no

current flows throu h it.

Counter electrode: The counter electrode is a conductor that

completes the cell circuit. It is generally innert conductor. The

current flows into the solution via the working electrode leaves

the solution via the counter electrode. It does not role in the redox

.


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electrodes but has conductivity

Linear

erent a pu se

Square wave

Cyclic


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Sensor of Electronic Tongue

electrode

,

rhodium,platinum,

.

pure; dia- 1mm

palladium, Gold

Counter Platinum do

Reference Ag/Agcl

Set of electrode

Electrodes Pin configuration


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Electronic Tongue

Wate

Tea

Liquor

r

Array of


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Current Status vis--vis Work Plan

11th Plan Project

proposed

Pilot Level Deployment

NTRF Funding

Future Scope of ResearchHybrid sensor array consisting of MOS, CP

Development of new sensor array sensitive

Development of more efficient algorithmsor e er c us er ng an c ass ca on

Techniques for drift compensation

Integration of E-Nose with E-Tongue andE-Vision s stems --- ENTV S stem


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