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UNIT IIELECTRICAL AND ELECTRONICS INSTRUMEN

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ANALOG INSTRUMENTS

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GIVING SENSE TO ANALOG INSTRUMEN

A measuring instrument in which the output is a continuous unction

an! shou"! maintain constant re"ationship with the input#

Its not wi!e"$ use! now %ut sti"" it cannot %e rep"ace! %$ other t$pemeasuring instruments &"i'e !igita" measuring instruments( in some

app"ications "i'e ammeters) *o"tmeters in "a%oratories#

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CLASSI+ICATION O+ ANALOG INSTRUME

C"assi,e! as

In!icating Instruments

Recor!ing Instruments

Integrating Instruments

In!icating Instruments- These are which in!icate the magnitu!e o a .uantit$ %eing measure! %$ using a

poiner arrangement

E/amp"es- or!inar$ Ammeters an! Vo"tmeters in "a%s#

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CLASSI+ICATION O+ ANALOG INSTRUMENTS &CONT

Recor!ing Instruments- These instruments gi*e a continuous recor! o the .uantit$ %eing meas

perio! using a pen attache! to mo*ing s$stem#

E/amp"e- Rea!ing Vo"tmeters in a su%station &An out0!ate! metho! or storinor a perio! o time# Now using SCADA computers(

Integrating Instruments- These instruments tota"i1e the e*ents o*er a perio! i#e#) the output o s

instruments are the pro!uct o time an! e"ectrica" .uantit$#

E/amp"e- An househo"! Energ$ meter which gi*es the power consume! in a time#

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2RINCI2LE O+ O2ERATION O+ ANALOGINSTRUMENTS

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2RINCI2LES O+ O2ERATION

Magnetic e3ect

4eating e3ect

E"ectrostatic e3ect

E"ectromagnetic e3ect

4a"" e3ect

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2RINCI2LES O+ O2ERATION&CONTD#)(

Magnetic e3ect-

The e3ect !ue to the current carr$ing con!uctor p"ace! in a magnetic ,e

Use! in- 2MMC) mo*ing iron attraction an! repu"sion t$pe#

4eating5 Therma" e3ect-

Current to %e measure! is ma!e to pass through a e"ement which gets hthis rise in temperature is measure! %$ a thermocoup"e#

Thermocoup"e is %asica""$ a trans!ucer which con*erts heat energ$ to itse"ectrica" energ$#

Use! in- temperature measurements in %oi"ers#

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2RINCI2LES O+ O2ERATION &CONTD#)(

E"ectrostatic e3ect-

6hen two p"ates are charge!) there is a orce e/erte! %5w them which mo the p"ates#

Use! in- E"ectrostatic Vo"tmeters

E"ectromagnetic e3ect- 6hen an non0magnetic !isc is p"ace! in an a"ternating e"ectrica" ,e"!) a

in!uce! in the !isc) which causes 7ow o current#

The orce pro!uce! %$ this in!uce! current an! the a"ternating ,e"! mo

Use! in- househo"! Energ$ meters &now using !igita" energ$ meters (

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2RINCI2LES O+ O2ERATION &CONTD#)(

4a"" e3ect-

I a strip o con!ucting materia" is p"ace! in a

trans*erse magnetic ,e"!) an em is in!uce! %5wtwo e!ges o the con!uctor which can %emeasure! ater amp"i,cation#

The magnitu!e o this em !epen!s on theamount o current 7owing through the strip) 7u/!ensit$ an! this e3ect is ca""e! 4a"" e3ect#

Use! in- 7u/ meter&magnetic measurements(

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O2ERATING +ORCES O+ INDICATINGMEASUREMENTS

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O2ERATING +ORCES

T$pes o operating orces or satisactor$ operation oin!icating meters are -

De7ecting orce

Contro""ing orce an!

Damping orce

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O2ERATING +ORCES &CONTD#)(

De7ecting orce-

It8s the orce re.uire! or mo*ing the pointer rom 1ero position#

The s$stem pro!ucing !e7ecting orce is ca""e! !e7ecting s$stem whiche"ectric current into mechanica" orce which !e7ects the point %$ an$ ooperating princip"es&i#e#) 4a"" e3ect) therma" e3ect) etc#)( as !iscusse! e

Contro""ing orce-

Opposing orce to the !e7ecting orce pro!uce! %$ the s$stem is ca""e! orce-

Main unctions-

To pro!uce e.ua" an! opposite orce to !e7ecting orce in or!er to ma'e !e7!e,nite magnitu!e#

To %ring %ac' pointer to 1ero position ater !e7ecting orce is remo*e!#

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O2ERATING +ORCES &CONTD#)(

Damping orce-

De7ecting an! contro""ing orce pro!uce! %$ the s$stems which ha*e inwhich !oesn8t a""ow s$stem to sett"e in short perio! o time#

So) in or!er to %ring the s$stem to rest !uring short span) there is a !ams$stem which pro*i!es necessar$ !amping orce#

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ANALOG AMMETERS AND VOLTMETERS

E/cept e"ectrostatic t$pe o instruments a"" other t$pes o instrumenon the operating princip"e o the !e7ecting tor.ue is pro!uce! %$ e"

current#

In ammeters) !e7ecting tor.ue is pro!uce! %$ the current to %e me

In *o"tmeters) !e7ecting tor.ue is pro!uce! %$ the current proportio

*o"tage to %e measure!#

4ence) ammeters an! *o"tmeters a"" current measuring !e*ices#

Ammeters with "ow e"ectrica" resistance are connecte! in series withcircuit#

Vo"tmeters with high e"ectrica" resistance are connecte! in para""e" w

circuit#

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T92ES O+ ANALOG INSTRUMENTS

T$pes o ana"og ammeters an! *o"tmeters are-

2ermanent magnet mo*ing coi" instrument &2MMC(

Mo*ing iron t$pe instrument

E"ectro !$namometer t$pe instrument

4ot wire t$pe instrument

Thermocoup"e t$pe instrument

In!uction t$pe instrument

E"ectrostatic t$pe instrument

Recti,er t$pe instrument

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2ERMANENT MAGNET MOVING COIL INSTRU&2MMC(

Out o : t$pes 2MMC can %e use! on"$ or D#C# measurements on"$#

It gi*es accurate rea!ing in D#C#

2RINCI2LE

Motoring princip"e0 current carr$ing con!uctor p"ace! in a magnetic ,e"!a orce#

As coi" in the instrument is mo*ing an! the magnet is a permanent magas permanent magnet mo*ing coi" instrument#

Amount o orce e/perience! %$ the coi" is proportiona" to the current pathe coi"#

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CONSTRUCTION AND 6OR;

The circu"ar or rectangu"ar coi" is p"ace! ,e"! o permanent magnet#

The iron core is i coi" is circu"ar an! its cthe coi" is rectangu"ar !ue to which the !tor.ue is pro!uce!#

Contro""ing tor.ue is pro!uce! %$ the spmetho!

Damping tor.ue is pro*i!e! %$ the methcurrent#

2ointer o "ight weight is connecte! to thwhich mo*er on a gra!uate! sca"e# Mirro%e"ow the pointer era!icates the para""a/

Tota" weight o 2MMC is %a"ance! %$ a %aweight#

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TOR

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TOR

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ERRORS IN 2MMC INSTRUMENTS

+rom a%o*e e.uation we can iner that the !e7ection o pointer is pr

to the current

o 6ea'ening o permanent magnets !ue to ageing an! temperature e3ecto 6ea'ening o springs !ue to ageingo Change o resistance o coi"

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ADVANTAGES DISADVANTAGE

Low power consumption

4igh sensiti*it$

+ree rom h$steresis error

E3ecti*e !amping Not a3ecte! %$ e/terna" magnetic

,e"!s

4igh accurac$

It can %e use! on"$ or D#C#

measurements

Cost is high

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MOVING IRON INSTRUMENTS

A!*antages are - "ow cost) high accurac$) rugge!ness

C"assi,cation are-

MOVING IRON ATTRACTION T92E INSTRUMENTS)

MOVING IRON RE2ULSION T92E INSTRUMENTS

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MOVING IRON ATTRACTION T92E INSTRUMEN

It has a 7at coi" an! a narrow s"ot "i'eopening whi"e mo*ing iron is eccentrica""$

mounte!

Current to %e measure! 7ows through thecoi") causes magnetic ,e"! which attracts

mo*ing coi") thus ma'ing pointer to mo*e

Springs pro!uce necessar$ contro""ingtor.ue

Air riction !amping is pro*i!e! with "ight A"

piston attache! to it#

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MOVING IRON RE2ULSION T92E INSTRUMEN

This t$pe consists o two *anes-

+i/e!

Mo*a%"e

Current to %e measure! 7ows in %oth *anes) so there is a pro!uctionorce which mo*es the pointer#

Di3erent !esigns are-

Ra!ia" *ane t$pe

Coa/ia" *ane t$pe#

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RADIAL VANE T92E

Two *anes here are two ra!ia" strips o iron

which are p"ace! with in the coi"#

+i/e! *ane is attache! to the coi"

Mo*a%"e *ane is attache! to the spin!"e o theinstrument which in turn is attache! to the

pointer

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COA=IAL VANE T92E

4ere) %oth *anes are sections o coa/ia"c$"in!er

Contro" tor.ue is pro!uce! %$ springs an! airriction !amping is use!

E!!$ current !amping cannot %e use! inmo*ing iron instruments as it wou"! !istort

magnetic ,e"!# Mo*ing iron t$pe can %e use! to measure %oth

ac an! !c %ecause) irrespecti*e o the !irectiono the current) iron *anes can %e magnetise!#

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TOR

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TOR

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TOR

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TOR

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ERRORS IN MOVING IRON INSTRUMENT

49STERESIS ERROR

This is !ue to !i3erence in the *a"ue o 7u/ !ensit$ or same current or aan! !escen!ing *a"ues#

This can %e minimise! %$ ma'ing iron parts sma""er so that he$ !emagnet

TEM2ERATURE ERROR

Its !ue to e3ect o temperature on the temperature co0e>cient o spring aheating o coi"s

This can %e minimise! %$ using manganin as a materia" or series resistan

STRA9 MAGNETIC +IELDS

Since operating ,e"! o this t$pe o instrument is *er$ "ow) it8s easi"$ !istue/terna" ,e"!s

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ERRORS IN MOVING IRON INSTRUMENT

+RE