電流表內(nei)外接法(fa)產生誤差的(de)原因

當選用外接法時，電壓表(biao)與電阻(zu)并聯，電壓表(biao)的(de)(de)讀(du)數就是電阻(zu)兩端的(de)(de)電壓，但電流(liu)(liu)(liu)(liu)表(biao)測量(liang)的(de)(de)是通過電阻(zu)和電壓表(biao)的(de)(de)總電流(liu)(liu)(liu)(liu)，正泰電流(liu)(liu)(liu)(liu)表(biao)哪家好(hao)，因(yin)此測量(liang)值(zhi)(zhi)(zhi)要小(xiao)于真(zhen)實(shi)值(zhi)(zhi)(zhi)，實(shi)際上測量(liang)的(de)(de)電阻(zu)值(zhi)(zhi)(zhi)是電壓表(biao)內電阻(zu)和電阻(zu)并聯的(de)(de)阻(zu)值(zhi)(zhi)(zhi)。如(ru)果(guo)電阻(zu)Rx的(de)(de)值(zhi)(zhi)(zhi)遠小(xiao)于電壓表(biao)的(de)(de)內阻(zu)RV，電壓表(biao)分(fen)去的(de)(de)電流(liu)(liu)(liu)(liu)很小(xiao)，這時電流(liu)(liu)(liu)(liu)表(biao)測量(liang)的(de)(de)電流(liu)(liu)(liu)(liu)就接近于通過電阻(zu)的(de)(de)電流(liu)(liu)(liu)(liu)，所以外接法適合于測小(xiao)電阻(zu)。

將靈敏電流計改裝成

電流表

指針(zhen)式電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)都是由(you)靈(ling)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)計(ji)(ji)改裝而(er)來的(de)(de)。靈(ling)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)計(ji)(ji)即使(shi)靈(ling)敏(min)度再高，江蘇正泰電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)，通過(guo)(guo)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不(bu)超(chao)過(guo)(guo)30微安(an)，而(er)學生用電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)測得(de)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)強度都是0.6A，正泰電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)報價，或者3A，遠遠超(chao)出醉大值(zhi)。電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)既要(yao)讓電(dian)(dian)(dian)(dian)(dian)(dian)路上的(de)(de)全部電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通過(guo)(guo)，又不(bu)允許(xu)通過(guo)(guo)線(xian)圈的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)超(chao)過(guo)(guo)安(an)全限(xian)度。電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)是與被測用電(dian)(dian)(dian)(dian)(dian)(dian)器串聯的(de)(de)，所以改裝時(shi)要(yao)分(fen)流(liu)(liu)。將(jiang)靈(ling)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)計(ji)(ji)與一個阻值(zhi)較小的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻并聯，這樣就會使(shi)大部分(fen)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)阻，正泰電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)表(biao)(biao)供應(ying)商，小部分(fen)經(jing)過(guo)(guo)表(biao)(biao)頭(tou)。這時(shi)將(jiang)表(biao)(biao)頭(tou)標上新的(de)(de)刻度，就可以了。

明泰(tai)(tai)電(dian)(dian)(dian)(dian)(dian)氣（蘇州(zhou)）有(you)限公司是正泰(tai)(tai)集團在蘇州(zhou)地(di)區(qu)一家授權的經銷企業(ye)，連續十年(nian)銷量居正泰(tai)(tai)營銷網(wang)絡(luo)名，公司主要(yao)經營“正泰(tai)(tai)”牌配電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)器(qi)、控制電(dian)(dian)(dian)(dian)(dian)器(qi)、終端電(dian)(dian)(dian)(dian)(dian)器(qi)、電(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)器(qi)、電(dian)(dian)(dian)(dian)(dian)力(li)電(dian)(dian)(dian)(dian)(dian)子、儀(yi)器(qi)儀(yi)表、建筑電(dian)(dian)(dian)(dian)(dian)器(qi)、高壓電(dian)(dian)(dian)(dian)(dian)器(qi)及成套(tao)設備。

對(dui)于幾(ji)安的(de)電(dian)(dian)(dian)流(liu)(liu)，可在電(dian)(dian)(dian)流(liu)(liu)表(biao)內設置分(fen)(fen)(fen)流(liu)(liu)器(qi)。對(dui)于幾(ji)安以上的(de)電(dian)(dian)(dian)流(liu)(liu)，則采(cai)用(yong)外附(fu)(fu)分(fen)(fen)(fen)流(liu)(liu)器(qi)。大電(dian)(dian)(dian)流(liu)(liu)分(fen)(fen)(fen)流(liu)(liu)器(qi)的(de)電(dian)(dian)(dian)阻(zu)(zu)值很小，為避免引線(xian)電(dian)(dian)(dian)阻(zu)(zu)和接觸電(dian)(dian)(dian)阻(zu)(zu)附(fu)(fu)加(jia)于分(fen)(fen)(fen)流(liu)(liu)器(qi)而(er)引起誤差，分(fen)(fen)(fen)流(liu)(liu)器(qi)要制成四端形(xing)式(shi)，即有兩(liang)個(ge)電(dian)(dian)(dian)流(liu)(liu)端，兩(liang)個(ge)電(dian)(dian)(dian)壓端。例如，當用(yong)外附(fu)(fu)分(fen)(fen)(fen)流(liu)(liu)器(qi)和毫伏(fu)表(biao)來測量(liang)200A的(de)大電(dian)(dian)(dian)流(liu)(liu)時，若(ruo)采(cai)用(yong)的(de)毫伏(fu)表(biao)標準化(hua)量(liang)程(cheng)為45mV（或75mV），那(nei)么分(fen)(fen)(fen)流(liu)(liu)器(qi)的(de)電(dian)(dian)(dian)阻(zu)(zu)值為0.045/200=0.000225Ω（或0.075/200=0.000375Ω）。若(ruo)利用(yong)環形(xing)（或稱(cheng)梯級）分(fen)(fen)(fen)流(liu)(liu)器(qi)，可制成多量(liang)程(cheng)電(dian)(dian)(dian)流(liu)(liu)表(biao)。