Temperature, Light & Pressure Sensors

7/23/2019 Temperature, Light & Pressure Sensors

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AUTOMATION & ROBOTICS

TEMPERATURE, LIGHT & PRESSU

SENSORS

Engr Haider-e-Karar

Teaching Assistant

Mehran Universit !" Engineering and Techn!#!g

Engr Haider-e-Karar



Temperature Sensors

•Sens!rs $hich are %sed t! eas%re the thera# are ca##ed Te'erat%re Sens!rs

• Te'erat%re is a ver critica# (%antit t! )e c!nin an e#ectr!nic a''#icati!ns, s%ch as an%"a

!" seic!nd%ct!r devices etc*

• M!re!ver, in an a''#icati!ns r!)!ts are %sed high te'erat%res are inv!#ved* S%ch r!)!ts havte'erat%re sens!rs, t! eas%re the desired

te'erat%re ratings Engr Haider-e-Karar



Temperature Sensors

•S!e !" the )asic thermo sensitive devices are+

• Ther!c!%'#es

• Therist!rs

• Resistance te'erat%re detect!rs

Engr Haider-e-Karar



Thermocouples

•

Ther!c!%'#e is genera## %sed as a 'riar tra"!r te'erat%re eas%reent in $hich changeste'erat%re are direct# c!nverted int! an e#ectsigna#

•

The ther!c!%'#e )ehavi!r can )e e'#ained !n)asis !" ther!e#ectric 'hen!ena nae# See)e.ect, Pe#tier e.ect and Th!'s!n e.ect*

Engr Haider-e-Karar



Ther!e#ectric Phen!ena

•

In /01/, the great scientist Pr!"* See)ec disc!vethat i" the t$! $ires !" di.erent eta#s are 2!inet!gether "!ring c#!sed circ%it and i" the t$! 2%n"!red are at di.erent te'erat%res, an e#ectric3!$s ar!%nd a c#!sed circ%it*

•

This is ca##ed Seed)ec e.ect• He a#s! !)served that i" the t$! eta#s %sed are

and ir!n, then the c%rrent 3!$s "r! c!''er t! ih!t 2%ncti!n and "r! ir!n t! c!''er at c!#d 2%nc



• I" the c!''er $ire*is c%t, the e**" a''ears acr!s!'en circ%it as sh!$n in the 4ig* This e**"* is c!n!$n as See)ec e**"* This See)ec e**"* is'r!'!rti!na# t! the di.erence in the te'erat%ret$! 2%ncti!ns*



Pe#tier E.ect

•

In /015, Pr!"* Pe#tier disc!vered a reverse 'hen!He !)served that $hen t$! dissii#ar eta#s "!r 2%ncti!ns as sh!$ in the 4ig* and i" an eterna# ec!nnected as sh!$n, then the c%rrent 3!$s thr!

2%ncti!ns*

•

6hen c%rrent 3!$s thr!%gh c!''er-ir!n 2%ncti!n"r! c!''er t! ir!n, heat is a)s!r)ed aing 2%nh!t

• 6hen c%rrent 3!$s thr!%gh ir!n-c!''er

2%ncti!n 7T/8 "r! ir!n t! c!''er, heat is

#i)erated aing T1 2%ncti!n c!#dPe#tier E.ect



Ther!c!%'#e 9!nstr%cti!n

•

A ther!c!%'#e is the !st c!!n# %sedther!e#ectric transd%cer* Ther!c!%'#e is adt$! $ires !" dissii#ar eta#s 2!ined t!gether t!t$! 2%ncti!ns as sh!$n in the 4ig*



Ther!c!%'#e 6!ring

•

O%t !" t$! 2%ncti!ns T/ and T1, T1 is e't at c!nstant rte'erat%re* Hence it is re"erred as cold junction

• 6hi#e the te'erat%re changes t! )e eas%red ares%)2ected t! the 2%ncti!n T/ $hich is re"erred as hot

• 6hen the h!t 2%ncti!n te'erat%re is greater as c!the c!#d 2%ncti!n, e**"* is generated d%e t! the te'gradient*



Ther!c!%'#e 6!ring

•

The agnit%de !" the e**"* generated de'ends ateria# %sed "!r the $ires and te'erat%re di.)et$een the t$! 2%ncti!ns

• The h!t 2%ncti!n is s!eties ca##ed eas%ring

$hi#e the c!#d 2%ncti!n is ca##ed re"erence 2%ncti!



Advantages and Liitati!ns !" Ther!c!%'#e

/* The ther!c!%'#e is r%gged in c!nstr%cti!n1* It c!vers a $ide te'erat%re range, "r! :1;<=9 t

>* Using etensi!n #eads and c!'ensating ca)#es, #!ntransissi!n distances "!r te'erat%re eas%re'!ssi)#e*

5* The ther!c!%'#e is c!'arative# chea'er in c!st

?* The ca#i)rati!n can )e easi# checed*

@* S'eed !" res'!nse is high

0* Meas%reent acc%rac is (%ite satis"act!r*



isadvatages

/* 4!r acc%rate te'erat%re eas%reents, c!#d c!'ensati!n is necessar

1* The e" ind%ced vers%s te'erat%re characters!e$hat n!n#inear

>* Stra v!#tage 'ic%' is '!ssi)#e

5* In an a''#icati!ns, a'#iBcati!n !" signa# is



Ther!c!%'#e Avai#a)i#it

I $ant t! Ther!c

• K-T'e @<<9 Ther!c!%'#e Te'erat%re

Pr!)e Sens!r

S'eciBcati!ns+

• Indeing n%)er+ K-t'e

• M!de#+ K-<1 , D5 >< 1M

• Te'erat%re range+ < F @<< egree

•

9!re diaeter+ <*5MM 1• Ins%#ati!n ateria#+ G#ass B)er inside the !%ter stain#ess stee# )raided et

a# shie#d

• 9!re Materia#+ Nice# - chr!i% a##!

• 9!#!r-c!ded+ red "!r the '!sitive )#%e is negative*

• 6e)site+ htt'+$$$*e$a##'*c!

• Price+ >;< PKR

http://www.ewallpk.com/





Ther!'i#es

•

A series !" ther!c!%'#e c!nnected t!gether is ther!'i#e

• Using ther!'i#e, $e can get !re sensitive e#ec!'ared t! sing#e ther!c!%'#e



Ther!'i#e

•

In ther!'i#e, a## eas%ring 2%ncti!ns are at sate'erat%re $hi#e a## the re"erence 2%ncti!ns arean!ther te'erat%re*

• The care %st )e taen t! ens%re acc%rate readindivid%a# ther!c!%'#es are e#ectrica## ins%#ateeach !ther

• The chr!e#-c!nstantan ther!'i#e 'r!vides /c!nsists !" 1? ther!c!%'#es* J %sing this theat te'erat%re change as sa## as <*<</=4 can detected

•

Ther!'i#es are %sed t! eas%re r!!t te'erat"%rnaces



Therist!rs

•

Jasica## therist!r is a c!ntracti!n !" a $!rd thresist!rs

• The resist!rs de'ending !n te'erat%re are theresist!rs* Th%s resistance ther!eters are a#s!therist!rs having '!sitive te'erat%re c!eci

•

J%t genera## the resist!rs having negative te'c!ecients 7NT98 are ca##ed therist!rs* The res!" a therist!r decreases as te'erat%re increa

• The therist!rs are ver sensitive and can detecsa## changes in te'erat%re t!!



•

Therist!rs are $e## s%ited "!r 'recisi!n te'ereas%reent, te'erat%re c!ntr!#, and te'erc!'ensati!n, )eca%se !" their ver #arge changresistance $ith te'erat%re

•

The are $ide# %sed "!r eas%reents in the te'erat%re range -/<< t! 1<< 9e#si%s*

• The eas%reent !" the change in resistance $te'erat%re is carried !%t $ith a 6heatst!ne )r



Resistance Te'erat%re9haracteristics•

The atheatica# re#ati!nshi' acc!rding t! $hicresistance !" therist!r )ehaves as te'erat%regiven )



!#tage 9%rrent 9%rve

What is Self Heating CharacteristicsOf thermistors ?



Advantages & Liitati!n

/* Sa## in sie

1* L!$ in c!st

>* Large change in resistance "!r sa## change in te'erat%re

5* Signa# c!nditi!ning circ%it re(%ired is si'#e

?* Te'erat%re transd%cers %sing therist!rs are having "ast,

and sta)#e res'!nseLIMITATIONS

/* The resistance vers%s te'erat%re characteristic is high#

1* N!t s%ita)#e !ver a $ide te'erat%re range



Signa# 9!nditi!ning 9irc%it

•

M!st !" the ties, the signa# c!nditi!ning circ%ittherist!r inc#%des a 6heatst!ne )ridge and a This is sh!$n in the 4ig*



!esistance Temperature"etectors #!T"s$•

RTs are $ire $!%nd and thin B# devices that eas%te'erat%re )eca%se !" the 'hsica# 'rinci'#e !" the 'te'erat%re c!ecient !" e#ectrica# resistance !" et

• The h!tter the )ec!e, the #arger !r higher the va#%e#ectrica# resistance

• P#atin% RT and PT/<<s are the !st '!'%#ar RT tnear# #inear !ver a $ide range !" te'erat%res and ssa## en!%gh t! have res'!nse ties !" a "racti!n !" a

Engr Haider-e-Karar



Assignent

•

9!nstr%cti!n and 6!ring !" RT• Advantages and isadvantage

• RT Err!r S!%rces

• !esistance Thermometer Wiring Con%guratT&o Wire



Light Sens!rs

•

In !st 'r!cess c!ntr!# re#ated a''#icati!ns, theradiati!n #ies in the range "r! IR thr!%gh visi)#es!eties U )ands

• The eas%reent sens!rs genera## %sed are c photo detectors

•

E#ectr!agnetic radiati!ns %sed as the )asic #ighsens!rs c!'!nent can )e acting in three "!rsradiati!ns+

• isi)#e radiati!ns R

• In"rared radiati!ns IR

• U#travi!#et radiati!ns U



/* Ph!t! etect!rs

•

In !st 'r!cess c!ntr!# re#ated a''#icati!ns, theradiati!n #ies in the range "r! IR thr!%gh visi)#es!eties U )ands

• The eas%reent sens!rs genera## %sed are ca

'h!t! detect!rs* S!e !" the )asic 'h!t! detectdevices are+

/* Ph!t! c!nd%ctive detect!rs

1* Ph!t! v!#taic detect!rs

>* Ph!t! di!de detect!rs



/* Ph!t! 9!nd%ctive etect!rs

•

One !" the !st c!!n 'h!t! detect!rs is )asthe change in the conductivity !" a seic!nd%ctateria# $ith radiati!n intensit*

• The change in c!nd%ctivit a''ears t! )e the ch

the resistance, s! these devices are a#s! ca##ed'h!t!c!nd%ctive ce##s



•

The 'h!t!c!nd%ctive ce## is a seic!nd%ct!r dev$h!se resistance varies inverse# $ith the inten#ight that "a##s %'!n its 'h!t!sensitive ateria#* 4sh!$s t'ica# 'h!t!c!nd%ctive ce## and the sches)!#*

• These devices are a#s! ca##ed 'h!t!resistive ce##'h!t!resist!rs, since the change in c!nd%ctivit as a change in resistance



9!nstr%cti!n

•

The 'h!t!c!nd%ctive ateria# %sed is %s%a## cadc!'!%nds s%ch as cadi% s%#'hide 79dS8 !r case#enide 79dSe8

• This 'h!t!c!nd%ctive ateria# $ith s%)strate is en$ith s%ita)#e enc#!s%re taing !%t 'h!t!c!nd%ctivateria# c!ntacts as eta##ic #eads

• The g#ass $ind!$ !r #ens is added at the t!' !" thenc#!s%re t! 'ass #ight !n 'h!t!c!nd%ctive ateri



Princi'#e

•

As $e n!$ that in seic!nd%ct!rs, energ ga' )et$een c!nd%cti!n e#ectr!ns and va#ence e#ect

• 6hen 'h!t!ns are a)s!r)ed in a 'h!t!c!nd%ctivateria#, d%e t! a)s!r'ti!n !" the 'h!t! energ,e#ectr!ns are ecited int! c!nd%cti!n )and, red%resistance !" the 'h!t!c!nd%ctive ateria#



• An radiati!n $ith a $ave#ength greater than th'redicted ) E(%ati!n cann!t ca%se an resistanchange in the seic!nd%ct!r



•

The gra'h !" change in resistance !" 'h!t!c!nd%ateria# $ith #ight intensit is sh!$n )e#!$

• 6ith n! incident #ight, the 'h!t!c!nd%ctive ce##resistance is ai%* This is ca##ed the dark

resistance, $hich is !" the !rder !" /<<Q*

•

As the #ight intensit increases, the resistance decreases signiBcant#*



A''#icati!ns

• Ph!t!c!nd%ctive ce##s are %sed in vari!%s a''#ics%ch as s!e detect!r, !%td!!r #ighting c!ntr!



Ea'#e



1* Ph!t!v!#taic etect!rs

• An!ther i'!rtant c#ass !" 'h!t! detect!rs that generate

v!#tage $ith the change in the intensit !" #ight is ca##edphoto'oltaic detectors

• The are a#s! ca##ed photo'oltaic cells )eca%se !" theigenerating characteristic

• The act%a## c!nvert the EM energ int! the e#ectrica# en

• A''#icati!ns are "!%nd as )!th EM radiati!n detect!rs ands!%rces c!nverting s!#ar energ int! e#ectrica# '!$er



6!ring Princi'#e

• 6hen s%n#ight hits the N t'e side !" a 'h!t!v!#ce##,the e#ectr!ns in the ce## )ec!e ecited* Theani!%s t! get !ving that the## g#ad# g! t! tht'e side !" the ce## i" given the 'r!'er 'ath

•

That 'ath inv!#ves a 2%ncti!n )et$een the '!sitinegative side !" the ce##*



• This '!sitive-negative 2%ncti!n 7!r PN 2%ncti!n8 adi!de, a##!$ing the e#ectr!ns t! 'ass "r! the '!7)!tt!8 side t! the negative 7"r!nt8 side !" the n!t in the reverse directi!n

•

This eans the e#ectr!ns 3!$ "r! the negativethe ce## thr!%gh the circ%it and t! the

'!sitive side !" the ce##



• As !re e#ectr!ns !ve "r! the negative side t'!sitive side, the e#ectr!ns !n the '!sitive side a'%shed %' thr!%gh the PN 2%ncti!n t! the negati!" the ce##, and the 'r!cess c!ntin%es as #!ng ass%n#ight is 'resent

• The PN 2%ncti!n ens%res that the e#ectr!ns !vethr!%gh the circ%it*



>* Ph!t!di!de etect!rs

• Ph!t!di!de is a seic!nd%ct!r PN 2%ncti!n $h!s!" !'erati!n is #iited t! reverse )iased regi!n

• The 'h!t!di!de is designed s%ch that it is sensitthe #ight



Ph!t!di!de

• 6hen there is n! #ight, the reverse )iased 'h!t!carries a c%rrent $hich is ver sa## and It is denI, ca##ed dar( current* It is '%re# d%e t! thergenerated in!rit carriers



6!ring Princi'#e

• 6hen #ight is a##!$ed t! "a## !n a '-n 2%ncti!n thrsa## $ind!$, 'h!t!ns trans"er energ t! va#ence#ectr!ns t! ae the "ree

• Hence reverse c%rrent increases* It is 'r!'!rti!n#ight intensit* The 4ig* sh!$s the 'h!t!di!decharacteristics*

• The 4ig* 7a8 sh!$s the re#ati!n )et$een reverse and #ight intensit $hi#e the 4ig* 7)8 sh!$s re#ati!)et$een reverse v!#tage and reverse c%rrent atdi.erent #ight intensities



Ph!t!di!de 9haracteristics

• It can )e seen that reverse c%rrent is n!t de'endreverse v!#tage and t!ta## de'ends !n #ight inte

Use !" Ph!t!di!de as aria)#e



Use !" Ph!t!di!de as aria)#eResist!rs



6h t! )e %sed inReverse )iased



Ph!t!di!de A''#icati!ns

• A#ar 9irc%it and O)2ect 9!%nter

Ph!t!di!de in O)2ect 9Ph!t!di!de in A#ar Sste



5* Ph!t!eissive etect!rs

• Ph!t!eissive detect!rs are either evac%ated !rB##ed t%)es c!ntaining a cath!de and !ne !r !ran!des

• 6hen 'h!t!ns i'act !n the cath!de, the e#ectre2ected "r! the cath!de s%r"ace and are acce#et!$ard the an!de that is at a '!sitive '!tentia# $res'ect t! the cath!de

• The 'h!t!e#ectric c%rrent increases 'r!'!rti!na#intensit !" the i##%inati!n



Ph!t!-eissive E.ect



6!ring Princi'#e

• The cath!de is ade %' !" 'h!t!sensitive ateria#

acts as a 'h!t!eitter

• The an!de acts as an e#ectr!n c!##ect!r $hich c!##e#i)erated e#ectr!ns* The an!de is aintained at s!deBnite '!sitive '!tentia# $ith res'ect t! cath!de

• 6hen cath!de is s%)2ected t! radiati!n, it eits the#ectr!ns $hich '!ssess a range !" initia# ve#!citiesve#!cities var )et$een er! t! a deBnite ai%



Ph!t!%#ti'#ier

• In !rder t! increase the sensitivit, severa# !re

e#ectr!des 7dn!des8 are added t! the c!nstr%ctthe detect!r* In this device, ca##ed a 'h!t!%#ti'e#ectr!ns that are e2ected "r! the cath!de are "!n !ne !" the dn!des*

• A 'h!t!e#ectr!n "r! the cath!de stries the Brs

dn!de $ith s%cient energ t! e2ect severa# e#• A## !" these e#ectr!ns are acce#erated t! the sec!

dn!de, $here each stries the s%r"ace $ith s%energ t! e2ect severa# !re e#ectr!ns



• This 'r!cess is re'eated "!r each dn!de %nti# th

e#ectr!ns that reach the an!de are great# %#tin%)er As a res%#t, the !%t'%t c%rrent has asigniBcant# increased agnit%de, $hich deBneshigh sensitivit !" the detect!r*



P S



Press%re Sens!rs

• M!st 'ress%re sens!rs %sed in 'r!cess c!ntr!# r

the transd%cti!n !" 'ress%re in"!rati!n int! a 'dis'#aceent*

• Meas%reent !" 'ress%re re(%ires techni(%es "!'r!d%cing the dis'#aceent and eans "!r c!nvs%ch dis'#aceent int! a 'r!'!rti!na# e#ectrica#

• This is n!t tr%e, h!$ever, in the ver #!$ 'ress%regi!n 7at8, $here an '%re# e#ectr!nic ea'ress%re eas%reent a )e %sed

•

i h



ia'hrag

• One c!!n e#eent %sed t! c!nvert 'ress%re

in"!rati!n int! a 'hsica# dis'#aceent is thedia'hrag 7thin, 3ei)#e 'iece !" eta#8 sh!$n ia 'ress%re '/ eists !n !ne side !" the dia'hrag'1 !n the !ther, then a net "!rce is eerted give

A dia'hrag Area in

'/ and '1, 'ress%re in N

•



• A dia'hrag is #ie a s'ring and there"!re eten

c!ntracts %nti# a H!!es #a$ "!rce is deve#!'ed )a#ances the 'ress%re di.erence "!rce

• This is sh!$n in 'revi!%s 4ig "!r '/ greater than

• N!tice that since the "!rce is greater !n the '/ sthe dia'hrag, it has de3ected t!$ard the '1 si

• The etent !" this de3ecti!n, i*e*, the dia'hragdis'#aceent, is a eas%re !" the 'ress%re di.e



• 4!r the eas%reent !" the a)solute pressure

!''!site side !" the dia'hrag is a vac%%

• 4!r the eas%reent !" di*erential pressure,'ress%re di.erence the 'ress%res are c!nnectedside !" the dia'hrag

• 4!r the gauge pressure, i*e* the 'ress%re re#atithe at!s'heric 'ress%re, the !''!site side !" tdia'hrag is !'en t! the at!s'here





• The !veent !" the center !" a dia'hrag can

!nit!red ) s!e "!r !" dis'#aceent sens!r• 4ig sh!$s the "!r that ight )e taen $hen str

ga%ges are %sed t! !nit!r the dis'#aceent, thga%ges )eing st%c t! the dia'hrag and changresistance as a res%#t !" the dia'hrag !vee

• T'ica## s%ch sens!rs are %sed "!r

'ress%res !ver the range /<< Pa t! /<< MPa

MP/<<AP



MP/<<AP

• One "!r !" dia'hrag 'ress%re ga%ge %ses stra

ga%ge e#eents integrated $ithin a si#ic!n dia'hand s%''#ied, t!gether $ith a resistive net$!r "signa# 'r!cessing, !n a sing#e si#ic!n chi' as theM!t!r!#a MP 'ress%re sens!r

• 6ith a v!#tage s%''# c!nnected t! the sens!r, i

an !%t'%t v!#tage direct# 'r!'!rti!na# t! the 're

Je##!$s



Je##!$s

• A )e##!$s, sh!$n in 4ig, is an!ther device %ch

dia'hrag that c!nverts a 'ress%re di.erentia# i'hsica# dis'#aceent, ece't that here thedis'#aceent is %ch !re a straight-#ine e'an

• The acc!rdi!n-sha'ed sides !" the

)e##!$s are ade "r! thin eta#*

6hen there is a 'ress%re di.erence,

a net "!rce $i## eist !n the 3at, "r!nt

s%r"ace !" the )e##!$s



• The )e##!$s asse)# $i## then c!##a'se #ie an

acc!rdi!n i" '1 is greater than '/ !r e'and i" '1than '/

• Again, $e have a dis'#aceent $hich is 'r!'!rt'ress%re di.erence* This c!nversi!n !" 'ress%re dis'#aceent is ver near# #inear*

• There"!re, an LT can )e %sed t! eas%re thedis'#aceent* This sens!r $i## !%t'%t an LT v!a'#it%de that is #inear# re#ated t! 'ress%re*



EN O4 LE9TURE

Engr Haider-e-Karar

Documents

Temperature, Light & Pressure Sensors