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
5
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-BKHN(2005)
- Bi ging Cm bin v k thut o:P.T.N.Yn, Ng.T.L.Hng BKHN (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
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 o nhit (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 3
Hoang Si Hong-HUST 4
Chng 3: Cm bin quang
Ni dung Khi nim chung v nh sng v ngun sng
Quang in tr, t bo quang in v b nhn quang in
Photodiode
Phototranzito
T bo quang in
Ngun sng
hay ngun thu
nh sng?
Hoang Si Hong-HUST 5
Cc khi nim chung v nh sng
- nh sng l mt sng in t, vng nh sng nhn thy c c bc sng
t 0.4 n 0.75m.
- nh sng c tnh cht sng v ht.
- Vn tc nh sng trong chn khng v = 299792 km/s
- Vn tc nh sng trong mi trng vt cht c chit sut n l v = c/n
- Mi lin h gia bc sng nh sng v tn s nh sau: = c/ (chn
ko) v = v/
-Ultraviolet (t ngoi). Infrared (hng ngoi)
Hoang Si Hong-HUST 6
Cc khi nim chung v nh sng
- Tnh cht ht th hin qua s tng tc ca n vi vt cht. nh sng l cc
ht phton mang nng lng Ept= h. Trong h l hng s planck =
6,6256.10-34 J.s
- Khi dng nh sng xuyn qua mt cht no c th b hp th hoc tn x
Hoang Si Hong-HUST 7
Nguyn l chung
-Bc sng ln nht ca nh sng c th gy nn hin tng gii phng in t vi
iu kin nng lng photon Ept > Edt nng lng lin kt ca in t
max = h.c/Edt-Nh vy iu kin gii phng in t ph thuc vo kiu nh sng v bn cht vt
liu b chiu sng
- Hin tng gii phng cc ht dn di tc dng ca nh sng do hiu ng
quang in s gy nn s thay i tnh cht in ca vt liu. l nguyn l c
bn ca cc cm bin quang in
- S in t c gii phng trong mt giy G = (1-R) /h.c
-:Hiu sut, R: h s phn x v thng lng nh sng
Hoang Si Hong-HUST 8
Cc n v o
-Nng lng bc x Q : l nng lng pht x, lan truyn hoc hp th di dng bc
x c o bng Jun (J)
-Quang thng : l cng sut pht x lan truyn hoc hp th, o bng ot (W) v l
i lng c trng cho ngun sng: = dQ/dt
- Cng sng I: l quang thng pht ra theo mt hng di mt n v gc khi,
c n v l W/steradian: I = d/d
- chi nng lng L: l t s gia cng sng pht ra bi mt phn t b mt
dI theo mt hng xc nh v din tch hnh chiu vung gc ca phn t b mt
dAn, c n v l W/steradian.m2 :L = dI/dAn
- ri E: l t s gia quang thng thu c bi mt phn t b mt v din tch
ca phn t , c n v l W/m2 :E=d/dA
- n v th gic /v nng lng
- Thng lng lumen (lm) oat (W)
- Cng candela (cd) oat/sr (W/Sr)
- chi cd/m2 W/Sr.m2
- ri lumen/m2 (lux) W/m
- Nng lng lm.s
- nhy ca mt ngi cc i vi bc sng =0,555 micromet
Hoang Si Hong-HUST 9
Cc n v o
-Nng lng bc x Q : l nng lng pht x, lan truyn hoc hp th di dng bc
x c o bng Jun (J)
-Quang thng : l cng sut pht x lan truyn hoc hp th, o bng ot (W) v l
i lng c trng cho ngun sng: = dQ/dt
- Cng sng I: l quang thng pht ra theo mt hng di mt n v gc khi,
c n v l W/steradian: I = d/d
- chi nng lng L: l t s gia cng sng pht ra bi mt phn t b mt
dI theo mt hng xc nh v din tch hnh chiu vung gc ca phn t b mt
dAn, c n v l W/steradian.m2 :L = dI/dAn
- ri E: l t s gia quang thng thu c bi mt phn t b mt v din tch
ca phn t , c n v l W/m2 :E=d/dA
- n v th gic /v nng lng
- Thng lng lumen (lm) oat (W)
- Cng candela (cd) oat/sr (W/Sr)
- chi cd/m2 W/Sr.m2
- ri lumen/m2 (lux) W/m
- Nng lng lm.s
- nhy ca mt ngi cc i vi bc sng =0,555 micromet
Hoang Si Hong-HUST 10
Cc ngun sng c bn
n si t
n ne-on
Laser
Led
LCD ?
Hoang Si Hong-HUST 11
n si t
- L bng thu tinh cha kh him hoc halogen v si t lm bng vonfram. Pht ra
nh sng nhn thy c
- u im: thng lng nh sng ln, di ph rng, c th thay i c thng lng
nh sng
- Nhc im: thi gian s dng ngn hn so vi led, d v, qun tnh ln
Very thin metal wire
emitting light rays when
an electric current passes
though it
tungsten filament
Hoang Si Hong-HUST 12
n Led (LIGHT EMITTING DIODE)
- Nguyn l: nng lng (quang nng) c gii phng khi c s ti
hp cp t-l trng phn tip gip p-n v pht sinh ra cc phton.
- u im ca led v led 7 thanh:
+ Tn s hot ng cao, bn tt, tin cy cao, tui th cao (10
nm).
+ Cng sut tiu th b, khng gy st p khi bt u hot ng
+ Khi tng nhit v dng cung cp cho led khng i th cng
sng s gim trung bnh khong 1.5 n 2 mV/ oC
+ Kch thc b c th ghp ni din tch rng
+ Cng sng ph thuc vo dng in i qua, do c th iu
khin c cng sng thch hp
+ Mu sc nh sng ph thuc vo vt liu v d: GaAs: , GaAsP
hoc vng, GaP hoc xanh.
+ Kh nng chuyn mch nhanh ( 1 ns)
+ in p st trn led ph thuc vo mu vi dng thun cung cp c
20 mA
+ Bc x ca led l n sc
Hoang Si Hong-HUST 13
How does it work?
P-n junction Electrical Contacts
Recombination
produces light!!
Junction is biased to produce even more
e-h and to inject electrons from n to p for
recombination to happen
g = hc/Eg
A typical LED needs a p-n junction
There are a lot of electrons and holes at
the junction due to excitations Electrons from n need to be injected to p
to promote recombination
Hoang Si Hong-HUST 14
Visible LED
Definition:
LED which could emit visible light, the band gap of the materials that we use must
be in the region of visible wavelength = 390- 770nm. This coincides with the
energy value of 3.18eV- 1.61eV which corresponds to colours as stated below:
Violet ~ 3.17eVBlue ~ 2.73eVGreen ~ 2.52eV Yellow ~ 2.15eVOrange ~ 2.08eVRed ~ 1.62eV
Colour of an LED should
emits
The band gap, Egthat the
semiconductor must posses to emit each light
Led in p st p khong 1.6 n 2 VLed da cam in p st p khong 2.2 n 3 VLed l cy in p st p khong 2.7 n 3.2 VLed vng in p st p khong 2.4 n 3 VLed xanh da tri in p st p khong 3 n 5 V
Hoang Si Hong-HUST 15
LED 7 thanh
Hoang Si Hong-HUST 16
Laser
Laser (c l la-de) l tn vit tt ca cm t Light Amplification
by StimulatedEmission of Radiation trong ting Anh, v c ngha l "khuch i nhsng bng pht x kch thch".
http://vi.wikipedia.org/wiki/Laser
Electron tn ti cc mc nng lng ring bit trong mt nguyn t. Cc mc nng
lng c th hiu l tng ng vi cc qu o ring bit ca electron xung quanh ht
nhn. Electron bn ngoi s c mc nng lng cao hn nhng electron pha trong.
Khi c s tc ng vt l hay ha hc t bn ngoi, cc ht electron ny cng c th
nhy t mc nng lng thp ln mc nng lng cao hay ngc li. Cc qu trnh ny
c th sinh ra hay hp th cc tia sng (photon) theo gi thuyt ca Albert Einstein. Bc
sng (do mu sc) ca tia sng ph thuc vo s chnh lch nng lng gia cc mc.
C nhiu loi laser khc nhau, c th dng hn hp kh, v d He-Ne, hay dng cht
lng, song c bc x ln nht vn l tia laser to bi cc thnh phn t trng thi cht
rn.
Hoang Si Hong-HUST 17
Laser
http://vi.wikipedia.org/wiki/Laser
Mt v d v c ch hot ng ca laser c th c miu
t cho laser thch anh.
Di s tc ng ca hiu in th cao, cc electron ca
thch anh di chuyn t mc nng lng thp ln mc
nng lng cao to nn trng thi o nghch mt ca
electron.
mc nng lng cao, mt s electron s ri ngu nhin
xung mc nng lng thp, gii phng ht nh
sng c gi l photon.
Cc ht photon ny s to ra nhiu hng khc nhau t
mt nguyn t, va phi cc nguyn t khc, kch thch
eletron cc nguyn t ny ri xung tip, sinh thm cc
photon cng tn s, cng pha v cng hng bay, to nn
mt phn ng dy chuyn khuych i dng nh sng.
Cc ht photon b phn x qua li nhiu ln trong vt liu,
nh cc gng tng hiu sut khuch i nh sng.
Mt s photon ra ngoi nh c gng bn m ti mt u
ca vt liu. Tia sng i ra chnh l tia laser.
Hoang Si Hong-HUST 18
Tnh cht Laser v an ton
http://vi.wikipedia.org/wiki/Laser
- nh hng cao: tia laser pht ra hu nh l chm song song do kh nng chiu
xa hng nghn km m khng b phn tn.
- Tnh n sc rt cao: chm sng ch c mt mu (hay mt bc sng) duy nht. Do
vy chm laser khng b tn x khi i qua mt phn cch ca hai mi trng c chit
sut khc nhau. y l tnh cht c bit nht m khng ngun sng no c.
- Tnh ng b ca cc photon trong chm tia laser.
- C kh nng pht xung cc ngn: c mili giy (ms), nano giy, pico giy, cho php tp
trung nng lng tia laser cc ln trong thi gian cc ngn.
Laser vi cng thp, ch l vi miliwatt, cng c th nguy him vi mt ngi. Ti bc sng
m gic mc mt v thy tinh th c th tp trung tt, nh tnh ng nht v s nh hng cao ca
laser, mt cng sut nng lng ln c th tp trung vo mt im cc nh trn vng mt. Kt qu
l mt vt chy tp trung ph hy cc t bo mt vnh vin trong vi giy, thm ch c th nhanh
hn. an ton ca laser c xp t I n IV. Vi I, tia laser tng i an ton. Vi IV,
thm ch chm tia phn k c th lm hng mt hay bng da. Cc sn phm laser cho dn dng
nh my chi CD v bt laser dng trong lp hc c xp hng an ton t I, II, hay III. (Xem
thm an ton laser)
Hoang Si Hong-HUST 19
u im v ng dnghttp://vi.wikipedia.org/wiki/Laser
- Tnh cht ny cho php laser c th lu tr vi gigabyte thng tin trn cc rnh
ca DVD. Cng l iu kin cho php laser vicng sut nh vn c th tp
trung cng sng cao v dng ct, t v c th lm bc hi vt liu trong
k thut ct bng laser. u c CD v DVD hot ng theo cng c ch, duy ch
c iu DVD cha c lng d liu nhiu hn bi s dng tia laser bc sng
ngn hn (650 nano-mt so vi 780 nano-mt ca CD). Bc sng ngn hn cho
php tng tn sut va chm, sn sinh photon v tng ng vi n l d liu. D
kin, th h quang mi da trn cng ngh ghi a laser xanh (vi bc sng
khong 405 nano-mt), c kh nng lu tr nhng b phim cht lng cao (High
Definition- HD).
-My o khong cch bng laser trong qun s l loi thit b quan trng
-Rada laser c chnh xc cao hn rada thng thng, c th hng dn hai tu
v tr ghp ni chnh xc trn khng gian. Tuy nhin, nhng thit b laser u chu
nh hng ca thi tit, tri m hoc ma th khong cch o b gim i nhiu.
- My in laser, xo vt xm, y t
-u im: Ngun n sc, chi ln, bc sng xc nh, thng lng ln,
chm tia mnh, i nh hng cao v truyn i xa
Lu v cu hi
Hoang Si Hong-HUST 20
Cn tip phn 5-2 !!!