萬用表又叫多用表、三用表、復用表，萬用表分為指針式萬用表和數字萬用表。是一種多功能、多量程的測量儀表，一般萬用表可測量直流電流、直流電壓、交流電壓、電阻和、音頻電(dian)平等，有的還可以測(ce)交(jiao)流(liu)電(dian)流(liu)、電(dian)容量(liang)(liang)、電(dian)感量(liang)(liang)及(ji)半導(dao)體的一些參數。萬用(yong)表(biao)由(you)表(biao)頭、測(ce)量(liang)(liang)電(dian)路及(ji)轉換開(kai)關(guan)等三個主要部分組成。萬用(yong)表(biao)(biao)的(de)工作原理(li)是利用(yong)一只靈敏的(de)磁電(dian)(dian)(dian)(dian)(dian)式直流(liu)電(dian)(dian)(dian)(dian)(dian)流(liu)表(biao)(biao)（微(wei)安表(biao)(biao)）做(zuo)表(biao)(biao)頭。當微(wei)小電(dian)(dian)(dian)(dian)(dian)流(liu)通(tong)過表(biao)(biao)頭，就會有電(dian)(dian)(dian)(dian)(dian)流(liu)指示。但表(biao)(biao)頭不能通(tong)過大電(dian)(dian)(dian)(dian)(dian)流(liu)，所以，必須(xu)在表(biao)(biao)頭上并聯(lian)與(yu)串聯(lian)一些(xie)電(dian)(dian)(dian)(dian)(dian)阻進行分流(liu)或降壓，從而測出電(dian)(dian)(dian)(dian)(dian)路中的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)壓和電(dian)(dian)(dian)(dian)(dian)阻。

小編在這里提醒大家：1、在使用萬用表之前，應先進行“機械調零”，即在沒有被測電量時 ，使萬用表指針指在零電壓或零電流的位置上。2、在使用萬用表過程中，不能用手去接觸表筆的金屬部分 ，這樣(yang)一(yi)方(fang)面可以保證測量的準(zhun)確，另一(yi)方(fang)面也可以保證人身安全(quan)。3、在(zai)(zai)測(ce)量某一(yi)電(dian)(dian)量時，不能(neng)在(zai)(zai)測(ce)量的(de)同(tong)時換(huan)(huan)(huan)檔，尤其是在(zai)(zai)測(ce)量高電(dian)(dian)壓或大(da)電(dian)(dian)流(liu)時 ，更應注(zhu)意。否則，會使萬用表毀(hui)壞(huai)。如需換(huan)(huan)(huan)檔，應先斷開(kai)表筆，換(huan)(huan)(huan)檔后(hou)再去(qu)測(ce)量。