Cov lus qhia tseem ceeb rau kev tiv thaiv Digital Multimeter puas

Cov lus qhia tseem ceeb rau kev tiv thaiv Digital Multimeter puas

Thaum ua kev ntsuas hluav taws xob, xaiv qhov siab -rhiab heev multimeter muaj peb yam tseem ceeb hauv qab no:
Thaum ntsuas qhov voltage nrog lub multimeter nyob rau hauv parallel nrog lub Circuit Court raug kuaj, nws yuav tsim ib tug shunt nyhuv. Qhov siab dua qhov voltage rhiab heev, qhov siab dua qhov kev tiv thaiv sab hauv (piv txwv li ntsuas input resistance) ntawm multimeter. Qhov me me tam sim no rub los ntawm kev sim ntsuas, qhov cuam tshuam tsawg dua nws muaj rau kev ua haujlwm ntawm lub ntsuas hluav taws xob, uas tuaj yeem txo qhov yuam kev tsim tawm thaum ntsuas qhov siab sab hauv lub zog hluav taws xob. Thaum ua kev ntsuas hluav taws xob, qhov kev tiv thaiv sab hauv ntawm qhov ntsuas hluav taws xob (xws li AC lub zog hluav taws xob) tsawg heev. Yog li ntawd, cov nyhuv shunt ntawm multimeter tuaj yeem tsis quav ntsej, thiab xaiv qhov tsis tshua muaj siab multimeter tuaj yeem xaiv.

Qhov siab dua qhov voltage rhiab heev, qhov me me ntawm lub zog hluav taws xob Pv siv los ntawm multimeter thaum ntsuas qhov hluav taws xob. Piv txwv tias ntsuas qhov ntsuas hluav taws xob yog U, kev sib raug zoo yog:

3. Yooj yim los tsim kev thaiv siab. Vim tias qhov hluav taws xob rhiab heev yog qhov siab, nws txhais tau hais tias qhov rhiab heev ntawm lub taub hau meter siab. Ib qho kev sim me me tam sim no tuaj yeem ua rau tus pointer deflect mus rau qhov ntsuas tag nrho, ua tiav ohmic zeroing ntawm qhov tsis kam. Txawm nyob rau hauv qhov siab impedance, lub roj teeb qis dua tuaj yeem siv tau.

Qhov yuam kev hauv kev ntsuas qhov hluav taws xob nrog lub multimeter tuaj yeem txheeb xyuas siv cov duab hauv qab no. Piv txwv tias qhov ntsuas qhov ntsuas hluav taws xob yog U thiab nws qhov kev tiv thaiv sab hauv (lossis sib npaug sab hauv) yog r. (b) Lub thawv dashed ntawm sab xis ntawm daim duab yog qhov sib npaug ntawm qhov sib npaug ntawm qhov hluav taws xob, nrog rau sab hauv ntawm RV thiab 0 qhia qhov ntsuas ntawm xoom sab hauv tsis kam (ib yam hauv qab no). Txuas lub multimeter nyob rau hauv parallel mus rau lub Circuit Court nyob rau hauv kev sim, thiab teem lub nyeem ntawv ntawm lub multimeter rau U. Qhov kev sib raug zoo yog:

(a) Sib npaug Circuit Court ntawm qhov ntsuas voltage; (b) Tus txheeb ze ntsuas qhov yuam kev ntawm qhov sib npaug Circuit Court thaum ntsuas voltage yog:

Yog rv<0 in the equation, it indicates that U1100r,|rv |<1%, and the measurement error can be ignored. However, when the internal resistance of the tested circuit is high and comparable to Rv, significant measurement errors will occur.