Keeb kwm ntawm multimeters
Thawj pointer meter rau ntsuas tam sim no, hu ua galvonometer, tau tsim nyob rau hauv 1820. Siv Wheatstone Choj ua ke tuaj yeem sib piv qhov tsis paub txog qhov tsis kam thiab qhov voltage los ntsuas nrog qhov paub qhov voltage thiab tsis kam, thiab tom qab ntawd ntsuas qhov cuam tshuam voltage, tam sim no, tsis kam. , thiab lwm yam. Kev siv cov qauv no los ntsuas hauv chav kuaj mob hnyav thiab tsis yooj yim. Cov cuab yeej no yog cumbersome thiab nyuaj thiab tsis yooj yim rau nqa.
▲ Galvanometer
Lub galvanometer tsuas tuaj yeem cuam tshuam txog qhov muaj nyob ntawm tam sim no, tab sis tsis tuaj yeem muab tus nqi meej ntawm qhov loj tam sim no. Lub ammeter siv lub active coil mechanism (D'Arsonval / Weston kis tau tus mob mechanism) tuaj yeem pom qhov loj ntawm qhov tam sim no.
Lub hollow coil qhov txhab nrog zoo enameled hlau yog raug tshem tawm nyob rau hauv lub magnetic ncej ntawm cov hlau nplaum mus tas li, thiab rotating torque tuaj yeem tsim tom qab dhau DC tam sim no los tsav lub pointer tig. Lub nplhaib sib nqus yog tsim los ua lub nplhaib ncig, kom lub zog ampere ntawm lub kauj tam sim no tsis muaj dab tsi cuam tshuam nrog lub kaum sab xis, thiab nyias nyias lub caij nplooj ntoos hlav hlau ua rau lub zog rov qab los, uas ua rau lub kaum sab xis ntawm qhov kev sib hloov ntawm lub pointer thiab cov hlau nplaum. tam sim no dhau ntawm lub coil. proportional. Lub tshuab no, hu ua D'Arsonval iav mechanism, tseem siv dav hauv analog hluav taws xob saib lub taub hau ntawm txhua yam.
▲ D'Arsonal kis tau tus mob mechanism
Ib qho ammeter raws li lub tshuab txav coil tshem tawm qhov xav tau ntawm tus choj Wheatstone kom yooj yim thiab yooj yim ntsuas tam sim no. Rau lub hauv paus no, los ntawm kev ntxiv shunt tsis kam, series kuj thiab ruaj khov DC fais fab mov, qhov voltage, tam sim no thiab tsis kam ntawm cov iav sib txawv tuaj yeem ntsuas.
Hauv xyoo 1820, raws li cov khoom siv raj tau siv dav dua, lub tshuab multimeter tau yug los. Nws yog hais tias thawj multimeter nyob rau hauv lub niaj hnub kev xav tau tsim nyob rau hauv 1920 los ntawm Donald Macaie, ib tug engineer ntawm British Post Office. Hauv nws txoj haujlwm, txhawm rau tswj cov chaw sib txuas lus, nws yog ib qho tsim nyog yuav tsum ntsuas qhov voltage, tam sim no, tsis kam, thiab lwm yam hauv Circuit Court. Nws tsis tuaj yeem sawv ntsug qhov teeb meem ntawm kev nqa ntau lub 'meter' tib lub sijhawm, yog li nws tau tsim lub multimeter uas tuaj yeem ntsuas qhov voltage, tam sim no thiab tsis kam nyob rau tib lub sijhawm, uas hu ua Avometer thaum lub sijhawm ntawd.
▲ Donald Macadi's multimeter
Amvohm multimeter txais ib tus taw tes ammeter nrog lub tshuab hluav taws xob ua haujlwm, thiab tau nruab nrog lub ntsuas hluav taws xob sib cais thiab shunt tsis kam. Nws siv lub iav hloov thiab lub qhov (socket) los xaiv qhov ntsuas qeb thiab txheej txheem ntau yam.
Macadie hloov lub Avometer nws tsim los rau Lub Tuam Txhab Tsis Siv Neeg Winding thiab Hluav Taws Xob Hluav Taws Xob (ACWEEC, tsim nyob rau xyoo 1923), thiab nws tau dhau los ua kev lag luam thiab muag khoom xyoo ntawd. Avometer, ua ntej kev txhim kho 8, tsuas yog ntsuas DC voltage thiab tam sim no cov cim.
Lub hnab tshos saib-style voltmeter kuj tseem nrov thaum lub sijhawm, nrog cov hlau casing, uas yog pheej yig dua li Avometer. Nws lub plhaub feem ntau txuas nrog qhov tsis zoo ntawm qhov ntsuas qhov ntsuas. Txawm hais tias qhov kev ua kom yooj yim no yooj yim rau kev khiav lag luam, nws kuj ua rau ntau tus kws kho hluav taws xob tsis saib xyuas thaum lub sijhawm ntawd raug kev kub ntxhov ntau heev.
Hom kev saib no feem ntau kuj yooj yim. Piv txwv li, phau ntawv qhia tsuas yog 33Ω / V, lub dial feem ntau tsis sib xws, thiab tsis muaj tus taw tes xoom hloov kho ntsia hlau.
▲ Pocket saib voltmeter
Tus pointer-type multimeter feem ntau yuav tsum nqus tau qee qhov tam sim no los ntawm kev ntsuas Circuit Court kom tsav lub kauj kauj, xws li cov ntsuas puv 50 microampere meter, feem ntau siv high-rhiab ntsuas ntsuas. Thaum lub sij hawm ntsuas, yog tias tus pointer yog tag nrho offset, nws yuav tsum tau mus txuas ntxiv tau txais 50 microamps ntawm tam sim no los ntawm Circuit Court nyob rau hauv kev ntsuam xyuas, uas yuav cuam tshuam rau kev ntsuas ntawm ib co high-impedance circuits, ua tus nqi nyeem ntawv qis dua tus nqi ib txwm.
Nws yog ib qho tsim nyog yuav tau siv lub tshuab nqus tsev vacuum los ua kom cov input impedance ntawm multimeter, thiab lawv hu ua lub tshuab nqus tsev multimeters (VTVM, VVM). Lub tshuab nqus tsev twj siv hluav taws xob no feem ntau muaj qhov input impedance ntau dua 1MΩ. Nws siv lub tshuab nqus tsev cathode raws cov zis (voltage series tsis zoo tawm tswv yim) Circuit Court kom nce cov input impedance, yog li ntawd lub multimeter yuav tsis muaj kev cuam tshuam tseem ceeb ntawm Circuit Court hauv kev ntsuas thaum ntsuas.
▲ Lub tshuab nqus tsev multimeter
Ua ntej tsim cov digital (integrated) multimeter, high impedance analog transistor circuits, lossis Field Effect Triodes (FETs), tau siv los hloov cov raj nqus tsev hauv cov khoom siv multimeter. Niaj hnub nimno digital multimeters siv high-impedance integrated circuits, nrog input impedances uas yuav phim los yog tshaj tus thawj lub tshuab nqus tsev raj multimeters.
▲ Niaj hnub nimno digital multimeter
Niaj hnub no cov multimeters tau ntxiv ntau lub zog ntxiv, xws li decibel meters rau kev ntsuas lub zog, ntsuas lub peev xwm, triode nce, zaus, lub voj voog ua haujlwm, tso saib tuav thiab lwm yam. Lub buzzer ntawm lub multimeter tuaj yeem suab thaum lub ntsuas hluav taws xob qhib thiab tawm, muab cov lus qhia ceev ceev.
