thuc hanh cam bien hieu.pdf

HNG DN THC HNH CM BIN - 1 -

TRNG CKT CAO THNG B MN C IN T

HNG DN

THC HNH

CM BIN



MC LC

Trang

BI 1: CM BIN TIM CN NAM CHM A. c tnh ca cm bin tim cn nam chm c tip im .............................................. B. c tnh ca cm bin tim cn nam chm khng tip im ........................................

BI 2: CM BIN TIM CN CM NG IN T A. Khong cch ng ngt ca cm bin tim cn cm ng in t ................................. B. nhy ca cm bin vi cc loi vt liu khc nhau ................................................. C. nh hng ca b mt vt liu n khong cch nhn bit ca cm bin (Influence of the object surface on the switching distance) ...............................................

BI 3: CM BIN TIM CN CM NG IN DUNG A. Khong cch nhn bit ca cm bin tim cn in dung ............................................ B. nh hng b dy vt liu n khong cch nhn bit ca cm bin

tim cn in dung ........................................................................................................

BI 4: CM BIN QUANG A. c tnh p ng ca cm bin quang 2 u thu pht c lp ...................................... B. c tnh p ng ca cm bin quang 2 u thu pht chung ....................................... C. Dy nhn bit ca cm bin quang khuch tn ............................................................. D. Dy nhn bit ca cm bin quang khuch tn vi cp quang .....................................

BI 5: CM BIN SIU M ................................................................................................



MT S IU SINH VIN CN LU

a. Yu cu:

- Sinh vin vo phng thc hnh cm bin phi mc ng phc, chn mang giy - Ch s dng ngun in c in p khng qu 24V - Khng t cc thit b nhy vi t trng ( a, th ATM) n gn bn thc hnh - Ch c bt ngun in khi kt ni hon chnh v gio vin kim tra - Tt ngun in trc khi ngt kt ni thit b - Ch khi bt ngun in ng c s quay vi tc rt cao (2500 vng/pht) - c k hng dn thc hnh trc khi lp rp mch

b. S kt ni dy:

(a) (b)

(a) Cm bin tim cn 3 dy (b) Cm bin tim cn 4 dy (L) Ti

c. in p hot ng v mu dy:

Cc dng Nu (1)

Cc m (0V) Xanh (3)

Tn hiu ra (cm bin loi 3 dy) en (4)

Tn hiu ra (thng h, cm bin loi 4 dy) en (2)

Tn hiu ra (thng ng, cm bin loi 4 dy) Trng (4)

d. K hiu mu dy:

en BK

Nu BN

Xanh BU

RD

Xm GY

Trng BK



BI 1: CM BIN TIM CN NAM CHM

A. C TNH CA CM BIN TIM CN NAM CHM C TIP IM (Reed sensor)

1. Mc ch: Nghin cu nh hng kch c i tng n khong cch nhn bit ca cm bin cm ng in t Nghin cu v tnh cht ng/m ca cm bin tim cn nam chm c tip im (reed contact) bng hm v tr v hng ca nam chm 2. Dng c th nghim:

Stt Tn M s

1 Bng nhm 1100x700 (profile plate) 159411

2 Ngun in 24V (power supply unit) 162417

3 Hp phn phi in (distribution unit)

162248

4 Thc dn hng (positioning slide) 034094

5 Calib (venier caliper) 035653

6 Cm bin nam chm 1 (Magnetic sensor unit 1, D:ER-SMEO)

7 Th nam chm1 Part 1

8 Th nam chm 2 Part 2

3. Cch b tr thit b:



4. Kt ni in:

5. S mch in:

6. Cc bc tin hnh:

Bc 1: Tin hnh g lp thit b v kt ni in nh 3 hnh v bn trn (lu : lp cm bin cch calib khong 5cm)

Bc 2: Bt ngun in Bc 3: Th nghim 1:

- Gn th nam chm 1 (part 1) ln calib - Xoay calib v v tr 0 - Di chuyn tnh tin th nam chm dc theo trc ca cm bin. Vit ra nhng im m ti cm bin pht hin c th nam chm. ( thc hin di chuyn th nam chm t pha tri sang phi) - Khong cch dch chuyn gia nam chm v cm bin mi bc tin l 2mm

Th nghim 2: thc hin tng t vi th nam chm 2 (part2) 7. Lu :

- Thc hin ni mch in cn lu cc im sau: + Mu sc m ha v xc nh kt ni



in th Mu K hiu

Cc dng Nu (Brown) BN

Cc m Xanh (blue) BU

Ng ra

Vi 3 dy ni khng phn bit chc nng

en (black) BK

Vi 4 dy ni

Thng m en (black)

Thng ng Trng (White) WH

(RED) RD

xm (Grey) GY

Khi thc hin php o cn thc ch cc im switch-on v switch-off ca cm bin vi nhng khong cch khng trng nhau. Di chuyn th nam chm tip cn theo bn tri t trng thi khng hot ng ca cm bin cho n khi CB i trng thi hot ng. Phng php tip cn nam chm vi cm bin c thc hin bng cch dch chuyn part1, 2 t tri, cm bin thay i trng thi hot ng ca cm bin l t on sang off Bi tp: nh du cc im m cm bin pht hin nam chm



Stroke: c hot ng Distance: khong cch nhn bit



9. Nhn xt: ...................................................................................................................................................

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

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

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

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

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

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

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

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

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



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

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

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

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

Gi nhn xt: Tnh cht hng t trng ca tng tm nam chm nh hng n vng nhn bit ca cm bin. Nhn xt v hot ng ca cm bin Reed.

B. C TNH CA CM BIN TIM CN NAM CHM KHNG TIP IM

1. Mc ch: Nghin cu v cc c tnh chuyn i ca cm bin tim cn nam chm khng tip im vi ng ra l c tnh dng in ph thuc vo v tr v hng ca nam chm.

2. Dng c th nghim

Stt Tn M s




162248



6 Cm bin nam chm 2 (Magnetic sensor unit 2, D:ER-SMTO-...)

7 Th nam chm1 Part 1

8 Th nam chm 2 Part 2

3. Cch b tr thit b:



4. Kt ni in:

6. S mch in:

6. Cc bc tin hnh:

Bc 1: Tin hnh g lp thit b v kt ni in nh 3 hnh v bn trn (lu : lp cm bin cch calib khong 5cm)

Bc 2: Bt ngun in Bc 3: Th nghim 1:

- Gn th nam chm 1 (part 1) ln calib - Xoay calib v v tr 0 - Di chuyn tnh tin th nam chm dc theo trc ca cm bin. Vit ra nhng im m ti cm bin pht hin c th nam chm. ( thc hin di chuyn th nam chm t pha tri sang phi) - Khong cch dch chuyn gia nam chm v cm bin mi bc tin l 2mm

Th nghim 2: thc hin tng t vi th nam chm 2 (part2) 7. Lu :

Khi thc hin php o cn thc ch cc im switch-on v switch-off ca cm bin vi nhng khong cch khng trng nhau. Di chuyn th nam chm tip cn theo bn tri t trng thi khng hot ng ca cm bin cho n khi CB i trng thi hot ng. Phng php tip cn nam chm vi cm bin c thc hin bng cch dch chuyn part1, 2 t tri, cm bin thay i trng thi hot ng ca cm bin l t on sang off Bi tp: nh du cc im m cm bin pht hin nam chm



Stroke: c hot ng Distance: khong cch nhn bit



9. Nhn xt: ...................................................................................................................................................

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Gi nhn xt: Tnh cht hng t trng ca tng tm nam chm nh hng n vng nhn bit ca cm bin khng tip im th nghim 1 v th nghim 2. Nhn xt v nu hot ng ca 2 cm bin tin cn nam chm c tip im v khng tip im nh th no ( A v B). So snh u v nhc im ca tng loi cm bin th nghim phn A v B.



BI 2: CM BIN TIM CN CM NG IN T

B. NHY CA CM BIN VI CC LOI VT LIU KHC NHAU (Sensing of different metals with inductive proximity sensors)

1. Mc ch: Nghin cu nh hng ca vt liu kim loi n khong cch o mch ca cm bin tim cn cm ng in t

2. Dng c th nghim:

Stt Tn M s




162248



6 Cm bin tim cn cm ng in t 1 (Inductive sensor unit 1, D:ER-SIEH-M18B-...)

7 L thp nh S 235 JR (mild steel) Part 3

8 L thp khng g (stainless steel) Part 4

9 L Nhm Al Part 5

10 L ng thau Part 6

11 L ng Part 7

3. Cch b tr thit b:



4. Kt ni in:

7. S mch in:

6. Cc bc tin hnh:

- Bc 1: Tin hnh g lp thit b v kt ni in nh 3 hnh v bn trn (lu : lp cm bin cch calib khong 5cm)

- Bc 2: Bt ngun in - Bc 3: Thc hin cc bc o khong cch o mch ca cm bin bi th nghim 1

v 2. o khong cch o mch ca cc cm bin cho cc tm kim loi lm bng vt liu khc nhau.

+ Ly tm thp nh (S 235 JR, part3) v gn cht n vo slide nh v + o khong cch o mch ca cm bin. Ghi cc im m ti s thay i tn hiu xy ra khi cc tm kim loi tip cn gn vi cm bin, v cng ghi li cc im m s thay i tn hiu xut hin khi di chuyn tm kim loi xa cm bin. S khc nhau gia hai im ny l hin tng tr (ca) cm bin

Hysteresis (mm) = Switch-off point (mm) Switch-on point (mm)

- Mang cc tm kim loi khc nhau (thp khng g, nhm, ng thau v ng ) t cc tp cc i tng kim tra v thc hin cc php o tng t

- Xc nh h s suy gim ca cc khong cch o mch ca cm bin. H s suy gim ca (S 235 JR, part3) l 1.



- xc nh h s suy gim ca cc loi vt liu cn li bng cch ly cc gi tr u hoc cui ca khong cch o mch ca vt liu chia cc gi tr c nh r bi khong cch o mch ca thp nh

8. Kt qu th nghim:

Vt liu th nghim

M s Switch-on point [mm]

Switc-off point [mm]

Hysteresis [mm]

Reduction factor

L thp nh S 235 JR (mild steel)

Part 3 1

L thp khng g (stainless steel)

Part 4

L Nhm Al Part 5

L ng thau Part 6

L ng Part 7

L thp nh S 235 JR (mild steel)

Part 3

9. Nhn xt:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Gi nhn xt: - Nhn nh yu t g ca tng vt liu nh hng n h s suy gim v tr ca tng tm kim loi - Nhn xt v h s suy gim ca tng loi vt liu



D. NH HNG B MT VT LIU N KHONG CCH NHN BIT CA CM BIN CM NG IN T (Influence of the object surface on the switching distance)

1. Mc ch: Nghin cu nh hng kch c i tng n khong cch nhn bit ca cm bin cm ng in t

2. Dng c th nghim:

Stt Tn M s



3 Hp phn phi in (distribution unit) 162248



6 Cm bin tim cn cm ng in t (inductive proximity sensor)

177466

7 L thp 30x30 (mild steel) Part 11

8 L thp 25x25 Part 12





3. Cch b tr thit b:



4. Kt ni in:

5. S mch in:

6. Cc bc tin hnh: Bc 1: Tin hnh g lp thit b v kt ni in nh cc hnh v bn trn

(lu : lp cm bin cch calib khong 5cm) Bc 2: Bt ngun in Bc 3:

- G l thp (part 11) ln calib

- Xoay calib v v tr 0 - Tnh tin l thp trn thc dn hng li gn cm bin. n khi no cm bin pht hin c l thp th ghi li khong cch nhn bit vo bng kt qu bn di - Tin hnh tng t cho cc l thp cn li



7. Lu : - Khong cch nhn bit danh ngha (nominal switching distance) ca mi cm bin cm ng in t phi c xc nh vi l thp mng tiu chun c kch c nh sau: B dy l 1mm, chiu rng bng ng knh b mt hot ng ca cm bin v chiu di gp 3 ln khong cch nhn bit danh ngha ca cm bin .

- Cm bin s dng trong bi thc hnh ny c khong nhn bit danh ngha l 7mm, ng knh b mt hot ng ca cm bin l 16mm. Do , chiu di l thp mng tiu chun c chn phi l 21 mm.

8. Kt qu th nghim:

Vt liu th nghim M s Khong cch nhn bit

(mm)

L thp 30x30 Part 11

L thp 25x25 Part 12

L thp 20x20 Part 13

L thp 15x15 Part 14

L thp 10x10 Part 15

L thp 05x05 Part 16

9. Nhn xt:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Gi nhn xt: - Khong cch nhn bit ca cm bin tim cn cm ng ph thuc vo yu t no? - Khong cch nhn bit thc t so vi khong cch nhn bit danh ngha nh th no?



BI 3: CM BIN QUANG E. C TNH P NG CA CM BIN QUANG 2 U THU PHT C LP (Response characteristic of a through beam sensor)

1. Mc ch th nghim: Nghin cu p ng ca cm bin quang 2 u thu pht c lp v cch xc nh vt liu thch hp

2. Dng c th nghim:

Stt Tn M s




4 Cm bin quang, b pht (optical sensor, emitter)

167064

5 Cm bin quang, b thu (optical sensor, reciever)

167067

6 Th Kodak xm 100x100 (Kodak grey card)

Part 17

7 L thp mm 90x30 (mild steel) Part 3

8 L thp khng g 90x30 (stainless steel) Part 4

9 L nhm 90x30 (aluminium) Part 5

10 Ba cng 90x30 (cardboard) Part 8

11 Nha trong sut 90x30 (transparent plastic) Part 10

12 inh c (srew driver) Part 36

3. Cch b tr thit b:



4. Kt ni in:

5. S mch in:


(lu : lp b pht cch b thu 30cm) Bc 2: Bt ngun in Bc 3:

- Kim tra kh nng nhn bit ca cm bin vi cc loi vt liu khc nhau: + Xoay trc vis b chit p (potentionmeter) ca cm bin thu theo chiu kim ng h gia tng nhy ca n gi tr ti ta (xoay khong 12 vng) + Cho ln lt tng vt liu qua gia b pht v b thu, xem trng thi ng ra ca b thu v ghi li kt qu vo bng 1

- Xc nh im switch on v im switch off ca cm bin: + t nhy ca cm bin gi tr ti a + Lt m giy bn di b pht + t th Kodak xm vo ga b pht v b thu (t gn b pht) vi mt mu trng quay v pha b pht + Di chuyn th Kodak xm t tri qua phi mt cch t t cho n khi b thu i trng thi, ti y ta ghi li im switch on



+ Sau , di chuyn th Kodak xm t phi qua tri mt cch t t cho n khi b thu i trng thi ln na, ti y ta ghi li im switch off, khong cch gia im switch on v switch off l tr (hysteresis) + Tin hnh xc nh li im switch on v switch off thng qua vic gia tng khong cch gia th Kodak v b pht thm 3cm cho mi ln, ghi li kt qu vo bng 2

8. Kt qu th nghim: Bng 1:

Vt liu th nghim M s Pht hin (c/khng)

Th Kodak xm 100x100 Part 17

L thp mm 90x30 Part 3

L thp khng g 90x30 Part 4

L nhm 90x30 Part 5

Ba cng 90x30 Part 8

Nha trong sut 90x30 Part 10

Bng 2:

Khong cch gia th Kodak v b pht (cm)

im switch on (mm)

im switch off (mm)

tr (mm)

3

6

9

12

15

18

21

24

27

30

Hnh 1:

ng cong p ng ca cm bin thng qua vic xc nh im switch on v switch off



9. Nhn xt:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Gi nhn xt:

- nh hng ca cc loi vt liu n kh nng nhn bit ca cm bin nh th no?

- nhn bit c vt liu trong sut ta phi lm g?



F. DY NHN BIT CA CM BIN QUANG KHUCH TN (Sensing range of a dissuse optical sensor)

1. Mc ch th nghim: Nghin cu nh hng b mt vt liu n dy nhn bit ca cm bin quang khuch tn v cch v ng cong p ng.

2. Dng c th nghim:

Stt Tn M s






6 Thc t l 1020mm (measure scale) 035697

7 Cm bin quang khuch tn RT1 (diffuse sensor)

167068

8 Cm bin quang khuch tn RT2 167166

9 Tm Kodak xm 100x100 (grey Kodak) Part 17

10 Th nha trong sut 100x100 (transparent plastic)

Part 18

11 Th nha 100x100 (plastic) Part 19

12 Th nha xanh 100x100 Part 20

13 Th nha en 100x100 Part 21

14 Ba cng 100x100 (cardboard) Part 22


16 L thp khng g 90x30 (stainless steel) Part 4

17 L nhm 90x30 (aluminium) Part 5

18 L ng thau 90x30 (brass) Part 6

19 L ng 90x30 (copper) Part 7

20 L cao su 90x30 (rubber) Part 9

21 Giy m (graph paper pad) 034085

22 inh c (crew driver) Part 36



3. Cch b tr thit b:

4. Kt ni in: Th nghim 1:

Th nghim 2:



5. S mch in: Th nghim 1:

Th nghim 2:

6. Cc bc tin hnh: Th nghim 1: Xc nh c tnh ng ngt ca cm bin RT1

Bc 1: Tin hnh lp cm bin RT1 v thc t l ln bng nhm, kt ni in nh hnh v bn trn Bc 2: Bt ngun in Bc 3: Tin hnh calib cm bin bng cch t th Kodak xm ln calib v iu chnh cm bin cm bin nhn bit c th Kodak (mt trng) khong cch 30cm Bc 4: Xc nh im switch on, im switch off v tr ca cm bin vi cc loi vt liu cn li, ghi li kt qu vo bng 1, tt ngun in

Th nghim 2: Xc nh c tnh ng ngt ca cm bin RT2 Bc 1: Thay cm bin RT1 bng cm bin RT2 Bc 2: Bt ngun in Bc 3: Tin hnh calib cm bin bng cch t th Kodak xm ln calib v iu chnh cm bin cm bin nhn bit c th Kodak (mt trng) khong cch 15cm Bc 4: Tin hnh tng t nh bc 4 trong th nghim 1, ghi li kt qu vo bng 2

Th nghim 3: V ng cong p ng ca cm bin Bc 1: Gi nhy ca cm bin gi tr khng i



Bc 2: Di chuyn th Kodak xm t tri qua phi mt cch t t cho n khi b thu i trng thi, ti y ta ghi li im switch on + Sau , di chuyn th Kodak xm t phi qua tri mt cch t t cho n khi b thu i trng thi ln na, ti y ta ghi li im switch off, khong cch gia im switch on v switch off l tr (hysteresis) + Tin hnh xc nh li im switch on v switch off thng qua vic gia tng khong cch gia th Kodak v b pht thm 3cm cho mi ln, ghi li kt qu vo bng 2

8. Kt qu th nghim: Bng 1:

Vt liu M s im switch on

(mm)

im switch off (mm)

tr (mm)

Th Kodak xm, mt trng 100x100 Part 17

Th Kodak xm, mt xm 100x100 Part 17

Th nha trong sut 100x100 Part 18

Th nha 100x100 Part 19

Th nha xanh 100x100 Part 20

Th nha en 100x100 Part 21

Ba cng 100x100 Part 22



L nhm 90x30 Part 5

L ng thau 90x30 Part 6

L ng 90x30 Part 7

L cao su 90x30 Part 9

Bng 2:

Vt liu M s im switch on

(mm)

im switch off (mm)

tr (mm)

Th Kodak xm, mt trng 100x100 Part 17

Th Kodak xm, mt xm 100x100 Part 17

Th nha trong sut 100x100 Part 18

Th nha 100x100 Part 19

Th nha xanh 100x100 Part 20

Th nha en 100x100 Part 21

Ba cng 100x100 Part 22



L nhm 90x30 Part 5

L ng thau 90x30 Part 6

L ng 90x30 Part 7

L cao su 90x30 Part 9

Hnh 1: ng cong p ng ca cm bin RT1



Hnh 2: ng cong p ng ca cm bin RT2

9. Nhn xt:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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



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

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

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

Gi nhn xt: - Khong cch nhn bit ti a ca tng loi cm bin? - B pht cm bin RT1 pht loi nh sng g? u nhc im khi s dng loi nh sng ny?

- C nhn xt g v ng cong p ng ca cm bin RT2, ng cong p ng ny ph thuc vo yu t no?



BI 4: CM BIN TIM CN IN DUNG E. NH HNG B DY VT LIU N KHONG CCH NHN BIT CA CM BIN TIM CN IN DUNG (Influence of material thickness on the switching distance of a capacitive sensor)

1. Mc ch th nghim: Nghin cu nh hng b dy vt liu n khong cch nhn bit ca cm bin tim cn in dung

2. Dng c th nghim:

Stt Tn M s






6 Cm bin tim cn in dung (capacitive proximity sensor)

177470


8 Th nha dy 2mm (plastic, 2mm thickness) Part 23

9 Th nha dy 3mm Part 24






15 inh c (srew driver) Part 36

3. Cch b tr thit b:



4. Kt ni in:

5. S mch in:


(lu : lp thc dn hng cch b mt cm bin khong 5cm) Bc 2: Bt ngun in Bc 3:

- t l thp mm ln calib, iu chnh nhy cm bin cm bin pht hin c l thp khong cch 8mm - Tip theo, ta kho st khong cch nhn bit ca cm bin vi cc th nha c b dy khc nhau (part 23 n part 29). Ghi li kt qu vo bng bn di, v biu th hin mi quan h gia b dy vt liu v khong cch nhn bit ca cm bin



8. Kt qu th nghim:

Vt liu th nghim M s Khong cch nhn bit

(mm)

Th nha dy 2mm Part 23







Biu th hin mi quan h gia b dy vt liu v khong cch nhn bit

9. Nhn xt:

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

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

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

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

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

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

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

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

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

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

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

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

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



PH LC

1. Cm bin tim cn nam chm:

a. Nguyn l hot ng:

b. S khi

2. Cm bin tim cn cm ng in t

3. Cm bin tim cn in dung

4. Cm bin tim cn quang

5. Cm bin tim cn siu m

6. Cm bin o lc

thuc hanh cam bien hieu.pdf

Documents