Ktcambien Sv Cq

8/13/2019 Ktcambien Sv Cq

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Kthut cm bin

TS. Nguyn ThLan Hng

Bmn Kthuto v Tin hc Cng nghip


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2

Ti liu tham kho

[1] Cc bcm bin trong kthuto lng viu khin,

Nh XB Khoa hc Kthut (2001), Chbin tp PGS.TS.L Vn Doanh

[2]Cm bin, Nh XB Khoa hc kthut (2000), Phan QucPh, Nguync Chin

[3] Process/Industrial Instruments and Controls Handbook,Mc GRAW-Hill (1999), Gregory K.McMillan; Douglas M.

Considine,


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Ni dung ging dy

Khi nim cm bin v xu hng pht trin

c tnh kthut ca cm bin Cc kthut cm bin cbn dng trong cng nghip Nguyn l v hiung vt l ca cc chuyni scp

ng dng cc chuyni scp cho vico cci

lng vt l- thit bv cm bino o nhit o p sut, o lu lng o ti trng

o mc o tc ng c o gia tc chuynng


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Chng 1. Khi nim v ccc tnh kthut cacm bin

Cm bin l g ?

Bbini t i lng khngin thnhi lngi lngin

i lng khngin l nhngi

lng no?Cci lngin:

in p, dngin, in tchThng smchin

Cn li l cci lng khngin


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Chng 1. Khi nim v ccc tnh kthutca cm bin (2)

S cc cm bin trong cng nghip

KC

CB

C

SC

LTNH

X U, I

RLC

ADC XL4-20mA

X DAC4-20mA

RS-232,485

CB thng minh

CB tng t


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1.1 Phn loi Cm bin

Theo nguyn l hotng Chuyniin tr Chuyniin t Chuyni nhitin Chuyniin tv ion Chuyni hain Chuyni tnhin Chuyni lng t

Theo kch thch: quang, chc, m hc

Theo tnh nng Theo ng dng Theo m hnh thay th: Tch cc v th ng


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i lng Thng s bin i Vt liu lm cm bin

Nhit

Nhit rt thp

in tr sut

Hng s in mi

Kim loi : platine, nickel,ng, cht bn dnThu tinh

Bin dngin tr sut

t thm

Hp kim niken v silic mHp kim st t

V tr in tr sut T tr

T thng ca bc x

quang

in tr sut Bn dn

m in tr sutHng s in mi

Chlorure de lithiumHp kim polymere

Mc Hng s in mi Cch in lng

V d v cm bin th ng


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V d v cm bin tch cc

i lng vt l cn o Hiu ng s dng Tn hiu ra

Lcp sutGia tc

p in in tch

Nhit Nhit in in p

Tc (vn tc) Cm ng in t in p

V tr Hiu ng Hall in p

T thng bc x quangHoa quangPht x quangHiu ng quang p

Hiu ng quang in t

in tchDng inin p

in p


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2.2. cim ca cc phng phpo cci lng khngin

c. Cc loi cm bin hay c s dng trong cngnghip v dn dng

Cm bin o nhit (37,29%*) Cm bin o v tr(27,12%*) Cm bin o di chuyn (16,27%*)

Cm bin o p sut (12,88%*) Cm bin o lu lng (1,36%*) Cm bin o mc (1,2%*) Cm bin o lc (1,2%*) Cm bin o m (0,81%*)

*: Xp theo s lng cc loi cm bin bn c ti Php nm2002


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cim ca cc phng phpo cci lng khngin

d. Cc lnh vc ng dng

Xe hi : (38%*) Sn xut cng nghip: (20%*) in gia dng: (11%*) Vn phng: (9%*)

Y t: (8%*) An ton: (6%*) Mi trng: (4%*) Nng nghip: (4%*)

*: Xp theo s lng cc loi cm bin bn c ti Php nm2002


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S chuyni gia cci lng - cc loi

cm binEncoder

BintrTrt

1

2

incm

3

5

in trlc cng

pin

4

7p t

6

Quangin tr

Nhitin tr

Quangin

11

10

Nhitin

8

9

T(M,)

T(L,)

T(t,)

T(Ls,t)

T(M,t)

T(L,)

T(L, U)

T(C, U)

T(R, U)T (L,U)

T (L,C)

T (M,U)

T (M,R)

T (M,L)

T (t,U)

T (t,R)

T (,U)

T (,R)Quang

Nhit

Di chuyn

kch thc(L)

Khi lnglc (M)

U, I

R

L

C

T ( , L)

indung


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1.3. Bini gia cci lng (in) ca tnhiu- Bini thng nht ha


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Ho hp ti gia cm bin v mch o

Cp ngun cho cm bin th ng Tuyn tnh ho c tnh phi tuyn ca cm bin Tuyn tnh ho tn hiu ra ca mnh o (VD cuWheastone)

Khuych i tn hiu ra ca cm bin Lc nhiu tc ng ln tn hiu ra ca cm bin Khuych i o lng trit tiu hoc lm gim ccnhiu tc ng (in p k sinh v dng in r trn ngtruyn)

A. Cc dng bin i chun ho thng gp


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Vn ca bthng nht ho

Cm binCm bin

Chun ho tnhiu

Signal

Cm binCm binThng nht ho

cm binth ng

Signal Tn hiu thng nht

ho

Thch ng v tr khngtuyn tnh ho

Khuch i

Thng nhtHo cm bin

th ng


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B. V dChuyn i /tn hiu

Cp nhit ngu

Nhit in tr RTD

Cm bin in trlc cng

t chunghoc n p cao

Cc tI yu cu chuynmch xoay chiu hocdng in ln

Cc tn hiu vinhiu tn s cao

Khuch i, tuyn tnh ho

v b u t do

Thng nht ha tn hiu

Ngun nuI, cu hnh 4 dyv 3 dy, tuyn tnh ha

Ngun in p cung cp

cho cu, cu hnh vtuyn tnh ho

Khuch i cch ly(cch ly quang)

Rle in c hoc rlebn dn

Lc thng thp

Thit b DAQ


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Ho hp trkhng

VO = Vi .R2

R1+R2

ViR1 R2 0

Mt chui o c th coi l mtphn p

VO = Vi .R2

R1+R2Vi

R1 R2

Z1


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Ho hp trkhngNgun in tch

khuch i in tch

in tch c a vo mt t in khng i Cr, khi tch lu vo t to ra mt in p trncc ca t in tl vi in tch np vo

Khuch i o lng

Mch vo vi saiMch vo vi sai


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1.4. Thng skthut ca cm bin

Dio, ngng nhy v phn gii kh nng phn ly nhy v Tnh tuyn tnh ca thit b Sai s hay chnh xc c tnh ng Mt s thng s khc nh: cng sut tiu th, tr

khng, kch thc, trng lng ca thit b


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A. nhyPhng trinh c bnY= F(X,a,b,c...)

F/X - nhy vi x (Sensibility)F/a - nhy ca yu t anh hng a hay nhiuF/X = KXt- nhy theo X Xt hay ngi ta cn k hiu l S

Khi K=const -> X,Y l tuyn tnh.K=f(X) -> X, Y l khng tuyn tnh - > sai s phi tuyn.

Vic xc nh K bng thc nghim gi l khc thit b o. Vi mt gi trca X c th c cc gi tr Y khc nhau, hay K khc nhau.

dKXt/KXt(Repeatability)Th hin tnh n nh ca thit b o hay tnh lp lica thit b o .

dKXt/KXt = dS/S=s- Sai s nhy ca thit b o -> nhn tnh.(Hysteresis)


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nhy


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Trhay trca thit b(Hysteresis)


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Tnh lp li


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B. Hsphi tuyn ca thit b nh gi tnh phi tuyn ca thit b o ta xc nh h sphi tuyn ca n.

H s phi tuyn xc nh theo cng thc sau:

. Xmax- l sai lch ln nht

Ta thng dng khu b phi tuyn

Scb.Sb= K

(Nonlinearity Error)

n

maxpt X

XK

=

X

Y

X

Y


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C. Khongo, ngng nhy

v khnng phn ly Khong o (Span/Full Scal/Range): Dx = Xmax

Xmin Ngng nhy, kh nng phn ly (Resolution):Khi gim X m Y cng gim theo, nhng viX X khi

khng th phn bit cY, X c gi lngng nhy ca thit b o.

Kh nng phn ly ca cm bin-Thit b tng t

-Thit b s:

X

xX

DR

=

ng

XX N

DR =

=


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D. c tnh ng ca thit b (1)

Hm truyn c bn : Y(p)=K(p).X(p)

c tnh ng:+ c tnh qu + c tnh tn+ c tnh xung

Khi i lng X bin thin theo thi gian ta s c quan h (t)=St[X(t)]Quan h c biu din bng mt phng trnh vi phn. Phng trnh

vi phn y c vit di dng ton t.(p)=S(p).X(p)

S(p)- Gi l nhy ca thit b o trong qu trnh o i lng ng

X4

X3

X2

X1

X


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c tnh ng ca cm bin (2)

Khi i lng X bin thin theo thi gian ta s c quan h

(t)=St[X(t)]

Quan h c biu din bng mt phng trnh vi phn. Phng trnh vi phn yc vit di dng ton t.

(p)=S(p).X(p)

S(p)- Gi l nhy ca thit b o trong qu trnh o i lng ng


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c tnh ng ca cm bin (2)Nu i lng vo c dng xung hp

X(t)= Xt(t-).

S(p)- th hin di dng hm h(t) c trng cho c tnh xung cathit b o.c tnh xung thit b o c th c giao ng hoc khng tu theoS(p)

Nu i lng c dng xung bc nhyXt=Xt.1(t-)

S(p) - th hin di dng h(t) theo quan h S(p) c trng cho c tnh qu ca thit b o v tu theo

phng trnh c tnh ca n, n c th giao ng hoc khng giaong .

t

(t)

Xt


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Mt sdngpng bc 1


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Chng II. Cc cm bino nhit

Cm bin nhitin tr

Cm bin cp nhit ngu

Cm bin da trn lp chuyn tip bn dn

Cm bin da trn bc xquang hc


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2.1. Nhit k nhit n trNhit in tr l l in tr thay i theo s i nhit ca n: RT= f(t

0),o RT c th suy ra nhit .

Nhit in tr c chia ra thnh:Nhit in tr kim loi v nhit in tr bn dn.

in tr kim loi ( RTD) theo nhit RT=R0(1+ t + t2 + t3)

Vi Pt: = 3.940. 10-3/0C

= -5.8 10-7/ oC2 ; 0 trong khong 0-6000C; = -4 10-12/0C3

vi ng t -500C n 2000C: = 4.27 10-3/0C

vtrong phm vi s dng v chnh xc khng cao th coi nh khng ngk v quan h RTv t coi nh tuyn tnh.


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A, Nhit in tr kim loi

in tr chun ho R0=100 ti 00C


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Hsnhitca mt skim loiCu Ni Pt W

Tf

, 0C 1083 1453 1769 3380

C, J0C1kg-1 400 450 135 125

t, W0C-1m-1 400 90 73 120

l, 0C-1 16,7.10-6 12,8.10-6 8,9.10-6 6.10-6

, m 1,72.10-8 10.10-8 10,6.10-8 5,52.10-8


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Nhit in tr kim loi o nhng nhit t -500C -6000C ngi ta thng dng nhit in tr

PT-100 (Platin 100 00C

Cu -100 (ng 100 00C)

Ni-100 (Ni 100 00C)

Quan h gia nhit v in tr ca Pt100nhit, 0C

-200 -190 -180 -170 -160 -150 -140 -130 -120 -100 nhit, 0C

17.28 21.65 25.98 39.29 34.56 38.80 43.02 47.21 51.38 55.52

0C -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0C

59.65 63.75 67.84 71.91 75.96 80.00 84.03 88.04 92.04 96.03

0C 0 10 20 30 40 50 60 70 80 90 0C

100.00

103.96

107.91

108.5 115.78

119.70

123.10

127.49

131.37

135.24


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B, Nhit in tr bn dn (NTC-PTC)

Nhit in tr bn dn

A v u khng n nh. Ta cng c th tnh

= (-2.5% +-4%)/ 0C

/TTR Ae

=

Thng thngc chto tcc oxit bn dna tinhth: MgO, MgAl2O4, Mn2O3, Fe3O4, Co2O3, NiO, ZntiO4

Cc bt oxitc trn theo mt tlthch hp, sauc nn vinh

dng v thiu ktnhit10000C


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Nhit in tr bn dn

Mt s nhit n tr bn dn

a) KMT v MMT b) MKMT c) Quan h gia RT(0t)

1.Nhit in tr ng 2. Nhit in tr bn dn


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Nhit in tr bn dn


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C, Cu to

Cu to bn ngoi Cu to bn trong

u bt

Nt yu dybn trong

ng cchnhit

Mi hn

Phn tin tr

ng bo v

mi hn

tm chn

Gi


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D, Mcho- phng php ngun dng

1

2

1

2 .R

RRI

R

RUU

tRtR

==


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Mch to ngun dng

Iref = Vref/R1.


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Phng php sdng ngun p

4

2 3 4

tR

t

R RU ER R R R

= + +

B in tr dy


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S b bin i nhit in tr

Ngun dng 2.5mA to ra mt s bin thin inp trn in tr l 100mV/1000C.

RT = R0 (1+t); = 0.385% / 0C Nu RTc cung cp bng ngun dng 2.58 mAth khi nhit bin thin 1000CU = RT . I. = 0.385 x100

0Cx 2.58 =100mV in p ri trn RTc a vo khuch i b

in p 00C v bin i p thnh dng (4-20mA) a vo h thng thu thp s o.

1- Nhit in tr 2- Modul vo3- Dng cung cp (hng)

4- in p mt chiu khuch i5- Modul ra 6- iu chnh in p

Mch chun ho

V d


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2.2. Cp nhit nguNguyn l : Hiu ng Seebeck

Da trn hin tng nhit in. Nu haidy dn khc nhau (hnh v) ni vi nhauti hai im v mt trong hai im ct nng th trong mch s xut hin mtdng in gy bi sc in ng gi l scin ng nhit in, c cho bi cng

thc

ET = KT(tn - ttd)

Trong : KT- h s hiu ng nhit in

tn - nhit u nng

ttd - nhit u t do a

b

t2

t1t1


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V dcu to bn trong ca cm bin


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Cc kiu cp nhit nguK hiu K hiu hinhthc

Vt liu cu thnh Dc im cn lu tm

B - Patin Rhodium 30-Platin.Rhomdium 6

Dy dng nh l hp kim 70%Pt, 30% Rh.Dy m l hp kim 94%Pt, 6% Rh. Loi B

bn hn loi R, giai o nhit n18000C, con cc c tnh khc th nh loiR

R - PtRh 13 - Pt Dy dng l loi hp kim 87% Pt, 13%Rh. Dy m l Pt nguyn cht. Cp ny rtchnh xc, bn vi nhit v n nh. Khngnn dng nhng mi trng c hi kim

loiS - PtRh10-Pt Dy dng l hp kim 90% Pt, 10%Rh.

Dy m l Pt nguyn cht. Cc c tnhkhc nh loi R

K CA Cromel-Alumel Dy dng l hp kim gm ch yu l NivCr. Dy m l hp kim ch yu l Ni. Dng

rng ri trong Cng nghip, bn vi mitrng oxy ho. Khng c dng mitrng c CO, SO2 hay kh S c H

E CRC Cromel- Constantan Dy dng n ivi loi K. Dy m nh loi J. C sc n ng nhit in cao vthng dng mi trng acid


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Cc kiu cp nhit ngu


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Gii hn nhit v cc ng bo v

Dng ca cp nhit

Dng knh ca dy Gii hn nhit lm vic ng bao v O.D x I.D

k hiu ngknh bnngoi

gii hnchun

gii hn trn ng bao v bngim loi ( mm)

ng bao vkhng bng kimloi ( mm)

B Pt Rh 30%/ PtRh 6%

L 0.5 15000C 17000c _ 15 x11

R Pt Rh 13%- Pt L 0.5 14000C 16000C _ 15 x 11

S Pt Rh 10%-Pt L 0.5 14000C 16000C _ 15 x 11

K (Chromel_Alumel) D 3.2 10000C 12000C 21.7 x 16.1 17 x 13

C 2.3 9000C 11000C 21.7 x 16.1 17 x 13

B 1.6 8600C 10500C 15 x 11 15 x 11

A 1.0 7500C 9500C 12 x 9 15 x11

H 0.65 6500C 8500C 10 x7 10 x 6


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C, Phng phpo nhitbng cp nhit ngu

Thng nht ho bng mchin p tch cc

Bu tdo

Bin trdy ni

++=

2

31

4

5 1R

RR

R

REUra


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B nhit u t o

Mch b nhit u t do c thc hin bng 1 mch cu 4nhnh trn y c mt nhit in tr, hot ng ca n nh sau: 00C4 nhnh ca cu cn bng in p ng cho cu U=0, khi

nhit trn u hp ni dy tc l nhit u t do thay i:

tdCC

T

TCC tU

R

RUU =

=

44Ta li c ET= KT(tnng- ttdo) = KT tnng -KTtt do

== TCCdot

CCdotT

KUt

UtK

4

4

b nh hng ca nhit u t do ta c


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B cp nhit ngu ca SIEMENS

IA v UH - Tn hiu ra mt chiu v ngun cung cp.

1- Cp nhit ngu 2- u vo ca mchcu

3- u lnh ca cp nhit 4- ngun dng hng5- in p mt chiu khuch i 6- Modul ra

7- iu chnh in p

V d

V d


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IA v UH - Tn hiu ra mt chiu v ngun cung cp.

1- Cp nhit ngu 2- u vo ca mchcu

3- u lnh ca cp nhit 4- ngun dng hng5- in p mt chiu khuch i 6- Modul ra

7- iu chnh in p

V d


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2.3. o nhitbngit v transitor Da trn lp chuyn tip bn dn

Quan hca dngn theo nhit

n p ra cait c thvit nhsau:

= 10 kT

qv

expII

LogC.q

kTmLogT.q

kTLogIq

kTvv +=

Thng thngnhy -2,3 mV/0C vi

dngin khong 1uA


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d 335


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V dvLM335

Nhit i t b d


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Nhit in tr bn dn

Ngun p : LM35

Mch o vi nhit in tr bn dn

Nhit i t b d


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Nhit in tr bn dn

Gi s 2 Transistor ging nhau, c cng nhit

=

= /17,86ln

2

121 V

q

kavec

I

IT

q

kVV

C

CBB

SRr

rVIRIR BCC +== 22211

+

+=

2

11 ln1

R

R

q

kTV

r

RS BT : S = fct(T) c ci thin

Mch chun ho

nhy nhitca diode vtrans. mc theokiu diode:

S=dV/dT c-25mV/0C


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M h


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Mcho

B bi i th i h hit d


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B bin i thng minh o nhit

Siemens

V d


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u voCc du vo (2)Hp knh MUX (3)Khuch i (4)Ngun dng dng o nhit Nhit in tr (1)Mch khc (9)Vi iu khin(10)B bin i tng t s (5)Lc thng thp l bng kt qu (6)Khi tuyn tnh ho phc v cho cc c tnh phi tuyn ca cm bin (7)B iu ch rng xung u ra (8)


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u raB cch ly v in (13)B ra vi tn hiu xung iu ch rng (17) v b bin i s tng tu ra kim tra theo di tn hiu ra (18)Cm bin ph, rle (14)

Kim tra v hin thGiao din ni tip (11) hi p v t cc thng sNt n kim tra cho nhit in tr hay khc cc cm bin in

tru bo (lm vic v c s c)

Ngun cung cp 24V mt chiu ni vo li in

2 4 Ho quang k


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2.4. Ho quang k

o nhit khng tip xc di nhit cao >16000C

Mt ph nng lng pht x theo bc sng cavt en l tng khi b t nng

- bc sng; T - nhit tuyt i ;C1= 37,03 .10-17 Jm2/s0C ; C2= 1,432. 10-2 m0C

3 phng php: Ho quang k bc x Ho quang k cng sng Ho quang k mu sc:

1

1/

51 2

= TC

eCE


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Phn b ph ca cc vt


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Phn bphca cc vt

2.4.1. Ho quang k bc x


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a) b)

- a) C u to ca ho quang k bc x

b) Cp nhit hnh r qut cromel-copel

1. Thn dng c 2- vt chnh vt knh

3- Vt knh 4- Rnh t cp nhit thu

5- Thn g cp nhit 6- Toa nhit u t do 7- u ra ca b thu 8- Gi vt knh

9- vt knh 10- lc nh sng

11- u dy cp ra 12 - ng dn cp ra

13- Tai g thit b 14- chnh tiu im

2.4.2. o nhit bng phng php quang


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hc: hng ngoi IR Nng lng bc x:

ET=.Ebx=T4

Ngi ta dng it hng ngoi thu nng lng ny Ngi ta t mt it lazer pht ra mt trm tia hp song

song vi vi trc ca ho quang k. Vng trn sng caLazer chnh vo vng ta o nhit


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2.4.3. Ha quang kmu sc


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c tnh phca

vtt nng(nhitthpitng pht ra nhsng, nhit

cao pht ra nhsng xanhntm)

Ha quang kmu sc


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q g

V d. Ha quang kmu sc


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q g A-i tngo nhit; 1- vt knh; 2-a lc xanh; 3- mt ng b; 4- tbo quangin; 5- khuchi; 6- T ng chnh hskhuchi; 7- lc 8- khoi ni; 9- logomet chiaxanh

a) c tnh ph c vt t nng

b) s khi ca ho quang k mu sc

b)

a)

2.4.3. Ha quang kcngsng


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q g g g

1 2

345

a) b) c)

1. n si t2. Vt knh, chnh vt knh3. ng trt v vt knh

4. Chit p chnh dng in tn

5. Thu knh

a) Nhit dy n bng nhit itng

b) Nhit dy n cao hn nhit itng

c) Nhit dy n thp hn nhit i tng

Nguyn l ca ha quang kcngsng


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Chunthit b


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V d


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Camera hng ngoi


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V d


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Chng 3. Cm bino lc, bin dng, psut, hiu p sut v lu tc

3.1. Cc loi cm bin c s dng o


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lc Cm bin in tr lc cng

Cm bin p in

Cm bin in cm Cm bin p t

A, Cm bin n tr lc cng


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Nguyn l lm vic : hiu ng tenzo (piezoresistive/ straingauge),

Cm bin loi ny c 3 thng s chnh Kch thc ca Gi tr in tr Rcb

Dng n ti a cho php a) in tr lccng l mng;b) in tr lc

cng kiu mngmng

A, Cm bin n tr lc cng (2)


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Ta c

hay R = l

Mt khc ta c

R= + l -STrong c hc ta cS =-2KPl ; Kp h s Poisson

R = l (1+ 2Kp + m) = Kl

nhy ca chuyn i: K = R/l = 1+ 2Kp + m

)l

l(f

R

R =

S

S

l

l

R

R

+

=


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Bng gi ca cm bin


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B. Cm bin p in


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Da trn hiu ng p in. Vt liu dng ch to cc chuyn i p in thngl tinh th thch anh (SiO2), titanatbari (BaTiO3), mui

Xenht, tuamalin ...,, ngay nay ngi ta cn tm ra cc vtliu polymer nh PZT,PVDF, ..

Lc FX gy ra hiu ng p in dc vi in tch q=d1Fx

Nu tc ng mt lc theotrc Y, gy ra hiu ng p inngang vi in tch q, ph thucvo kch thc hnh hc ca

chuyn i: q= -d1(y/x)Fy.d1 - hng s p in ( gi l mdun p

in)y, x - kch thc ca chuyn i theo

trc X v Y

V d: hiung pin trn mt tinh ththch anh


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Mch tngng

T in !!!

B. Cm bin p in (2)


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Tn sdaong ring ca tinh thpin


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l- chiu dy ca tm tinh th

C- hsca tinh th

Nhvy tn sdaong thayi trong khong

V d


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Mt sthuc tnh ca vt liu pin


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C. Cm bin p t


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Di tc dng ca bin

dng n hi c hc, tthm v cc tnh chtkhc ca vt liu st tthay i.

in cm ca

chuyn i p t

l

S..W

R

WL

22 ==

W- s vng cun dyR- t tr ca mch tS, l - din tch v chiu di ca mch t t thm ca li thp

D. Cm bin in cm


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Nu b qua in tr thun ca cun dy v t tr ca lithp

==

S..W

R

WL 0

22

E. Cm bin in cm


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Nh vy c tuyn ca chuyn i in cm khi d di kheh khng kh thay i Z=f() thng l phi tuyn v phthuc vo tn s ca ngun kch thch. Tn s dng kch

thch cng ln th nhy cng cao.

+

= d

LdS

S

LdL

2

0

0

0'

1

1

/

Z/ZS

+

=

=

E. Cm bin h cm


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T thng tc thi

i- gi tr dng tc thi trongcun dy kch thch W1.

Sc in ng ca cun dyo W2:

==

SiW

R

iW 011t

dt

diSW.W

dt

d

We 012t

2

=

=

3.2. o bin dng


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Bin dng

di l

ll

=

Mi cm bin dng ochiu di hay di chuyn

u c th dng o bindng

o bin dng (tip)


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Chn v tr o bin dng v d kin gi tr bin dng tini o.

Vic chn v tr o bin dng da trn s phn tch v lcphn b trn cc chi tit.

Dn cm bin vo chi tit : Nguyn tc dn cm bin l

cm bin bm cht vo chi tit cho bin dng ca chi tittruyn vo cm bin.

S dng mch cu v khuch i dng o bin dng.

Mt scch dn cm bin


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in p ra ca ng cho cu ca

V d o bin dng


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R3U

UCC

R2 R

R

CB

CB

in p ra ca ng cho cu cacu 2 nhnh hot ng c tnh:

kcb l nhy ca cm bin ( nu cmbin l dy mnh hay l mng kcb=1.8-2.2 cn cm bin bn dn kcb c th

ln ti 200)o U c th suy ral

lcbCC

cb

cbCC kU

R

RUU

22

=

=

U ch c gi tr c mV vvy cn phi khuch itrc khi vo b t ghi hayb thu thp s liu

V dmy kim tra bin dng


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3.3. o lc v trng lng


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Hin nay cc lc k da trn nguyn tc sau:F : Lc bin thnh bin dng

F : Lc bin thnh di chuyn

Lc k kiu b: Fxll= F

klk

ll cch tay n bn phi lc o

lk tay n bn pha lc b

Cn bng cch tayn


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A, Lc k kiu bin dng ( Load Cell)


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Trong loi lc k ny lc tc dng Fgy ra ng sut v bin dng, sau bin dng c bin thnh in p

hoc tn sCm binngang

Cm bin

dc

V d


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Siemens ch to loadcell SiwarexK vi cc thng s sau

Ti trng 2.8 6 13 28 60 130 280 tn

Sai s 0.2% 0.1%

H s nhit 0.050%/ 0C.

nhy 1.5mV/V

in tr ra 245 0.2

in tr cch in >20M

V d


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Lc k kiu bin dng

Bi d hF


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Bin dng c tnh

F - lc tc ng ln loadcell

S- tit din phn t n hi

E - modul n hi thp lm loadcell

Cm bin in tr lc cng c nui cy trn phn t n hi. N gm 4 ntr, 2in tr dc l in tr tc dng, 2 in tr ngang l in tr b nhit . 4in tr ny c ni thnh cu hai nhnh hot ng. in p cho cu:

UCC - in p cung cp cho cu

- bin thin in tr do bin dng ca phn t n hi

l - bin dng tnh theo cng thc trnk - nhy ca cm bin in tr lc cng.

Khi ch to xong nh ch to cho ta nhy ca load cell l (mV/V)

SEl =

lCCCC kU

RRUU =

=

22

R

R

Lc k kiu bin dng xuyn


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Fng

d

a) b) c)

a) bin dng ngang v dc ca dm hnh xuyn. b) cu to bn ngoi ca cm bin

sirieR ca Siemens. c) cu to v kch thc ca cm bin


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Mounn hi ca mt svt liu nhsau


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Chuyni kt cu


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n hi

Chuyni kt cu (tip)


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Bi tp

Mt cm bin tng t (4-20mA) on trng lng c


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Mt cm bin tng t(4 20mA) on trng lng cnhy cu l 1,5mV/V. Trng lng ca vt l 0-50kg.Tnhin p ca cu khi c mt khi lng 25kg bitphn gii l 500. Tnh dngin ca cm bin.

B, Lc k kiu di chuyn

Mt phn t hay mt dm n hi lc chu tc dng


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Mt phn t hay mt dm n hi, lc chu tc dngca mt lc, s c bin dng v to ra di chuyn (kt

cu cng xn)

h

hF

la)

F

lb)

a) Dm cng xn tit din ub) Dm dng cng xn ng sut u

EJ

Fl

2

1 3

=

12

bh

J

3

=

B, Lc k kiu di chuyn (2)

Fr3


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Lc k dm cngxn kp

Lc k dm ko

Lc k nn hnhxuyn

Lc k ko hai udng bin tr

EJ

Fr149.0v =

Cm bin hcm

C cu n hi bin lc thnh di


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chuyn

Cm bin c gn cun dy

phn tnh ln im c nh ngoidm, li thp di chuyn c gnvo dm v c th chuyn ngtrong cun dy phn tnh. Bng

s cm bin h cm vi sai , tac

M- bin thin ca h cm lcli thp di chuyn

- tn s ca ngun cung cp

Ik - dng kch t s cp

M=f(), nh vy U=g().Quan h ny khng tuyn tnhdo phi b sai s phi tuyn.

2

IMMI)MM(U;

2

EEU k0k021

+=

=

V dvlpt hthng cn


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3.3. o p sut

SFP=p sut:

F l d l b d


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F- lc tc dng ln b mt tc dngS- Din tch thnh ca mt tc dng

p sut tuyt i p sut tng i n v o

M thng dng n v psi

A. Bng chuyni gia ccn v


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Mt sloi hnh chuyni p sut


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Mt sloi hnh chuyni p sut (2)


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B. Cc loi cm bino p sut

Cm bin sdng nguyn l ca t in (cm binind ) i l h h kh kh 107


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dung): sai sln, nhy thp, khongo khong 107Pa

Mng do

C. o p sut

Ap sut c truyn ln mt mng o,l t bi d t t


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d2R

P

t

Bin dng di tcdng ca P

249.0 Ed

PR

=

l mt mng bin dng trn y c mtcu o bng 4 in tr lc cng bn

dn. Trn mng bin dng ny bindng ( tm) c tnh:

ng sut bin

2

2

75.0 d

PR

b =

Di chuyn to nn tm mng3

4

17.0Ed

PR=

?

D. Mcho


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Bin dng mng

pe- p sut, bin u vo


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IA, UH - tn hiu vo v ngun cung cp

1 -ng dn kt ni

2 -mng chn

3 -cht lng truyn p sut

4 -cm bin n tr lc cng mng silic5 -khuch i o lng

6 -chuyn i p tn

7 -vi iu khin

8 -chuyn i s tng t

9 -hin th tng t ( la chn)

V d: p sut MPX (s dng cm bin Piezo)


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Cu to ca cm bin


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c tuyn ca cm bin loi ny


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3.5. o hiu p sut

2 - 60 mbar loi C8.3 - 250 mbar loi D20 600 b l i E


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1 - u nhn p sut P1P2; 2 - thn ca b bin i

3- Cht lng truyn p sut 4 - mng mng5 - vng O; 6 - gia ca mng

7 - cm bin in tr lc cng silic

8 - khuch i o lng

9 - chuyn i p tn; 10 - vi x l

11 - chuyn i s tng t; 12 - LCD

13 - ch th tng t

20 - 600 mbar loi E53 -1600 mbar loi F

160 - 5000 mbar loi G


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Cng thc Bernoulli


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Mt skiu lchn


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Mn chn


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q 0 1 3 5 8 10 20 30 40 50 60 70 80 90 100%

p

0 0.01

0.09 0.25

0.64

1 4 9 16 25 36 49 64 81 100%

B. Lu tc k kiu cm ng


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Cht lng c chuyn trong mt ng cch in (Teflon) 2 in cc t vunggc vi t trng tc ng, t i tm qua ng dn. Quan h gia sc inng cm ng v lu tc cho bi e = BdV

e- sc in ng cm ng (V)

B - t cm ng ca t trng xuyn qua cht lng (Tesla)d- ng knh trong ca ng (m)

V- tc trung bnh ca cht lng (m/s)


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cim ca phng php

Di kch thc rng, c thdng o dng lng hng

chnh xc c th t ti 0,5%


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Khngnh hng bi sthayi canht v ttrngcht lng

Ch oc cht lng cdnin cao 5S/cm (trng hpc bit 0,1 S/cm). C th oc cht trn

phc tp Phim bo cc lp tch tkhng bm vo bn cc

C. Lu tc k kiu siu m


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C. Lu tc k kiu siu m

Ft SA ThuSA

Cp in

thnhng

tinh th pin


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V

a) Hiu ng Doppler trong o lu tc bng siu m.

b) nguyn l my o lu tc bng siu m

Nu b pht siu m v b phn thu t cch nhau 1 khong D, ta c thi giantruyn ca sng siu m t u pht n u thu:

Thun chiu Ngc chiu

v ta c

VC

D

T +=1 VC

DT

=

2

)(2

21121

21

FFD

vD

v

TT ==

Vn tc ca m thanh trong cc mi trng khcnhau


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Mt sla chn tn ssiu m


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Mt sla chn tn ssiu m

ng dng Tn slm vic (kHz)

Trong khng kh 50-60


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Trong y t Thng sdng di dng xung

Nguyn l truyn sng siu m


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Nguyn tc truyn sng m


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Nguyn tc pht sng siu m

Da trn tn scng hng ca lp tinh th


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Kch thch cng hng bng mtin p


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D. Lu tc kiu cnh qut


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o tc quay ca cch qut c th suy ra v.

Tn hiu ra


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E. o lu lng bng phng php nhit dn

C thphn tch thnh 6 dngo nhsau:


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Dng dy sit v phimt

Phng trnhin trca dy dn nhsau


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Trong : R-in trca dy dnnhitT

Rr- in trca dy dnnhitTrhsnhit

Thng dy dn kim loi l Pt; volfram, Pt-Iridi Da trn cng sut ta nhit (chnh lch nhit) m suy

ra lu lng ca dng chy

Dng dy sit v phimt (tip)

Btr trn knh dn


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Cc dnguo nhit


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Mcho cbn (1)


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Mcho cbn (2)


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Phng phpo thng qua cng sut ta nhit

Phng php nyo thng qua phn bnhit xung quanhut nng


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Phng phpo thng qua thi gian truyn nhit


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Chng 4. Thit b o mc

Bng la chn cm bin theo mc


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Tip


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4.1. o mc bng phng php phao ni

R

puli

sensor quang

Khi qu nng ri xung puli quay v gc quay binthnh s xung

x - gc quay n

=2

0


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Hch

hx

hmc

NX - s xung m c

0 - gc ca mt lng t gc quay

n- s xung tng ng vi 1 vng quay ca

encoder.

Ngi ta b tr nh sau: Khi qu nng i qua mtim chun, mt t bo quang in khi ng b m.Khi qu nng tip xc vi mt nc mt b phn t

ng (rle ti hn) ng mch in. Ta c

hx = Hch - hmc = (NX/n)2R

Mc nc : hmc = Hchun - hx

Cu hnh ca thit b o


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Bin trtrt


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V dPhng php kiu phao


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4.2. Phng php mc p sut

t d i t t


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p sut di y ca mt ct ncc tnh

P = h.

P- p sut y ct nc

- trng lng ring ca cht lng

h- chiu cao ct nc hay mcnc

V d:

Tnh tan p sut ca ct nc cao 5m ? Trng lng ring ca nc 9800N/m3

p sut ca ct nc

9800 5 49 kN/ 2 49kP


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9800 x 5m = 49 kN/m2 = 49kPa


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4.3. Phng php n dung o mc

in dung ca mt t phng c tnh

C- in dung ca t in

- hng s n mi ca cht cch in gia hai bn cc

d - khong cch cc in cc

d

SC

=


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d khong cch cc in cc

Khi mc du 0 tc l trong thng khng c du, ta c

C0 - in dung ca t khi in mi l khng kh

h - chiu cao bn cc

b - chiu rng bn cc

d - khong cch cc bn cc

Khi y du

Khi du mc hx ta chia c thnh hai phn

o Cx c th suy ra h. Trong cm bin ny C0, CX u nh (c pF) vth nn mch o thng dng tn s cao.

0 0

0

( )H h bC d

=

d

hbC dd

=

0 0( )dx h b b H h hCd d

= +

V d i vi nc


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Hng s in mi


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4.4. Dng siu m o mc

Ni dung phng php nh sau: trn nh xil tmt ngun pht siu m mnh. Ngun pht pht ralung siu m theo chiu xung y xil. Khi lung

siu m gp mt cht lng (hot ht) n phn x ln vn u thu thi gian t lc pht n lc thu


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gp g ( ) p n u thu, thi gian t lc pht n lc thu

TX - thi gian t lc pht n lc thu siu m

d- khong cch t nh xil n mt cht lng.

C - tc truyn siu m trong khng kh (vo

khong 300m/s).

2X

dT

C

=

Mcho

To daong


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oin dung bng phng phpm xung


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Mt sm hnh cng tc mc


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M hnh hthngng ngt mc


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Chng 5 . Phng phpo thng schuynng v kch thc hnh hc


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ng v kch thc hnh hc

Cc thng s chuyn ng

Di chuyn hay khong di A

Tc chuyn ng dt

dAv=


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Gia tc chuyn ng

i vi chi tit giao ng hnh sin th tc giaong

Gia tc

2

2

dt

Ad

dt

dv==

tcosAdt

)tsinA(dv m

mi =

=

tsinAdt

dv 2mt ==

5.1. o di chuyn

Di chuyn thng bng bin trtrt

Sdng cm binin cm, hcm.

Sdng cm binin dung


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A. Cc phpo di chuyn

V dnh in cm- hcm


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o di chuyn bngin dung


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in dung

5.2. o khong cch

Thng thng y sdng sng m,laze, hay rada, nhsng

Phng php pht tia laze/rada vi khong cch xa- thng

qua thi gian truyn sngT h l h h


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Tnh gc lch pha ca sng

Phng php quang hc

Phng php thng qua vn tc quay

A. Phng php thi gian truyn (TOF)

Xcnh thi gian truyn sng: Pht v thu sng sau khiphn x


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Phng php ny dng nhiu nht l sng siu m

C th o ti 35ft, gc nghin l 120

B. Phng php thi gian truyn (TOF)

TOF tnh theo binphn xln nht


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C. Di chuyn theo gc lch pha

Chsdng khi khong cch nhhn mt bc sng


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S ca thit b


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V d


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V dvloin Laser

Kh Helium-Neon


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5.3. o vn tc

A. Phng phpin cm

S dng my pht tc: mt chiu v xoay chiu

Sc in ng cm ng: E= KWn

tsinmaxt =

Sc in ng cm ng dtde t= tcosEtcose mmax ==


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B. o di chuyn kiu a quang


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V d: Encorder


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TX KT X CT

K

- PhotoitTX - To xung

KT- Kho in tX- m xungCT- Ch thk - iu khin

Tng quan vphng phpo


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Chiu quay


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C. Cm bin quang

Photo diot (tbo quangin)

Quang tr(quangin tr)


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Tbo quangin


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I= f(). I: dng quangin pht ra tpht dit.

: Quang thng tbo quangin.

Mch tng dng ca photodiot (a) v ctuyn Vn-Ampe (B)


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Mcho thng thng


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Quangin tr


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Cng nh photo diot quangin trlin trthayitheo quang thng nh sng chiu ln quang trR:

R= f().

Vt liu chto cm bin

Cm bin quang thng c ch to bng cc bn dn atinh th ng nht hoc n tinh th, bn dn ring hocbn dn pha tp, th d:- a tinh th: CdS, CdSe, CdTe

PbS, PbSe, PbTe- n tinh th: Ge, Si tinh khit hoc pha tp Au,Cu,Sb,In

SbIn,AsIn, Pin, CdHgTe


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Mcho- Sdng chuyni dng thnh p


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D. Cm bin Hall o di chuyn

Di chuyn gc


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Di chuyn thng

Hiung Hall

Scinng Hall c tnh

Cng in trng H


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Trong : N s in ttdo; Cngnh sng c

Mch tngng ca cm bin Hall


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V d: Mt s c tnh ca cm bin Hall


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Mq=KI.B.IC

R

BK

R

E

I 2cu

c

== = R

BKKM

2

21q

D. Phng php cmng


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Tc k mu cm bin

1- a nhm; 2- kim ch; 4- l xophn khng

=K. hay =Kn.

V dv


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5.4. Phng phpo gia tc

Cm bin pin Cm binin dung


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B. Gia tc k kiu p in

in tch sinh ra trong chuyn i p in q=d1F

q gy ra in p trn in cc ca chuyn i p in

q=CU =C

MdU 1


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Gia tc k kiu p in

1- Thn cm bin; 2- Renbt vo i tng; 3-

Chuyn i p in ; 4-Khi qun tnh; 5- u dyra; 6- cp ng trc


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C. o gia tc kiu in dung


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5.6.o mmen xon- cng sut

Cng thc tnh cng sut ca mt vt chuynng N=M.

Trong: M- mmen xon (N.m); - vn tc gc


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Ginbtr cc thit b c dng ommen v cng sut

Phng phpo gc lch ca 2 cun dy cmng


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5.7. Cc loi cm bin tim cn

Ttnh Cmng

Siu m

Vi sng Quang

in dung


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in dung

Ktcambien Sv Cq

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Transcript of Ktcambien Sv Cq