Giao Trinh Cam Bien Moi

8/12/2019 Giao Trinh Cam Bien Moi

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K thut cm bin Khoa C kh - ng lc Trng Cao ng Ngh Cng Ngh v Nng Lm ng Bc

http://www.ebook.edu.vn 1

BNNG NGHIP V PHT TRIN NNG THN

TRNG CAO NG NGHCNG NGHV NNG LM NG BC

GIO TRNH

KTHUT CM BIN

NGH: IN CNG NGHIPTRNH : CAO NG NGH

Lng Sn thng 04 nm 2010


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LI NI U

Trn cschng trnh khung o to ca BLTB & XH ban hnh,Trng Cao ng NghCng Nghv Nng Lm ng Bc tchc binson cc ti liu hng dn gio vin v hc tp, thc tp ca hc sinh, sinh vin

ngh lp t, sa cha thit bin cng nghip trong thi khin i ho cng nghip ho t nc. Trong ti liu K thut cm bin ng vai trquan trng trong vic o to cc k thut vin, cc nhn vin lnh nghangtheo hc v hnh nghin cng nghip.

Ti liu c thit k theo tng bi trong h thng mun ca chngtrnh, c mc tiu hc tp, thc tp cho mun, phn l thuyt cbn hc vincn phi nm vng thc hnh thc tp. Cui mi bi sau phn l thuyt c

bn u c cc bi tp ng dng gio vin v hc sinh thc hnh thc tp.y l ti liu do cc c gio, thy gio trong t bmn in ca nh

trng cht lc trong cc qu trnh ging dy, tham kho cc ti liu, gio trnhca cc Trng i hc nhi hc Bch Khoa H Ni, Bch Khoa ThnhphHCh Minh, i hc sphm k thut Hng Yn, i hc Cn Thbin son, ti liu ny ch lm ti liu ging dy v tham kho ni bcho ccgio vin v hc sinh ca Trng, khng pht hnh lu thng ra bn ngoi./.


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GII THIU VMUN

Vtr, ngha v vai tr ca mun:Trong nn cng nghip sn xut hin i ngy nay, rt nhiu nh my x

nghip ang trang b cho mnh nhng dy chuyn sn xut hon ton tng

hoc bn tng. Cc loi cm bin c mt trong hu ht cc lnh vc iukhin tng, n ng mt vai tr rt quan trng, khng mt thit bno c ththay thc. Vic trang bcho mnh mt kin thc vcc loi cm bin l nhucu bc xc ca cc k thut vin, k s ca ngnh in cng nhcc ngnhkhc.Mun k thut cm bin l mt mun chuyn mn ca hc vin ngnh sacha thit b in cng nghip. Mun ny nhm trang b cho hc vin cctrng cao ng ngh, trung cp ngh v cc trung tm dy nghnhng kinthc v nguyn l, cu to, cc mch ng dng trong thc t ca mt s loi

cm bin...vi cc kin thc ny hc vin c thp dng trc tip vo lnh vcsn xut cng nhi sng. Ngoi ra cc kin thc ny dng lm phng tinhc tip cc mn chuyn mn ca ngnh in nhtrang bin, PLC...

Mc tiu munSau khi hc xong mun ny, hc vin c nng lc:

- C kin thc phn bit c cc loi cm bin, phm vi dng ca chng.- Lp t c mt smch iu khin dng cm bin- Kim tra c cc mch in lp t cm bin, pht hin scv c bin phpkhc phc

Ni dung chnh ca mn hc/munMn hc/mun gm 05 bi:

Bi mu: Khi nim c bn v cc b cm bin.Bi 1: Cm bin nhit .Bi 2: Cm bin tim cn v cc loi cm bin xc nh v tr, khong cch.Bi 3: Cm bin o lu lng.Bi 4: Cm bin o vn tc vng quay v gc quay.


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CC HOT NG CHNH CA MUN/MN HC

* Hot ng trn lp:Hc vin c gio vin ging dy hng dn cch nhn bit, cch phn

bit vhnh dng kch thc cc loi cm bin, c nghe gio vin ging gii,

phn tch v gii thch vcu to, nguyn l lm vic v ng dng ca cc loicm bin. Hc vin c gio vin ging dy hng dn hc sinh tho lun tmhiu vcc loi cm bin v ng dng ca n ngay trn lp hc.

* Hot ng ti xng thc hnh:

Hc vin c gio vin hng dn thc hnh hng dn vcch lp tcc loi cm bin, cch o kim tra cc tnh, cht lng cc cm bin, lp t v

pht hin cc sai hng ca cc mch cm bin.* Hot ng thc:

Hc vin tsu tm cc ti liu lin quan n lnh vc cm bin, lm ccbi tp do gio vin hng dn giao cho.


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BI MUKHI NIM CBN VCC BCM BIN

GII THIU

Cc bcm bin c sdng nhiu trong cc lnh vc kinh tv k

thut, cc bcm bin c bit rt nhy cm c sdng trong cc thnghim, cc lnh vc nghin cu khoa Trong lnh vc tng ho ngi ta sdng cc sensor bnh thng cng nhc bit. Cm bin c rt nhiu loi, rta dng v phong ph, do nhiu hng sn xut, gip con ngi nhn bit ccqu trnh lm vic tng ca my mc, trong tng ho cng nghip dngrt nhiu cm bin.

MC TIU BI HC

Sau khi hc xong bi ny hc vin c khnng:

- nh gi/xc nh c v tr, nhim v v ng dng ca cc b cm bintrong cuc sng sinh hot cng nhsn xut trong cc ngnh kinh tcn c tng ho cao..- M tc chc nng, nhim vv cc iu kin lm vic ca cc bcm

bin, cc tnh cht ng cc bcm bin.- Bit c phm vi ng dng ca cc bcm bin.

NI DUNG

* Khi nim cbn vcc bcm bin.*Phm vi ng dng.* Phn loi cc bcm bin.

HOT NG I : HC L THUYT TRN LP

1. Khi nim cbn vcc bcm bin.Cm bin l mt thit bchu tc ng ca cc i lng cn kim tra m

khng c tnh cht in v cho ta mt c trng mang mt bn cht in (nhin tch, in p, dng in hoc trkhng), k hiu l s. c trng in s lhm ca i lng cn o m. ( )mfs= Trong s l i lng u ra hoc phn ng ca cm bin v m l i lngu vo hay kch thch (c ngun gc l i lng cn o. Vic o c s cho

php nhn bit gi trm.i vi mi cm bin, c thkhai thc biu thc trn cn phi chun

cm bin, vi mt lot gi tr bit chnh xc ca m, o gi trtng ng ca sv dng ng cong chun, ng cong chun ny cho php xc nh mi gitrca m1ts1dsdng, thng thng ngi ta ch to cm bin sao cho c s lin htuyn tnh gia bin thin u ra s v bin thin u vo m.

s = S. m


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trong S l nhy ca cm binVn quan trng y l khi thit k, chto v sdng cm bin lm

sao cho nhy S ca chng khng i, ngha l S t phthuc vo cc yu tsau:

- Gi trca i lng cn o m (tuyn tnh) v tn sthay i ca n(di thng)

- Thi gian sdng (gi ho)- nh hng ca cc i lng vt l khc (khng phi i lng cn o)

ca mi trng xung quanh

2. Phm vi ng dng.Cc b cm bin c s dng nhiu trong cc lnh vc kinh t v kthut, cc bcm bin c bit rt nhy cm c sdng trong cc th nghim,

i lng cn o (m)

i lng in (s)

Cm bin

m

st

t

t1 t2 tn

t1 t2 tn

Hnh 1.1:S bin i ca i lng cn kim tra m v phn ng s theo thi gian

m1 m1m2

s1

s2

s1

s s

t t

Hnh 1.2:Dng ng cong t cc gi tr bit ca m, xc nh m1t gi tr s1


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cc lnh vc nghin cu khoa Trong lnh vc tng ho ngita sdng ccsensor bnh thng cng nhc bit.```````````````````3. Phn loi cc bcm bin.

-Theo nguyn l chuyn i gia kch thch v p ng.Hin tng chuyn i gia kch thch v p ng.

V t l

Nhit in.Quang inQuang tin tTin

Ho hcBin i ho hcBin i in hoPhn tch ph

Sinh hc

Bin i sinh ho

Bin i vt lHiu ng trn cthsng

-Theo dng kch thch.Kch thch Cc c tnh ca kch thch.

m thanhBin pha, phn ccPhTc truyn sng

in

in tch, dng in

in th, in pin trngin dn, hng sin mi

TTtrngTthng, cng ttrngtthm

C

VtrLc, p sutGia tc, vn tc, ng sut, cngMmenKhi lng, ttrngnht

QuangPhTc truynHspht x, khc x

NhitNhit Thng lngTnhit

Bc xKiu

Nng lngCng


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Theo tnh nng.

+ nhy+ chnh xc+ phn gii

+ tuyn tnh+ Cng sut tiu thTheo phm vi sdng.

+ Cng nghip+ Nghin cu khoa hc+ Mi trng, kh tng+ Thng tin, vin thng+ Nng nghip+ Dn dng

+ Giao thng vn ti...Theo thng sca m hnh mch in thay th.+ Cm bin tch cc (c ngun) : u ra l ngun p hoc ngun dng+ Cm bin th ng (khng c ngun): Cm bin gi l th ng khi

chng cn c thm ngun nng lng phhon tt nhim vo kim, cnloi cc tnh th khng cn. c c trng bng cc thng s: R, L, C...tuyntnh hoc phi tuyn.

HOT NG II: HC VIN TNGHIN CU TI LIUHc vin tham kho cc ti liu di y:

in tcng sut - Nguyn Bnh Nh xut bn KHKTin tcng sut v iu khin ng cin - Dch tting Anh

HOT NG III: HC TP, THC TP TI XNG TRNG

* Ni dung:- Nghin cu ng dng ca tng loi cm bin.- Tm hiu cch phn loi cm bin.

1/ Hnh thc tchc:Chia thnh cc nhm nht2 n 3 hc sinh di shng dn ca gio vin.2/ Dng c: Giy A0, bt d,3/ Quy trnh thc hin:- Gio vin tp trung clp hc vin, slc vcch nhn bit, ng dng cacc bcm bin.


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BI 1: CM BIN NHIT

GII THIU

Cm bin nhit c sdng nhiu trong cc lnh vc kinh tv kthut, v cm bin nhit ng vai tr quyt nh n tnh cht ca vt

cht. nhit c thlm nh hng n cc i lng chu tc dng ca n, vdnhp sut, thtch cht kh ... vv.cm bin nhit rt nhy cm c sdng trong cc th nghim, cc lnh

vc nghin cu khoa Trong lnh vc tng ho ngi ta sdng cc sensorbnh thng cng nhc bit.

MC TIU BI HC

Sau khi hc xong bi ny hc vin c khnng:- nh gi/xc nh c v tr, nhim v v ng dng ca cc b cm binnhit .

- M tc chc nng, nhim vv cc iu kin lm vic ca cc bcmbin nhit .- Bit c phm vi ng dng ca cc bcm bin nhit .

NI DUNG

* i cng.*Nhit in trvi Platin v Nickel.* Cm bin nhit vi vt liu silic.* IC cm bin nhit .

* Nhit in trNTC.* Nhit in trPTC.* Cc bi thc hnh ng dng cc loi cm bin nhit .


1. i cngTrong tt ccc i lng vt l, nhit l mt trong cc i lng c

quan tm nhiu nht v nhit ng vai tr quyt nh n nhiu tnh cht cavt cht, nhit c thlm nh hng n cc i lng chu tc dng ca n,v dnhp sut, thtch cht kh ... vv.

o c trschnh xcca nhit l mt vn khng n gin,nhit l i lng chc tho gin tip trn cstnh cht ca vt phthuc vo nhit . Trc khi o nhit ta cn cp n thang o nhit .1.1 Thang o nhit Vic xc nh thang o nhit xut pht tcc nh lut nhit ng hc

- Thang o nhit tuyt i c xc nh da trn tnh cht ca kh ltng. nh lut Camot nu r: Hiu sut ( ca mt ng cnhit thun nghchhot ng gia 2 ngun c nhit l 1 v 2 trong mt thang o bt kch

phthuc vo 1 v 2:


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Dng ca hm F chphthuc vo thang o nhit , ngc li, vic la chnhm F squyt nh thang o nhit . t F()= T chng ta sxc nh T nhl nhit nhit ng hc tuyt i v hiu sut ca ng cnhit thun nghchsc vit nhsau:

2

11T

T=

Trong T1v T2l nhit nhit ng hc tuyt i ca 2 ngun.a/ Thang nhit ng hc tuyt i: Kelvil, n vo l K. thang ny

ngi ta gn cho nhit ca im c 3 trng thi l nc , nc v hi,mt gi trbng 273,150k. Tthang ny cn xc nh theo mt sthang khc.

b/ Thang nhit celsius: o bng 0c, 10c = 1 kelvilhay ( ) ( ) 000 15,273= KTCT

c/ Thang nhit Fahrenheit: (0F)

( ) ( ){ }9

5.3200 = FTCT

( ) ( ) 325

9 00 += CTFT

Bng 1-1: Thng sc trng ca mt sthang o nhit khc nhauNhit Kelvin (0K) Celsius (0C) Fahrenheit

(0F)

im 0 tuyt i 0 - 273,15 - 459,67Hn hp nc nc 273,15 0 32Cn bng nc nc - hi

nc

273,16 0,01 32,018

Nc si 373,15 100 212

1.2. Nhit c o v nhit cn o.Trong tt ccc i lng vt l th nhit (t0) c quan tm nhiu nht v nng vai tr quan trng nh hng rt nhiu n cc tnh cht vt cht nht vthn trong cng nghip v i sng th vic o nhit l rt cn thit. oc trschnh xc ca nhit l cng vic rt kh khn v phc tp, phnln cc i lng vt l so snh vi gi trmu cn nhit th khng v n li lng gia tng. thit lp thang o nhit v o nhit c mt s

phng php sau:- Phng php quang da vo sp

hn bphbc xdo dao ng nhit (hiu ng Doppler)- Da vo sgin nca vt rn, cht lng, cht kh hoc da trn tc

ca m- Da vo sphthuc ca in trvo nhit (hiu ng seebeek)- Da trn spht trin ca tn sdao ng ca thch anh

2. Nhit in trvi Platin v Nickel2.1.in trkim loi thay i theo nhit .

c sdng cc kim loi nguyn cht (Pt; Cu; Ni) vi hsnhit intrcng ln cng tt


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Pt lm vic nhit 1900C n 6500CCu lm vic nhit 500C n 1500C

Ngi ta ko chng thnh si mnh qun trn khung chu nhit ri t vo hpvc bit v a ra 2 u ly tn hiu vi in tr (R) ch to khong t10()n 100()

Trong R0l in trti thi im ban u

..

1

en=

Trong : n l sin ttdo trong mt n vdin tche l in tch ca in ttdol tnh linh hot ca in t, c c trng bi tc ca in t

trong ttrng).

- nhy ca in trkim loi thay i theo nhit S cng cao cng tt, (S l khi nim cm nhn spht trin ca nhit )Phng trnh m tkhu nhit l phng trnh vi phn bc nht

( ) ( ) ( )tKtRST ..1. =+ in trkim loi thay i theo nhit c u im c sdng rt rng di vc sdng nhiuXong nhc im ca in trkim loi thay i theo nhit l kch thc ln,cng knh, c qun tnh ln2.2. Nhit in trPlatin.

Platin l vt liu cho nhit in tr c dng rng di trong cngnghip. C 2tiu chun i vi nhit in trplatin, sklhc nhau gia chngnm mc tinh khit ca vt liu. Hu ht cc quc gia sdng tiu chunquc tDIN IEC 751 1983 (c sa i ln thnht vo nm 1986, ln th2vo nm 1995). USA vn tip tc sdng tiu chun ring.

c2 tiu chun u sdng phng trnh Callendar VanDusen:R(t) = R0(1 + A.t + B.t

2+ C [t 1000C].t3)R0 l trsin trnh mc 00C

StandardAlpha

ohms/ohm/0C

R0

ohmsHs t nc

IEC 751(Pt100)

0,003855055 100 2000C


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B = - 5,77500 x 10-7C = -4,18301 x 10-1200C


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a = alpha = 0,00672 0CT ddng chuyn i thnh gi trnhit :

T = (Rt/R0 1) / a = (Rt/R0 1)/0,00672

Cm bin nhit ZNI 1.000 do hng ZETEX Semiconductors sn xut sdngnhit in trNi, c thit kc gi tr1.000( ti 00C).2.4. Cch ni dy o.

Nhit in tr thay i in tr theo nhit , vi mt dng in khngi qua nhit in tr, ta c tho c U = R.I, cm bin khng bnng lnqua php o, dng in cn phi nht khong 1 mA. Vi Pt 100 0C ta c inthkhong 0,1 vn, in thny cn c a n my o qua dy o. Ta c 4kthut ni dy o:

Tiu chun IEC 751 yu cu dy ni n cng u nhit in trphi c mu

ging nhau (hoc trng) v dy ni n 2 u phi khc mu.* Kthut hai dy:

2.200

2.000

1.800

1.600

1.400

1.200

1.000

800

600

- 60 - 40 - 40 0 20 40 60 80 100 120 140

Resistance(Ohms

Temperature (0C)

Hnh 1.2: ng c tnh cm bin nhit ZNI 1.000

Trng

Trng

Trng

Trng

2 dy 3 dy 4 dy

Hnh 1.3: Cch ni dy nhit in tr


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Gia nhit in trv mch in tc ni bi 2 dy, bt cdy dnin no u c in tr, in tr ny ni ni tip vi in trca 2 dy o,

mch in trsnhn c mt in thcao hn in thcn o, kt quta cchthnhit kcao hn nhit cn o, nu khong cch qu xa, in trdyo c thln n vi m.

V dvi dy ng: Din tch mt ct dy o = 0,5 mm2. in trsut =0,0017 (/mm2m-1). Chiu di = 100m.

R = 6,8, vi 6,8 tng ng cho nhit in tr Pt 100 mt thay inhit l 170C. m trnh sai sca php o do in trca dy o gy ra,ngi ta b trin trca dy o bng mt mch in nhsau: Mt bin tr

b trc ni vo mt trong hai dy o v nhit in rc thay thbng

mt in tr100. Mch in tc thit kvi in trdphng ca dy ol 10. Ta chnh bin trsao c chth00C: Bin trv in trca dy o l10.

* Kthut 3 dy:

Tnhit in trca dy o c ni thm mt in tr(hnh 1.5). Vi

cch ni dy ny ta c 2 mch o c hnh thnh, mt trong hai mch cdng lm mch chun, vi kthut 3 dy, sai sca php o do in trdy o

ResistanceElement

Bridge Ouiput

Power Supply

R1 R2

R3

vb S

Hnh 1.4: K thut ni 2 dy

ResistanceElement

Bridge Ouiput

Power Supply

R1 R2

R3

vb S


Lead Resistance


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v s thay i ca n do nhit khng cn na. Tuy nhin 3 dy o cn ccng trskthut v c cng mt nhit . Kthut 3 dy rt phbin.

* Kthut 4 dy

Vi k thut 4 dy ngi ta t kt quo tt nht, hai dy c dngcho mt dng in khng i qua nhit in tr. Hai dy khc c dng lmdy o in thtrn nhit in tr, trng hp tng trng vo ca mch o rtln so vi in trdy o, in trdy o coi nhkhng ng k, in thoc khng bnh hng bi in trdy o v sthay i ca n do nhit.2.5. Cc cu trc ca cm bin nhit platin v nickel.

* Nhit in trvi kthut qun dy.- Nhit in trvi vgm: Si Platin c gicht trong ng gm s

vi bt it nhm, di o t 2000C n 8000C.- Nhit in trvi vthu tinh: Loi ny c bn chc v nhy

cao, di o t 2000C n 4000C, c dng trong mi trng ho cht c n mn ho hc cao.

- Nhit in tr vi v nha: Gia 2 lp nha polyamid dy platin cng knh khong 30 mm c dn kn. Vi cu trc mng, cm bin ny cdng o nhit bmt cc ng hay cun dy bin th. Di o t 800C n2300C.

- Nhit in trvi kthut mng mng: Loi ny c cu trc cm bingm mt lp mng mng (platin) t trn nn ceramic hoc thutinh. Tia lazerc sdng chun ho gi trin trca nhit in tr.2.6. Mch ng dng vi nhit in trplatin.

ADT70 l IC do hng Analog Devices sn xut, cung cp skt hp ltng vi Pt1.000, ta s c di o nhit rng, n cng c th s dng viPt100. Trong trng hp c scch bit, vi nhit in trPlatin kthut mngmng, ADT70 c tho t 500C n 5000C, cn vi nhit in trPlatin tt, ctho n 1.0000C. chnh xc ca h thng gm ADT70 v nhit in trPlatin thang o -2000C n 1.0000C phthuc nhiu vo phm cht ca nhitin trPlatin.

* Cc thng sthit bADT70:

- Sai s: 10

C- in p hot ng: 5 vn hoc 5 vn

Resistance

Element

Bridge Ouiput

Power Supply

R1 R2

R3

vb S


Lead Resistance


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- Nhit hot ng: T 400C n 1250C (dng 20 lead DIP, SOpackages)

- ng dng: Thit bdi ng, biu khin nhit .

ADT70 c 2 thnh phn chnh: Ngun dng c thiu chnh v bphnkhuych i, ngun dng c thiu chnh bphn khuych i. Ngun dngc sdng cung cp cho nhit in trv in trtham chiu. Bphnkhuych i so snh in p trn nhit in trv in p trn in trthamchiu, sau a tn hiu in p tng ng vi nhit . (ADT70 cn c 1opamp, 1 ngun p 2,5 vn).

Di o ca ADT70 phthuc vo c tnh ca nhit in tr, v vy iuquan trng l phi chn la nhit in trthch hp vi ng dng thc t.2.7. Mch ng dng vi nhit din trNi

Zni 1.000 vi ZMR500 c dng vi DVM nhl nhit k3. Cm bin nhit vi vt liu silic

Cm bin nhit vi vt liu silic ang ngy ng vai tr quan trngtrong cc hthng in t, vi cm bin silic, bn cnh cc c im tuyn tnh,schnh xc, ph tn thp, cn c th tch hp trong mt IC cng vi bphn

khuych i v cc yu cu sl tn hiu khc, hthng trln nhgn, mcphc tp cao hn v chy nhanh hn. K thut cm bin truyn thng nhcp nhit, nhit in trc c tuyn khng tuyn tnh v yu cu siu chnhc thchuyn i chnh xc tgi trnhit xang i lng in (dng hocp), ang c hay thdn bi cc cm bin silicvi li im l snhgn camch in tch hp v dsdng.3.1. Nguyn tc

Hnh v1.8 thhin cu trc cbn ca mt cm bin, kch thc camt cm bin l 500 x 500 x 200(mt trn ca cm bin l mt lp SiO2c mt

vng hnh trn c mkim loi c ng knh khong 20m, ton bmt yc mkim loi

SHUTDOWN

+INO

RGA RGB RGCSENSE

OUTSA AGND -Vs DGND

-1NiA

-1NiA

IOTB

IOTA

NULLA NULLB BIAS 25V REFOUT

1NSTAMP

2,5VREP

MATCHEOCURRENTSOURCES

SHUTDOWN

-INOA

OUTOA

+VS

Hnh 1.7: S khi ADT70


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Hnh v1.9 biu dinmch in tng ng tngtrng thay thcho cm bin

silic (sn xut theo nguyn tcin trphn ri). Ssp xpny dn n sphn bdngqua tinh thc dng hnh nn,y l ngun gc c tn giin trphn ri.

in trcm bin nhit R c xc nh nhsau:R =/d

Trong R l in trcm bin nhit; l in trsut ca vt liu silic(lthuc vo nhit ); d l ng knh ca hnh trn vng mkim loi mttrn.3.2. c trng k thut c bn ca dng cm bin KTY (hng Philips sn

xut).Vi schnh xc v n nh lu di ca cm bin vi vt liu silic KYT

sdng cng nghin trphn ri l mt, sdng thay th tt cho cc loicm bin nhit truyn thng.* u im chnh:- Sn nh: Githit cm bin lm vic nhit c gi trbng mt na gitr nhit hot ng cc i, sau thi gian lm vic t nht l 45.000 gi(khong 51 nm) hoc sau 1.000 gi (1,14 nm), hot ng lin tc vi dngnh mc ti gi trnhit hot ng cc i cm bin silic scho kt quovi sai snhbng di y (bng 1 3)

Bng 1 3: Sai sca cm bin silic (do thi gian sdng)TYPE Sai stiu biu (K) Sai sln nht (K)

KTY 81 1KTY 82 - 1

0,20 0,50

KTY 81 2

KTY 82 2 0,20 0,80KTY 83 0,15 0,40

n-si

n+dopingd

Sio2

metallwion

ne of force

Equipotental plane

n+dopingmetalization

Hnh 1.8:

Hnh 1.9


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- Sdng cng nghsilic: Do cm bin c sn xut da trn nn tng cngnghsilic nn gin tip chng ta c hng li ch tnhng tin btrong lnhvc cng nghny ng thi iu ny cng gin tip mang li nhng nh hngtch cc cho cng nghng gi, ni m lun c xu hng thu nh.- Stuyn tnh: Cm bin vi vt liu silic c hsgn nhl hng strn ton

bthang o, c tnh ny l mt iu l tng khai thc sdng (c trngkthut ca KYT 81).Nhit hot ng ca cc cm bin silic thng thng b gii hn

1500C. KYT 84 vi vbc SOD68 v cng nghni c bit gia dy dn vchip c thhot ng n nhit 3000C.

* c im sn phm:Tn snphm

R25 () R Thang o(0C)

Dng IC

KYT 81 1 1.000 ( 1% ti ( 5% - 55 ti 150 SOD 70KYT 81 - 2 2.000 ( 1% ti ( 5% - 55 ti 150 SOD 70

KYT 82 1 1.000 ( 1% ti ( 5% - 55 ti 150 SOT 23KYT 82 2 2.000 ( 1% ti ( 5% - 55 ti 150 SOT 23KYT 83 1 1.000 ( 1% ti ( 5% - 55 ti 175 SOD 68 (DO

34)KYT 84 - 1 1.000

(R100)( 1% ti ( 5% - 40 ti 300 SOD 68 (DO

34)

i vi loi KYT 83, ta c phng trnh ton hc biu din mi quan hgia in trv nhit nhsau:

( ) ( )21 refrefrefT TTBTTARR ++=

-100 -50 0 50 100 150 200

0,8

1,6

2,4

R (k)

Hnh 1.10: c trng k thut ca KYT 81


19/77



RT l in tr nhit ; Rref l in tr ti Tref (1000C vi loi KYT 84 v250C vi cc cm bin cn li); A,B l cc hs.

i vi KYT 81/82/84:( ) ( ) ( )DrefrefrefT TTCTTBTTARR 1

21 ++=

T1 l nhit m dc ca ng cong bt u gim. Nu T(T1 th hsC =

0; C v D l cc hs.Loi cm bin A (K 1) B (K 2) C(1)(K D) D T1(

0C)

KYT 81 1 7,874 x 10-3 1,874 x 10-5 3,42 x 10-8 3,7 100KYT 81 - 2 7,874 x 10-3 1,874 x 10-5 1,096 x 10-6 3,0 100KYT 82 1 7,874 x 10-3 1,874 x 10-5 3,42 x 10-8 3,7 100KYT 82 2 7,874 x 10-3 1,874 x 10-5 1,096 x 10-6 3,0 100

KYT 83 7,635 x 10-3 1,731 x 10-5 - - -KYT 84 6,12 x 10-3 1,1 x 10-5 3,14 x 10-8 3,6 250

* Ch : Vi loi cm bin KYT 83/84 khi lp t cn ch n cc tnh,

u c vch mu cn ni vo cc m, cn KYT 81/82 khi lp t ta khng cnquan tm n cc tnh.3.3. Mch in tiu biu vi KTY81 hoc KTY82

Hnh v1.11 cho ta mt mch in in hnh c thit kcho cm binKYT 81 110 hoc KYT 82 110 (nhit t00C n 1000C). in trR1vR2, cm bin v cc nhnh in trR3, bin trP1v R4 to thnh mt mchcu.Gi trR1v R2c chn sao cho gi trdng in qua cm bin gn bng 1Av tuyn tnh ho cm bin trong di nhit cn o. in p ng ra thay i

tuyn tnh t0,2VS n 0,6 VS (VS = 5 vn th Vout thay i t1 vn n 3vn). Ta iu chnh P1Vout = 1 vn ti 00C, ti 1000C iu chnh P2Vout = 3

vn, vi mch in ny vic iu chnh P2 khng nh hng n vic chnhzero.

KYT81-110

R13,3k

R34k

P1220

P2

4,7k

R66,8k

R533k

R222k

R41k

Hnh 1.11: Mch o nhit s dng KYT81-110

VB

V0


20/77



4. IC cm bin nhit .Rt nhiu cng ty, cc hng chto v sn xut IC bn dn o v hiu

chnh nhit IC cm bin nhit l mch tch hp nhn tn hiu nhit chuyn thnh tn hiu di dng in p hoc tn hiu dng in. Da vp ccc tnh rt nhy cm ca cc bn dn vi nhit , to ra in p hoc dng

in t l thun vi nhit tuyt i C, F, K hay tu loi. o tn hiu in tacn bit c nhit cn o. Tm o gii hn t -550C n 1500C, chnhxc t1% n 2% tutheo tng loi.

S tc ng ca nhit s to ra in tch tdo v cc l trng trongcht bn dn bng sph v cc phn t, bt cc electron thnh dng tdo dichuyn qua cc vng cu trc mng tinh th, to sxut hin cc ltrng nhitlm cho tlin ttdo v cc ltrng tng ln theo quy lut hm smvinhit . Kt quca hin tng ny l di mc in p thun, dng thun cami ni p n trong diode hay transistor stng theo hm smtheo nhit .

Trong mch thp, cm bin nhit thng l in p ca lp chuyn tipp n trong mt transistor loi bipolar, Texinstruments c STP 35 A/B/C;National Semiconductor LM 35/4.5/50vv.4.1. Cm bin nhit LM 35/ 34 ca National Semiconductor.

Hu ht cc cm bin nhit phbin u sdng c phn phc tp,chng hn cp nhit ngu c mc ng ra thp v yu cu b nhit, thermistorth khng tuyn tnh, thm vo ng ra ca cc loi cm bin ny khng tuyntnh tng ng bt kthang chia nhit no. Cc khi cm bin tch hp cch to khc phc c nhng c im , nhng ng ra ca chng quan hvi thang o Kelvin hn l Celsius v Fahrenheit.

* Loi LM35: Precision Centigrade Temperature Sensor: Vi loi ny tac in p ng ra t l trc tip vi thang nhit Celsius (thang bch phn).

+ VS(4v TO 20V)

OUTPUT10,0mV/0C

+ VS

VOUT

R1

- VS

LM 35

LM 35

Hnh 1.12: Cch kt ni cm bin nhit LM35

Thang o: +20C n 1500CVS= 4 vn ti 30 vn

Thang o: -550C n 1500CR1= VS/50 AVS= 4 vn ti 30 vnVouT = 1500mV ti +1500C

= +250mV ti +250C= -550mV t i -550C


21/77



Nhthmt mch in b trim zero ca thang Kelvin (thang nhit tuyti) khng cn cn thit nhmt sIC cm bin nhit khc.

- c im: in p hot ng: Vs= 4 vn n 30 vn;in p ng ra tuyn tnh: 10 mV/0C

- Thang o: - 550

C n 1500+

C vi LM 35/35A;- 400C n 1100C vi LM 35C/35CA;00C n 1000C vi LM 35D;

- Stnung nng rt nh: 0,080C (trong mi trng khng kh)- Mc khng tuyn tnh ch1/40C)* Cch kt ni* Loi LM 34: Ging nh LM 35 nhng c thit k cho thang o

Fahrenheit t-50 n + 3000F, chnh xc 0,40F.LM 34 c ng ra 10mV/0F

in p hot ng: T5 vn DC n 20 vn DCTrkhng ng ra LM 34 thp v c im ng ra tuyn tnh lm cho gitrc ra hay iu khin mch in ddng.4.2. Cm bin nhit AD 590 ca Analog Devices

Cm bin AD 590 (Analog Devices) c thit klm cm bin nhitc tng trng ra kh ln (10 M(), vi mch c cn bng bi nh sn xut,khin cho dng mA ra tng ng vi chun nhit K. in p lm vic cngnhcng tt trnh hin tng tgia nhit, khi cp in p thay i, dng inthay i rt t.

Thang o: - 550C n 1500Cin p hot ng: T4 vn DC n 30 vn DCDng in ra tl: 1 A/0K

4.3. Mch ng dng.* Mch o nhit bng LM 35.

R3= 1

5 vn

LM

TL 082 TL 082R3= 1

R4= 1

R4= 1R6= 2,2

R7= 10

R1= 8,2

R2 = 10

R5= 1,8

VAK

1212 - 150

5 vn


22/77



* Mch ng dng LM35 vi thit bkhuych i m thanh.

Trong mch ng dng ny, nhit IC khuych i m thanh (IC1) l ilng c quan tm. LM35 v IC1 c sgn kt vnhit, tn hiu ng ra ca

b so snh s xung mc thp nu nhit vt qu gii hn (thng s nyc chn bng R1 v R2 v in p tham chiu). H thng c thit kqut hot ng khi nhit vt qu khong gi tr 800C v tt khi nhit xung di 600C.5. Nhit in trNTC

NTC (Negative Temperature Conficient) l nhit in trc h snhitin trm ngha l gi trin trgim khi nhit tng, gim t3% n 5%trn 1 .5.1. Cu to.

NTC l hn hp a tinh thca nhiu xit gm c nung chy nhitcao(1.0000C n 1.4000C) nhFe2O3; Zn2TiO4; MgCr2O4TiO2hay NiO vCO vi Li2O. c cc NTC c nhng c trng kthut n nh vi thi gian

di, n cn c sl vi nhng phng php c bit sau khi chto.5.2.c tnh cm bin nhit NTC.

* ng c tnh cm binNhit - in trNTC m sA34-2/30: RNTC (5,5 kw nhit mi trng200C RNTC 400 w nhit mi trng 100

0C. * c tnh dng/p ca NTCc tnh dng p ca NTC cung cp nhiu thng tin hn cc tnh in tr

Nhit . c tnh ny cng dng c ctrong trng hp dng qua NTC lmnhit ca n cao hn nhit mi trng.

c tuyn ny cng c gi l c tuyn tnh ca NTC, in p ri trn

NTC chc ghi nhn khi t c trng thi cn bng gia in nng cungcp v ngun nhit (thng ly mi trng nhit 250C, trong iu kin lnggi).

Q1 NDS

LM3886+28 vn

Themmally

IC1LM 35IC2

IC3

LMC7211

LM 4041-

IC4

12vn

12

-28 vn

20 k

1 k 4,7 k

10 F

3,3 F

R3= 10

R1= 10

10 k

R4= 560

Audio

Hnh 1.12: LM35 vi b phn khuych i m thanh cng sut


23/77



c tuyn trn chia ra lm 3 vng:- Vng bt u c tuyn (gii hn vng ny l khu vc 10 mW), nng

lng in cung cp cho NTC khng ng k, lng nhit sinh ra do dng inkhng ng k, trong vng ny, in trca NTC xc nh chdo nhit mitrng. nhy ng knu sdng NTC lm cm bin nhit trong vng

ny.

- Vng 2: Do stng dng, nhit ca NTC tng cao hn nhit mitrng, do tlm nng, in trca NTC gim ng k, mt gi trdng chosn, p tng ti a.

Vng 3: Nu dng vn tng thm, in p ri strln b, cui ngc tuyn in trca NTC gn nhdo nng lng in chuyn i, chc mtt do tc ng nhit ca mi trng.

* Mt sthng sca NTCR20 hay R25: in trngui hay in trbiu kin l gi trnhit caNTC 200C hoc 250C (tuy nhin sai sl t5% n 25%).

K

101

100

10-1

100 200 3000C

10-2

5

5

5

0

Hnh 1.13: ng c tnh cm bin nhit

Hnh 1.14: c tuyn U/I ca NTC

500C 1000C

2000C

3000C

4000C

100k 10k 1k

10

100

1 mw

10 mw

100 mw

1w

10w


24/77



Tmin; Tmax l gii hn nhit hot ng ca NTC.Pmax l cng sut ln nht cho php chuyn i ra nhit trong NTC.

5.3. ng dng.NTC c rt nhiu ng dng, c chia ra lm 2 loi l loi dng lm

o lng v loi lm btr.

* Loi dng lm o lng: trong o lng v tc ng b, cn trnh hintng t sinh nhit do dng NTC ln, nhvy NTC hot ng chyu trongvng tuyn tnh, nh m ttrc y, trong vng ny in trca NTC cxc nh bng nhit mi trng, phm vi chyu ca NTC trong lnh vcny l o nhit , kim tra, iu khin. Tuy nhin NTC cng c dng btnh phthuc nhit ca in tr, lm n nh nhit cho cc mch in tdng bn dn.

* Loi dng lm b tr: NTC c tnh cht tr, khi dng in qua n lnn ni in trgim nhiu do qu trnh t tonhit, ti cng ln th in tr

NTC cng gim mnh. Nhit in trNTC to tc dng trnhm trit dng nhtrong mch n chiu sng loi c tim, mch ng ccng sut nh, mch ttim cc bng in t, mch c tnh dung khng (t).

* Mch ng dng vi NTC.Hot ng ca cm bin da trn skhc nhau vkhnng lm mt ca

cht lng v khng kh hoc hi nc trn cht lng, khi NTC c nhng vocht lng, n c lm mt nhanh chng, in p ri trn NTC tng ln, do hiung ny NTC c thpht hin c stn ti hay khng ca cht lng mt vtr.

* Biu khin nhit : NTC c sdng rt nhiu trong cc hthngiu khin nhit bng cch sdng mt nhit in trtrong mch so snh c

bn, khi nhit vt qu mc ci t, ng ra schuyn trng thi tOff sangON.

* B nhit: Nhiu cht bn dn v IC cn c s b nhit c shotng n nh trn di nhit rng, bn thn chng c hsnhit dng chonn NTC c bit thch hp vi vai tr b nhit.

* Rle thi gian dng NTC: Rle thi gian ngy nay t chnh xccao bng cch sdng phn tRC v cng tc in t. Tuy nhin khi khng cnchnh xc cao, c thdng NTC theo 2 mch in cbn sau y:

- Mch A l rle thi gian ng chm, sau khi ni ngun S1, dng qua

cun dy rle, nhng bgii hn bi in trngui ca NTC ln, sau mt thigian do qu trnh t gia nhit v dng qua n, in trNTC gim, tng dngkhin rle tc ng.

- Mch B l rle thi gian mchm, khi ng S2, dng qua nhit in tr,bt u qu trnh tgia nhit, in p ri qua RS tng, sau mt thi gian rlekhng cn duy tr, bngt, thi gian tr tu thuc vo mi trng tonhitca NTC.6. Nhit in trPTC.

Nhit in tr PTC (Positive Temperature Coefficent) l loi nhit in

trc hsnhit in trdng (gi trin trtng khi nhit tng). Trongmt khong nhit nht nh PTC c hsnhit Rrt cao.6.1. Cu to.


25/77



Vt liu chto PTC gm hn hp barium carbonate v mt vi xit kimloi khc c p v nung, nhiu tnh cht vin khc nhau c tht c

bng cch gia gim cc hp cht trn khc nhau vnguyn vt liu bng cchgia nhit theo nhiu phng php khc nhau, sau khi gia nhit nung kt cc mini c hnh thnh trong thermistors sau trong qu trnh sn xut cc

dy ni dn ra ngoi c thm vo, nhit in trPTC thng thng c phbn ngoi mt lp v c cu to nh vecni chng li nh hng ca mitrng khng kh.6.2.c tnh cm bin nhit PTC.

* ng c tnh in trnhit PTC chia lm 3 vng:- Vng nhit thp: Ging nhnhit in trNTC c hsnhit m- Vng hsnhit tng chm (TA; TN): sau mt vi khong nhit

t c th bt u nhit in trbin i xang tnh cht dng bt u timTA, gi tr ca nhit in trPTC im TA c xem nh l in trkhi

im, RA l gi trin trthp nht m PTC thhin.- Vng lm vic (TN


26/77



Tnh cht dng vdng v p ca nhit in trPTC cng c hnh dngging nhl tnh cht ca nhit in trNTC.

* Mt sthng sc trng ca PTC- TNOM(TN): Nhit danh nh, ti gi trnhit RN= 2*RA- R: Hsnhit nhit in trPTC.

- TUPPER: Nhit gii hn vng lm vic.- R25: in trca PTC khi mi trng nhit 250C.

6.3. ng dng.Nhit in trPTC lm vic nhcm bin c nhy caong dng tnh cht gi tr in tr tng: Khi ng bng n hunh

quang, mch bo vqu ti ...vv.* Mch ng dng vi PTC.

Nhit in trPTC c mc trong mt cu o ca mch so snh (hnh1.16), ti nhit bnh thng RPTC ( RS, in p ng ra mc thp, khi s

tng nhit vt qu ngng xut hin, PTC bnung nng nn RPTC ( RS nnin p ng ra V0 ln mc cao (hnh 1.17).

* Mch bo vng c.PTC c dng pht hin stng nhit bt thng trong ng cbng

cch o trc tip, cm bin nhit c gn chm trong cun Stato, tn hiu csl nhmt thit biu khin dn n tc ng (Hnh 1.18).

Thit biu khin KLIXON 40/41/42AA series.Thit bc sdng kt hp vi cm bin nhit PTC, chng tng

thch vi loi cm bin Klixon BA series.

R1

R2

RS

RP

PTC

R1

V0

RL

Hnh 1.16: Mch so snh Hnh 1.17: c tuyn ca V0

RPRSR1= R2

V0

T0CSwtich

temperature

PTC

PTCPTC

Hnh 1.18: Mch bo v ng c


27/77



Nu nhit trong cun dy ng c trng thi bnh thng th cmbin in trgim xung n mc thp cn thit Reset, thit btng reset nuthit bkhng ci t reset bng tay.

Skt ni cm bin vi biu khin loi 40AA, 42AA Series.7. Cc bi thc hnh ng dng cc loi cm bin nhit .

7.1. Thc hnh vi cm bin nhit Platin Pt 100, Pt1000 v ADT70.* Yu cu mc ch:a/ Thit b- Kho sats cm bin nhit Pt100, Pt1.000.

* Thit b: - Cm bin Pt100 v Pt1000, IC ADT70* Thc hin - Lp t mch o nhit s dng nhit tr Pt100,

Pt1000 vi IC ADT 70- Lp mch nhhnh 1.19.o gi trin p ng ra (VOUT IA v im ni mass)

VOUT=- Tnh gi trnhit mi trng ca phng th nghim:t =* Pt 100

- Lp mch nhhnh 1.19, nhng cn lu thay gi trin trRG= 4,99knhhnh 1.20.- Thay in trtham chiu 1000bng in tr100Vic thay RGgip gitlin p ng ra v nhit nhkhi dng Pt1000

- o gi trin p ng ra (chn VOUT IA v im ni mass)VOUT=

- Tnh gi trnhit mi trng ca phng th nghim: t =

NULLA

SHUTDOWN

NULLB BIAS 2,5VREFOUTATD70

+ 5V

IOUTA

IOUTB

-INIA

-INIB

VOUT5mV

1KREF

1KPRTD

RESISTOR

RGA

49,9K

RGB GNDSENSE

OUTIA

RGND DGND

INDEPENDENT

OP AMP

-INOA

+INOAOUTA

2,5VREF

SHUTDOWN

MATCHEOCURRENTSOURCES

-1V


28/77



7.2. Thc hnh vi cm bin LM 35* Yu cu mc ch:Kho st IC LM 35.

* Thit b:IC LM 35, in tr.Diod 1N914, diod zener.Mili vn k

* Thc hinVi IC LM35in p ng ra t l trc tip vi thang o Celsius. Thc t ICLM35 c 4 dng nhsau:

* Schn ca IC LM35

* Rp mch nhhnh 1.21(thang o:+20C n 1500C)-Sdng Milivn ko gi trin p VOUT: VOUT=Tnh nhit t =a cm bin n gn ngun nhit theo di sthay i ca VOUT.

* Rp mch nhhnh 1.22 (thang o:-550C n 1500C)-Gi trR1c chn tuthuc vo VS, R1= - VS/50A.Sdng milivn ko gi trin p VOUT: VOUT=

Tnh nhit t: t =a cm bin n gn ngun nhit theo di sthay i ca VOUT.

4,98K

-INIA

+INIA

RG

RG

OUTGNDSENSE

INST

AMP

Hnh 1.20: ADT70 v Pt100

Dng SO-8 Dng TO-46 Dng TO-92 Dng TO-220

VOUT

+VS VOUT GND LM35DT

GND

NC

NC

+VS

NC

NC

NC

+VS VOUT

GND o

GND VOUT+VS

BOTTOM VIEWBOTTOM VIEW


29/77



* Rp mch nhhnh v1.23 (thang o t-550C n 1500C)

Sdng milivn ko gi trin p VOUT: VOUT=Tnh nhit t: t =

a cm bin n gn ngun nhit theo di sthay i ca VOUT.* Rp mch nhhnh 1.24

- Ch trong mch ny gi trin p ra tlvi nhit thang o Fahrenheit.Sdng milivn ko gi trin p VOUT: VOUT=

Tnh nhit t: t =a cm bin n gn ngun nhit theo di sthay i ca VOUT.7.3. Thc hnh vi cm bin nhit in trNTC.

* Yu cu - mc ch

Ly ng c tnh ca mt intrNTC, R = f() v I = f(U), sthay i in trxy ra do tlmnng (ti tng).

* Thit b:Nhit in trNTC (NegativeTemperature Coeffcient), vnk, miliampek.

* Thc hin:

Ghi ch: S thay i in trc thto ra qua vic thay i nhit ca mitrng xung quanh hoc qua vic tnng cng nh lm lnh tu theo ti in

+VS(4V TO 20V)

VOUTLM35 LM35

+VS

-VS

VOUT

RT

Hnh 1.21 Hnh 1.22

+VS

VOUT

12K 10%

Hnh 1.23

LM35

1N914

1M1%

48,5K1%

18K

+VS6, 10, 20V

LM385

VOUT-

26,4K1%

Hnh 1.24

LM35

10K1%

K hiu ca nhit in trNTC


30/77



khc nhau. ng c tnh ca in trNTC l ng biu din hm sm, nphthuc vo vt liu sdng, dng cu to cng nhsthay i nhit .

Bqua sthay i in trdo nhit ca mi trng v trong phng thnghim, nhit coi nhkhng i.

Lp th nghim theo mch hnh 1.25, o dng in qua in trNTC theo

cc in p cho trong bng di y, chnh c trng thi nhit nnh khi thay i in p, cc php o c thc hin ln lt theo khong cchvthi gian l 30s.

xy dng c tnh ca R = f() cn i hi cc gi trin trca intrNTC c xc nh tcc gi trdng in o v cc in p cho trc

bng sau y:Bng gi trin p

U(V) 5 10 15 20 25 28I(mA)

R(k)

U: 0 30V R25= 6k

mA

V

Hnh 1.25

0

1

2

3

4

5

6

7

0

4,2

4,6

5,0

5,4

5,8

6,2

6,6

0 0 10 15 20 25 30 35U(V)

I(mA) R(k


31/77



7.4. Thc hnh vi cm bin nghit in trPTC.* Yu cu - mc ch

Ly ng c tnh ca mt intrPTC, R = f() v I = f(U), ctnh R = f() c to ra qua vic

tlm nng (tng in p t von)* Thit b: Nhit in tr

PTC (Positive TemperatureCoeffcient), vit nam k, miliampe k.

* Thc hin:Ghi ch: S thay i in trc thto ra qua vic thay i nhit ca mitrng xung quanh hoc qua vic tnng cng nh lm lnh tu theo ti inkhc nhau. B qua s thay i in tr do nhit ca mi trng v trong

phng th nghim, nhit coi nhkhng i.V ng c tnh ca in trPTC khng chph thuc vo nhit ca nm cn phthuc mt t vo ln in p t vo n, do trong cc bi thnghim sau bqua trng hp phthuc vo in p.

* Lp th nghim theo mch hnh 1.26 v o dng in qua in trPTC theo cc in p cho trong bng.

c thchnh c trng thi in trn nh khi thay i in p, ccphp o dng in c thc hin ln lt theo khong cch vthi gian l 30s.

xy dng c c tnh ca R = f() cn i hi cc gi trin trcain trPTC c xc nh tcc gi trdng in o v cc in p chotrc bng sau y:

Bng gi trin pU(V) 1 2 4 5 6 10 12 16 20 24

I(mA)R(k)

K hiu ca nhit in trPTC

U: 0 30V R25= 80

mA

V

Hnh 1.26


32/77



HOT NG II: HC VIN TNGHIN CU TI LIU

Hc vin tham kho cc ti liu di y:1. Cc bcm bin trong kthut o lng v iu khin.

L Vn Doanh, Phm Thng Hn, Nguyn Vn Ho, o Vn TnNh xut bn Khoa hc v kthut H Ni.

2. Cm bin ng dng Dng Minh Tr - Nh xut bn Khoa hc v kthut H Ni.

3. Gio trnh cm bin - Phm Quc Ph, Nguyn c Chin - Nh xutbn Khoa hc v kthut H Ni.

4. Gio trnh cm bin Trung tm Vit - c pht hnh


* Ni dung:- Nghin cu ng dng ca tng loi cm bin nhit .- Tm hiu cch phn loi, ng dng ca tng cm bin nhit .1/ Hnh thc tchc:

Chia thnh cc nhm nht2 n 3 hc sinh di shng dn ca gio vin.2/ Dng c, thit b: Cc loi cm bin nhit , dng ckim tra nhnhit kvv.3/ Quy trnh thc hin:

0

20

40

60

80

100

120

140

0

200

400

600

800

1.000

1.200

1.400

0 4 8 12 16 20 24 28U(V)

I(mA) R(k


33/77



- Gio vin tp trung clp hc vin, slc vng dng ca cc bcm binnhit , lm mu cch lp t, cch o v hiu chnh cc bcm bin nhit .- Chia mi nhm t2 n 3 hc vin thc hnh thc tp vi cc bcm binnhit di shng dn ca gio vin.- Cui bi hc, gio vin kim tra nh gi, nhn xt ti tng hc vin trong qu

trnh thc tp.


34/77



BI 2CM BIN TIM CN

V CC LOI CM BIN XC NH VTR, KHONG CCH

GII THIU

Cm bin tim cn c sdng nhiu trong cc lnh vc tngho qu trnh sn xut, trong cc dy truyn tng ho sn xut, trong cc nilm vic kh khn, c hi, v cm bin tim cn dng nhn bit c hockhng cc vt th.

MC TIU BI HC

Sau khi hc xong bi ny hc vin c khnng:- nh gi/xc nh c v tr, nhim v v ng dng ca cc b cm bintim cn.- M tc chc nng, nhim vv cc iu kin lm vic ca cc bcm

bin tim cn.- Bit c phm vi ng dng, cch lp t cc bcm bin tim cn .

NI DUNG

* Cm bin tim cn (Proximity Sensor).*Mt sloi cm bin xc nh vtr, khong cch khc.* Cc bi thc hnh ng dng cc loi cm bin tim cn.


1. Cm bin tim cn (Proximity Sensor).1.1. i cng.

* c im: - Pht hin vt khng cn tip xc.- Tc p ng nhanh.- u sensor nh, c thlp c nhiu ni.- C thsdng trong mi trng khc nghit.

Cm bin tim cn l mt k thut nhn bit sc mt hay khng cmt ca mt vt thvi cm bin in tkhng cng tc (khng ng chm),

cm bin tim cn c mt vtr rt quan trng trong thc t, v dpht hin vttrn dy chuyn rbt bt gily, pht hin chai, lon nhm trn dy chuyn,bng chuyn ...vv. Tn hiu ng ra ca cm bin tim cn thng dng logicc hoc khng.

* Mt snh ngha:- Khong cch pht hin: L khong cch xa nht tu cm bin n v

tr vt chun m cm bin pht hin c.- Khong cch ci t: L khong cch cm bin c thnhn bit vt

mt cch n nh (thng bng 70% n 80% khong cch pht hin).

- Thi gian p ng: t2l thi gian tlc i tng i vo vng cm binpht hin ca cm bin n lc cm bin bo hiu. t2 l thi gian t lc itng i ra khi vng pht hin cho n khi cm bin ht bo tn hiu.


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1.2. Cm bin tim cn in cm (Inductive Proximity Sensor).Cm bin tim cn in cm c nhiu kch thc v hnh dng khc nhau

tng ng vi cc ng dng khc nhau. Cm bin tim cn in cm c dngpht hin cc i tng l kim loi (loi cm bin ny khng pht hin cc

i tng c cu to khng phi l kim loi).* Cu trc ca cm bin tim cn in cm: Gm 4 phn chnh- Cun dy v li ferit.- Mch dao ng.- Mch pht hin.- Mch u ra.* Nguyn l hot ng ca cm bin tim cn in cm.Cm bin tim cn in cm c thit kto ra mt vng in trng,

khi mt vt bng kim loi tin vo khu vc ny, xut hin dng in xoy (dng

in cm ng) trong vt thkim loi ny. Dng in xoy gy nn s tiu haonng lng (do in trca kim loi) lm nh hng n bin sng dao ng,n mt trsno tn hiu ny c ghi nhn. Mch pht hin spht hin s

Khong cchpht hin

OFF ON

Cm bin tim cn

Khong cch ResetHnh 2.1

Khong cch trc lng ci t

Sensing object

Khong cch ci t

Cm bin tim cn

Hnh 2.2


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thay i tn hiu v tc ng mch ra ln mc ON. Khi i tng ri khi khuvc ttrng, sdao ng c ti lp, cm bin trli trng thi bnh thng.

* Phn loi cm bin tim cn in cm.Cm bin tim cn in cm c thchia ra lm 2 loi: Loi c bo v

(Shielded) v loi khng c bo v (Unshielded), loi khng c bo v

cthng c tm pht hin ln hn loi c bo v.* Nhng yu tnh hng n tm pht hin ca cm bin tim cn incm:

- Kch thc, hnh dng, vt liu li v cun dy.- Vt liu v kch thc i tng.- Nhit mi trng.c im ca i tng tiu chun (mc tiu): Hnh vung, di cnh

bng d (ng knh ca bmt cm bin), dy 1mm v lm bng thp mm (mildsteel).

Nu i tng cn pht hin c kch thc nhhn tiu chun, tm phthin ca cm bin sgim (do dng in xoy yu). Nhng nu kch thc lnhn kch thc tiu chun khng c ngha l tm pht hin tng ln.

hiu chnh khong cch tm cm bin phthuc vo vt liu ngi tasdng cc vt liu v hsnhbng 1 v 2 di y.

Bng 1

Vt liuHs1

Shielded Unshielded

Thp mm (mild steel) 1.00 1.00Thp khng g(300) 0,70 0,80ng thau 0,40 0,50

Nhm 0,35 0,45ng 0,30 0,40

Bng 2Kch thc i tng so

vi kch thc tiuchun

Hs2

Shielded Unshielded

25% 0,56 0,5050% 0,83 0,7375% 0,92 0,90

100% 1,00 1,00

+ Snew = Sn* hs+ Snew: Tm pht hin mi ca cm bin tng ng vi kch thc v vt

liu ca cm bin.+ Sn: Tm pht hin ca cm bin vi i tng tiu chun.dy ca i tng cng l mt yu tnh hng n tm pht hin

ca cm bin, i vi vt liu khng mang t tnh (khng cha cht st) nh


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ng, nhm, ng thau chu nh hng ca hiu ng bmt. Tm pht hin cacm bin tng ln khi dy i tng gim.

* u nhc im ca cm bin tim cn in cm.- u im:

+ Khng chu nh hng ca m.

+ Khng c bphn chuyn ng.+ Khng chu nh hng ca bi bm.+ Khng phthuc vo mu sc.+ t phthuc vo bmt i tng n so vi cc kthut khc.+ Khng c khu vc m (blind zone: cm bin khng pht hin ra i

tng mc d i tng gn cm bin).- Nhc im:

+ Chpht hin c i tng l kim loi.+ C thchu nh hng bi cc vng in tmnh.

+ Phm vi hot ng ngn hn so vi cc kthut khc.* Mt sng dng ca cm bin tim cn in cm:1.3. Cm bin tim cn in dung (Capacitive Proximity Sensor).

Cm bin tim cn in dung ging vkch thc, hnh dng, cshotng so vi cm bin tim cn in cm. im khc bit cn bn gia chng lcm bin tim cn in dung to ra vng in trng cn cm bin tim cn incm to ra vng in ttrng. Cm bin tim cn in dung c thpht hin itng c cht liu kim loi cng nhkhng phi l kim loi.

* Cu trc ca cm bin tim cn in dung.Ging nhcu trc ca cm bin tm cn in cm, cm bin tim cn

in dung cng c 4 phn:- Bphn cm bin (cc bn cc hay in cc cch in)- Mch dao ng.- Mch ghi nhn tn hiu.- Mch in ng ra.* Nguyn l hot ng ca cm bin tim cn in dung.Tin gm 2 bn cc v cht in mi gia, khong cch gia 2 in

cc nh hng n khnng tch trin tch ca mt tin (in dung l mti lng c trng cho khnng tch trin tch ca mt tin)

- Nguyn tc hot ng ca cm bin tim cn in dung da trn sthayi in dung khi vt thxut hin trong vng in trng, t s thay i nytrng thi On hay Off ca tn hiu ng ra c xc nh.

- Mt bn cc l thnh phn ca cm bin, i tng cn pht hin l bncc cn li.

- Mi quan hgia bin sng dao ng v vtr i tng cm bintim cn in dung tri ngc so vi cm bin tim cn in cm.

- Cm bin tim cn in dung c thpht hin bt cloi i tng noc hng sin mi ln hn khng kh, vt liu no c hng sin mi cng

cao th cng dc cm bin pht hin, v dnc v khng kh, cm bin timcn in dung rt dpht hin ra nc (v hng sin mi ca nc = 80, cnkhng kh = 1).


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- i vi cc cht kim loi khc nhau, khnng pht hin ca cm bin lkhng i, cn cc cht khc th phm vi pht hin ca cm bin l khc nhau tutheo tng cht.

V vy cm bin tim cn in dung c thdng pht hin cc vt liuc hng sin mi cao nhcht lng d n c cha trong hp kn lm bng

vt liu c hng sin mi thp nh thu tinh, plastic, cn chc chn rng itng cm bin pht hin l cht lng chkhng phi l hp.* Phn loi cm bin tim cn in dung: C hchia ra lm 2 loi l

loi c bo v(Shielded) v loi khng c bo v(Unshielded).Loi c bo v (Shielded) c vng kim loi bao quanh gip hng

vng in trng pha trc v c tht ngang bng vi bmt lm vic.Loi khng c bo v(Unshielded) khng c vng kim loi bao quanh

v khng tht ngang bng vi bmt lm vic. Xung quanh cm bin phi cmt vng trng (ging cm bin tim cn in cm loi khng c bo v

Unshielded), kch thc vng trng tuthuc vo tng loi cm bin.* Cc yu tnh hng n tm pht hin ca cm bin tim cn indung.

- Kch thc ca in cc cm bin.- Vt liu v kch thc i tng.- Nhit mi trng.- i tng tiu chun v hng sin mi: i tng tiu chun c

chnh rin vi tng loi cm bin tim cn in dung, thng thng cht liuca i tng tiu chun c nh ngha l kim loi hoc nc.

* u nhc im ca cm bin tim cn in dung:- u im:

+ C thcm nhn vt dn in v khng dn in.+ Tnh cht tuyn tnh v nhy khng tu thuc vo vt liu kim

loi.+ N c thcm nhn c vt thnh, gn, nh.+ Vn tc hot ng nhanh.+ Tui thcao v n nh cng cao i vi nhit .

- Nhc im:+ Bnh hng bi m.

+ Dy ni vi sensor phi ngn in dung dy khng nh hngn cng hng ca bdao ng.

* Mt sng dng ca cm bin tim cn in dung:- Dng trong cng nghip thc phm.- Dng o mc cht lng.- Dng trong sn xut chbin g.

1.4. Cm bin tim cn siu m (Ultrasonic proximity sensor).Cm bin tim cn siu m c thpht hin hu ht cc i tng nhl

kim loi hoc khng phi l kim loi, cht lng hay vt rn, vt trong hay mc

(nhng vt c hsphn xsng m thanh ln)* Cu trc ca cm bin tim cn siu m.Gm c 4 phn chnh:


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- Bphn pht v nhn sng siu m (Transducer/Receiver).- Bphn so snh (Comparator).- Mch pht hin (Detector Circuit), khi cm bin nhn c sng phn

hi, b phn so snh tnh ton khong cch bng cch so snh thi gian pht,nhn v vn tc m thanh.

- Mch in ng ra (Output), tn hiu ng ra c thl digital hoc analog,tn hiu tcm bin digital bo c hay khng sxut hin i tng trong vngcm nhn ca cm bin, tn hiu tcm bin analog cha ng thng tin khongcch ca i tng n cm bin.

* Nguyn l hot ng ca cm bin tim cn siu m.- Kthut cm bin siu m da trn c im vn tc m thanh l hng

s, thi gian sng m thanh i tcm bin n i tng v quay trli lin htrc tip n di qung ng, v vy cm bin siu m thng c dngtrong cc ng dng o khong cch.

- Tn shot ng: Nhn chung cc cm bin cng nghip hot ng vitn s25 khz n 500 khz, cc cm bin trong lnh vc y khoa th hot ng vikhong tn st5 Mkhz trln. Tn shot ng ca cm bin tlnghch vikhong cch pht hin cm bin. Vi tn s50 khz, phm vi hot ng ca cm

bin c thti 10m hoc ln hn, vi tn s200 khz th phm vi hot ng cacm bin bgii hn mc 1m.

- Vng hot ng: L khu vc gia 2 gii hn khong cch pht hin lnnht v nhnht. Cm bin tim cn siu m c mt vng nhkhng thsdnggn bmt cm bin gi l khu vc m (blind zone).

Kch thc v vt liu ca i tng cn pht hin quyt nh khongcch pht hin ln nht.

* Cm bin tim cn siu m loi c thiu chnh khong cch pht hin(Background Suppression).

Mt s dng cm bin ng ra analog cho php iu chnh khong cchpht hin, chng c thtchi vic pht hin cc i tng sau mt khong cchxc nh, khong cch pht hin c thiu chnh bi ngi sdng. Ngoi ra cm bin khng pht hin i tng d chng di chuyn vo vng hot ng cacm bin, ngi ta c thto 1 lp vbng cht liu c khnng khng phn xli sng m thanh.

* u nhc im ca cm bin tim cn siu m.- u im:

+ Khong cch m cm bin c thpht hin vt thln ti 15m.+ Sng phn hi ca cm bin khng ph thuc vo mu sc ca b

mt i tng hay tnh cht phn xnh sng ca i tng v dbmt knhtrong sut, bmt gm mu nu, bmt plastic mu trng, hay bmt cht liunhm sng, trng ...l nhnhau.

+ Tn hiu p ng ca cm bin tim cn siu m analog l tltuyntnhvi khong cch, iu ny c bit l tng cho cc ng dng nh theo di

cc mc ca vt cht, mc chuyn ng ca i tng.- Nhc im:


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+ Cm bin tim cn siu m yu cu i tng c mt intch bmt ti thiu (gi trny tuthuc vo tng loi cm bin).

+ Sng phn hi cm bin nhn c c thchu nh hng ca ccsng m thanh tp m.

+ Cm bin tim cn siu m yu cu mt khong thi gian sau mi

ln sng pht i sn sng nhn sng phn hi, kt quthi gian p ng cacm bin tim cn siu m nhn chung chm hn cc cm bin khc.+ Vi cc i tng c mt vt cht thp nhbt hay vi (qun o)

rt kh pht hin vi khong cch ln.+ Cm bin tim cn siu m bgii hn khong cch pht hin nh

nht.+ S thay i ca mi trng nh nhit (vn tc m thanh ph

thuc vo nhit i), p sut, schuyn ng khng ng u ca khng kh, bibn bay trong khng kh gy nh hng dn kt quo ca cm bin.

+ Nhit bmt i tng nh hng n phm vi hot ng cacm bin, hi nng tora ti tng c nhit cao lm mo dng sng, lmcho khong cch pht hin ca i tng ngn li v gi trkhong cch khngchnh xc.

+ Bmt phn hi nng lng ca sng m thanh tt hn bmt ggh, tuy nhin bmt trn phng li c i hi kht khe vv tr gc to thnhgia cm bin v mt phng i tng.

* Mt sng dng ca cm bin tim cn siu m.- Pht hin shin din, khng hin din ca i tng trong sut bng

thutinh.- Dng trong iu khin mc cht lng.- Dng o khong cch, cao, hay v tr ca phin g trn dy

chuyn.1.5. Cu hnh ng ra ca cm bin tim cn.

* Ng ra dng Transittor NPN v Transittor PNP.(hnh 2.3 v 2.4)Vi in p DC thp, cm bin c 2 dng cu hnh ng ra phbin l kiu

NPN Transittor v PNP Transittor.

* Ng ra dng Transittor FETS:

Ng ra

Ti

Hnh 2.3: NPN transitor

Ng ra

Ti

Hnh 2.4: PNP transitor


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Ng ra dng khc l kiu TransittorFETS cung cp p ng nhanh, dngtiu hao rt nh, dng iu khinthay i trng thi chcn c30(A, xong nhn chung gi thnh

cao hn so vi 2 loi trn. C thkt ni song song ng ra ca FETnhtip im ckh ca rle (c

in p AC hay DC). Dng FET cng sut th tip im ng ra c thchu c dng n 500 mA.

* Ng ra dng Triac.Cm bin ng ra dng triac c thit kc thsdng nhcng tc

cho in AC. Cm bin dng ny cung cp ng ra c th chu c dng ln,in p ri thp do thch hp vi vic kt ni vi cc cngtc tln. Dng tiu hao ca n ln hn so vi FETS, gi trny vt qu 1mAdo khng thch hp kt ni vi cc thit bnhPLC.

* Ng ra dng Analog.Cm bin c thcung cp tn hiu ng ra di dng dng v p tng ng

(hay nghch o stng ng) vi spht hin. Trng thi ng ra ca cm binc th l thng ng (NO) hoc thng m (NC). V d cm bin loi PNP,trng thi ng ra l Off khi khng c i tng xut hin th n l loi thit bthng m, ngc li trng thi ng ra On khi khng c i tng xut hin thn l loi thng ng. Ngoi loi 3 dy, cm bin cn c loi 4 dy v loi 2dy, vi loi 4 dy trong mt cm bin c 2 loi ng ra l thng ng vthng m.

1.6. Cch kt ni cc cm bin tim cn vi nhau.Trong mt sng dng i hi phi sdng nhiu hn 1 cm bin, cccm bin c thni song song hoc mc ni tip, khi mc song song, ng ra ln

Hnh 2.5: transitor FETS

AC

AC

Ng ra

Hnh 2.6: Triac

I (mA)

4

20

1 2 3 4 5

Khong cch (m)

Hnh 2.7: Analog

Dng 1

Dng 2


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On khi tt ccc cm bin u ln On, cn khi mc ni tip, chcn trong scccm bin ln On th ng ra ln On.2. Mt sloi cm bin xc nh vtr, khong cch khc.2.1. Xc nh vtr v khong cch bng bin tr.

* Cu trc:

Gm mt in trcnh Rn v mt tip xc in c thdi chuyn gnvi chuyn ng cn o gi l con chy, vtr con chy tlvi gi trin trtiu ra ca tip xc im.

Cn cvo hnh dng ca Rn v dng chuyn ng ca con chy ngi tachia ra lm 2 loi l loi dch chuyn thng v dch chuyn quay.

* c tnh:- phn gii: Thng thng t c10 m.- Tui thca con chy: 106 ln vi dng xoay v 107 n 108 ln vi

dng dch chuyn.

- tuyn tnh: Gi trca tsR(x)/Rn 2 u ca in trkhng nnh, do u ng chy hoc cui ng chy th tuyn tnh km.* Cc loi bin tr:Gi trin trRn t1kn 100 k, i khi ln ti hng M, tutng

trng hp cthchnh xc ca in trl 20%, 10% v i khi t ti 5%.Trn thc tkhng cn i hi chnh xc cao v tn hiu o chphthuc vot sR(x)/Rn, c nhiu loi bin tr, tu theo tng ng dng m ngi ta chnloi bin trthch hp.

- Bin trdy kim loi: Loi bin trny dng vi dng in kh cao,n c hsnhit thp, t ting n cho mch in tv trsin trkhng btri theo thi gian v do nh hng ca kh hu, nhc im l phn gii thp.

- Bin trvi lp Polymer: Lp in trc cu to bi mt loi snhu ctrn vi mui than v bt graphit, lp in tloi ny rt trn phng, kh

bmi mn, tuy nhin n c hsnhit kh ln (300 n 1.000ppm/K), do n nh ca n so vi bin trdy kim loi nhit cao km.

- Bin trvi it kim loi thutinh (cermet).Loi in tr ny c ti nhit kh cao khong 8000C n

9000C, cho nn rt cng, tuy nhin bmt nhm, khng thch hp cho sdchchuyn con chy nhiu ln, bin trny chthch hp cho vic iu chnh in p

trong cc mch in.- Bin trvi mng mng kim loi.Vi phng php phun phhay phun bi catot, ngi ta c thto mt

lp kim loi thc phng trn mt nn thutinh, vt liu c thl hp kim Ni/Crhay it kim loi Ta2o5. Mng mng kim loi c bdy khong 1 (m.

Trong cc loi bin trtrn chc loi bin trvi lp polyme l thchhp hn cho ccng vic nh vv tnh khong cch.2.2. Xc nh vtr v khong cch bng tcm.

* Cu trc, nguyn l hot ng ca cm bin tcm.

- Cu trc n gin ca mt cm bin tcm dng o khong cch, ogc gm mt cun dy v mt li st dch chuyn.


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- Nguyn l hot ng: i lng vo lm thay i tcm v tng trca cm bin cng thay i theo. ng sc i qua 3 vng, trong st (lFe, AFe)trong khng kh bn trong cun dy (l, A) v trong vng bn ngoi cun dy (Sa,la).

mR

NL

2

=

Trong : N l svng dy ca cun dy; Rm l in trtca cun dy.in trtca cun dy vi li st:Trong : ( ca st rt ln (khong 103 n 104) cho nn coi sthay i

ca phn in trttrong st khi li st di chuyn coi nhkhng ng k.Din tch Aa trong khng kh bn ngoi cun dy rt ln hoc c

thbc cun dy bng vst mm v hu nhtt ccc ng sc u chy voy vi in trtcoi nhrt nh.

Do tv bqua R0.

AlRm0

= ;lk

lAN

RNL

m

=== 022

Nhthtcm cng ln khi li st cng nm su bn trong cun dy.Khi li st dch chuyn tv tr I0 ra bn ngoi cun dy 1 on (l, tcm

gim i tl

kL =1 thnh

ll

kL

+=2

Vy L phi tuyn theo I, tnh cnh hng sthay i ca ttrqua li st vgim bt mc phi tuyn, ngi ta dng cu trc cm bin li chm vi sai.

* Cm bin tcm vi li chm vi sai.

- Cu trc: Gm 2 cun dy cch bit, mt li st c t bn trong 2cun dy, khi li st c dch chuyn, tcm ca 1 cun dy gim v cun khctng ln. Vi cu trc i xng ng trc, cm bin ny c th dng okhong cch, vi cu trc vnh khn v xoay, n c dng o gc.

o khong cch, c2 cun dy c t trong na cu o.2.3. Xc nh vtr v khong cch bng cm bin in dung.

* Nguyn l hot ng: Cm bin in dung da trn tc ng tng hgia 2 in cc to thnh tin, in dung ca n thay i di tc ng cai lng vo. in dung sph thuc vo tit din, khong cch 2 bn cc vin mi gia 2 bn cc C(x) = f(A,d,().

Vi trng hp n gin tin phng ta c:trong A l din tch bncc; a l khong cch gia 2 bn cc; (0 l hng sin mi trong chn khng((0 = 8,85.10-12 F/m); (r l hng sin mi.

Cm bin c c trng bi nhy:+ nhy in dung: SC = (C/(x+ nhy in khng: Sz = (z/(x

* Sthay i khong cch ca 2 bn cc.in dung ca tin t lnghch vi khong cch bn cc, khi khong

cch b i in dung ln hn v ngc li.Xt tin phng: nhy(


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Nhvy s thay i tng i ca in dung tlvi s thay i tngi ca khong cch.

Khi a tng 1 khong, in dung gim tnKhi tin nm 1/4 cu:; in thcu chtltuyn tnh gn ng vi sthay i khong cch bn

cc:a

a

U

aa

aUUC

+

= .

42.

2 0

0

0

0

Skhng tuyn tnh mt i trong trng hp vi tvi sai (2 tin vibn cc chung nm gia)3. Cc bi thc hnh ng dng cc loi cm bin tim cn.3.1. Thc hnh vi cm bin tim cn in cm.a/ Thc hnh vi cm bin tim cn in cm 1

* Mc ch - yu cu

Kho st cm bin tim cn in cm IW-2008-BRKG/IW5039* Thit b: + cm bin tim cn in cm IW-2008-BRKG/IW5039+ Ti: Relay sdng in p mt chiu.

* Thc hin* Ghi cc thng skthut

Ngun gc: ..............................................................................................Cng ty sn xut: ....................................................................................M ssn xut sn phm: ......................................................................in p hot ng: .................................................................................Dng in: ..............................................................................................c tnh hot ng: ................................................................................Khong cch tc ng: ...........................................................................Tiu chun cch in: ............................................................................* Sni cm bin:

* Nhng ghi ch khi thc hnh:............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................b/ Thc hnh vi cm bin tim cn in cm 2

* Mc ch - yu cu

Kho st cm bin tim cn in cm IW-5020-IVE3020-BPKG* Thit b: + cm bin tim cn in cm IW-5020-IVE3020-BPKG

+ Ti: Relay sdng in p mt chiu.


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* Thc hin* Ghi cc thng skthut

Ngun gc: ..............................................................................................Cng ty sn xut: ....................................................................................M ssn xut sn phm: ......................................................................

in p hot ng: .................................................................................Dng in: ..............................................................................................c tnh hot ng: ................................................................................Khong cch tc ng: ...........................................................................Tiu chun cch in: ............................................................................* Sni cm bin:

* Nhng ghi ch khi thc hnh:................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

c/ Thc hnh vi cm bin tim cn in cm 3* Mc ch - yu cu

Kho st cm bin tim cn in cm IYB3000-8BNOG/IY5015* Thit b: + cm bin tim cn in cm IYB3000-8BNOG/IY5015

+ Ti: Relay sdng in p mt chiu.* Thc hin* Ghi cc thng skthut

Ngun gc: ..............................................................................................Cng ty sn xut: ....................................................................................M ssn xut sn phm: ......................................................................

in p hot ng: .................................................................................Dng in: ..............................................................................................c tnh hot ng: ................................................................................Khong cch tc ng: ...........................................................................Tiu chun cch in: ............................................................................* Sni cm bin:

* Nhng ghi ch khi thc hnh:........................................................................................................................................................................................................................................................


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............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

............................................................................................................................

d/ Thc hnh vi cm bin tim cn in cm 4* Mc ch - yu cu

Kho st cm bin tim cn in cm IF5639/IFK3002/MS* Thit b: + cm bin tim cn in cm IF5639/IFK3002/MS

+ Ti: Relay sdng in p mt chiu.* Thc hin

* Ghi cc thng skthutNgun gc: ..............................................................................................Cng ty sn xut: ....................................................................................M ssn xut sn phm: ......................................................................in p hot ng: .................................................................................Dng in: ..............................................................................................c tnh hot ng: ................................................................................Khong cch tc ng: ...........................................................................Tiu chun cch in: ............................................................................* Sni cm bin:

* Nhng ghi ch khi thc hnh:............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

............................................................................................................................

............................................................................................................................

............................................................................................................................3.2. Thc hnh vi cm bin tim cn in dung.a/ Thc hnh vi cm bin tim cn in dung1

* Mc ch - yu cuKho st cm bin tim cn in dung KIE3015-FPKG

* Thit b: + cm bin tim cn in dung KIE3015-FPKG+ Ti: Relay sdng in p mt chiu.

* Thc hin* Ghi cc thng skthutNgun gc: ..............................................................................................


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Cng ty sn xut: ....................................................................................M ssn xut sn phm: ......................................................................in p hot ng: .................................................................................Dng in: ..............................................................................................c tnh hot ng: ................................................................................

Khong cch tc ng: ...........................................................................Tiu chun cch in: ............................................................................* Sni cm bin:


........................................................................................................................................................................................................................................................

............................................................................................................................

............................................................................................................................

........................................................................................................................................................................................................................................................

b/ Thc hnh vi cm bin tim cn in dung2* Mc ch - yu cu

Kho st cm bin tim cn in dung KD-2050-BB0A* Thit b: + cm bin tim cn in dung KD-2050-BB0A

+ Ti: Relay sdng in p mt chiu.* Thc hin* Ghi cc thng skthut

Ngun gc: ..............................................................................................Cng ty sn xut: ....................................................................................M ssn xut sn phm: ......................................................................in p hot ng: .................................................................................Dng in: ..............................................................................................c tnh hot ng: ................................................................................

Khong cch tc ng: ...........................................................................Tiu chun cch in: ............................................................................* Sni cm bin:


........................................................................................................................................................................................................................................................

............................................................................................................................


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....................................................................................................................................................................................................................................................................................................................................................................................

HOT NG II: HC VIN TNGHIN CU TI LIU

Hc vin tham kho cc ti liu di y:1. Cc bcm bin trong kthut o lng v iu khin.L Vn Doanh, Phm Thng Hn, Nguyn Vn Ho, o Vn Tn

Nh xut bn Khoa hc v kthut H Ni.2. Cm bin ng dng Dng Minh Tr - Nh xut bn Khoa hc v kthut H Ni.

3. Gio trnh cm bin - Phm Quc Ph, Nguyn c Chin - Nh xutbn Khoa hc v kthut H Ni.4. Gio trnh cm bin Trung tm Vit - c pht hnh


* Ni dung:- Nghin cu ng dng ca tng loi cm bin tim cn.- Tm hiu cch phn loi, ng dng ca cc loi cm bin tim cn.1/ Hnh thc tchc:

Chia thnh cc nhm nht2 n 3 hc sinh di shng dn ca gio vin.2/ Dng c, thit b: Cc loi cm bin tim cn, cc m hnh lp t, kim tra,

3/ Quy trnh thc hin:- Gio vin tp trung clp hc vin, slc vcch nhn bit, ng dng cacc cm bin tim cn.- Gio vin hng dn lm mu cch cch kho st, lp t cc bcm bin timcn nhcm bin tim cn xc nh vtr, cm bin tim cn xc nh khongcch.- Cui bi, gio vin kim tra, nh gi v nhn xt ti tng hc vin trong qutrnh thc hnh thc tp.


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BI 3PHNG PHP O LU LNG

GII THIU

Cm bin o lu lng c sdng nhiu trong cc lnh vc o ccht lng, cht kh, dng trong cc mi trng c tnh cht l ho cao, c hi,

ngoi ra n cn lm nhim vgim st v iu khin tng trong qu trnhsn xut.

MC TIU BI HC

Sau khi hc xong bi ny hc vin c khnng:- nh gi/xc nh c vtr, nhim vv ng dng ca cc bcm bin olu lng.- M tc chc nng, nhim vv cc iu kin lm vic ca cc bcm

bin o lu lng.

- Bit c phm vi ng dng, cch lp t cc bcm bin o lu lng.NI DUNG

* i cng.* Phng php o lu lng da trn nguyn tc chnh lch p sut.* Phng php o lu lng bng tn sdng xoy.* Cc bi thc hnh ng dng cmbin o lu lng.


1. i cng.Cc cm bin o lu lng c sdng o ccht lng v cht khtrong nhiu ng dng gim st v iu khin, vi cht lng, khi lng ring cthcoi l hng snn vic o lu lng nhn chung dthc hin hn. Mt skthut hot ng vi ccht lng v cht kh, mt schhot ng vi dng lucht xc nh. Vic o lu lng thng bt u bng vic o tc dng chy.1.1. Khi nim chung vo lu lng.

Mt trong cc tham squan trng ca qu trnh cng ngh l lu lngcc cht chy qua ng dn, mun nng cao cht lng sn phm v hiu quca

h thng iu khin tng cc qu trnh cng nghcn phi o chnh xc thtch v lu lng cc cht.Mi trng o khc nhau c c trng bng tnh cht l ho v cc yu

cu cng nghdo ta c nhiu phng php o da trn nhng nguyn l khcnhau, slng vt cht c xc nh bng khi lng v thtch ca n tngng vi cc n vo (kg, tn) hay n vo thtch (m3, lt), lu lng vt chtl s lng cht y chy qua tit din ngang ca ng dn trong mt n v thigian.

- Lu lng thtch:- n vo m3/S; m3/gi...vv.- Lu lng khi:

n vo kg/s; kg/gi; tn/gi...vv.


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Cn phi phn bit s khc nhau gia lu lng tc thi v lu lngtrung bnh. Chng hn lu lng thtch: lu lng trung bnh Qtb= V(t1 t2),Lu lng tc thi: QV= dV/dt(V l thtch vt cht o c trong thi gian (t1t2).

i vi cht kh, kt quo khng ph thuc vo iu kin p sut,

nhit , ta quy i viu kin chun (nhit 2000

C, p sut 760 mm thungn).thch ng vi cc nhu cu khc nhau trong cng nghip, ngi ta pht

trin rt nhiu phng php khc nhau o lu lng cht lng, hi nc.1.2.c trng ca lu cht.

Mi lu cht c c trng bi nhng yu tsau:- Khi lng ring.- Hsnht ng lc.- Hsnht ng hc.

* Khi lng ring: l khi lng ca 1 n vthtch lu cht:Trong m l khi lng ca lu cht, V l thtch ca khi lu cht.

(P) kg/m3

1.000

900

800

700300250200150100500

Nc ( trngthi bo ho)

Temperture (0C)

(P) kg/m3

50

40

20

0

300250200150100500

Hi nc bo ho)

Temperture (0C)

10

30

Hnh 3.1: Khi lng ring ca nc v hi nc trngthi bo ho vi cc iu kin nhit khc nhau


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* Tnh nht: l tnh chng li sdch chuyn, n biu hin sc dnh phn thaykhnng lu ng ca lu cht, y l mt tnh cht quan trng ca lu cht vn l nguyn nhn c bn gy ra s tn tht nng lng khi lu cht chuynng, gia chng c schuyn ng tng i, ny sinh ma st to nn sbini mt phn cnng thnh nhit nng v mt i, tnh nht c c trng bi

tnh nht ng lc, hsny phthuc vo tng loi lu cht.C nhiu cch o nht, cch thc n gin thng c cc phngth nghim cc trng i hc sdng chng minh stn ti nht v xcnh gi trl: Cho mt qucu ri trong cht lng di tc dng ca trng lc,o khong cch (d) v thi gian (t) qucu ri, tnh vn tc u.

Hsnht ng lc stnh theo phng trnh sau:u

rgp

9

..2 2=

Trong : ( l hsnht ng lc (Pas)p : S khc nhau gia khi lng ring ca qu cu v cht lng

(kg/m3

). g l gia tc trng trng = 9,81 m/s2r l bn knh qucu (m)u l vn tc ri ca qucu: u = d/t (m/s)

n vca hsnht ng lc: Pas = Ns/m2 = 103 cP (centiPoise) = 10 P(Poise)

nhn mnh mi quan h gia tnh nht v khi lng ring ca lucht ngi ta a ra hsnht ng hc: Trong : v l hsnht ng hc, n vcentistokes (cSt)

( l hsnht ng lc( l khi lng ring ca lu cht (kg/m3)n vhsnht ng hc l cSt (centistokes), St (stokes), m2/s1St = 100 cSt = 1 cm2/s = 10-4m2/s

nht phthuc vo nhit v p sut, nht ca cht lng tng khi nhitgim v khi p sut tng, i vi cht kh th ngc li.

* TrsReynold (Re).Tt ccc yu t ktrn u c nh hng n dng chy ca lu cht

trong ng dn, ngi ta kt hp chng vi nhau to ra 1 i lng duy nht thhin c trng ca lu cht.

TrsReynold:Trong : ( l khi lng ring ca lu cht (kg/m3)

D l ng knh trong ca ng dn lu cht (m)U l vn tc ca lu cht (m/s)( l hsnht ng lc (Pas)

1.3. Hiu chun khi lng ring.Khi lng ring ca cht lng, cht kh trong mi trng o nh hng

n php o lu lng, thc cht khi lng ring thng khng l hng s.Khi lng ring ca cht lng tuthuc vo nhit , mun hiu chun

khi lng ring cht lng ta phi cn o nhit .


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Kh thng l mt hn hp gm nhiu thnh phn, khi lng ring cakh lthuc vo p sut v nhit , hiu chun ta cn o ci lng ny (lychun khi lng ring iu kin 0oC, p sut kh quyn).1.4. Trng thi dng chy.

Nu bi nh hng ca nht v sma st vi thnh ng dn th vntc dng chy snhnhau p mi vtr trn mt ct ngang ca ng dn (hnh v3.2).

Tuy nhin chl trng hp l tng, trong thc tnht nh hngn tc dng chy, cng vi sma st ca ng dn lm gim vn tc ca lucht vtr gn thnh ng (hnh 3.3).

Vi trsReynold nh (Re 2.300), cht chuyn ng thnh lp (chytng). Tt c cc chuyn ng xut hin theo dc trc ca ng dn, di nhhng ca tnh nht v lc ma st vi thnh ng dn, tc lu cht ln nht vtr trung tm ng dn (hnh 3.4).

Khi tc tng v trsReynold vt qu 2.300, dng chy tng dn hnlon vi cng lc cng nhiu cc dng xoy (trng thi qu ) (hnh 3.5). Vi Ret10.000 trln, dng chy hon ton hn lon (trng thi chy ri).

Cc kh (trng thi bo ho) v hu ht cc cht lng thng c vnchuyn bng ng dn trng thi dng chy ri.2. Phng php o lu lng da trn nguyn tc schnh lch p sut.dng cm bin p sut o lu lng , ngi ta o schnh lch p sut (hiup) gia 2 vtr ng c tit din dng chy khc nhau, cc lu lng ko datrn hiu p (differentia pressure flowmeter) c sdng rt phbin, c bit

l dng vi cc cht lng, cc thit bny cng nhhu ht cc lu lng kkhc gm 2 thnh phn cbn.

Dng chy Dng chy

Dng chy Dng chy

Hnh 3.2: Vn tc dng chy(trng hp l tng)

Hnh 3.3: Vn tc dng chy vi nhhng ca tnh nht v lc ma st

Hnh 3. Hnh 3.5


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- Thnh phn 1: L nguyn nhn gy ln s thay i trong nng lngng hc, to nn s thay i p sut trong ng, thnh phn ny phi ph hpvi kch thc ca ng ng, iu kin dng chy, tnh cht ca lu cht.

- Thnh phn 2: o schnh lch p v tn hiu u ra c chuyn ithnh gi trlu lng.

2.1. nh ngha p sut.* p sut l lc tc dng trn mt n vdin tch: o p sut ngi ta sdng mt nguyn tc ging nhau, p sut c

cho tc dng ln mt bmt xc nh, nhthp sut bin thnh lc, vic o psut c a vo lc, tt ccc lc tc dng ln mt mt phng xc nh lthc o p sut.

S

FP=

Trong : P l p sut; S l din tch; F l lc.* n vp sut.Uban quc tcho vic o c vi nh lut chn Pascal (Pa) = N/m2

l n vp sut (ISO 1.000, DIN 1.301). Vic phn chia thang o ca my o psut c dng vi bi sca n vPa.

1 mbar = 102Pa; 1 bar = 105Pa.Nhng n vcdng phbin trc y:

1 mmHg = 1,0000 Torr.1 atm =760 Torr (atm n vp sut kh quyn vt l).1 Torr = 1,333224.102Pa.1 kp/cm2= 0,980665.105Pa.

1 at = 1 kp/cm2 = 0,980665.105 Pa (at n v p sut kh quyn kthut).

1 mm nc = 9,80665 Pa.Ngoi ra cc nc Anh, Mngi ta cn dng cc n vp sut sau:

1 pound-force/square yard (Lb/yd2) = 5,425.10-5at1 pound-force/square foot (Lb/ff2) = 4,883.10-4at1 pound-force/square inch (Lb/in2= psi) = 7,531.10-2at1 ounce/ square foot (oz/ff2) = 3,052. 10-5at

1 ounce/ square inch (oz/in2) = 4,394. 10-3at1 Ton/ square foot (Ton/ff2) = 2,540. 10-3at1 inch of water (trong nc) = 2,40. 10-3at1 inch of mecuri (trong thungn) = 3,455. 10-2at

2.2. Bphn to nn schnh lch p sut.D hin nay c nhiu phng php o lu lng c pht trin,

phng php o lu lng bng ng co vn c ng dng rt rng ri trongcng nghip v cc lnh vc khc, ng co dng to schnh lch p sut (gia

vtr ng cha co v ng co), nn ng co phi dng cc linh kin chc rtbn b, cu trc n gin v khng c cc phn tdi ng chu c nhngiu kin v cng khc nghit trong cng nghip. Phng php o sdng Pitot


54/77



tube cng da trn s chnh lch p sut nhng khng to s co trc tip trndng chy.

* ng co Venturi.- Nguyn tc: Phng php o lu lng bng ng co da trn nh lut

lin tc v phg trnh nng lng ca Bernoulli.

Phng trnh lin tc: Phng trnh Bernoulli: p dng cho trng hp ng co venturi:

222

211 22

uPuP

+=+

Trong : A1 l din tch trc co.A2 l din tch vtr co.u1l vn tc trc vtr co.u2l vn tc vtr co.

p1l p sut trc vtr co.

P2l p sut vtr co.l khi lng ring.h1l cao vtr trc co.h2l cao vtr sau co.

ni ng c din tch b thu nh, vn tc dng chy gia tng, vi phng trnhnn lng ca Bernoulli, nng lng ca dng chy l tng nng lng p suttnh v ng nng (vn tc) l mt hng s.

( )212221 2uuPPP ==

Gii phng trnh trn theo v2 ta c:

( ) ( ) 22

2

1

221

2121

22 .

22u

A

APPuPPu

+=+=

tl hng sdng chy, ta c:.T ta c lu lng tnh theo thtch v khi lng nhsau:

Hnh 3.6

A1 A2A1

u1u1 u2

P1

P2

p


55/77



PkPPAuAQv === ...2

... 21222

PkPPAuAQm === ...2...!

21222 Nhthlu lng tlvi cn sbc 2 ca hiu p khi khi lng ring l

hng s.* Oriffice plateOriffice plate l mt trong cc cch thc n gin nht v kinh tnht

tc ng n dng chy, t c thtnh c lu lng.

Oriffice plate dy khong 1/16 n 1/4 inch, thng c 3 loi Orifficeplate l Concentric (ng tm); Eccentric (lch tm); Segmental (hnh cung)nhhnh v3.7.

Trong 3 loi, loi Concentric (ng tm) c sdng nhiu nht, khi lucht I qua Oriffice plate, dng chy hi t, tc lu cht tng ln mc ti a,ti im ny, p sut l nhnht, khi dng chy phn k, tc lu cht gimtrli mc ban u.

Hai loi Eccentric (lch tm); Segmental (hnh cung) cng c chc nnghon ton ging nhConcentric (ng tm), thit bc lp t ng tm ving dn lu cht (ng dn t nm ngang), vi loi Segmental (hnh cung), vtrhnh cung trn (phn c ct) phthuc vo dng cht lng c thtrnhoc di nhm mc ch ngn chn xc. Loi Eccentric (lch tm) cng c

thit kvi cng mc ch trn.2.3. Bphn o schnh lch p sut.Bphn o schnh lch p sut ny c thit ko p sut da trn

cc nguyn tc:- Chuyn i p sut kiu in dung.- Chuyn i p sut kiu bin p vi sai.- Chuyn i p sut kiu in trp in.- Chuyn i p sut kiu mng sc co gin ...vv.* Cm bin p sut kiu in trp in.Cm bin p sut kiu in tr p in thay i in tr tng ng vi

bin dng trn bn thn n.+ Cm bin bin dng p in trkim loi.

Concentric Eccentric Segmental

Hnh 3.7: Cc dng ng co Oriffice plate


56/77



+ Cm bin bin dng p in trbn dn.- Cc thng scbn:

2.4. Mch ng dng (xem mc 4 bi ny)3. Phng php o lu lng bng tn sdng xoy.3.1. Nguyn tc hot ng.

Phng php o lu lng bng dng xoy da trn hiu ng spht sinhdng xoy khi mt vt cn nm trong lu cht, cc dng xoy xut hin tun tv bdng chy cun i. Hin tng ny c Leonardo da Vinci ghi nhnStrouhal trong nm 1878 cgng gii thch ln u tin, ng nhn thy rngmt si dy nm trong dng chy c sdung ng nhmt dy n, sdao ngny tlthun vi vn tc dng chy v tlnghch vi ng knh si dy.

Theo dor von Karman tm thy nguyn nhn gy ra sdao ng ny: l ssinh ra v bin mt ca cc dng xoy bn cnh vt cn, mt con ngdng xoy hnh thnh pha sau vt cn khi mt vt c t trong mt dng chy.

Cc dng xoy ny ri bvt cn tun tv tri theo dng chy, pha sauvt cn hnh thnh con ng ca dng xoy c t tn l con ng xoyKarman. Cc dng xoy 2 bn ca vt cn c chiu xoy ngc nhau, tn ss

bin mt (v csxut hin) l hiu ng dng o lu lng bng thtch.Lord Rayleigh tm thy s lin h gia kch thc hnh hc vt cn,

vn tc lu cht v v tndsbin mt ca dng xoy f, slin hny c dintvi trsStrouhal:.

Trong l ng knh vt cn; f l tn sdng xoy; v l vn tc dngxoy.

TrsStrouhal l hm ca trsReynold (Reynold: l tlgia lc quntnh v lc nht trong mt lu cht, biu thsma st ca mt dng chy. lkhi lng ring ca lu cht, u l vn tc ca lu cht, D l ng knh bntrongng dn, ( l nht).

Hnh dng ca vt cn phi c cu to sao cho trong mt khong trsReynold kh rng m trsStrouhal vn l hng s. Hnh v3.8 di ay cho taslin hgia trsStrouhal Strouhal v trsReynold vi 2 vt cn khc nhau,vi vt cn hnh lng knh trsS n nh trong sut mt di trsRe kh rng.

10 10 10 10 10


57/77



Vi iu kin hng sStrouhal S khng tuthuc vo trsReynold ta c

thtnh lu lng thtch trn n vthi gian theo cng thc sau:

fAaS

Q ...1

=

Trong A l in tch mt ct ngang ca dng chy.* Nguyn tc tn sdng xoy.Vi sbin mt v xut hin ca dng xoy, vn tc ca dng chy 2 bn ca

vt cn v trn ng dng xoy thay i mt cch cc b. Tn sdao ng cavn tc c tho vi nhng phng php khc nhau. Cc nh sn xut cc lulng ksdng nguyn tc tn sdng xoy dng cc kthut khc nhau ghi nhn tn s. Mt ssdng cc vy c ckh ghi nhn nhng dung ngca dng chy. Mt skhc sdng kthut cm bin p in hoc sng sium cm nhn sthay i ca p sut, ngoi ra cn c mt sphng phpkhc ghi nhn sliu nho sdao ng p sut vi mng sc co ginvv.3.2. Cc u im ni bt v hn ch ca phng php o lu lng vinguyn tc tn sdng xoy.

* Cc u im:- Rt kinh tv c tin cy cao.- Tn sdng xoy khng bnh hng bi sdbn hay hhng nh

ca vt cn, ng biu din ca n tuyn tnh v khng thay i theo thi giansdng.

- Sai sphp o rt b.

- Khong o lu

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