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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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