Hng dn s dng my hin sng (oscilloscope)

Hng dn s dng my hin sng (oscilloscope)

Ngun : internet . File My hin sng (Oscilloscope) l mt dng c o trc quan tr lc hu ch cho anh em sa cha nghin cu in t, in thoi, my hin sng c kh nng hin th cc dng tn hiu, xung ln mn hnh mt cch trc quan m ng h khng th hin th c, hn na c nhng khu vc tn hiu ch th hin di dng xung, ng h o volt khng th pht hin c c tn ti hay khng m ch c my hin sng mi th hin c, thc t c rt nhiu loi my hin sng:- My hin sng dng n hnh (CRT: Cathode Ray Tube) loi ny n hnh dng si t c tim, in p t khong 6V, loi ny c cu trc knh cng, thng l cc i my c, tn s o t vi trm KHz n vi trm MHz.- My hin sng dng tinh th lng (LCD: Liquid Crystal Display), my c cu trc gn nh, hin i, c kh nng giao tip my tnh v in ra dng sng, tn s o khong vi chc MHz n vi trm MHz. Hin nay ph bin loi LCD, tuy nhin gi thnh ca my cn kh cao.I. CNG DNG CC NT CHNH TRN MY HIN SNG1. POWER: Tt m ngun cung cp cho Oscillocope (P.ON/P.OFF).2. INTENSITY: iu chnh sng tia qut.3. TRACE ROTATION: Chnh vt sng v v tr nm ngang (khi vt sng b nghing).4. FOCUS: iu chnh nt ca tia sng.5. COMP. TEST (Component Test): Dng kim tra linh kin (t, in tr).6. COMP TEST JACK: Dng ni mass khi th.7. GND: Mass ca my ni vi sn my/linh kin.8. CAL (2VPP): Cung cp dng sng vung chun 2Vpp, tn s 1KHz dng kim tra chnh xc v bin cng nh tn s ca my hin sng trc khi s dng, ngoi ra cn dng kim tra li s mo do u que o (probe) gy ra. Ty theo loi my m tn s v bin sng vung chun a ra c th khc nhau.9. BEAM FIND: n nt ny, vt sng s xut hin tm mn hnh khng b nh hng ca cc nm khc, mc ch dng nh v tia sng. y, chng ti hng dn s dng loi my hin sng hai tia.* IU CHNH KNH A (CHANNEL A)10. POSITION: Dng iu chnh v tr tia sng ca knh A theo chiu dc., 25PF (jack): Jack ny dng cp tn hiu cho channel (A). N cng l ng vo hng ngang trong ch hot ng X-Y.(11. 1M12. VOLTS/DIV = Volt/divider = in p/1 chia.Chnh tng nc thay i cao ca tn hiu vo thch hp cho vic c gi tr volt nh nh (Vpp Peak to Peak Voltage) trn mn hnh. Gi tr c trn mt thang o l Vpp/ chia.Th d: Volt/div = 2V cao 1 tng ng vi 2Vpp ca tn hiu.13. VAR PULL X5 MAG: (ng trc vi Volt/div) chnh lin tc thay i cao ca dng tn hiu trong gii hn 1/3 tr s t bi nm Volt/div. Khi vn ti a theo chiu kim ng h. cao dng sng s t tr s c t bi Volt/div.Nu ko nm VAR th chiu cao dng tn hiu s ln gp 5 ln gi tr c, lc ny tr s thc l tr s hin th chia 5.14. AC-DC-GND: Chn ch quan st tn hiu. + AC: Quan st dng sng m khng cn quan tm thnh phn DC.+ DC: Dng o mc DC ca tn hiu. Bt v v tr ny, dng sng khng xut hin, ch xut hin ng sng nm ngang ca thnh phn DC.+ GND: Ng vo tn hiu ni mass khng hin th c dng tn hiu trn mn hnh.* IU CHNH KNH CH-B (CHANNEL B)i vi cc nm sau, cch iu chnh tng t knh A:15. POSITION16. 1MHz 25PF17. Volt/ Div18. VAR Pull x5 mag19. AC-GND-DC* CC NM IU CHNH CHUNG CHO C HAI KNH20. VERT MODE: Kha in ny c 4 v tr+ CHA: Ch hin th knh A.+ CHB: Ch hin th knh B.+ DUAL: Hin th cho c A v B.+ ADD: Cng hai dng sng knh A v knh B li vi nhau (v bin ) cho ra dng sng tng.21. TRIGGER LEVEL: Cho php hin th mt chia tn hiu ng b vi im bt u ca dng sng (chnh sai, hnh b tri ngang).22. COUPLING: t ch kch khi trong cc trng hp sau:+ Auto: Mch qut ngang t ng qut, ch ny ch cho (php) kch khi cc tn hiu ln hn 100Hz. i vi cc tn hiu nh hn 100Hz. i vi cc tn hiu nh hn 100MHz hy t ch normal.+ Normal: Ch kch khi bnh thng. ch ny khi mt tn hiu kch khi mch qut ngang ngng hot ng tc mt vt sng trn mn hnh.+ TV-V: Loi b thnh phn DC v xung ng b tn s cao ca tn hiu hn hp hnh nh. Tn s kch khi nh hn 1KHz. 100KHz.(+ TV-H: Loi b thnh phn DC v xung ng b tn s thp ca tn hiu hn hp hnh nh. Di tn hot ng t: 1KHz 23. SOURCE: Chn ngun tn hiu kch khi, nu chn sai, hnh s b tri.+ CHA: Tn hiu knh A.+ CHB: Tn hiu knh B.+ LINE: Tn s in nh AC.+ EXT: Tn hiu c cung cp t Jack EXT TRIGGER.+ EXT EXTENAL: Bn ngoi.24. HOLD OFFS dng nt iu chnh ny trong trng hp dng sng c to thnh t cc tn hiu lp i lp li v nm TRIGGER LEVEL khng t c dng sng n nh.25. PULL CHOP: ch ny hai knh A, B c hin th lun phin xut hin vi tn s kh cao lm cho ta cm thy dng sng l lin tc, ch ny thch hp vi vic quan st hai tn hiu c tn s kh cao (> 1ms/div).26. EXT TRIGGER: Jack ni vi ngun tn hiu bn ngoi dng to kch khi cho mch qut ngang. s dng ng ny bn phi t nt SOURCE v v tr EXT.27. POSITION: Chnh v tr ngang ca tia sng trn mn hnh, n cng chnh v tr X (ngang) trong ch X-Y.PULL X10 MAG: Khi ko ra b ngang ca tia sng c ni rng gp 10 ln.28. TIME/DIV = Time/divider = thi gian qut / chia. nh thi gian qut tia sng trn mt chia. Khi o tn hiu c tn s cng cao phi t gi tr Time/div v gi tr cng nh.Khi t gi tr Time/div v v tr cng nh b rng ca tn hiu cng rng ra do nu t Time/div v v tr cng nh (vt qu gi tr cho php) th tn hiu hin th trn mn hnh s bin thnh ln sng nm ngang (v vt qu b rng mn hnh).29. VAR: Chnh b rng ca tn hiu hin th trn mn hnh.Th d: Khi hin th xung vung c tn s 1KHz.

Chu k ca tn hiu l: T = 1/f = 1/1000 ms

- Nu t Time/div = 0.5m/s S theo chiu ngang ca 1T (chu k) l:(

S = 1/(Time/Div) = 1/0,5 = 2

- Nu t Time/div = 1ms S theo chiu ngang ca 1 chu k l 1 (

s (qu nh)(- Nu t Time/div = 1

Kt lun:( Phi t gi tr Time/div v v tr thch hp.II. MT S NG DNG CA MY HIN SNG1. o in p nh nh (Peak to Peak Voltage)- in p nh nh ca tn hiu (Vpp) l in p c tnh t nh di n nh trn ca tn hiu. Th d:

Th t tnh Vpp trn my hin sng:a. c gi tr Vol/divb. c s theo chiu dc Vol/Div(c. Vpp = s theo chiu dc Th d: a/ Tnh in p nh nh (Vpp) ca dng sng sau, gi s ta ang t v tr Volt/div = 50mv.

Theo hng dn trn ta d dng tnh c:Vpp = 3 x 50mv = 150mVTh d: b/ Tnh Vpp ca dng sng sau, bit v tr Volt/div ca my hin sng ang c t v tr: 0.5V.

Theo hng dn trn ta d dng tnh c:Vpp = 4 x 0.5V = 2V2. Tnh chu k (T) v tn s (f) ca tn hiuTh t tnh chu k, tn s ca tn hiuBc 1. c s Time/div.Bc 2. m s theo chiu ngang 1 chu k. Time/div.(Bc 3. Chu k ca tn hiu: T = s /1T T = s f = Hz(Bc 4. Tn s ca tn hiu f = nu f = KHz(T = ms

s(T = f = Hz(Th d: Khi o trn my hin sng, tn hiu c dng sng nh hnh di y, v tr Time/div ang bt l 5ms, tnh chu k, tn s ca tn hiu.

Bit Time/div = 5ms( 5 = 20ms(T = 4 f = = KHz = 50Hz

Nu s ca mt chu k l s l, s /1 chu k c m s khng chnh xc, do ta phi m chu k tng ng vi s chn, sau ly s chu k chia cho s bit c s trong mt chu k.Th d:

s(- Bit Time/div = 2 2 chu k(Ta c 5 Do : - S /T = 5/2- Chu k T = time/div)(s (s /1T (s = 5( 2(

- Tn s ca tn hiu s l: f = = MHz = 200KHz

Bi tp: Tnh chu k, tn s cc tn hiu sau:a/

Bit Time/div = 0.5msb/

s(Bit Time/div = 50 3. Tnh in p DC ca tn hiu:Th t thc hin tnh in p DC ca tn hiuChnh tia sng nm tm mn hnh.- Khi o in p DC tia sng b dch chuyn theo chiu dc. volt/div.(- in p DC: VDC = s dch chuyn Th d:

5 = 10 V( VDC = 2 (Bit Vol/div = 5V/ in p DC ca tn hiu l 10VDC4. o lch pha gia hai tn hiu:- Bt my v ch hin th 2 knh.- lch pha ca tn hiu:+ Tnh s trn mt chu k (n)+ Tnh s lch nhau gia 2 chu k (m)+ lch pha: Th d:

Time/div = 0.5ms, m = 1, n = 4

lch pha:( = 900

III. PHNG PHP CHUN LI MY HIN SNG * Thc t my hin sng thng chnh sai, kt qu o b sai.Trc khi s dng ta phi chun li my kt qu c c t tin cy cn thit.* Phng php: Dng ng ra chun (cal). V d trn my Pintek l 2Vpp-1KHz.- Chnh cao: Bt volt/div = 0.5V, vn nm Pull x 5Mag (ng trc vi s (nm volt/div) sao cho b cao ca tn hiu l 4 (do Vpp = 2V theo chiu cao = = 4?

- Chnh rng:Bt Time/div = 0.5msXoay nm var sao cho b rng ca mt chu k tn hiu l 2 .(S ca mt chu k = = 4)Kinh nghim: Vi mt my hin sng tt, nt VAR v PULL x 5Mag thng c chnh theo chiu kim ng h v v tr ti a l c th s dng chnh xc.