Instrumentation-Lecture 3_1.pptx

8/17/2019 Instrumentation-Lecture 3_1.pptx

1/74

Principle of Sensors

Dr. Zulfatman, M.Eng.Dept. of Electrical Engineering

Faculty of Engineering

University of Muhammadiyah Malang

Lecture !a


2/74

Definition

A sensor is a device that receives a stimulus andresponds with an electrical signal.

2

Fig 1.1

Level control system. A sight tube and theoperator’s eye form a sensor.


3/74

Detectable Phenomenon

Stimulus Quantity

Acoustic Wave (amplitude, phase, polarization), Spectrum, WaveVelocity

Biological & Chemical luid Concentrations (!as or "i#uid), $adiation,%oisture

lectric Charge, Voltage, Current, lectric ield (amplitude,phase, polarization), Conductivity, 'ermittivity

%agnetic %agnetic ield (amplitude, phase, polarization), lu,'ermeaility

*ptical $e+ractive nde, $e+lectivity, Asorption

-hermal -emperature, lu, Speci+ic .eat, -hermal Conductivity

%echanical 'osition/0isplacement, Velocity, Acceleration, orce,Strain, Stress, 'ressure, -or#ue, lo1, "ight


4/74

The Response is an Electrical Signal

When we say electrical wemean a signal which can bechanneled, amplied and

modied by electronicdevices:

Voltage

urrent

harge

!he voltage, current orcharge may be describe by:

Amplitude"re#uency

$hase

%igital code

4


5/74

Any sensor is an energy converter

!his conversion can be direct or it mayre#uire transducers.

&'ample:A chemical sensor may have a part which

converts the energy of a chemical reaction intoheat (transducer) and another part, athermopile, which converts heat into an

electrical signal. 5

Fig 1.2


6/74

Need for Sensors*ensors are omnipresent. !hey

embedded in our bodies, automobiles,

airplanes, cellular telephones, radios,chemical plants, industrial plants andcountless other applications.

Without the use of sensors, there would

be no automation ++


7/74

Choosing a Sensor


8/74

Physical Principles of Sensing

harges, elds potentials

apacitance

-agnetism

nduction

/esistance

$ie0oelectric e1ect

*eebec2 and $eltiere1ects

!hermal properties ofmaterials

3eat transferLight

8


9/74

Types of Sensor

%irectA sensor that can convert a non4electrical

stimulus into an electrical signal with

intermediate stages. !hermocouple (temperature to voltage)

ndirectA sensor that multiple conversion steps to

transform the measured signal into anelectrical signal. A ber4optic displacement sensor:

urrent →photons →current

9


10/74

Electric Charges, Fields, Potentials

0q

f E =

10

Any charged ob5ect is sub5ect to a force whenin the region of an electric eld.A eld can be used to detect the presence of charge

or the opposite can be true and the force on a charge

determined to detect a eld.

!

"# r

q E

πε =


11/74

$ther %eometries

r E

"!πε

λ

= "!ε

σ = E

11

λ=charge/unit length σ=charge/unit area

The field is strongest atareas of highestcurvature


12/74

Electric Dipole

&

"

&

" '# r p

r qa E

πε πε ==

12

%ipoles are found in crystalline materials and form afoundation for pie0oelectric and pyroelectric detectors. !he dipole is a combination of 6 opposite charges placed a

apart. !he electric eld is the vector sum to the two elds.

pE=τ

p represents the dipole moment

n the presence of an &eld the dipole willdevelop a tor#ue


13/74

Capacitance

d

A

V

qC "

ε ==

1

!wo isolated conductive ob5ects of arbitrary shapewhich can hold an electric charge is called acapacitor.An E eld is developed between the two conductors.


14/74

Capacitor as Displacement Sensor

( )ab

l C

(ln

! "πε =

14

f the inner conductor can be moved in and out,the measured capacitance will be a function of l.


15/74

Dielectric Constant

d

A

V

qC "

κε κ ==

15

!he material between the plates of the capacitor can also beused to sense changes in the environment.When vacuum (or air) is replaced by another material, the

capacitance increases by a factor of κ , 2nown as the dielectricconstant of the material

!he increase in is due to the polari0ation of the molecules ofthe material used as an insulator.


16/74

E)ample * A +ater evel Sensor

( ) ( )[ ]κ πε

−−=

+=

-(ln

!"

h H abC

C C C

h

filled freeh

1!

!he total capacitance of the coa'ial sensor shown below isthe capacitance of the water4free portion plus thecapacitance of the water4lled portion. As the level of thewater changes, the total capacitance changes.


17/74

.agnetism !here are two methods of generating a magnetic

eld: $ermanent magnets (magnetic materials).

!he magnetic eld generated by a current.

1"

Force is generatedon a test magnetin the field ofmagneticmaterials.

# compass needle$ill respond to themagnetic fieldgenerated %& acurrent.

'agnetic field( B

)flu*+ is the field densit&( Φ,


18/74

So/rces of .agnetic Field

18

-lectric current sets acircular magnetic fieldaround a conductor.

'oving electron setsa field( superpositionof field vectorsresults in acom%ined magnetic

field of a permanentmagnet.

'agnets are useful for fa%ricating magnetic sensors for the detectionof motion( displacement( and position.


19/74

0nd/ction

( )

dt

di L

dt

dLi

dt

nd v B −=−=

Φ−=

19

A phenomenon related to magnetism isinduction, the generation of voltage from achanging magnetic eld.

f the coil has no magnetic core, the 7u' is proportionalto current and the voltage proportional to di/dt.


20/74

Resistance

( )

a

l

a

l

il

Va R

liVa

ail V

j E

i

V R

ρ

ρ

=⋅=

=⋅==

=

(-

20

f we apply a battery across two points of a piece ofmaterial, an E eld will be set up where E=V/l

!he tendency of the material to resist the 7ow of electrons iscalled its resistivity, ρ , and we say that the material has aparticular electrical resistance, R.


21/74

Sensitivity of Resistance

( )[ ]"" - t t −+= α ρ ρ

21

!o !emperature:

pecific resistivit& oftungsten as a function of

temperature.

α is the temperaturecoefficient of resistivit&.


22/74

Application for Temperat/re 0ndication /sing a

aminate of .aterials 1ith T1o Different α2s3

22


23/74

To Strain4

Eel

dl E

a

F ===σ

-

-!

!

5#6

5&6

5!6

5-6

R R ReS

RdR

l

dl S R

l

dl S

a

l dl

l a

l S ldl

vS dR

l v

S dl

dR

l v R

e

eeee

e

−==

==

⋅==

=

=

ρ ρ ρ

ρ

ρ

2

train changes thegeometr& of a conductorand its resistance.

tress = oungs 'odulus * strain

ince length is changing the factor of 2 in the second euation%ecomes a varia%le $hich depends on the material.


24/74

To .oist/re4

24

For the h&gristor( the resistance of the pol&mer changes $ith thea%sorption of $ater molecules.


25/74

The Pie7oelectric Effect

!he pie0oelectric e1ect is the generation ofelectric charge by a crystalline material uponsub5ecting it to stress.

25


26/74

Pie7oelectric Sensor

x

x x F C

d

C

QV

==

2!

ie3oelectric cr&stals aredirect converters ofmechanical energ& intoelectrical energ&.

,ecause a cr&stal $ith depositedelectrodes forms a capacitor the voltagedeveloped can %e e*pressed as

here d x is the pie3oelectric coefficient in

the * direction and F x is the applied force

in the * direction.

6aminated 27la&er pie3oelectric sensor


27/74

Pyroelectric Effect

dT

dP P sQ =

T h

P h A

T A P

C

T A P

C

QV

then

h

A

V

QC

T A P Q

r

Q

r

QQ

r

Q

∆=∆

=∆

=∆

=∆

=∆∆=

∆=∆

""

"

( ε ε ε ε

ε ε

2"

&roelectric materials arecr&stals capa%le of generatingan electrical charge in responseto heat flo$.

P Q is the p&roelectric charge

coefficient and P s is related to the

charge developed on theelectrodes $hen the sensor is

su%ected to heat flo$.

f the sensor has the )capacitor+form


28/74

28

The electric charge reaches its pea:nearl& instantaneousl& and then deca&s$ith a thermal time constant( τT

The material loses its usefulness atthe ;urie Temp < the point at $hichpolari3ation disappears.


29/74

Seebec8 and Peltier Effects

!he *eebec2 e1ect is a direct conversion ofthermal energy into electric energy.

29

The var&ing temperaturealong the %ar is a source ofelectromotive forcevoltage> and current $illflo$.

This is the principle %ehindthe thermocouple.


30/74

Thermoelectric oops

( )( )T V B A AB ∆−=∆ α α

0

f a loop of conductor has pointsat 2 different temperatures(

current flo$s. ,ut if there is asingle conductor no measura%lenet current flo$s.

f a loop of conductor has points at 2different temperatures( again current flo$s.

f the loop is composed of 2 differentconductors( measura%le net current flo$sdue to a difference in the ee%ec:coefficients.

α# and α, are the ee%ec: coefficients


31/74

$/tp/t 9oltage from Standard Thermoco/ples

1


32/74

T:PES * .ATER0AS * TE.PERAT;RE RAN%ES

2

"hermocouple "ype #ames of Materials Useful $pplication %ange

& Platin/m&"< Rhodi/m 6=5 Platin/m >< Rhodi/m 6?5

!@"" ?&-""F-&"?-""C

' +@Re T/ngsten @< Rheni/m 6=5

+!>Re T/ngsten !>< Rheni/m 6?5 &"""?#!""F->@"?!&-@C

E Chromel 6=5Constantan 6?5!""?->@"FB@?B""C

( 0ron 6=5Constantan 6?5 !""?-#""FB@?>"C

) Chromel 6=5Al/mel 6?5!""?!&""FB@?-!>"C

# Nicrosil 6=5

Nisil 6?5-!""?!&""F>@"?-!>"C

%

Platin/m -&< Rhodi/m 6=5

Platin/m 6?5

->""?!>#"F

'"?-#@"C

S Platin/m -"< Rhodi/m 6=5

Platin/m 6?5-'""?!>#"FB'"?-#@"C

" Copper 6=5Constantan 6?5?&&"?>>"F?!""?&@"C


33/74

The Peltier Effect

The eltier effect concerns the reversi%le a%sorption of heat $hich

usuall& ta:es place $hen an electric current crosses a unction%et$een 2 dissimilar metals.

t can produce heat or cold depending on the direction of electriccurrent through the unction.


34/74

ight 6Electromagnetic Radiation5

λ υ

hh E ==

4

?@ and visi%le photons have relativel& high energ& levels and areeasil& detected. n the far A the energies %ecome ver& small andthermal detectors are used.

- is the energ& of theradiation

c = c * 108 m/s

h = !.! * 1072 B7s

λ is the $avelength of theradiation


35/74

Concl/sions A sensor is a device that receives a stimulus and

responds with an electrical signal. !he nal stage of any sensor is dependent upon

the electrical properties of the sensor materials. !he materials introduced today are used in the

design and fabrication of many di1erent types ofsensors.

5


36/74

Sensors "echnology

Dr. Zulfatman, M.Eng.Dept. of Electrical Engineering

Faculty of Engineering

University of Muhammadiyah Malang

Lecture !*


37/74

Categorization of Sensor

lassication based on physical phenomena-echanical: strain gage, displacement (LV%!), velocity

(laser vibrometer), accelerometer, tilt meter, viscometer,pressure, etc.

!hermal: thermal couple8ptical: camera, infrared sensor8thers 9

lassication based on measuring mechanism/esistance sensing, capacitance sensing, inductance

sensing, pie0oelectricity, etc.

-aterials capable of converting of one form ofenergy to another are at the heart of manysensors. nvention of new materials, e.g., smart; materials,

would permit the design of new types of sensors.


38/74

Paradigm of Sensing SystemDesign

Chang D #:tan( 2005


39/74

Instrumentation Considerations

*ensor technology<

*ensor data collection topologies<

%ata communication<

$ower supply<%ata synchroni0ation<

&nvironmental parameters andin7uence<

/emote data analysis.


40/74

Measurement

h&sicalphenomenon Sensor System

'easurementEutput

Measurement output

• interaction %et$een a sensor and the environmentsurrounding the sensor

• compound response of multiple inputs

Measurement errors• &stem errors imperfect design of the measurement

setup and the appro*imation( can %e corrected %&cali%ration

• Aandom errors variations due to uncontrolled varia%les.;an %e reduced %& averaging.


41/74

Sensors

Denition: a device for sensing a physicalvariable of a physical system or an environment

Classication of Sensors

Mechanical quantities: displacement, *train,rotation velocity, acceleration, pressure,force=tor#ue, twisting, weight, 7ow !hermal #uantities: temperature, heat. &lectromagnetic=optical #uantities: voltage,

current, fre#uency phase< visual=images, light<magnetism. hemical #uantities: moisture, p3 value


42/74

Specications of Sensor

Accuracy: error between the result of ameasurement and the true value beingmeasured.

Resolution: the smallest increment ofmeasure that a device can ma2e.Sensitivity: the ratio between the change

in the output signal to a small change in

input physical signal. *lope of the input4output t line.Repeataility!Precision: the ability of

the sensor to output the same value for

the same input over a number of trials


43/74

Accuracy vs" Resolution

True value

measurement


44/74

Accuracy vs" Precision

recision$ithoutaccurac&

#ccurac&

$ithoutprecision

recision

and accurac&


45/74

Specications of Sensor

Dynamic Range: the ratio of ma'imum recordableinput amplitude to minimum input amplitude, i.e.%./. > 6? log (-a'. nput Ampl.=-in. nput Ampl.) d@

#inearity: the deviation of the output from a best4

t straight line for a given range of the sensor$ransfer %unction ("re#uency /esponse): !herelationship between physical input signal andelectrical output signal, which may constitute acomplete description of the sensor characteristics.

&and'idt(: the fre#uency range between thelower and upper cuto1 fre#uencies, within which thesensor transfer function is constant gain or linear.

)oise: random 7uctuation in the value of input thatcauses random 7uctuation in the output value


46/74

Attriutes of Sensors

*perating Principle: &mbedded technologies that ma2esensors function, such as electro4optics, electromagnetic,pie0oelectricity, active and passive ultraviolet.

Dimension of +ariales: !he number of dimensions ofphysical variables.

Size: !he physical volume of sensors.Data %ormat: !he measuring feature of data in time<

continuous or discrete=analog or digital. Intelligence: apabilities of on4board data processing and

decision4ma2ing.Active versus Passive Sensors: apability of generating

vs. 5ust receiving signals.P(ysical Contact: !he way sensors observe the

disturbance in environment.Environmental duraility: will the sensor robust enough

for its operation conditions


47/74

Strain ,auges"oil strain gauge

Least e'pensiveWidely usedot suitable for long distance &lectromagnetic nterference *ensitive to moisture humidity

Vibration wire strain gauge%etermine strain from fre#. of A signal @ul2y

"iber optic gauge mmune to &- and electrostatic noise ompact si0e3igh cost "ragile


48/74

Strain Sensing

/esistive "oil *train Bage !echnology well developed< Low cost3igh response speed broad fre#uency

bandwidthA wide assortment of foil strain gages

commercially available*ub5ect to electromagnetic (&-) noise,

interference, o1set drift in signal.Long4term performance of adhesives

used for bonding strain gages is#uestionable

Vibrating wire strain gages can 8!be used for dynamic applicationbecause of their low responsespeed.

8ptical ber strain sensor


49/74

Strain Sensing

$ie0oelectric *train *ensor $ie0oelectric ceramic4based or $ie0oelectric polymer4based

(e.g., $V%") Very high resolution (able to measure nanostrain) &'cellent performance in ultrasonic fre#uency range, very high

fre#uency bandwidth< therefore very popular in ultrasonicapplications, such as measuring signals due to surface wavepropagation

When used for measuring plane strain, can not distinguish thestrain in C, D direction

$ie0oelectric ceramic is a brittle material (can not measurelarge deformation)

;ourtes& of ;,

ie3otronics


50/74

Acceleration Sensing

$ie0oelectric accelerometeron0ero lower cuto1 fre#uency (?.E F E 30 for

GH)Light, compact si0e (miniature accelerometer

weighing ?.I g is available)-easurement range up to J=4 G?? gLess e'pensive than capacitive accelerometer*ensitivity typically from G F E?? mv=g

@road fre#uency bandwidth (typically ?.6 F G 230)8perating temperature: 4I? F EG?

hoto courtes& of ;, ie3otronics


51/74

Acceleration Sensing

apacitive accelerometerBood performance over low fre#uency range, can

measure gravity+3eavier (K E?? g) and bigger si0e than pie0oelectric

accelerometer

-easurement range up to J=4 6?? g-ore e'pensive than pie0oelectric accelerometer*ensitivity typically from E? F E??? mV=g"re#uency bandwidth typically from ? to ?? 308perating temperature: 4MG F E6?



52/74

Accelerometer


53/74

%orce Sensing

-etal foil strain4gage based (load cell)Bood in low fre#uency response3igh load rating/esolution lower than pie0oelectricity4

based/ugged, typically big si0e, heavy weight

;ourtes& of avidson'easurement


54/74

%orce Sensing

$ie0oelectricity based (force sensor) lower cuto1 fre#uency at ?.?E 30

can 8! be used for static load measurement

Bood in high fre#uency

3igh resolutionLimited operating temperature (can not be used for

high temperature applications)

ompact si0e, light

;ourtes& of ;, ie3otronics


55/74

Displacement Sensing

LV%! (Linear Variable %i1erential !ransformer): nductance4based ctromechanical

sensor nnite; resolution

limited by e'ternal electronics

Limited fre#uency bandwidth (6G? 30typical for %4LV%!, G?? 30 for A4LV%!)

o contact between the moving coreand coil structure no friction, no wear, very long operating

lifetime

Accuracy limited mostly by linearity ?.EH4EH typical

-odels with stro2es from mm’s to E mavailable

hoto courtes& of '


56/74


Linear $otentiometer /esolution (innite), depends onN

3igh fre#uency bandwidth (O E? 230)

"ast response speedVelocity (up to 6.G m=s)

Low cost

"inite operating life (6 million cycles) due to

contact wearAccuracy: J=4 ?.?E H 4 P H "*8

8perating temperature: 4GG K E6G

hoto courtes& of uncan-lectronics


57/74

Displacement $ransducer

-agnetostrictive Linear %isplacement !ransducer&'ceptional performance for long stro2e position

measurement up to P m8peration is based on accurately measuring the distance

from a predetermined point to a magnetic eld produced

by a movable permanent magnet./epeatability up to ?.??6H of the measurement range./esolution up to ?.??6H of full scale range ("*/)/elatively low fre#uency bandwidth (4Pd@ at E?? 30)Very e'pensive

8perating temperature: ? F I?

hoto courtes& of chaevit3


58/74


%i1erential Variable /eluctance !ransducers/elatively short stro2e

3igh resolution

on4contact between the measured ob5ect and sensor

T&pe of ;onstruction tandard tu%ular

Fi*ing 'ode %& 8mm diameter

Total 'easuring Aange 2G/71>mm

neumatic Aetraction Ho

Aepeata%ilit& 0.1um

Eperating Temperature 6imits 710 to G!5 degrees ;

;ourtes& of 'icrostrain( nc.


59/74

+elocity Sensing

*canning Laser Vibrometryo physical contact with the test ob5ect< facilitate

remote, mass4loading4free vibration measurements ontargets

measuring velocity (translational or angular)automated scanning measurements with fast scanning

speed

3owever, very e'pensive (O QE6?R)

hoto courtes& of ,ruel D Iaer

hoto courtes& of ol&tec


60/74

#aser +irometry

ReferencesStructural health monitoring using scanning laser

vibrometry,; by L. -allet, *mart -aterials *tructures, vol. EP, 6??S, pg. 6ME

the technical note entitled Princile ofVibrometry ; from $olytec


61/74

S(oc- .(ig(/,0 Sensing

*hoc2 $ressure *ensor-easurement range up to MT -$a (E?

2si)3igh response speed (rise time U 6 µ

sec.)

3igh fre#uency bandwidth (resonantfre#uency up to O G?? 230)8perating temperature: 4I? to EP? Light (typically weighs K E? g)

*hoc2 Accelerometer-easurement range up to J=4 I?,??? g"re#uency bandwidth typically from ?.G

F P? 230 at 4P d@8perating temperature: 4S? to ? Light (weighs K G g)



62/74

Angular Motion Sensing .$iltMeter0

nertial Byroscope (e.g., http:==www.'bow.com) used to measure angular rates and C, D, and acceleration.

!ilt *ensor=nclinometer (e.g., http:==www.microstrain.com) !ilt sensors and inclinometers generate an articial hori0on

and measure angular tilt with respect to this hori0on.

/otary $osition *ensor (e.g., http:==www.msiusa.com) includes potentiometers and a variety of magnetic and

capacitive technologies. *ensors are designed for angulardisplacement less than one turn or for multi4turn

displacement.

Photo co/rtesy of .S0 and Crossbo1


63/74

Light *ensorLight sensors are used

in cameras, infrareddetectors, and ambientlighting applications

*ensor is composed ofphotoconductor suchas a photoresistor,

photodiode, orphototransistor


64/74

-agnetic "ield *ensor-agnetic "ield

sensors are usedfor power steering,security, and

currentmeasurements ontransmission lines

3all voltage isproportional tomagnetic eld

t qn

B ! V H

⋅⋅

⋅=


65/74

ltrasonic *ensor

ltrasonic sensors areused for positionmeasurements

*ound waves emittedare in the range of 64EP -30

Sound )avigation And

Ranging (*8A/)Radio Dection And

Ranging (/A%A/) F&L&!/8-AB&!

WAV&* ++


66/74

$hotogate$hotogates are used

in countingapplications (e.g.

nding period ofperiod motion)

nfrared transmitter

and receiver atopposite ends of thesensor

!ime at which light

is bro2en is recorded


67/74

86 Bas *ensor

86 sensor measures

gaseous 86 levels in

an environment

-easures 86 levels in

the range of ?4G???ppm

-onitors how muchinfrared radiation isabsorbed by 86

molecules


68/74

MEMS $ec(nology

What is -&-*NAcronym for -icroelectromechanical *ystems-&-* is the name given to the practice of ma2ing and

combining miniaturi0ed mechanical and electricalcomponents.;! ". #abriel, Sci$m, Set %&&'.

*ynonym to:-icromachines (in Xapan)-icrosystems technology (in &urope)

Leverage on e'isting 4based fabrication techni#ues (butnow e'tend to other non techni#ues)

$otential for low cost through batch fabrication !housands of -&-* devices (scale from K ?.6 µm to E

mm) could be made simultaneously on a single siliconwafer


69/74

MEMS $ec(nology

o4location of sensing,computing, actuating,control, communication power on a small chip4si0e

device3igh spatial functionality and

fast response speedVery high precision in

manufacture

miniaturi0ed componentsimprove response speed andreduce power consumption

-&-* " b i ti


70/74

-&-* "abrication

!echni#ue

;ourtes& of #.. isano(#A#


71/74

Distinctive %eatures of MEMSDevices

-iniaturi0ationmicromachines (sensors and actuators) can handle

microob5ects and move freely in small spaces

-ultiplicitycooperative wor2 from many small micromachinesmay be best way to perform a large tas2

ine'pensive to ma2e many machines in parallel

-icroelectronicsintegrate microelectronic control devices withsensors and actuators

Fuita( roc. ---( @ol. 8!( Ho 8


72/74

MEMS Accelerometer

apacitive -&-*accelerometer3igh precision dual a'is

accelerometer with signalconditioned voltageoutputs, all on a singlemonolithic

*ensitivity from 6? to E???mV=g

3igh accuracy3igh temperature stability

Low power (less than I??uA typical)G mm ' G mm ' 6 mm L

pac2ageLow cost (QG K QES=pc. in

Dr. 6??S);ourtes& of #nalog evices(

nc.


73/74

-&-* Accelerometer$ie0oresistive -&-* accelerometer

8perating $rinciple: a proof mass attached to a siliconhousing through a short 7e'ural element. !heimplantation of a pie0oresistive material on the uppersurface of the 7e'ural element. !he strain e'perienced

by a pie0oresistive material causes a position changeof its internal atoms, resulting in the change of itselectrical resistance

low4noise property at high fre#uencies

;ourtes& of B 6&nch( ? 'ich.


74/74

-&-* %ust-&-* dust here has the same scale as a

single dandelion seed 4 something so smalland light that it literally 7oats in the air.

ource istri%uted '-' He$ ;hallenges for;omputation %&

Date post:	06-Jul-2018
Category:	Documents
Upload:	adisebastian
View:	222 times
Download:	0 times

Instrumentation-Lecture 3_1.pptx

Documents