Post on 24-Jan-2019
2. 2.2 Rezistoare dependente
2.2.3 Rezistoarele dependente de fluxul luminos – Fotorezistoare
Fotorezistoarele (LDR – L ight DHSHQGHQW5HVLVWRUVVXQWUH]LVWRDUHDFURUUH]LVWHQ GHSLQGH GH IOX[XO OXPLQRV LQFLGHQW SH VXSUDID D HOHPHQWXOXL UH]LVWLY9DULD LDUH]LVWHQ HLHVWHFDX]DWGHHOLEHUDUHDGHHOHFWURQLSULQHIHFWXOIRWRHOHFWULFLQWHUQ ÌQ JHQHUDO OD UHDOL]DUHD IRWRUH]LVWRDUHORU VH XWLOL]HD] PDWHULDOHsemiconductoare cunoscute sub numele generic de materiale fotoconductoare.6WUXFWXUD GH IRWRUH]LVWRU HVWH DVWIHO UHDOL]DW vQFkW OD vQWXQHULF WRWDO V FRQ LQ
IRDUWH SX LQL HOHFWURQL OLEHUL SUH]HQWkQG DVWIHO R UH]LVWHQ ULGLFDW 2GDW FXDEVRUE LD IOX[XOXL OXPLQRV WRW PDL PXO L HOHFWURQL VXQW HOLEHUD L UH]LVWHQ DPDWHULDOXOXLVF]kQGFRUHVSXQ]WRU
Pentru structura din figura 2.180VHSRDWHFRQVLGHUDFQXPUXOGHHOHFWURQLHOLEHUD LSHVHFXQGvQPDWHULDOHVWH1 ηLld, unde ηHVWHRFRQVWDQWFHGHSLQGHGHOXQJLPHDGHXQGDUDGLD LHL/LQWHQVLWDWHDUDGLD LHLOXPLQRDVHOÂGVXSUDID DLQFLGHQW
l
d
U
(a) (b)
Fig. 2.180DVWUXFWXUIRWRFRQGXFWRDUHUHFWDQJXODUEIRUPDHOHFWUR]LORUXQXLIRWRUH]LVWRU
La aplicarea unei diferen HGHSRWHQ LDO8vQWUHHOHFWUR]LHOHFWURQLLYRUDYHDviteza v:
d
UEv µµ == (2.218)
cu µ - mobilitatea electronilor, E intensitatea câmpului electric./DFRQGXF LDFXUHQWXOXLYRUFRQWULEXLQXPDLHOHFWURQLLDIOD L ODGLVWDQ DYÂτ
de electrodul pozitiv, τ ILLQGGXUDWDPHGLH GH YLD D HOHFWURQLORU OLEHUL'HFL ODFXUHQWXO WRWDOYDFRQWULEXLQXPDL IUDF LXQHDYτ/d din totalul electronilor, curentulelectric fiind:
,d
UelL
d
veNI
τµητ == (2.219)
FXHVDUFLQDHOHFWURQXOXL'HDLFLUH]XOWUH]LVWHQ DPDWHULDOXOXL51
−== L
le
d
I
UR
µτη (2.220)
Cap.2 Rezistoare
2
'XUDWDGHYLD DHOHFWURQLORUOLberi τGHSLQGHGHOXQJLPHDGHXQGλúLGHLQWHQVLWDWHDOXPLQRDVGXSRUHOD LHGHWLSXO βλττ −= L)(0 , cu βRFRQVWDQWLDUτ0
DUHVHPQLILFD LDXQXLWLPSGHYLD GHUHIHULQ $VWIHOUHOD LDVHSRDWHSXQHVXEIRUPD
α−= ALR (2.221)
cu βαµτη
-1 ,0
==le
dA (2.222)
6HREVHUYFSHQWUXDDYHDRYDULD LHFkWPDLPDUHDUH]LVWHQ HLvQWUHVWDUHDGHvQWXQHULFúLVWDUHDGHLOXPLQDUHHVWHQHFHVDUFDYDORDUHDFRQVWDQWHL$VILHFkWPDLPLF$FHVW OXFUX VH UHDOL]HD] SULQ DOHJHUHD GHPDWHULDOH FX YDORUL FkWPDLmari pentru η, µ úL τ0 úL SULQ DVLJXUDUHD XQXL UDSRUW OG FkWPDL PDUH XWLOL]kQGHOHFWUR]LGHIRUPLQWHUGLJLWDO
3ULQFLSDOLLSDUDPHWULLDLIRWRUH]LVWRDUHORUVXQWSUH]HQWD LvQFRQWLQXDUH1) 5H]LVWHQ DODvQWXQHULF5D±UHSUH]LQWYDORDUHDUH]LVWHQ HLODLOXPLQDUHQXO2) 5H]LVWHQ D OD LOXPLQDUH ± UHSUH]LQW YDORDUHD UH]LVWHQ HL OD R LOXPLQDUH
VSHFLILFDWGHH[HPSOXOX[$WXQFL FkQG VH YRUEHúWH GH LOXPLQDUH WUHEXLH GHILQLWH FDUDFWHULVWLFLOH VXUVHL GHOXPLQ2FDUDFWHULVWLFDVXUVHORUHVWH LOXPLQDUHDH[SULPDW vQ OX[$OWXQLWDWHXWLOL]DW SHQWUX LOXPLQDUH HVWH IF GH OD IRRW FDQGOH IF OX[ 'HDVHPHQHD HVWH IRDUWH LPSRUWDQW FDUDFWHULVWLFD VSHFWUDO D VXUVHL GH OXPLQ 6HXWLOL]HD] FD VWDQGDUG R VXUV FH UDGLD] DVHPQWRU XQXL XQ FRUS QHJUX FXtemperatura de culoare de 2850 K.3) Sensibilitatea la fluxul luminos±HVWHDSUHFLDWSULQPDLPXO LSDUDPHWUL
- 6HQVLELOLWDWHDLQWHJUDO6HVWHUDSRUWXOGLQWUHIRWRFXUHQWGLIHUHQ DGLQWUHcurentul prin fotorezistor la iluminarea Φ, IΦúLFXUHQWXOODvQWXQHULF,D)
úLIOX[XOOXPLQRVLQFLGHQWφ
DIIS
−= Φ .
- 6HQVLELOLWDWHD VSHFWUDO ± HVWH UDSRUWXO GLQWUH IRWRFXUHQW úL IOX[XO
monocromatic (φλ) incident: λ
λ φφ λ DII
S−
= .
- Sensibilitatea fotorezistorului φφ
φφ
⋅−
=⋅
∆=
D
D
DR R
RR
R
RS .
- &DUDFWHULVWLFD VSHFWUDO D VHQVLELOLW LL ± UHSUH]LQW YDULD LD VHQVLELOLW LLspectrale SλFXOXQJLPHDGHXQGλ.
- &DUDFWHULVWLFDUH]LVWHQ ±LOXPLQDUH4) 3XWHUHD QRPLQDO 3N ± GHILQLW VLPLODU FD OD UH]LVWRDUH IL[H H[LVWkQG úL OD
IRWRUH]LVWRDUHGLDJUDPDGHVFGHUHDGLVLSD LHL5) Constanta de timp τGHILQLWVLPLODUFDODWHUPLVWRDUHFXGLIHUHQ DDSOLFULL
unui flux luminos în locul celui termic. Intervalul de timp egal cu constanta deWLPS VH RELúQXLHúWH V PDL ILH QXPLW WLPS GH UVSXQV FDUH SRDWH IL WLPS GH
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
3
FUHúWHUH ULVH WLPH VDX WLPS GH FGHUH IDOO WLPH &X SUHFL]DUHD FGHQXPLUHDSRDWHGXFHODXQHOHFRQIX]LLGLQPRWLYHFH LQGHILUHVFXOH[SULPULLvom utiliza aceste denumiri.
7LPSXO GH FUHúWHUH HVWH GHILQLW FD WLPSXO QHFHVDU FRQGXFWDQ HLIRWRUH]LVWRUXOXL SHQWUX D FUHúWH OD H GLQ YDORDUHD ILQDO FHHD FHFRUHVSXQGHXQHLWUDQ]L LLGHODvQWXQHULFODOXPLQ
7LPSXOGHFGHUHHVWHGHILQLWFDWLPSXOvQFDUHFRQGXFWDQ DIRWRUH]LVWRUXOXLVFDGHODH GLQYDORDUHDDYXWODRDQXPLWLOXPLQDUH
7LPSXO GH UVSXQV GHSLQGH GH QLYHOXO GH LOXPLQDUH GH PHPRULD VDXLVWRULDPDWHULDOXOXLúLGHWHPSHUDWXUDDPELDQWÌQJHQHUDOYLWH]DGHUVSXQVHVWHPDL PDUH FkQG VH OXFUHD] OD QLYHOH PDL PDUL GH LOXPLQDUH )HQRPHQXO GHKLVWHUH]LVPHPRULHSUH]HQWDWGHIRWRUH]LVWRDUHHVWHDVHPQWRUFXUHPDQHQ DSHUHWLQD RFKLXOXL OD WUHFHUHD EUXVF vQWUH QLYHOH GH LOXPLQDUH GLIHULWH 2 VWRFDUH DGLVSR]LWLYHORUvQvQWXQHULFYDGXFHODRYLWH]PDLPLFGHFkWvQFD]XOGHSR]LWULLODOXPLQ &X FkW VWRFDUHD H PDL vQGHOXQJDW FX DWkW HIHFWXO H PDL SURQXQ DW /DWHPSHUDWXULFRERUkWHYLWH]DGHUVSXQVHVWHPDLPLF
ÌQJHQHUDOWLPSXOGHFUHúWHUHHVWHGLIHULWGHWLPSXOGHFGHUHvQIXQF LHGHPDWHULDOXO úL WHKQRORJLD IRWRUH]LVWRDUHORU GH QLYHOXO GH LOXPLQDUH úL GH DO LSDUDPHWULDPLQWL LDQWHULRU6) Domeniul temperaturilor de lucru (T m, TM) 7HPSHUDWXUDPD[LP QX DUH
YDORULIRDUWHPDULODIRWRUH]LVWRDUHvQVSHFLDOGDWRULWJHQHUULLGHHOHFWURQLSHFDOHWHUPLF
La realizarea fotorezistoarelor au fost utilizate materialele: Seleniu cristalin-6H VXOIXU GHSOXPE 3E6 VXOIXU GH FDGPLX&G6 VHOHQLXU GH FDGPLX&G6HSeleniul cristalin are un domeniu spectral larg de utilizare dar are sensibilitateUHODWLY PLF 6XOIXUD GH SOXPE DUH PD[LPXO VHQVLELOLW LL VSHFWUDOH vQ GRPHQLXOLQIUDURúXúLSUH]LQWRLQHU LHPLF
Pentru domeniul vizibil, fotorezistoaUHOH SH ED] GH &G6 VXQW FHOH PDLXWLOL]DWH GDWRULW VHQVLELOLW LL LQWHJUDOH PDUL D FDUDFWHULVWLFLL 5φ H[SRQHQ LDOHOLQLDU OD VFDU ORJDULWPLF úL D FDUDFWHULVWLFLL VSHFWUDOH DVHPQWRDUH RFKLXOXLomenesc.
&DUDFWHULVWLFD VSHFWUDO D IRWRUH]LVWRDUHlor produse de EG&G Vactec esteSUH]HQWDW vQILJXUDLDUvQILJXUDHVWHSUH]HQWDWJUDILFXOUH]LVWHQ HL vQIXQF LHGHLOXPLQDUHSHQWUXDFHOHDúLFRPSRQHQWH
Cap.2 Rezistoare
4
Fig. 2.181&DUDFWHULVWLFDVSHFWUDOWLSLFDIRWRUH]LVWRDUHORUSHED]GH&G6>@
Fig. 2.182&DUDFWHULVWLFLOH5H]LVWHQ ,OXPLQDUHDOHIRWRUH]LVWRDUHORU(**9DFWHF>@
&k LYDGLQWUHSDUDPHWULLXQRUIRWRUH]LVWRDUHVXQWVLQWHWL]D LvQWDEHOXO 2.24.
Tabelul 2.243DUDPHWULLXQRUIRWRUH]LVWRDUHSHED]GH&G6
Parametru/ Tipfotorezistor
2322-600-93002Philips
2322-600-95001Philips
NSL19-M51RS Compo-
nents
NORP12RS Compo-
nents
VT43N2EG & GVactec
VT935GEG & GVactec
5H]LVWHQ D ODîntuneric RD
>1MΩ >10MΩ >20MΩ >1MΩ >300KΩ >1 MΩ
5H]LVWHQ D OD LOXminare 1000 lux
<110Ω 75-300Ω 5 kΩ(la 100 lux)
400Ω 8÷24 kΩ(la 10 lux)
10÷50 kΩ(la 10 lux)
3XWHUH QRPLQDO 340
(W)0,1 0,2 0.05 0,25 0,4 0,08
Domeniul temperatu-rilor de lucru
-30…+60°C -20÷60°C -25…75°C -60- -75°C -40- 75°C -40- 75°C
7LPSXO GH WUDQ]L LHFUHúWHUHFGHUH
10ms/200kΩ/s*
10ms/200kΩ/s*
45/55 ms 18/120 ms 90/18 ms 35/5 ms
* - parametru echivalent – rata de revenire
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
5
Din punct de vedere constructiv, fotorezistoarele sunt realizate prinGHSXQHUHD XQXL VWUDW VXE LUH IRWRFRQGXFWLY SH XQ PDWHULDO FHUDPLF &RQWDFWHOHPHWDOLFHVXQWGHSXVHSULQHYDSRUDUHvQYLGSHVXSUDID DPDWHULDOXOXLIRWRFRQGXFWRULDU WHUPLQDOHOHVXQWFRQHFWDWH ODDFHVWHVXSUDIH HPHWDOLFHFD vQ ILJXUD D0DWHULDOHOH IRWRFRQGXFWRDUH GHSXVH VXE IRUP GH VWUDWXUL VXE LUL DX R UH]LVWHQ VSHFLILF PDUH 3HQWUX DVLJXUDUHD XQHL UH]LVWHQ H UHGXVH OD QLYHOH GH LOXPLQDUHPRGHUDWH VSD LXO GLQWUH FRQWDFWH HVWH UHDOL]DW vQJXVW LDU HOHFWUR]LL DX IRUP
LQWHUGLJLWDO
(a) (b)Fig. 2.1836WUXFWXUDFRQVWUXFWLYDIRWRUH]LVWRDUHORUDGHWDOLXE>@
6H REVHUY GLQ ILJXUD2.183 E F UH]LVWHQ D IRWRUH]LVWRUXOXL OD QLYHOXO GH
iluminare L este l
dR SLL ρ= , cu ρSLUH]LVWHQ DVSHFLILFODLOXPLQDUHD/LDUGOHVWH
UDSRUWXOGHDVSHFW$úDFXPDIRVWSUH]HQWDWDQWHULRUDFHVWUDSRUWHVWHGHGRULWVILHFkWPDLPLF8]XDOVHSRWRE LQHSHQWUXGOYDORULvQWUHúL
([LVW úL YDULDQWHGH IRWRUH]LVWRDUHSHED] GH&G6 YH]L ILJXUD EUHDOL]DWH VXE IRUP GH GLVFXUL SULQ WHKQRORJLD FHUDPLF (OHFWUR]LL VH GHSXQ ODaceste variante de fotorezistoare tot prin evaporare în vid.
ÌQ ILJXUD VXQW SUH]HQWDWH GRX WLSXUL GH IRWRUH]LVWRDUH FX GHWDOLL GHrealizare a structurilor.
)D GHDOWHGLVSR]LWLYHRSWRHOHFWURQLFHVHPLFRQGXFWRDUHFXIXQF LLVLPLODUHcum ar fi fotodiodele sau fototranzistoarele, fotorezistoarele au câteva avantaje:• au cel mai redus cost;• DFRSHUXQGRPHQLXODUJDOLQWHQVLW LORUOXPLQRDVHSRUQLQGGHODQLYHOHIRDUWH
UHGXVH GH LOXPLQDUH OXPLQD OXQLL SkQ OD QLYHOH IRDUWH ULGLFDWH H[SXQHUHGLUHFWODVRDUH
Cap.2 Rezistoare
6
• DXRGLQDPLFGHYDULD LHGHFkWHYDRUGLQHGHPULPHvQWUHVWDUHDGHvQWXQHULFúLGHLOXPLQDUHH[LVWPXOWHYDORULGLVSRQLELOHDOHUH]LVWHQ HL
• SRWOXFUDúLvQFXUHQWDOWHUQDWLY• SRW IL XWLOL]DWH FX DSURDSH WRDWH VXUVHOH GH OXPLQ vQ GRPHQLXO YL]LELO úL
LQIUDURúX DSURSLDW /(' OPSL FX LQFDQGHVFHQ QHRQ úL IOXRUHVFHQWH ODVHUIODFUOXPLQVRODU
Fig. 2.184'RXYDULDQWHGHIRWRUH]LVWRDUH>@
$SOLFD LLOH IRWRUH]LVWRDUHORU VH vPSDUW vQ GRX FDWHJRULL ([LVW DSOLFD LLQXPLWH³GLJLWDOH´ODFDUHHVWHLPSRUWDQWQXPDLYDULD LDUH]LVWHQ HLvQWUHGRXVWULGHLOXPLQDUH$SOLFD LLOHGHWLS³DQDORJLF´XWLOL]HD]YDULD LDFRQWLQXDUH]LVWHQ HLcu iluminarea.
'LQ SULPD FDWHJRULH GH DSOLFD LL DPLQWLP FRQWUROXO LOXPLQDWXOXL QRFWXUQGHWHFWRDUHGHIXPFLWLWRDUHGHFDUWHOHVHQ]RULGHSUH]HQ úLGHSR]L LH LQVWDOD LLGHDODUPúLVHFXULWDWHHWF
ÌQ D GRXD FDWHJRULHGH DSOLFD LL vQWkOQLP FRQWUROXO H[SXQHULL OD FDPHUH GHILOPDUH úL YLGHR FLUFXLWH GH UHJODUH ³DXWRIRFXV´ FRQWUROXO LOXPLQULL FRQWUROXOWRQHUXOXLODPDúLQLGHIRWRFRSLDWFRQWUROXOVXUVHORUGHOXPLQPRGXODWHHWF
În figura 2.185 D HVWH SUH]HQWDW R DSOLFD LH WLSLF GH WLS ³GLJLWDO´ FXIRWRUH]LVWRUXO1253 úL DQXPHR FRPDQG RSWLF GH DF LRQDUH DXQXL UHOHX ODGHSúLUHDXQXLSUDJGHLOXPLQDUHSUHVWDELOLW3UDJXOGHFRPXWDUHVHSRDWHUHJODFXrezistorul semireglabil de 5kΩ.
ÌQ ILJXUD E HVWH SUH]HQWDW R DSOLFD LH GH WLS ³DQDORJLF´ XQH[SRQRPHWUX IRWRJUDILF )XQF LRQDUHD HVWH IRDUWH VLPSO FXUHQWXO SULQ FLUFXLWRIHULQG LQIRUPD LD GHVSUH VWDUHD GH LOXPLQDUH ([SRQRPHWUXO DUH GRX VFDOH GHsensibilitate comutabile, care se pot etalona din rezistoarele semireglabile R1úL52.
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
7
(a)
(b)
Fig. 2.185$SOLFD LLDOHIRWRUH]LVWRDUHORUDFRPDQGRSWLFEH[SRQRPHWUXIRWRJUDILF>@
2.2.4 Rezistoare dependente de câmpul magnetic - Magnetorezistoare
8QPDJQHWRUH]LVWRUHVWHXQUH]LVWRUDFUXLUH]LVWHQ VHPRGLILFvQSUH]HQ Dcâmpului magnetic.
Efectul magnetorezistiv FRQVW vQ PRGLILFDUHD UH]LVWHQ HL PDWHULDOXOXL vQSUH]HQ D FkPSXOXL PDJQHWLF GDWRULW FXUEULL WUDLHFWRULLORU HOHFWURQLORU GHFRQGXF LH
2EVHUYD LH Efectul magnetorezistiv este diferit de efectul Hall, efect produs tot înSUH]HQ DFkPSXOXLPDJQHWLF
0DJQHWRUH]LVWLYLWDWHD GHILQLW SULQ YDULD LD UHODWLY D UH]LVWLYLW LL( ) ( )
( )0
0
0 ρρρ
ρρ −=∆ H
HVWH vQ JHQHUDO SR]LWLY 9DULD LD FRQFUHW D UH]LVWLYLW LL
Cap.2 Rezistoare
8
depinde de material, de unghiul dintre câmpul magnetic aplicat H&
úL FkPSXOelectric E
&
.3HQWUX FkPSXULPDJQHWLFH VODEHPDJQHWRUH]LVWLYLWDWHD WUDQVYHUVDO ( )EH
&&
⊥
GHSLQGHSWUDWLFGH+ 2
0H≈
∆ρ
ρ
ÌQPDMRULWDWHDFD]XULORUH[LVWRYDORDUHGHVDWXUD LHDPDJQHWRUH]LVWLYLW LLE[LVW PDJQHWRUH]LVWRDUH UHDOL]DWH SH ED] GH PDWHULDOH VHPLFRQGXFWRDUH
(InSb), dar cel mai des sunt utilizate magnetorezisoarele bazate pe metaleferomagnetice anizotrope, componentele fiind cunoscute sub numele MR.
'HúLHIHFWXOPDJQHWRUH]LVWLYHVWHFXQRVFXWGHIRDUWHPXO LDQLDELDvQXOWLPLL DQL DX DSUXW DSOLFD LL SUDFWLFH SHUPLVH GH GH]YROWDUHD WHKQRORJLLORUPLFURHOHFWURQLFH&XWRDWHFHIHFWXOPDJQHWRUH]LVWLYHVWHSUH]HQWvQDSURDSHWRDWHPHWDOHOHDSOLFD LLDXJVLWVWUXFWXULOHED]DWHSHSHUPDOOR\DOLDM1L)HVDXSHDOWHPDWHULDOH IHURPDJQHWLFH /D DFHVWH PDWHULDOH H[LVW úL R SXWHUQLF DQL]RWURSLHVWUXFWXUDO FDUH LQIOXHQ HD] GHSHQGHQ D FRQFUHW D UH]LVWLYLW LL GH FkPSXOmagnetic.
ÌQXOWLPLLDQLDXDSUXWPDJQHWRUH]LVWRDUHED]DWHSHHIHFWXOPDJQHWRUH]LVWLYgigant (GMR) efect observat în structuri feromagnetice multistrat de tip special.(IHFWXO*05SRDWHSURYRFDRYDULD LHGHDUH]LVWHQ HLVXEDF LXQHDFkPSXOXLmagnetic.
5H]LVWHQ DPDJQHWRUH]LVWRDUHORUFODVLFHFkWúLDFHORU*05GHSLQGHSWUDWLFGHFkPSXODSOLFDWvQFRQVHFLQ QXSRWGHWHFWDSRODULWDWHDFkPSXOXLPDJQHWLF3HOkQJ GH]DYDQWDMXO QHOLQLDULW LL PDJQHWRUH]LVWRDUHOH DX XQ FRHILFLHQW GHWHPSHUDWXUDSUHFLDELO
'LQ DFHVW PRWLY PDJQHWRUH]LVWRDUHOH QX VH SURGXF VXE IRUP GHcomponente discrete comercializate individual ci sunt înglobate mai multeUH]LVWRDUHvQVWUXFWXULGHWLSVHQ]RU$VWIHOVHPLQLPL]HD]YDULD LDFXWHPSHUDWXUDDPULPLLGHLHúLUHúLVHvPEXQW HúWHOLQLDULWDWHDVHPQDOXOXL
2vPEXQW LUHDOLQLDULW LLVHDVLJXUúLSULQDSOLFDUHDXQXLFkPSPDJQHWLFde polarizare, câmp generat de obicei de un magnet permanent.
(IHFWXOPDJQHWRUH]LVWLYvQPHWDOHIHURPDJQHWLFHDIRVWREVHUYDWSULPDGDWGH:LOLDP7KRPVRQ/RUG.HOYLQvQDQXO$SOLFD LLOHDXDSUXWvQVDQLmai târziu atunci când tehnologiile microelectronice au permis utilizarea înSUDFWLFDVWUXFWXULORUPDJQHWRUH]LVWLYH
&RQVLGHUP XQ UH]LVWRU SHOLFXODU GLQ SHUPDOOR\ DOLDM 1L)H (IHFWXOPDJQHWRUH]LVWLYGHDQL]RWURSLH$05FRQVWvQH[LVWHQ DXQHLGLIHUHQ H∆Rmax întreYDORULOH UH]LVWHQ HL PVXUDWH SHQWUX R GLUHF LH D PDJQHWL]D LHL vQ VWUDW SDUDOHOUHVSHFWLYSHUSHQGLFXODUSHGLUHF LDGHFXUJHUHDFXUHQWXOXL ⊥−=∆ RRR ||max .
La aplicarea unui câmp magnetic extern H&
, în planul rezistorului vectorulPDJQHWL]D LH M
&
VHYDRULHQWDGXSGLUHF LDFkPSXOXLDSOLFDW IRUPkQGXQJKLXOθFXGLUHF LDGHFXUJHUHDFXUHQWXOXLJ
&
.
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
9
αM
J
H câmp aplicat
Fig. 2.186(IHFWXOPDJQHWRUH]LVWLYGHDQL]RWURSLH$05VWUXFWXUWLS05
6H SRDWH DUWD F UH]LVWHQ D PDJQHWRUH]LVWRUXOXL HVWH R IXQF LH GH FRV2θ,unghiul θ ILLQG GHSHQGHQW GH PULPHD FkPSXOXL DSOLFDW $VWIHO OD DFHVW WLS GHmagnetorezistor, cunoscut sub numele generic de MR, rotirea vectoruluiPDJQHWL]D LHVSUHYHFWRUXOGHQVLWDWHGHFXUHQWGXFHODFUHúWHUHDUH]LVWHQ HLURWLUHDvQ VHQV FRQWUDU GXFkQG OD VFGHUHD UH]LVWHQ HL 3H DFHDVW REVHUYD LH VH ED]HD]XWLOL]DUHDPDJQHWRUH]LVWRDUHORUODPVXUDUHDYDORULLFkPSXOXLPDJQHWLF'HRELFHLVHXWLOL]HD]XQDUDQMDPHQWVSD LDODOUH]LVWRDUHORUGHWLSSXQWHFDvQILJXUD2.187.
M
M
M
MJ
J
J
J
A
B D
C
HCâmpaplicat
+VA
R+∆R R-∆R
R-∆R R+∆R∆Vo=(∆R/R)*VA
∆Vo
A
B
C
D
Fig. 2.187$UDQMDUHDPDJQHWRUH]LVWRDUHORUvQVWUXFWXUWLSSXQWH
&HOH SDWUXPDJQHWRUH]LVWRDUH DX DFHHDúL UH]LVWHQ 5 GDU PDJQHWL]D LD ORUHVWH DOHDV DVWIHO vQFkW SHQWUX GRX UH]LVWRDUH DIODWH vQ EUD H RSXVH DOH SXQ LL VSURGXFPULUHDUHVSHFWLYPLFúRUDUHDUH]LVWHQ HL7HQVLXQHDGHLHúLUHDSXQ LLHVWHSURSRU LRQDOFXYDULD LDUHODWLYDUH]LVWHQ HL∆R/R, care în domeniul de liniaritateacceptat este ∆R/R=S⋅H, cu S sensibilitatea senzorului magnetorezistiv. Pentru
magnetorezistoarele firmei Honeywell, [40], S=3Oe
mV/V, iar domeniul de
liniaritate este de circa )/ 4/101(2Oe 3 mAOe π= .'DF FkPSXO PDJQHWLF DSOLFDW PDJQHWRUH]LVWRUXOXL GHS úHúWH YDORDUHD GH
VDWXUD LH DWXQFL YHFWRUXO M&
DUH SUDFWLF DFHHDúL GLUHF LH FX FkPSXO DSOLFDW H&
. În
Cap.2 Rezistoare
10
acest fel, θGHYLQHXQJKLXOGLQWUHGLUHF LDGHFXUJHUHDFXUHQWXOXLúLFkPSXODSOLFDW$VWIHOPDJQHWRUH]LVWRUXOSRDWH IL XWLOL]DW FD VHQ]RU DO GLUHF LHL FkPSXOXL DSOLFDWUH]LVWHQ D VD GHSLQ]kQG GH FRV2θ 'H RELFHL PDJQHWRUH]LVWRDUHOH FH OXFUHD] vQUHJLPGHVDWXUD LHVHXWLOL]HD]WRWvQFRQILJXUD LLWLSSXQWHFDvQILJXUD2.187.
Magnetorezistoarele bazate pe efectul GMR, pe scurt magnetorezistoare*05SHOkQJDYDQWDMXOXQHLYDULD LLPDLPDULDUH]LVWHQ HLFXFkPSXOPDJQHWLF(de 3-5 ori mai mare ca la MR), pot lucra la valori ale câmpului magnetice maiPDULGHFkWPDJQHWRUH]LVWRDUHOHFODVLFH050DJQHWRUH]LVWRDUHOH*05RSHUHD]GH UHJXO vQ UHJLXQHD GH VDWXUD LH úL VXQW XWLOL]DWH GHFL OD PVXUDUHD GLUHF LHLFkPSXOXLúLQXDLQWHQVLW LLVDOH9DULD LDUH]LVWHQ HLSRDWHILH[SULPDWSULQUHOD LD
( )θcos12 0
max
0−
∆=∆
R
R
R
R, cu Ro ± YDORDUHD PLQLP D UH]LVWHQ HL ∆Rmax valoarea
PD[LPDFUHúWHULLGHUH]LVWHQ ∆R=R-RoYDULD LD UH]LVWHQ HLθ- unghiuldintre câmpul aplicat H
&
úLPDJQHWL]D LDLQWHUQ oM&
.0RGXOGHYDULD LHDUH]LVWHQ HLSRDWHILXUPULWvQILJXUD
Fig. 2.1889DULD LDWLSLFDUH]LVWHQ HLODPDJQHWRUH]LVWRDUHWLS*05
$úD FXP VH REVHUY GLQ JUDILF PDJQHWRUH]LVWRDUHOH SUH]LQW XQ PLFhisterezis.
3DUDPHWULL PDJQHWRUH]LVWRDUHORU VXQW GH UHJXO H[SULPD L FD SDUDPHWULL DLstructurii complexe de senzor în care sunt înglobate.
Principalii parametrii ai unui magnetorezistor GMR de tip GMR S6 produsGH,QILQHRQ7HFKQRORJLHV6LHPHQVSRWILXUPUL LvQWDEHOXO
0DJQHWRUH]LVWRDUHOH 05 úL *05 VXQW UHDOL]DWH SULQ SURFHGHH FRPSOH[HVSHFLILFH WHKQRORJLHL VWUDWXULORU VXE LUL 6WUXFWXULOH FDUH SRW PHUJH GH ODPDJQHWRUH]LVWRDUHLQGLYLGXDOHODVWUXFWXULSXQWHFKLDUODGRXVDXWUHLFRQILJXUD LLSXQWH FRUHVSXQ]WRDUH FHORU WUHL D[H VXQW vQFDSVXODWH vQ FDSVXOH VSHFLILFH
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
11
circuitelor integrate SMD (SOIC, SOM) sau "through hole" (SIP, DIP). CapsulaSRDWHLQFOXGHúLDQXPLWHSU LDOHFLUFXLWXOXLHOHFWURQLFGHSUHOXFUDUHDVHPQDOXOXL
Tabelul 2.25 Parametrii magnetorezistoarelor GMR S6, [39].Parametru ValoareCurentul nominal de alimentare IN 4mA5H]LVWHQ DODθ=0, Ro >700ΩEfectul magnetorezistiv în gama H=5...15KA/m≅4%&RHILFLHQWXO GH WHPSHUDWXU DO UH]LVWHQ HL 5o
TCR0
+0.09...+0.12%/K
&RHILFLHQWXO GH WHPSHUDWXU DO HIHFWXOXLmagnetorezistiv TC∆R/R0
-0.27...-0.23%/K
Histerezis la H=10KA/m <2 gradeCâmp magnetic maxim 15KA/m7HPSHUDWXUDDPELDQWGHOXFUX7a -40...+150°C
În figura 2.189VXQWSUH]HQWDWHGRX WLSXULGHPDJQHWRUH]LVWRDUHDOH ILUPHLHoneywell.
Fig. 2.189 Capsule de magnetorezistoare MR ale firmei Honeywell, [40].
&LUFXLWXO+0&FRQ LQHRSXQWHGHPDJQHWRUH]LVWRDUH LDU+0&FRQ LQH GRX SXQ L GH PDJQHWRUH]LVWRDUH LGHQWLFH GDU FX GLUHF LLOH PDJQHWL]D LHLinterne rotite la 45°.
3ULQWUH DSOLFD LLOH FDUH XWLOL]HD] PDJQHWRUH]LVWRDUH DPLQWLP VHQ]RUL GHcurent, senzori de câmp magnetic, capete magnetice. Senzorii de câmp magneticSRWILXWLOL]D LúLFDGLVSR]LWLYHGHQDYLJD LHDYkQGRVHQVLELOLWDWHFDUHSRDWHGHWHFWDFkPSXOPDJQHWLF WHUHVWUX&DSHWHOHGHFLWLUHPDJQHWRUH]LVWLYHDXID GHFDSHWHOHGH FLWLUH FODVLFH LQGXFWLYH DYDQWDMXO F RIHU FD VHPQDO GH LHúLUH GLUHFW FkPSXOPDJQHWLF úL QX GHULYDWD VD $FHVW OXFUX SRDWH XúXUD FHULQ HOH SULYLQG DVLJXUDUHDXQHL DQXPLWH YLWH]H UHODWLYH FDS GH FLWLUH ± PHGLX PDJQHWLF 'HVLJXU H[LVWGH]DYDQWDMXOXWLOL]ULLFDSHWHORUPDJQHWRUH]LVWLYHQXPDL ODFLWLUHDLQIRUPD LHL$XIRVW UHDOL]DWH XQLW L GH GLVF ULJLGH KDUGGLVN FX FDSHWH FRPELQDWHmagnetorezistive - inductive.
În figura 2.190 D VH SUH]LQW XQ H[HPSOX GH XWLOL]DUH Dmagnetorezistoarelor la realizarea unui senzor de proximitate iar în figura 2.190EXQH[HPSOXGHXWLOL]DUHODUHDOL]DUHDXQXLVHQ]RUGHGHSODVDUHOLQLDU
Cap.2 Rezistoare
12
(a) (b)
Fig. 2.190 Utilizarea circuitelor cu magnetorezistoare în punte (a) senzor de proximitate, (b)VHQ]RUGHGHSODVDUHOLQLDU
În figura 2.191 este prezentat circuitul electronic complet al senzorului deSUR[LPLWDWHFLUFXLWFDUHFRPDQGDSULQGHUHDGLRGHLHPL WRDUHGHOXPLQ±/('
Fig. 2.191 Circuitul electronic al senzorului de proximitate realizat cu magnetorezistoare tip MR ale firmei Honeywell, [40].
2.2.5 Rezistoare dependente de tensiunile mecanice - Tensorezistoare
5H]LVWRDUHOHDFURUUH]LVWHQ GHSLQGHGHWHQVLXQLOHPHFDQLFHVXQWXWLOL]DWHvQJHQHUDOODPVXUDUHDUHVSHFWLYHORUWHQVLXQLHIRUWXULILLQGQXPLWHGXSIXQF LDSHFDUHRUHDOL]HD]WUDGXFWRDUHWHQVRPHWULFHUH]LVWLYHVDXSHVFXUWWHQVRPHWUH'HIDSW WHQVRPHWUHOH PVRDU GHIRUPD LLOH PHFDQLFH vQ JHQHUDO SURSRU LRQDOH FXeforturile mecanice.
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
13
&RQVLGHUP XQ UH]LVWRU GUHSWXQJKLXODU GH OXQJLPH O úL VHF LXQH $ FD vQfigura 2.192.
A
Efort longitudinal Nl
Fig. 2.1925H]LVWRUGUHSWXQJKLXODUVXSXVGHIRUPULORUORQJLWXGLQDOH
5H]LVWHQ DDFHVWXLUH]LVWRU5HVWH
A
lR ρ= (2.223)
3ULQGLIHUHQ LHUHDUHOD LHLDQWHULRDUHVHRE LQH
ρρρd
A
ldA
A
ldl
AdR +−=
2 (2.224)
sau ρρd
A
dA
l
dl
R
dR +−= (2.225)
3ULPLL GRL WHUPHQL GLQ H[SULP YDULD LD UH]LVWHQ HL GDWRULWPRGLILFULLGLPHQVLXQLORUIL]LFHILLQGGHFLXQHIHFWJHRPHWULFLDUFHOGHDO WUHLOHDWHUPHQ H[SULP PRGLILFDUHD UH]LVWLYLW LL PDWHULDOXOXL VXE HIHFWXO GHIRUPULLmecanice, efectul fiind cunoscut sub numele de efect piezorezistiv.
5HOD LDVHSXQHVXEIRUPDWUHFkQGODYDULD LLILQLWH
ρρνεε d
R
dR +−= 2 (2.226)
cu ε=∆OO DOXQJLUHD UHODWLY LDU ν FRHILFLHQWXO GH FRQWUDF LH WUDQVYHUVDO VDXcoeficientul lui Poisson, ν≅0,3 pentru materiale izotrope.
6HGHILQHúWHFRHILFLHQWXOSLH]RUH]LVWLYORQJLWXGLQDOπ1 ca:
ερρρ
ρ
πE
d
A
N
d
==1 (2.227)
cu NIRU DORQJLWXGLQDODSOLFDWUH]LVWRUXOXLE modulul lui Young.6HQVLELOLWDWHDWHQVRPHWUXOXL6GHGHILQHúWHFD
Cap.2 Rezistoare
14
( )( ) R
Rl/lR/R
Sε∆=
∆∆= (2.228)
8WLOL]kQGúLIDFWRUXO6GHYLQH
E21S 1 ⋅π+ν+= (2.229)
ÌQSUH]HQWVHXWLOL]HD]GRXWLSXULSULQFLSDOHGHWUDGXFWRDUHWHQVRPHWULFH• WUDGXFWRDUH PHWDOLFH UHDOL]DWH GLQ DOLDMH PHWDOLFH FX UH]LVWLYLWDWH PDUH úL
FRHILFLHQWGHWHPSHUDWXUUHGXVVXEIRUPGHILUHIROLLVDXVWUDWXULVXE LUL• WUDGXFWRDUH SH ED] GH PDWHULDOH VHPLFRQGXFWRDUH UHDOL]DWH GLQ
VHPLFRQGXFWRDUHPRQR VDX SROLFULVWDOLQH VXE IRUP GH ILODPHQWH FKLSXUL VDXVWUDWXULVXE LUL
În cazul traductoarelor rezistive metalice efectul piezorezistiv este foartemic π1≈úLSUHGRPLQHIHFWXOJHRPHWULF
S=1+2ν (2.230)&RQVLGHUP F ν 6 'H IDSW 6 LD YDORUL vQWUH úL IDSW
H[SOLFDELOSULQGLIHUHQ HOHvQYDORDUHDFRHILFLHQWXOXL3RLVVRQúLSULQIDSWXOFSRDWHVDSDUúLRXúRDUYDULD LHGHUH]LVWLYLWDWHGDWRUDWGHIRUPULORUπ1).
2ULFXP6!LDUXQFRHILFLHQW6!vQVHDPQRFUHúWHUHGHUH]LVWHQ vQFD]XODOXQJLULLúLRVFGHUHDUH]LVWHQ HLvQFD]XOFRPSULPULL
În cazul traductoarelor tensometrice realizate din materiale semiconductoareefectul piezorezistiv este predominant.
S≅ π1⋅E (2.231)
S= 30÷ SHQWUX WUDGXFWRDUH GLQ PDWHULDOH SROLFULVWDOLQH úL 6 ÷200 pentrumateriale monocristaline.
(VWHGHUHPDUFDWFVHQVLELOLWDWHD6GHIDSWπ1SRDWHDYHDúLYDORULQHJDWLYHvQIXQF LHGHWLSXOGRSULLúLGHRULHQWDUHDD[HORUFULVWDOLQH
Varianta de traductor tensometric rezistiv metalic care s-a impus este ceaUHDOL]DWGLQIROLLPHWDOLFHGHRELFHLGLQFRQVWDQWDQ
3HQWUX PULUHD VHQVLELOLW LL VH XWLOL]HD] R VWUXFWXU FX PHDQGUH )ROLDPHWDOLF GH ÷5µPRE LQXW SULQ ODPLQDUH HVWH IL[DW FXXQ DGH]LYSHXQ VXSRUWL]RODWRU SROLPHULF6WUXFWXUD WLSLF D DFHVWXL WUDGXFWRU SRDWH IL XUPULW vQ ILJXUD2.193.
&RPSRQHQWHúLFLUFXLWHSDVLYH Note de curs
15
Folieizolant
Foliemetalic( t t )
Terminale
Fig. 2.193 Structura traductorului tensometric rezistiv metalic.
$FHDVWFRQVWUXF LHFXQRVFXWVXEQXPHOHGHPDUFWHQVRPHWULFHVWHDSRLOLSLWDSOLFDWSHFRUSXODFUXLGHIRUPD LHVHGRUHúWHDILPVXUDW
$OWHYDULDQWHFRQVWUXFWLYHSRWILXUPULWHvQILJXUD
(a) (b) (c) (d)Fig. 2.1940UFLWHQVRPHWULFHDSHQWUXGLUHF LLOH°ESHQWUXGLUHF LLOH°,
FSHQWUXGLUHF LLOH°WLSUR]HWGSHQWUXPVXUDUHDSUHVLXQLL
7UDGXFWRDUHOHUH]LVWLYHWHQVRPHWULFHVHPLFRQGXFWRDUHVHUHDOL]HD]GHRELFHLGLQJHUPDQLXVDXVLOLFLX(OHSUH]LQWRVHQVLELOLWDWHVXSHULRDUFHORUPHWDOLFHGDUDX FRHILFLHQ L GH YDULD LH FX WHPSHUDWXUD PDL PDUL úL XQ GRPHQLX GH PVXU DOGHIRUPD LLORUFHYDPDLPLF
Fig. 2.195 Structura traductorului tensometric rezistiv semiconductor.
Cap.2 Rezistoare
16
De obicei traductoaUHOH WHQVRPHWULFH VH FRQHFWHD] vQ PRQWDMH WLS SXQWHSHQWUXPULUHDVHQVLELOLW LLúLFRPSHQVDUHDYDULD LLORUFXWHPSHUDWXUDÌQIXQF LHGHSUHFL]LDGRULWVHXWLOL]HD]SXQ LFXXQXOGRXVDXSDWUXWUDGXFWRDUH&RQHFWDUHDHOHFWULFDWHQVRUH]LVWRDUHORUODSXQWHDFXSDWUXWUDGXFWRDUHHVWHLGHQWLFFXFHDGLQILJXUDSUH]HQWDWODFDSLWROXO0DJQHWRUH]LVWRDUH
ÌQWDEHOXOVXQWSUH]HQWD LSULQFLSDOLLSDUDPHWULLDLXQRUWHQVRUH]LVWRDUHSURGXVHGH%/+(OHFWURQLFV,QFúL+RWWLQJHU%DOGZLQ0HDVXUHPHQWV,QF
Tabelul 2.26 Parametrii unor tensorezistoareSeria X
3URGXFWRUHBM
Seria Y3URGXFWRU
HBM
Seria traductoaremetalice
3URGXFWRU%/+
Seria traductoaresemiconductoare3URGXFWRU%/+
Tip tensorezistor metalic / folieconstantan
metalic/ folieconstantan
metalic/ folieconstantan
filamentsemiconductor
5H]LVWHQ DQRPLQDO5N (Ω)
120, 350, 700,1000
350 350-5000 120, 350, 1000,2000, 3000
7ROHUDQ D5N
(%)±0,3 ±0,3 ± (0,2 - 0,6) ±1, ±2
Sensibilitate S 2 2 2,05- 2,1 −110 ÷ +1507ROHUDQ 6
(%)±0,7 ±1,5 ±0,5 ±2
(ORQJD LDPD[LPµm/m)
50000 20000 >2250 5000
Domeniultemperaturilor de
utilizare
−70 ÷ +200°C −70 ÷ +200°C −75 ÷ +200°C −269 ÷ +372°C
3HQWUX UHDOL]DUHD FRPSHQVULL FX WHPSHUDWXUD SURGXFWRULL UHDOL]HD] FXDFHOHDúLPDWHULDOHúLFXVWUXFWXULVLPLODUHUH]LVWRDUHOLQLDUHIL[HFDUHQXVXQWVXSXVHGHIRUPD LLORUGDUSUH]LQWRYDULD LHFX WHPSHUDWXUDVLPLODU FX WHQVRUH]LVWRDUHOH3ULQWURJUXSDUHDGHFYDWvQVWUXFWXULGHWLSSXQWHHVWHSRVLELODVWIHOFRPSHQVDUHDYDULD LLORUUH]LVWHQ HLFXWHPSHUDWXUD