ng h vn nng | cu to | cch s dng, cch o in tr| t in, kim tra linh kin | LED| motor rung| loa| Transistor| photo transistor | MOSFET | IC | Bn phm |

ng h vn nng | cu to | cch s dng, cch o in tr| t in, kim tra linh kin | LED| motor rung| loa| Transistor| photo transistor | MOSFET | IC | Bn phm |My o VOM (o c Volt - Ohm - Milliampere) l mt dng c bt kh ly thn ca ngi th in t, qua my o a nng ny,chng ta bit c cng dng in chy vo - chy ra trn cc chn ca cc linh kin, bit c mc p cao thp trn cc ng mch. Tuy nhin, c th khai thc ht cng nng ca loi my o ny, chng ta phi hiu tht tng tn cu to mch in bn trong ca n. Qua bi vit ny, mong rng Bn s nhn thy c vai tr rt quan trng ca loi my o thng dng ny.Ch vi mt my o VOM thi cng cho Bn thm him vo ch su nht ca cc mch in.Bn xem hnh.

Trong bi ny, chng ti tp trung ni v chc nng o Ohm ca my o VOM SUNWA (YX960TR hay YX-360).

Bn xem s mch in:

Khi Bn dng VOM chc nng Ohm k, lc Bn s s dng dng in t ca ngun pin 3V gn trong my o bm dng in cho qua cc vt o m Bn ang t trn hai dy o.S mch in cho thy dng in t chy ra trn dy o mu , v chy vo dy o mu env ri s chy qua in tr thang o (RTD), y ngi ta t mt volt k c mc o p ti a 3V o mc p xut hin trn in tr RTD, v ty theo gc lch ca kim trn bng chia vch Ohm, Bn tnh ra tr s in tr ca vt c o. Mi khi Bn thay i thang o th trong mch in s cho thay i tr s ca in tr thang o RTH. Chng ta thy (Bn xem hnh).

- thang o Rx1: in tr thang o RTH=20 Ohm- thang o Rx10: in tr thang o RTH= 200 Ohm.- thang o Rx100 in tr thang o RTH=2K Ohm.- thang o Rx1K. in tr thang o RTH=20K Ohm.Khi o Ohm Bn c th c kt qu trn 3 vch chia c trn mt my o:- Vch chiaLV: Trn vch chia ny, Bn bit c mc p gim trn vt o t trn 2 dy o.- Vch chiaLI: Trn vch chia ny, Bn bit c mc dng chy qua vt o.- Vch chiaOhm: Trn vch chia ny, Bn xc nh c sc cn dng ca vt o.Bn thy, thang o Rx1, nu Bn chm hai dy o li, dng in chy trong mch s ln nht v bng 150mA (con s ny c ghi trn thang o Rx1).Bn thy, thang o Rx10, nu Bn chm hai dy o li, dng in chy trong mch s ln nht v bng 15mA (con s ny c ghi trn thang o Rx10).Bn thy, thang o Rx100, nu Bn chm hai dy o li, dng in chy trong mch s ln nht v bng 1.5mA (con s ny c ghi trn thang o Rx100).Bn thy, thang o Rx1K, nu Bn chm hai dy o li, dng in chy trong mch s ln nht v bng 150A (con s ny c ghi trn thang o Rx1K).Qua phn tch trn, chng ta rt ra c cc iu cn nh khi dng loi Ohm k YX-960TR. l:iu cn nh 1: Sc p ca in p trn hai dy o ca my o Ohm ny l 3V (do trong my dng 2 pin 1.5V).iu cn nh 2: Dng in t lun chy ra trn dy v chy tr vo qua dy en.iu cn nh 3: Khi Bn ly thang o Ohm nhs c dng chy trn dy o ln v ngc li.iu cn nh 4: C th xc nh mc p gim trn vt o v cng dng in t chy qua vt o khi c kt qu trn vch chiaLVv LI.iu cn nh 5: Vch chia theo vch Ohm trn in k xc lp theo t s V/I (theo lut Ohm).iu cn nh 6: Ch thang o Rx10K, in p trn dy o lc ny s l 12V.Dng Ohm k kim tra cc linh kin c trn my in thoi di ng.Chng ta thy cc linh kin trn board mch in ca cc my in thoi di ng u rt nh, nh li-ti, nn trc ht Bn phi cho thay u hai cy o bng hai cy kim may (ly loi kim may bao ln), Bn xem hnh. Bn gn kim may vo u dy o, loi kim may ny rt cng v c u kim rt nh nhn nn rt tin dng o cc linh kin nh trn board mch, nht l o trn cc chn ca cc IC. Dng u kim nh Bn d dng cho u kim qut qua cc hng chn tm n cc chn cn o.Khi dng Ohm k kim tra cc linh kin trn board mch in, Bn lun nh dng in t t cc m ca pin 3V gn trong my os bm dng ra trn dy mu , v sau khi chy qua cc b phn trong mch, dng in t s b ht vo dy o mu en v chy v cc dng ca pin. Dng in ny khi chy qua in tr thang o s lm lch kim trn bng chia vch ca mt Volt k. Kt qu o s c c trn 3 vch chia, l vch chiaLV( bit p c trn hai dy o),LI( bit dng chy ra chy vo cc chn ca vt o) v vch chiaOhm( bit sc cn dng ca mch v vt o). Sau y l cc th d:1.o in tr, nhit tr, t in, cun cm.Bn xem hnh:Dng Ohm k o tr s ca cc in tr.

Trc ht, Bn ly thang o Rx1K, chp hai dy o, chnh kim v ngay v tr 0 Ohm.Khi o, dng in ca ngun pin 3V trong my o s bm dng ra dy , dng qua in tr Rx=10K tr vo dy en, kim s ln ch ngay vch s 10, v in tr ang o l 10K. Kt lun: in tr tt.Dng Ohm k o cc nhit tr.

t nhit tr RTH vo hai dy o, dng in chy qua nhit tr, c kt qu trn vch chia Ohm. 25 C, kim s ch 47K. Bn th lm nng nhit tr RTH, Bn thy g? Kim trn vch chia Ohm s gim dn, iu ny cho thy nhit tng lm cho ni tr ca nhit tr gim xung (do Bn ang o l loi nhit tr m). Du hiu ny cho bit nhit tr tt.Dng Ohm k kim tra tnh r in ca cc t in.

Khi o t in ho hc, Bn nh t cc dng ca t ho phi trn dy en, khi t t ln hai dy o, dng in t ca ngun pin 3V s cho np dng vo t in, thi im u, dng np rt mnh, kim bc ln cao, kim s gim dn v v tr v cc khi t np y p (3V).Vic chn thang o: Nu Bn ly thang o ln, in tr thang o ln, dng chy trn dy o nh, thi gian t np y s lu hn, kim tr v v tr v cc chm. Nu Bn ly thang o nh, thi gian t np y s nhanh, kim v v cc rt nhanh. Do vy, khi kim tra cc t in c in dung nh, Bn phi ly thang o ln kp thy c dng np vo t.Kim ln khng v: T chm.Kim ln v khng ht: T r.Kim khng ln: T t.2.o Diode, Led, Led hng ngoi.Diode l mt van in. Khi phn cc thun s cho dng chy qua. V khi phn cc nghch, diode ng, ct dng.

Khi o diode, nn ly thang o Rx1 c dng chy trn dy o ln. Khi o cc linh kin thuc nhm bn dn Bn c kt qu trn:- Vch chiaLV bit diode ghim p my volt (thng l 1V dng ln, thang o Rx1).- Vch chiaLI bit cng dng in chy qua diode (thng vi chc mA).Ch : Trong cc my in thoi di ng, do ngun nui thp, nn ngi ta thng dng loi diode Schottky, c im ca diode Schottky l ghim mc p rt thp ( thang o Rx1, dng ln, mc p ngang diode Schottky ch gn 0.3V).

LED cng l mt diode. (1) Khi phn cc thun s c dng chy qua Led v Led pht sng. (2) Khi phn cc nghch, Led ng, ct dng v khng sng.Khi o Led nn ly thang o Rx1 c dng trn dy o ln. Lc ny Bn c kt qu trn vch chiaLV bit Led gi li my Volt v c trn vch chia LI bit cng dng in ang chy qua Led l bao nhiu.Bn hy th cho i thang o Ohm. Bn thy g? Khi Bn ly thang o Ohm cng ln, in tr thang o trong mch ln , dng chy trn dy o lc ny s nh v Led s sng m. Khi Bn o cc linh kin thuc nhm bn dn, Bn c kt qu trn thang o Ohm khng c nhiu ngha, v cc linh kin bn dn c tnh phi tuyn tnh, nn tr s Ohm thay i theo cng dng in, vy mi thang o, Bn s c c mt tr s Ohm khc nhau.o linh kin bn dn Bn ch cn bit mc volt gim trn vt o (c kt qu trnLV) v dng chy qua vt o (c kt qu trn LI).

Kim tra Led hng ngoi, cch o cng tng t nh cch o cc Led chiu sng. Lc phn cc thun, c dng, kim ln. Khi phn cc nghch, ct dng, kim khng ln. Vi Led hng ngoi (IR Led), khi c dng chy qua Led, kim ln, Led pht ra nh sng hng ngoi, mt thng khng th thy c loi nh sng ny. Led hng ngoi thng c dng trao i d liu vi cc my in thoi khc. Khi o Led hng ngoi, Bn c kt qu trn vch chiaLV( bit mc ghim p trn Led), v trn vch chia LI ( bit cng dng in ang chy qua Led).3.o motor rung. kim tra hot ng ca mt motor rung, Bn ly thang o Rx1 c dng chy trn dy o ln(dng in ti a l 150mA).

t motor ln hai dy o. Motor s c cp dng v s quay. Lc ny hy c kt qu trn vch chiaLV bit mc p trn motor v c kt qu trn vch chia LI bit cng dng in chy qua motor. Motor rung thng lm vic mc dng 100mA v mc p gim ngang motor l 1V.Nu Bn kim tra motor rung thang o Rx10, kim o c ln cho bit c dng chy qua motor (motor khng h mch), nhng motor khng quay v dng ly ra thang o Rx10, ti a ch c 15mA, khng ln lm quay cc motor rung. thang o Rx1, khi Bn o hai dy o, motor rung s quay ngc chiu.4.o Loa.Trong cc loa loi in ng lun c mt cun dy (gi l coil), cun dy gn trn mt mn rung, Bn dng thang o Rx1 ( ly dng ln), cp dng cho cun dy, cun dy s tr thnh mt nam chm in, lc ny cun dy s tng tc vi mt nam chm vnh cu (gn trn loa) v lm rung mn loa, pht ra ting ku rt rt. Du hiu ny cho bit loa cn tt. Nu Bn th thang o Rx10 dng in trn d o nh hn, m vn cn nghe loa ku, l loi loa nhy. Tr khng ca loa in thoi thng l 20 Ohm.

Khi o thang Rx1, thy kim ln m mn loa khng rung, cun coil b kt. Cun coil rt ra khng dnh vo mn loa, loa s ku rt yu. Loa b qu cng sut s b r. Loa gn khng cht vo v my cng s pht ra ting b r.5.o Microphone.Micro dng cc my in thoi di ng thng l micro in dung. Trong micro in dung lun c mt transistor FET nh.

Loi micro ny cn cp dng phn cc mi to ra c tn hiu. Chn S (Source) ca FET s cho ly dng vo t ng masse, dng chy ra trn chn Drain v chy v ngun dng. Do khi dng Ohm k kim tra micro, Bn t dy tn chn S, dy en trn chn D (chng ta bit, dy en ni vo cc dng ca pin). Lc ny s c dng chy qua knh dn ca transistor FET, kim s ln. Bn hy thi mnh vo micro, lm rung mng tnh in, nu kim o c dao ng nh l micro tt.6.o Transistor, quang transistor, transistor MOSFET.o transistor nh cc:

Transistor nh cc c hai mi ni PN, quen gi l transistor bipolar. N c 2 loi, transistor NPN v transistor PNP. Bn c th dng mt Ohm k kim tra cc loi transistor bipolar. Trnh t thng lm l:(1) Hy tm chn B.

Bn ly thang o Rx1, tm o trn hai chn ca transistor, o chiu ny kim khng ln, ri cho o dy o kim cng khng ln, Bn kt lun hai chn ang o l chn E (Emitter, chn phun dng) v chn C (Collector, chn thu gom dng), vy chn cn li chnh l chn B (Base, chn nn) ca transistor. (2) Hy kim tra hai diode ca mi ni B-E v B-C.Transistor tng ng nh hai diode, nn vic kim tra mt transistor tt/xu l kim tra hai diode (B-E v B-C). Vi transistor NPN, nu dy en (c tnh ht dng) t trn chn B, dy (c tnh bm dng) nm trn chn C. Kim phi ln do mi ni phn cc thun v dy t trn chn E, kim cng ln (cng do c phn cc thun). Ngc li, t dy trn chn B, dy en o trn chn C, ri o qua chn E, kim u s khng ln, v diode b phn cc nghch.

Ch : Vi cc transistor loi PNP th kt qu o s ngc li. Ngha l dy trn chn B, dy en trn chn E, ri trn chn C, kim s ln do phn cc thun v dy en trn chn B, dy trn chn C, ri chn E, kim phi khng ln v phn cc nghch.Hnh v trn cho thy, dy en trn chn B (cho ht dng ra chn B), dy trn chn E (cho bm dng vo trn chn E), kim ln v lc ny diode B-E ang phn cc thun.Nu t dy trn chn B, ly dy en t ln chn E, diode phn cc nghch, kim khng ln v dy en trn chn C, kim cng phi khng ln.(3) Hy xc nh chn E v chn C.Chng ta bit, mi ni bn dn B-C chu volt nghch cao (thng trn 60V), trong khi mi ni B-E chu volt nghch thp (thng khong 9V).

Do , Bn hy ly thang o ohm Rx10K, lc ny trn dy o s c 12V (t ngun pin 9V + vi ngun pin 3V), dng mc p ny o nghch trn mi ni B-C (kim s khng ln) v o nghch trn mi ni B-E, kim s ln, v sao c khc bit ny? v mi ni B-E chu p 9V b nh thng mc p 12V ca my o. Qua du hiu ny Bn d dng xc nh c chn C v chn E.(4) Hy xc nh li dng in ca transistor.Bn ly thang o ohm Rx10, chp hai dy o, chnh kim v vch 0 Ohm.Cm transistor C1815 vo ng chn C, B, E ca 3 l cm NPN trn my o. Kim ln, Bn c kt qu trn vch chia HEF. Kim ch 200, c ngha l li dng in ca transistor 2SC1815 l 200 ln (n c ngha dng in ICchy ra trn chn C ln hn dng in IBchy ra trn chn B l 200 ln). Tham s HFE cn gi l h s beta ca transistor.

Vi transistor PNP cng lm tng t, cm transistor vo 3 chn C, B, E ca b chn cm PNP v c kt qu trn vch chia HFE, Bn s bit c li dng in HFE ca transistor.o quang transistor:Quang transistor l linh kin bn dn 2 chn, chn E cho ly dng (dng chy vo chn E), dng chy ra trn chn C, khi Bn cho nh sng kch thch vo vng B ca transistor, khi mc sng yu, transistor dn in yu v khi cng nh sng mnh th quang transistor s dn in mnh hn. Vy o mt quang transistor, Bn t quang transistor trn hai dy o (Bn xem hnh).Khi c nh sng ri vo quang transistor, n s dn in, kim s ln, cng sng cng mnh, kim ln cng cao (ngha l dng chy qua quang transistor cng ln). Trong in thoi di ng, ngi ta dng quang transistor trao i tn hiu bit dng tia sng hng ngoi.o transistor MOSFET:Transistor MOSFET thng dng lm kho in bn dn ng m nhanh, Bn thng gp loi transistor ny cc b adaptor DC dng np li in cho pin. Cch o loi transistor MOSFET nh sau:Trong transistor MOSFET dng lm kho in ng m nhanh thng c thm diode dp in p ngc. Dng in chy vo trn chn Source v chy ra trn chn Drain, c dng in ny, chn Gate cn c in p dng phn cc. Do khi dng Ohm k o kim tra loi transistor ny. Trc ht, Bn hy ly thang o ohm Rx1, o thun nghch trn hai chn xc nh diode D v qua s bit c chn Source v chn Drain. Nu dy nm trn chn Source v dy en trn chn Drain, Bn s thy:kim khng ln, ngha l trong knh dn in loi P gia vng ging Source v ging Drain cha xut hin cc ht in t do (Bn xem hnh). Lc ny, Bn hy cho dy en chm nh vo chn Gate, v t li dy en trn chn Drain, Bn s thy kim ln. V sao? V Bn cho np in p dng vo chn Gate v lc ny trong vng gia ging Source v ging Drain c ht mang in, nn knh dn in.7.o cc IC.IC (Intergrated Circuit) l cc mch in tch hp, cu to ca IC c bn l cc cht bn dn, mun bm c dng in chy qua cc mi ni bn dn (vn c ro p l 0.6V) trong cc IC, Bn phi dng Ohm k loi kim (vn c in p trn hai dy o l 3V). Vy kim tra mt IC, trc ht Bn hy chn mt chn ca IC, cho bm dng vo chn ny (t dy mu ln chn IC chn), v cho ht dng ra trn mt chn khc vi dy o mu en, nu kim ln l c dng, dng in ny chy qua cu trc bn trong ca IC. Dng php o i chng cc mch in cng loi, cc IC cng loi bit IC ang kim tra tt xu.8.Kim tra bn phm.Th d 1:Hy kim tra IC my tnh thng qua cch o Ohm trn cc im ng ca mch in bn phm.Trong cc my in thoi di ng, ngi ta ly nhiu chn ca IC my tnh lp thnh bng ma trn, gm cc hng (row) v cc ct (column). Trn bng ma trn bn phm ny gn cc nt nhn, cng dng ca n l s lm chm mt hng vi mt ct v qua du hiu ny s c IC my tnh gii m tm ra ni dung ca phm nhn ri cho chp hnh. Ngi ta dng bn phm nhp lnh v nhp d liu vo khi my tnh.

Bn ly Ohm k chn thang o Rx100, dy chm vo ng masse (Cho bm dng vo ng masse). By gi cho dy en ln lt chm vo cc im ng ca ma trn bn phm, kim ln l c dng in chy ra trn mt chn ca IC. Dng cch kim tra ny, Bn s bit c c h chn bn di IC khng, c t mch khng. Hy so snh cc kt qu o c, nu thy cc s ohm o c u ging nhau l mch in bn phm tt.Ghi nhn: Sau khi o ly mu trn mch in bn phm ca my Nokia 8210, chng ti thy cc im o u c kt qu l 30K.9.Kim tra mn hnh.Th d 2: Hy kim tra IC my tnh thng qua cch o Ohm trn cc im ng ca mch in mn hnh.Trong cc my in thoi di ng, ngi ta dng cht tinh th lng to ra cc nh im sp trn mt mn hnh v dng cc nh im ny in ra cc hnh nh. Chng ta bit, khi tinh th lng b kch thch, n s che sng v cho ra mt im en hay mt im mu (R, G, B), khi khng b kch thch th cht tinh th lng khng che sng, trong sut. Ngi ta ch to chip mch in iu khin mn hnh v dn chip mch in ny bn di mn hnh (k thut COG). to kt ni gia board mch in v chip mch in mn hnh, trn board mch in dng cc di tip im hay dng b ni nhiu dy.

Nh vy, mch in mn hnh s c nhiu chn kt ni vi khi my tnh, do Bn c th dng mt Ohm k loi kim c in p trn dy o l 3V kim tra cc ng mch v kim tra cu trc bn trong ca chip IC. Cch o nh sau:Bn hy ly Ohm k, ly thang o Rx100, dy t trn ng masse (cho bm dng vo board mch in qua ng masse). Dy en t trn cc chn ng ca mch in mn hnh ht dng in ra. Nu kim ln, cho bit c dng in chy vobn trong IC v chy ra trn cc chn ca IC. Nu kim khng ln l c t mch hay h chn.Bn c th dng cch o ny o ly mu trn cc board mch in ca cc my tt v sau ny dng cc tham s ny so snh vi cc my h (cch o i chng), v qua tm ra kt lun nhanh v tnh trng tt hay xu ca my.Kt lun:i vi ngi th in t, my o VOM l con mt th ba ca h, ngi th dng my o ny cng nh dng con mt sng nhn v cc board mch v thy s vn hnh ca tt c cc b phn trong mch in, h cn thy dng in t ang chy vo / chy ra trn cc chn ca linh kin, cn thy mc p cao / mc p thp trn cc ng mch. Hin ny, ngi ta tm ra c 1001 cch s dng loi my o ny. Khi no c dp chng ta s tr li ti ny. Cho!