Muaj ib qho me me ntawm tooj liab hlau rau ntawm lub rooj tsav xwm digital multimeter, yog li cas lub luag haujlwm ntawm qhov me me ntawm tooj liab hlau ua si ntawm lub rooj tsavxwm? Tam sim no cia peb tham txog dab tsi no tooj liab hlau siv rau.
Daim duab saum toj no yog daim duab kos duab kos duab ntawm DC tam sim no iav ntawm digital multimeter. Hauv daim duab, R1 ~ R3 yog shunt resistors ntawm mA iav, thiab R4 yog shunt resistor ntawm 20A tam sim no iav. Txij li qhov ntsuas tam sim no ntawm cov ntaub ntawv mA me me (qhov siab tshaj 200mA), R1 ~ R3 precision hlau zaj duab xis resistors txaus. Qhov siab tshaj plaws tam sim no ntws los ntawm R4 ntawm 20A tam sim no muaj peev xwm ncav cuag 20A, thiab nws cov nqi kuj tsuas yog 10mΩ. Nyob rau tib lub sijhawm, qhov kub coefficient ntawm qhov kev tiv thaiv kuj tseem yuav tsum tau me me (tsawg ppm lossis tsawg dua), yog li cov hlau zoo tib yam cov yeeb yaj kiab resistors tsis muaj peev xwm. R4 feem ntau siv manganese tooj liab hlau tsis kam nrog siab precision, me me kub coefficient (40ppm) thiab zoo stability. Txawm li cas los xij, oxidation tsis kam ntawm manganese tooj liab hlau tsis zoo li cov hlau tsis tu ncua. (Qhov txawv ntawm manganese tooj liab hlau thiab constantan hlau yog: lub qub yog tooj liab thiab tom kawg yog nyiaj dawb).
Los ntawm txoj kev, thaum ntsuas qhov tam sim no loj tshaj 10A nrog 20A tam sim no, nws raug nquahu tias lub sijhawm ntsuas yuav tsum tsis pub tshaj 20 vib nas this. Vim tias qhov tam sim no loj ntws los ntawm R4 rau lub sijhawm ntev, nws yuav ua kom sov.
Daim duab saum toj no qhia tau hais tias lub rooj tsav xwm hauv Circuit Court ntawm VC930F ntxiv rau 4½-tus lej digital multimeter, thiab tooj liab hlau saum toj no yog manganese tooj liab hlau. Daim duab hauv qab no qhia txog lub rooj tsav xwm Circuit Court ntawm 3½-tus lej DMM.
Yog tias muaj qhov yuam kev hauv kev ntsuas ntawm 20A tam sim no, feem ntau nws tuaj yeem ntsuas tau los ntawm kev txiav qee qhov grooves ntawm manganese tooj liab hlau tsis kam raws li qhia hauv daim duab hauv qab no.
