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
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#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
istributed 7ontrol !ystemistributed 7ontrol !ystem
istributed 7ontrol !ystemistributed 7ontrol !ystem
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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
istributed 7ontrol !ystemistributed 7ontrol !ystem
)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
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