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Bi ging

K Thut Cm Bin (sensors)

1

Hoang Si Hong

----2011----

Faculty of Electrical Eng., Hanoi Univ. of Science and Technology (HUST),

Hanoi, VietNam

Hoang Si Hong-HUST

2

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Ngun tham kho

Note: Bi ging mn hc ny c tham kho, trch dn v lc dch t cc ngun sau:

Sch

- K thut o lng cc i lng in tp 1, 2- Phm Thng Hn, Nguyn Trng Qu.

- Cc b cm bin trong o lng-L Vn Doanh

- Cc b cm bin-Nguyn Tng Ph

- o lng in v cc b cm bin: Ng.V.Ho v Hong S Hng- Sensor technology handbook (edited by JON WILSON)

- Elements of Electronic Instrumentation and Measurement (Prentice-Hall Company)

- Sch gii thch n v o lng hp php ca Vit Nam

Bi ging v website:

- Bi ging k thut cm bin-Hong S Hng.(2005)

- Bi ging Cm bin v k thut o:P.T.N.Yn, Ng.T.L.Hng (2010)

- Bi ging MEMs ITIMS BKHN

- Mt s bi ging v cm bin v o lng t cc trng i hc KT khc Vit Nam

- Website: sciendirect/sensors and actuators A and B

Hoang Si Hong-HUST 2

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Ni dung mn hc v mc ch

Ni dungChapter 1: Khi nim chung v Cm bin (2b) Chapter 2: Cm bin in tr (2b) Chng 3: Cm bin nhit in (2b) Chng 4: Cm bin quang (2b)Chng 5: Cm bin tnh in (2b) Chng 6: Cm bin Hall v ho in Chng 6: Cm bin v PLC(1b)

Mc ch: nm c cu to, nguyn l hot ng v ng dng cacc loi cm bin thng dng trong cng nghip v i sng. Nmc xu th pht trin chung ca cng ngh cm bin trn th gii.

Hoang Si Hong-HUST 3

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c tnh ng ca cm bin

Hoang Si Hong-HUST 4

- Kn: Khi cho tn hiu o vo chuyn i thng xut hin qutrnh qu . Qu trnh ny c th nhanh hay chm tu thucvo dng chuyn i. c tnh ny c gi l tc ngnhanh. tc ng nhanh ca cm bin c nh hng n sai

s ca php o v nh hng n tc ca php o- Mt s dng p ng

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Tr khng ca cm bin

Hoang Si Hong-HUST 5

ZinZout

CB

Zout Zin

CB

- Cm bin c kiu ra l dng -> Zout >> Zin

- Cm bin c kiu ra l p -> Zout cng sut ra cng ln

- Trkhng vo cng ln-> khuych i cng sut cng ln

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Cm bin v mch o

Hoang Si Hong-HUST 6

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Gii hn lm vic ca cm bin

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Chun cm bin

Hoang Si Hong-HUST 8

- Chun trc tip: dng cc i lng mu kim tracm bin, t kt qu thu c s chnh cm bin

- Chun gin tip: dng cm bin c c tnh chun v

so snh kt qu vi b cm bin cn nh chun trongcng mt iu kin

- Chun nhiu ln: khi cm bin c cha cc phn t c tr th gi tr ca p ng ca chng s ph thucvo nhiu yu t. V vy phi thc hin chun nhiuln. Thng p dng cho cm bin c tr ln.

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Hoang Si Hong-HUST 9

- Nhiu ni ti: pht sinh do s khng hon thin cu trc thit k, ch tohoc vt liu cm bin. V vy p ng cm bin sai lch so vi p ngchun.

- Nhiu do truyn dn: gy ra do cc ngun nhiu nh t trng, ngun nui,trng in t tn s radio, s thay i ca nhit , lc hp dn, bc xion, m mi trng, cc tp cht ho hc

Nhiu trong cc b cm bin v truyn dn

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Hoang Si Hong-HUST 10

- Nhiu do ni nhiu t khc nhau

- Nhiu xung in p khi tt bt ng c hoc thit b in

- Nhiu th nhit in gy ra do hiu ng nhit in (seebeek..)

- Nhiu phng gy ra do cc phn t transistor, mch tch hpv thit b bn dn.

- Nhiu th ho in

Mt s nhiu in in hnh

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Hoang Si Hong-HUST 11

- Chng nhiu: chun ho v cng ngh mch in, s dng kthut vi sai trong truyn dn, truyn dng in, mi trngtruyn dn cp quang, s dng ni t, mch lc tng t, lcs

- Lc tng t dng phn t th ng- Lc tng t dng phn t ch ng

Mt s phng php chng nhiu

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Gii thiu chung v cc mch o v chun ho

Hoang Si Hong-HUST 12

- Cc b chun ho tn hiu gm c: cc b khuych i, cc btng thch ha gia tn hiu cm bin v thit b o. Mchcu o, mch tuyn tnh ho, tch phn, vi phn, lp, cng, tr..

- Lu rng tn hiu ra t cm bin c th l tn hiu s(encoder, chuyn mch) hoc tn hiu tng t (in p,dng in)

- Mch bin i tng t s (ADC), s tng t (DAC)

- Chun ho theo in p, dng in v tn s

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Mch cu in tr

Hoang Si Hong-HUST 13

- ng dng cho cc loi cm bin th ng.- Gi tr in tr ca phn t cm bin thng t 100 n vi trm k. V d nh

bng bn di.

- Thng gi tr in trthay i do tc ng ca i lng o l rt nh so vi gitr in trban u

- Thit k sao cho dng qua in tr nh khng t nng in trgy ra li

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Mch cu in tr

Hoang Si Hong-HUST 14

- tng nhy ngi ta dng cu 2 nhnh v 4 nhnh nh hnh v- Trong cu mt nhnh ng dng ch yu cho cm bin nhit in tr(RTD)

- Cu 2 hoc 4 nhnhng dng ch yu cho strain gages

- Nu ngun cp cho cu VB = 10 V, v in p ra ton thang l 10 mV th nhycu l 1 mV/V.

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Mch cu in tr

Hoang Si Hong-HUST 15

- Hnh 4.1.1, dng mt phn t khuych i thut ton khuych i tn hiu ra cacu. Trng hp ny cu kh cn bng v in trRf v dng lch ca khuych ithut ton. Ngoi ra chnh xc khuych i v phi tuyn khng cao.

- S hnh 4.1.8 s dng khuych i dng c ci thin c cc nhc imca s 4.1.1

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Sai s ca mch cu khi in tr ng dythay i

Hoang Si Hong-HUST 16

- V d hnh 4.1.13, phn t nhy strain gage c gi tr in tr chun ban u l350 c ni vi mt nhnh ca mch cu bng cp i dy xon bng ngc di 100 feet = 3047.6 cm = 30.5 m. in tr1 dy khong 1.05 / feet ti25C hay 10.5 cho 100 feet. Do in tr ca cp xon l 21 . Ngoi ra h sthay i nhit ca ng l 0.385%/C. Chng ta tnh ton gi tr in p ra v litri im khng khi nhit tng thm 10 C. ( cu in trc in p cp 10V)

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Sai s ca mch cu khi in tr ng dythay i

Hoang Si Hong-HUST 17

- Gi s s bin i ton thang ca in trstrain gage l khong 1% (3.5), khi in tr ca strain gage l 353.5 , v kt qu l gi tr in pra ca cu l +23.45 mV. Lu trng hp ny bao gm c 21 cho intrb (RCOMP) cu cn bng. Nu khng c in trb th in p ralch khng l 145. 63 mV.

- Nu gi s nhit ca cp dn tng 10 C khi in tr ca mt dy dnn s tng ln l +0.404 (10.5 x 0.00385/C x 10 C). Kt qu tngcng trn cp xon s l +0.808 . Gi s in trstrain khng i, kh in p lch khng ban u do in tr ng dy thay i l +5.44 mV.V kt qu lch ton thang khi strain thay i l +28.83 mV (in p thc

l 23.39 mV). Nh vy vi s tng nhit th li in p lch khng l+23% ton thang (FS)(+5.44 mV) v li in p ra l -0.26% FS (-0.06 mV= 23.39 mV- 23.45 mV). Lu trong trng hp ny khng xt n lithay i in tr ca strain do nhit thay i)

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Gim sai s ca mch cu khi in tr ngdy thay i

Hoang Si Hong-HUST 18

- Dng cu vi 3 dy ni nh hnh 4.1.14- Trong trng hp ny loi tr li lch khng

- Khi nhit tng 10 C th li in p ra l -0.02mV (0.08%FS).

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Cu 6 dy

Hoang Si Hong-HUST 19

- Thng ng dng cho Loadcell.- 2 dy cho tn hiu ra, 2 dy nhy c ni u vo ca khuych i thut

ton c trkhng cao. Vi cch mc ny ti thiu ho c sai lch dongun cp. Ngun cp lun n nh l Vb. Chn OP vi cc chir tiu lowoffset, low drift v low noise

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Mch khuych i cho chun ho tn hiu

Hoang Si Hong-HUST 20

Khi tn hiu ly ra t cm bin c gi

tr b, phi khuch i. C th dng mt khuch i thut ton Khuch i thut ton l tng phi :

C mt tng tr vo v cc Tng tr ra bng zero H s khuch i v cc

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Mt vi phng php kim tra hiu chnh

Hoang Si Hong-HUST 21

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Mch khuych i o lng vi sai (dng c)

Hoang Si Hong-HUST 22

- Trong cc thit b o tn hiu o c ly rat cc b cm bin c cng sut rt nh. Munkhuych i c nhng tn hiu nh vy cnphi c nhng b khuych i in tr u vophi rt ln.

-Chng nhiu tt, tr khng vo ln, h skhuych i ln.- H s khuych i G c tnh nh sau:

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Mch khuych i cch ly

Hoang Si Hong-HUST 23

bo v con ngi : v d trong cc thit b y t.

Bo v cho ch chung v chng nhiu tt

t khc nhau

phn t cch ly

in p ch chung

Ngun

Cch ly th binValnanic

hoc kiu quang hc

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Mch khuych i cch ly

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Ni tng quang hc

Cch mc chun b tnh

tuyn tnh ca phn o

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Mch cng o

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Mch tr

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Mch tch phn o

Hoang Si Hong-HUST 27

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Mch tch tng

Hoang Si Hong-HUST 28

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Mch vi phn

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B chuyn i tng t-s (ADC)

Hoang Si Hong-HUST 30

Chuyn i gin tip: tch phn 2 sn dc

u(t) => Time Interval/f/T => code

Chm, r tin ($s), phn ly v chnh xc cao

Dng cho o lng, thu thp s liu trong cngnghip... khng cn nhanh, loi c nhiu

Chuyn i trc tip: u(t) => code

Nhanh, phn ly thp hn [t tin], dng thu thp v x

l tn hiu bin thin nhanh Chuyn i song song: 10M..500 MSps

Chuyn i kiu xp x lin tip:10k..10MSps

T h h 2 d D l Sl

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Tch phn 2 sn dc - Dual SlopeIntegration ADC:

Hoang Si Hong-HUST 31

c im:Chm, hng chc..hng trm ms - converssion time. Loi b c nhiu licng nghip (50/60 Hz). R, phn li cao, chnh xc cao, nu InternalRefv clock th t hnDng o lng, thu thp s liu trong cng nghip

ICL 7107, 15..17k,In: -2V..2V, Out: -1999 => 1999, 4.000 counts 12 bit, LED 7 Seg drivedirectly w current soursers for display. Converssion time: 20..40ms

ICL 7135, 25..30k,Inp: -2V..+2V, Out: -19999 =>+19999, 40.000 count >

15bit, 400 ms converssion time

De-Multiplexed Out BCD for 5 digits of 7 Seg, scanned

ICL 7109, 120k, w REF & ClockInp: -2V..+2V, Out: 12 bin + pole, 8/16 bit interface to CS

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S nguyn l

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Hoang Si Hong-HUST 33

Nguyn l

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Hoang Si Hong-HUST 34

Nguyn l

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Hoang Si Hong-HUST 35

Nguyn l

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Hoang Si Hong-HUST 36

Mch cu v ADC

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Hoang Si Hong-HUST 37

ICL 7107

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Hoang Si Hong HUST 38

Digital to Analog-DAC