sensors automation

8/9/2019 Sensors Automation

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TransducersTransducers

Transduceris a devicethat converts fromsome other forms such

as pressure,temperature, ow,viscosity, motion intoelectrical energy for

the purpose ofmeasurement andcontrol.

Presentation by J. Majumder


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Process

Final Control

Element

Sensors

Transmitter

Signal

ConditionerController

Set point

Recorder

Indicator

Alarms

Interlocks

Disturbances


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Range of value of

Measured variablesAdusted range of t!e

Transmitted signal

500

0

250Degree

C

4 mA

20

mA

12

mA


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TransducersTransducers

Almost any physical property of aAlmost any physical property of amaterial that changes in response tomaterial that changes in response tosome excitation can be used tosome excitation can be used to

produce a sensorproduce a sensor

widely used sensors include those thatwidely used sensors include those that

are:are:

resistiveresistive

inductiveinductivecapacitivecapacitive


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Transmitter woringTransmitter woring

principleprinciple


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!ensor " signal!ensor " signal

conditionerconditioner


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SIGNAL CONDITIONINGSIGNAL CONDITIONING

!ome functions of signal conditionersare:

#. Ampli$cation of the sensor signals

%. !upply of &ac or dc' excitations to thesensors so changes in resistance,

inductance, or capacitance areconverted to changes in current

(. )iltering to eliminate noise or other

unwanted signal components


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*asic of !ignal conditioner*asic of !ignal conditioner

+

#

(

%

-

R!R"#R$!R%

+d/+ &(%0#-'1('3&%2-


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Resisti&e de&icesResisti&e de&ices

can be very simplecan be very simple

e.g. in a potentiometer, with a $xed voltagee.g. in a potentiometer, with a $xed voltageacross the outer terminals, the voltage onacross the outer terminals, the voltage on

the third is directly related to positionthe third is directly related to position

+s /+s / s x +s x +

#2s#2s where the resistance of the device changes

with the quantity being measured, this

change can be converted into a votage

signa using a !otentia divider "


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Temperature measurementTemperature measurement

TTThermocoupleThermocouple

ThermistorThermistor


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Temperature sensorsTemperature sensors

Resisti&e t'ermometersResisti&e t'ermometers typical devices use platinum wire &such atypical devices use platinum wire &such adevice is called a platinum resistancedevice is called a platinum resistancethermometers or 4T'thermometers or 4T'

linearlinearbut has poorbut has poor sensitivitysensitivity

A typical 4T elementA typical 4T element A sheathed 4T A sheathed 4T


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TTRTD PT (( )(( o'm at ( de*ree C+ incor,orates ,ure meta-or certain a--oys t'at increase in resistance as tem,erature

increases and decrease in resistance as tem,eraturedecreases.

RTDs act -i/e an e-ectrica- transducer con&ertin* c'an*es intem,erature to &o-ta*e si*na-s by t'e measurement o0resistance.

Co,,er 1 nic/e-

#em!erature

$es

ista

nce

RTD


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5nternal construction of T5nternal construction of T


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6nbalanced *ridge6nbalanced *ridge

7ircuit7ircuit

%00&

T


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T with temp.T with temp.

compensationcompensation

esistance changeue to temp. will89ect ( also

-

#1&(2r'/%1&-2r'

r


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T'ermistorsT'ermistors

These materials with a high thermalThese materials with a high thermal

coecient of resistancecoecient of resistance

sensitivesensitivebut highlybut highly non-linearnon-linear

A typical disc thermistorA typical disc thermistor A threaded thermistor A threaded thermistor


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T'ermistorT'ermistor

Thermistors are semiconductor materialsThermistors are semiconductor materialswith metallic oxides such as ;anganesewith metallic oxides such as ;anganese

whose electrical resistance can be any valuewhose electrical resistance can be any valuefrom #


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Temp. measurement usingTemp. measurement using

ThermistorThermistor


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Thermocouple for higherThermocouple for higher

temp.temp.

7old ?unction@=< 7


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8lectronic thermocouple8lectronic thermocouple


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+ariable inductance+ariable inductance

transducertransducer

isplacement fromsensor

7ore


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eft ight

;ax 0ve

;ax2ve


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4ressure measurement4ressure measurement


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)orce !ensors)orce !ensors

Strain *au*eStrain *au*e stretching in one direction increases thestretching in one direction increases the

resistance of the device.resistance of the device.

can be bonded to a surface to measurecan be bonded to a surface to measurestrainstrain

used within load cells and pressure sensorsused within load cells and pressure sensors

A strain gauge

Direction of sensitivity


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esistive sensor : strainesistive sensor : strain

gaugegaugeA strain gauge is a displacement sensor whoseA strain gauge is a displacement sensor whose

resistance changes in response to a change inresistance changes in response to a change inlength caused by an applied forcelength caused by an applied force

7onsider a wire with length, l and cross sectional7onsider a wire with length, l and cross sectional

area, A :area, A :

Bith no force applied :Bith no force applied :

Bith an applied force, the lengthBith an applied force, the length

increases byincreases by l.l.

!ince the total volume of the!ince the total volume of thematerialmaterialremains constant, theremains constant, the

change in area is given as :change in area is given as :

and the change in resistance as :and the change in resistance as :

A

lR =

Rl

l2

A

l

lA

)ll(R

2

+=

+= A)ll(lA

F

F

l

A


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!train gauges $tted in propeller shaft


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!train0Cage *ased 4ressure!train0Cage *ased 4ressure

7ell7ell


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7apacitive displacement7apacitive displacement

sensorsensor A capacitive displacement sensorA capacitive displacement sensorproduces an output signal due to theproduces an output signal due to thechange in capacitance caused by varyingchange in capacitance caused by varying

the distance between a $xed and athe distance between a $xed and a

movable plate :movable plate :

d

A

fixed plate

movable plate

d

AC

ro=


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7apacitance level transducer7apacitance level transducer


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7apacitance0*ased 4ressure7apacitance0*ased 4ressure

7ell7ell


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7apacitance 4 cell7apacitance 4 cell


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Dptical 4ressureDptical 4ressureTransducerTransducer


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4heiEo electric transducer4heiEo electric transducer


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Pie2oe-ectric Transducer


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3ecause t'e s,eed sensor detects 2ero4crossin*s t'e3ecause t'e s,eed sensor detects 2ero4crossin*s t'e

5a&e0orm s'ou-d cross 2ero on-y t5ice 0or eac' toot' )once5a&e0orm s'ou-d cross 2ero on-y t5ice 0or eac' toot' )once

*oin* ,ositi&e and once *oin* ne*ati&e. T'e sin*-e4,'ase AC*oin* ,ositi&e and once *oin* ne*ati&e. T'e sin*-e4,'ase AC

de&e-o,ed due to e-ectroma*netic induction.de&e-o,ed due to e-ectroma*netic induction.T'e cyc-es ,er second can be easi-y con&erted to re&o-utionsT'e cyc-es ,er second can be easi-y con&erted to re&o-utions

,er minute. T'is ,ro&ides t'e *o&ernor 5it' an indication o0,er minute. T'is ,ro&ides t'e *o&ernor 5it' an indication o0

,rime mo&er s,eed. T'e 0aster t'e 6y5'ee- turns t'e 0aster,rime mo&er s,eed. T'e 0aster t'e 6y5'ee- turns t'e 0aster

t'e induced 7M8 0re9uency. In t'is manner t'e *o&ernort'e induced 7M8 0re9uency. In t'is manner t'e *o&ernor

contro- senses t'e c'an*es in s,eedcontro- senses t'e c'an*es in s,eed

I d ti i it t


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Inducti&e ,ro!imity sensors *enerate ane-ectroma*netic :e-d and detect t'e eddy current -ossesinduced 5'en t'e meta- tar*et enters t'e :e-d.T'e :e-d is *enerated by a coi- 5ra,,ed round a 0errite

core 5'ic' is used by a transistori2ed circuit to ,roduceosci--ations. T'e tar*et 5'i-e enterin* t'ee-ectroma*netic :e-d ,roduced by t'e coi- 5i-- decreaset'e osci--ations due to eddy currents de&e-o,ed in t'etar*et.

I0 t'e tar*et a,,roac'es t'e sensor 5it'in t'e so4ca--ed;sensin* ran*e


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6ltrasonic evel6ltrasonic evel

;easurement;easurement


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6ltrasonic evel6ltrasonic evel

;easurement;easurement


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Tan AATan AA

T'e 0re9uency o0 t'e transmittedT'e 0re9uency o0 t'e transmittedsi*na-si*na-)? 3and (( G'2+decreases o&er a)? 3and (( G'2+decreases o&er atime ,eriod. T'e incomin* si*na- istime ,eriod. T'e incomin* si*na- is

com,ared 5it' t'e out*oin* si*na-.com,ared 5it' t'e out*oin* si*na-.T'e di@erence bet5een t'ese t5oT'e di@erence bet5een t'ese t5osi*na-s is a -o5 0re9uency4si*na-. Itssi*na-s is a -o5 0re9uency4si*na-. Its0re9uency is direct-y ,ro,ortiona- to0re9uency is direct-y ,ro,ortiona- tot'e distance 0rom t'et'e distance 0rom t'eTransmitter to t'e sur0ace o0 t'eTransmitter to t'e sur0ace o0 t'e,roduct.,roduct.


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Tan AATan AA


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THEBUBBLERSYSTEM


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THE BUBBLER SYSTEMLIQUID LEVEL MEASUREMENT


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5ntelligent transmitter5ntelligent transmitter


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Few generation transducerFew generation transducer

I --i T


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Inte--i*ent Tem,eratureTransmitterThe Intelligent Temperature Transmitter receives input signalsfrom RTDs, thermocouples, ohms sensors, or dc mV sources,and transmits a linear 4 to 20 mA dc or digital output

Signal.This microprocessor based transmitter is availablewith HART or Foxboro digital communications protocol forremote communication and database configuration from ahand-held terminal, personal computer, or I/A Series System.


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Sensor is a sim,-e tunin* 0or/ maintained in &ibratione-ectronica--y. T'e density is a 0unction o0 t'e resonant0re9uency t'e &iscosity is a 0unction o0 t'e band5idt'.It di*ita--y measures t'e 0re9uency at a ,oint A )t'e -o5er 4 %db,oint+ and t'en at ,oint 3 )t'e u,,er 4%db,oint+ . 8rom t'ese t5omeasurements it ca-cu-ates t'e band5idt' )34A+ resonant0re9uency ))A3+B$+ and 'ence t'e 9ua-ity 0actor )resonant0re9uencyBband5idt'+ to *i&e di*ita--y determined &a-ues o0 t'edensity and &iscosity 0or t'e 6uid.


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IBP Con&erter


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IBP Con&erter

Suppl" air

#rifice

Pneumatic

rela"

#ut put $%&' psi

Force

beam

Flapper

Force beammovement

Feedback

bello(

Coil

Pivot

)o**le

Current input

+%,- mAmp

Permanent

magnet

)

S

514 7514 7 t


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514 7onverter514 7onverter

T itt C lib tiT itt C lib ti


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Transmitter Calibration,Transmitter Calibration,

Zero setting errorZero setting error

T itt C lib tiT itt C lib ti


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Transmitter Calibration,Transmitter Calibration,

Span setting errorSpan setting error


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peration Amplifier

I ti A lifi


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Inverting Amplifier

89ect of e feed89ect of ve feed


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89ect of ve feed89ect of ve feed

bacbac

G= Gain+

-

F=Feedback

IN!"=#i

Amplifier

F#o #o = Ge

e = #i- F#o

$!" !"

#o= G ( #i-Fvo)

"otal Gain =#o%#i = G (&- F x #o%#i)

#o%#i (&+GF) = G

#o%#i = G%(& + GF)

- ve Feed back 'ive tabilit * accrate control

Non Inverting Amplifier


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Non Inverting Amplifier

!umming Ampli$er!umming Ampli$er


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!umming Ampli$er!umming Ampli$er

Differential Amplifier:Differential Amplifier:


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Differential Amplifier:Differential Amplifier:SubstractorSubstractor

Di@erentiatorDi@erentiator


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Inte*ratorInte*rator


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Inte*ratorInte*rator

8lectronic 4 " 5 7ontroller8lectronic 4 " 5 7ontroller


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8lectronic 4 " 5 7ontroller8lectronic 4 " 5 7ontroller

8lectronic 45 7ontroller8lectronic 45 7ontroller


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8lectronic 45 7ontroller8lectronic 45 7ontroller

8lectronic Covernor8lectronic Covernor


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8lectronic Covernor8lectronic Covernor

igital 7ontrollerigital 7ontroller


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gg

istributed 7ontrol !ystemistributed 7ontrol !ystem


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Process Control Stations

I.# Subs"stems

#perator /orkstation

Data 0ig!(a"

P1A)T F1##R




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Proprietar" Functionalit" and

Control Function

Proprietar" and DedicatedSoft(are

Proprietar" and Dedicated

)et(ork2Proprietar" 1a"er 3 TCP.IP 3 Et!ernet4

+%,- ma Devices


)oundation )ieldbus !ystem)oundation )ieldbus !ystem


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'(&

Digital Protocol for Field Devices5

E6c!anging Information5

And 1inking Devices5 In a )et(ork5

And PerformingDistributed Control

)oundation )ieldbus !ystem)oundation )ieldbus !ystem


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FIE1D78S 0& FIE1D78S 0&FIE1D78S 0&

Trul" Distributed (it! 0ori*ontal Communication

5!T5*6T8 A7G5T87T685!T5*6T8 A7G5T87T68

;D*6! T47154 ;aster1!lave;D*6! T47154 ;aster1!lave


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;D*6! T47154 0 ;aster1!lave;D*6! T47154 0 ;aster1!lave

FIE1D78S 0&

M#D78S TCP.IP

FIE1D78S 0&1C9-- 3 E)ET9--

DFI$-,

G!8 at Gost0evelG!8 at Gost0evel


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G!8 at Gost evelG!8 at Gost evel

)1 *iedbus Devices

&!eration +ngineering aintenance

Conventiona

Devices

DFI302

&ther -rotocos

sensors automation

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