Bi ging mn

K Thut Cm Bin (sensor)

1

Hoang Si Hong

----2011----

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

Hanoi, VietNam

Hoang Si Hong-HUST

Phn 2

Ni dung mn hc v mc ch

Ni dung Chapter 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 ca

cc loi cm bin thng dng trong cng nghip v i sng. Nm

c xu th pht trin chung ca cng ngh cm bin trn th gii.

Hoang Si Hong-HUST 2

c tnh ng ca cm bin

Hoang Si Hong-HUST 3

- Kn: Khi cho tn hiu o vo chuyn i thng xut hin qu

trnh qu . Qu trnh ny c th nhanh hay chm tu thuc

vo dng chuyn i. c tnh ny c gi l tc ng

nhanh. 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

Tr khng ca cm bin

Hoang Si Hong-HUST 4

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

- Tr khng vo cng ln-> khuych i cng sut cng ln

Cm bin v mch o

Hoang Si Hong-HUST 5

Gii hn lm vic ca cm bin

Hoang Si Hong-HUST 6

Chun cm bin

Hoang Si Hong-HUST 7

- Chun trc tip: dng cc i lng mu kim tra

cm 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 trong

cng 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 thuc

vo nhiu yu t. V vy phi thc hin chun nhiu

ln. Thng p dng cho cm bin c tr ln.

Hoang Si Hong-HUST 8

- Nhiu ni ti: pht sinh do s khng hon thin cu trc thit k, ch to

hoc vt liu cm bin. V vy p ng cm bin sai lch so vi p ng

chun.

- 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 x

ion, m mi trng, cc tp cht ho hc

Nhiu trong cc b cm bin v truyn dn

Hoang Si Hong-HUST 9

- 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 hp

v thit b bn dn.

- Nhiu th ho in

Mt s nhiu in in hnh

Hoang Si Hong-HUST 10

- Chng nhiu: chun ho v cng ngh mch in, s dng k

thut vi sai trong truyn dn, truyn dng in, mi trng

truyn dn cp quang, s dng ni t, mch lc tng t, lc

s

- Lc tng t dng phn t th ng

- Lc tng t dng phn t ch ng

Mt s phng php chng nhiu

Hoang Si Hong-HUST 11

Chng 2: Cm bin o nhit

Ni dung Khi nim chung

Nhit k gin n

Cm bin cp nhit in (Thermocouple)

Cm bin nhit in tr

Cm bin nhit da trn tnh cht ca diot v tranzito

Ho k

Bao nhiu ?

Hoang Si Hong-HUST 12

Khi nim

Hoang Si Hong-HUST 13

Khi nim

Hoang Si Hong-HUST 14

Nhit k gin n dng cht rn

Hoang Si Hong-HUST 15

Nhit k gin n dng cht lng

Hoang Si Hong-HUST 16

Cm bin cp nhit in

Nguyn l:

- Hiu ng thomson: vi vt liu ng nht A, trn n c hai im phn bit

khc nhau l M v N c nhit tng ng l t1 v t2, th gia chng s

xut hin mt sut in ng emn = tch phn (t t1->t2) ca dt, trong

l h s vt liu thomson cho trc

- Hiu ng Peltier: hai vt liu Av B khc nhau tip xc vi nhau ti mtim no th xut hin mt sut in ng eAB(t)

M

(t1)

N

(t2)A

A Bt

Hoang Si Hong-HUST 17

Cm bin cp nhit in

Nguyn l:

- Hiu ng seebeck: kt hp hai hiu ng ni trn -> xut hin sut in ng

nhit in eT(t) = tch phn t t1 n t2 ca (A B) dt + eKM(t) eJN(t)

- Trong A , B l h s vt liu thomson ca hai vt liu A, B tng ng.

t1 < t2 l nhit tng ng ti hai im khc nhau.

- Nu gi nhit mt u khng i bng khng C (0oC) (nhit u t

do) th xut hin sut in ng ra mt chiu u cn li (u lm vic,

nhit t) t l vi nhit : ET (t) = f(t) t1

M K

N J

t2

Hoang Si Hong-HUST 18

Vt liu ch to

Hoang Si Hong-HUST 19

Cu to

(hn im v cch li hnh vy c)

Hoang Si Hong-HUST 20

Cu to

Hoang Si Hong-HUST 21

Chng loi

Hoang Si Hong-HUST 22

Chng loi

Hoang Si Hong-HUST23

c tnh

Hoang Si Hong-HUST 24

Cc nguyn nhn gy sai s

- Sai s do nhit u t do

thay i. Khi khc , u t do

c t mi trng khng

C, nhng trong thc t nhit

u t do khc khng C

- Sai s do s thay i in tr

ng dy, cp nhit hoc ch th

- Sai s do t khng ng v tr,

hng

- ng dng: o nhit , o dng

tn s cao, hng chuyn ng,

lu tc, p sut nh..

Hoang Si Hong-HUST 25

Mch o

Hoang Si Hong-HUST 26

Mch o

Hoang Si Hong-HUST 27

Mch o

Hoang Si Hong-HUST 28

B nhit u t do

Hoang Si Hong-HUST 29

B nhit u t do

Hoang Si Hong-HUST 30

nh hng ca in tr mch o

Hoang Si Hong-HUST 31

nh hng ca in tr mch o