Kev nthuav dav ntawm Capacitance Measurement Function ntawm Digital Multimeter
1. Kev ntsuas hauv online ntawm capacitance
Raws li cov khoom ntawm cov khoom sib txawv thiab cov khoom sib txuas, kev ntsuas kev ntsuas hluav taws xob tuaj yeem hloov mus rau qhov ntsuas hluav taws xob.
Lub hauv paus tseem ceeb ntawm Circuit Court, CX / V, txais yuav ib qho yooj yim active RC inverse differential thiab ib lub voj voog. Lub Wen oscillator tsim ib lub sijhawm ruaj khov AC teeb liab Vr, uas zoo siab rau CX / V hloov pauv kom tau txais AC voltage V0 (V1) proportional to CX. Tom qab tau lim los ntawm kev txiav txim thib ob bandpass lim kom tshem tawm cov clutter sab nraud ntawm qhov chaw ruaj khov, nws raug xa mus rau AC / DC kom tau txais DC tso zis voltage V proportional rau CX. Thaum lub teeb liab AC Vr excites lub CX / V Circuit Court, cov zis voltage ntawm lub inverter integrator
Ntawd yog, ntsuas lub peev xwm CX yog proportional rau cov zis voltage C {{0}}, yog li ua tiav CX → V conversion. Txhawm rau sib piv cov theem pib ntawm lub capacitor mus rau 2V qib ntawm digital multimeter, qhov zaus oscillation ntawm Venturi oscillator raug xaiv raws li 400Hz, qhov zoo voltage tus nqi yog 1V, R1 yog npaum li 20k Ω, thiab C1 yog npaum li cas. 0.1 μ F. R2 hloov los ntawm 200 Ω -2k Ω -20k Ω -200k Ω -2M Ω, sib xws rau qhov ntsuas qhov ntsuas ntawm 20 μ F{{ 16}} μ F-200nF-20nF-2nF.
2. Ntsuas me me capacitance
Qhov ntau ntawm kev ntsuas capacitance nrog ib tug raug peb thiab ib nrab tus lej multimeter yog 2000pF ~ 20 μ F. Nws zoo nkaus li tsis muaj zog los ntsuas me me capacitors hauv qab 1pF. Raws li txoj kev capacitive impedance thiab kev siv cov teeb liab siab, qhov ntsuas me me tuaj yeem ua tiav. Daim duab ntsuas hluav taws xob tau qhia hauv daim duab 2. CX yog qhov ntsuas qhov ntsuas, thiab Rf yog qhov kev tawm tswv yim tawm tsam ntawm qhov rov qab theem kawg. Thaum lub input zaus ntawm sine teeb liab Vi yog f, qhov impedance nthuav tawm ntawm CX thiab qhov nce ntawm kev ua haujlwm amplifier yog: thaum A thiab Rf tsis tu ncua, sine teeb liab zaus f yog inversely proportional rau ntsuas capacitance CX. Txhawm rau ntsuas cov capacitors me me, cov teeb liab siab zaus yog siv rau kev ntsuas.
