(Technical Post) Digital Multimeter Repair Methods and Techniques
Lub ntsuas faulty yuav tsum xub xyuas thiab txheeb xyuas qhov tshwm sim txhaum yog qhov tshwm sim (tag nrho cov haujlwm tsis tuaj yeem ntsuas), lossis tus kheej (tus kheej lub luag haujlwm lossis tus kheej ntau), thiab tom qab ntawd sib txawv ntawm qhov xwm txheej, kev daws teeb meem.
1. Yog tias tag nrho cov iav tsis tuaj yeem ua haujlwm, yuav tsum tsom rau kev kuaj xyuas lub zog hluav taws xob thiab A / D converter circuit. Txheeb xyuas lub hwj huam mov, koj tuaj yeem tshem tawm cov roj teeb laminated, nias lub hwj huam hloov, nrog tus cwj mem zoo txuas nrog lub rooj ntsuas hluav taws xob tsis zoo, tus cwj mem tsis zoo txuas nrog lub hwj chim mov zoo (rau digital multimeter, thiab), qhov hloov yog ntaus rau cov ntaub ntawv ntsuas ob lub raj, yog tias cov zaub yog lub raj thib ob qhov zoo voltage, nws txhais tau hais tias lub hwj huam mov ib feem ntawm qhov zoo, yog qhov sib txawv loj, nws txhais tau hais tias lub hwj huam mov ib feem ntawm qhov teeb meem. Yog tias muaj qhov qhib Circuit Court, tsom mus rau kev tshuaj xyuas lub zog hloov pauv thiab cov roj teeb ua haujlwm, thiab lwm yam.. Yog tias muaj kev cuam tshuam luv luv, nws yuav tsum siv txoj kev sib txuas kom maj mam disconnect cov khoom siv hluav taws xob, tsom mus rau kev kuaj xyuas kev ua haujlwm. amplifier, timer thiab A/D converter, thiab lwm yam.. Yog hais tias ib tug luv luv Circuit Court tshwm sim, nws feem ntau puas ntau tshaj ib tug integrated tivthaiv. Kos lub A / D converter tuaj yeem ua tiav tib lub sijhawm raws li cov lus yooj yim, sib npaug rau DC lub taub hau ntawm analogue multimeter, cov kev kuaj tshwj xeeb:
(1) Qhov ntau ntawm cov lus ntsuas yog tig mus rau qhov qis tshaj DC voltage iav;
(2) Ntsuas seb qhov A / D converter kev khiav hauj lwm voltage yog li cas. Raws li cov lus siv hauv A / D converter qauv, sib haum rau V + ko taw thiab COM taw, qhov ntsuas tus nqi thiab nws cov nqi raug piv rau seb nws zoo ib yam.
(3) Ntsuas qhov siv hluav taws xob ntawm A / D converter, tam sim no feem ntau siv digital multimeter siv hluav taws xob feem ntau yog 100mV lossis 1V, uas yog, ntsuas DC voltage ntawm VREF + thiab COM, yog tias nws txawv ntawm 100mV lossis 1V, tuaj yeem hloov kho los ntawm lwm tus potentiometer.
(4) xyuas cov tswv yim yog xoom zaub, lub davhlau ya nyob twg zoo ntawm A / D converter IN + thiab lub davhlau ya nyob twg tsis zoo IN - luv, kom cov input voltage Vin=0, qhov ntsuas qhia tias "00 .0" or "00.00".
(5) Txheeb xyuas qhov ci ci tag nrho ntawm cov teeb pom kev zoo. Lub davhlau ya nyob twg xeem TEST taw thiab qhov zoo fais fab mov davhlau ya nyob twg V + luv, kom lub logic hauv av rau hauv lub peev xwm siab, tag nrho cov digital circuits nres ua haujlwm. Vim tias txhua qhov mob stroke ntxiv rau DC voltage, yog li txhua qhov strokes ci ntsa iab lub rooj zaub "1888", para rooj zaub "18888". Yog tias tsis muaj qhov tshwm sim ntawm qhov tshwm sim tsis zoo, tshawb xyuas A / D converter sib haum rau cov zis tus pin thiab cov roj hmab conductive (los yog kab), thiab cov zaub ntawm cov neeg pluag kev sib cuag thiab kev tsis sib haum xeeb.
2. Yog tias muaj teeb meem nrog ib tus neeg cov ntaub ntawv, nws txhais tau hais tias A / D converter thiab cov khoom siv hluav taws xob ua haujlwm tau zoo. Vim tias qhov hluav taws xob DC, cov ntaub ntawv tiv thaiv sib koom ua ke ntawm cov hluav taws xob faib hluav taws xob resistor; AC thiab DC tam sim no sib koom ib qho shunt; AC voltage thiab AC tam sim no qhia ib txheej ntawm AC / DC converter; lwm tus, xws li Cx, HFE, F, thiab lwm yam yog tsim los ntawm kev ywj pheej sib txawv converters. Nkag siab txog kev sib raug zoo ntawm lawv, thiab tom qab ntawd raws li daim duab qhia kev siv hluav taws xob, nws yooj yim los nrhiav qhov chaw txhaum. Yog tias qhov ntsuas ntawm cov cim me me tsis raug lossis cov duab duab dhia ntau, ces tsom mus xyuas seb qhov kev sib cuag ntawm qhov hloov pauv yog qhov zoo.
3. Yog tias cov ntaub ntawv ntsuas tsis ruaj khov, thiab tus nqi ib txwm nce ntxiv, luv luv cov tswv yim ntawm A / D converter, cov ntaub ntawv tso saib tsis yog xoom, nws feem ntau tshwm sim los ntawm kev ua haujlwm ntawm 0.1μF siv capacitor.
Raws li cov kev soj ntsuam saum toj no, qhov kev txiav txim siab ntawm kev kho cov digital multimeter yuav tsum yog: lub taub hau digital lub taub hau → DC voltage → DC tam sim no → AC voltage → AC tam sim no → cov ntaub ntawv tiv thaiv (nrog rau lub buzzer thiab xyuas qhov zoo voltage poob ntawm lub raj thib ob. ) → Cx → HFE, F, H, T thiab lwm yam. Txawm li cas los xij, nws yuav tsum tsis txhob ua ntau dhau, thiab qee qhov teeb meem uas pom meej meej tuaj yeem daws tau ua ntej. Txawm li cas los xij, thaum ua tiav, ces cov txheej txheem saum toj no yuav tsum tau ua raws.
