普通電(dian)(dian)(dian)(dian)阻(zu)(zu)的測(ce)(ce)(ce)量(liang)(liang)(liang)通常(chang)有低(di)電(dian)(dian)(dian)(dian)壓(ya)下(xia)測(ce)(ce)(ce)量(liang)(liang)(liang)和高電(dian)(dian)(dian)(dian)壓(ya)下(xia)測(ce)(ce)(ce)量(liang)(liang)(liang)兩種方式(shi)。而(er)絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)由于(yu)一般(ban)數值(zhi)較高（一般(ban)為(wei)兆(zhao)(zhao)歐(ou)級）。在低(di)電(dian)(dian)(dian)(dian)壓(ya)下(xia)的測(ce)(ce)(ce)量(liang)(liang)(liang)值(zhi)不能(neng)反映在高電(dian)(dian)(dian)(dian)壓(ya)條(tiao)件下(xia)工作的真正(zheng)絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)值(zhi)。兆(zhao)(zhao)歐(ou)表(biao)也叫絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)表(biao)。它是測(ce)(ce)(ce)量(liang)(liang)(liang)絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)常(chang)用(yong)的儀表(biao)。它在測(ce)(ce)(ce)量(liang)(liang)(liang)絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)時本身就(jiu)有高電(dian)(dian)(dian)(dian)壓(ya)電(dian)(dian)(dian)(dian)源，這就(jiu)是它與測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)阻(zu)(zu)儀表(biao)的不同之(zhi)處。兆(zhao)(zhao)歐(ou)表(biao)用(yong)于(yu)測(ce)(ce)(ce)量(liang)(liang)(liang)絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)即方便又(you)可靠(kao)。但(dan)是如果(guo)使(shi)用(yong)不當，它將給測(ce)(ce)(ce)量(liang)(liang)(liang)帶(dai)來不必要的誤差(cha)，我們必須正(zheng)確使(shi)用(yong)兆(zhao)(zhao)歐(ou)表(biao)絕(jue)緣電(dian)(dian)(dian)(dian)阻(zu)(zu)進(jin)行測(ce)(ce)(ce)量(liang)(liang)(liang)。

現代生活日新月異，人們(men)一(yi)刻(ke)也離(li)不開(kai)電(dian)(dian)(dian)(dian)(dian)。在用(yong)電(dian)(dian)(dian)(dian)(dian)過程(cheng)(cheng)中就存在著用(yong)電(dian)(dian)(dian)(dian)(dian)安全(quan)問題，在電(dian)(dian)(dian)(dian)(dian)器設備(bei)中，例如電(dian)(dian)(dian)(dian)(dian)機(ji)、電(dian)(dian)(dian)(dian)(dian)纜、家(jia)用(yong)電(dian)(dian)(dian)(dian)(dian)器等。它(ta)們(men)的正常運行之(zhi)一(yi)就是其絕(jue)緣材料的絕(jue)緣程(cheng)(cheng)度(du)即(ji)絕(jue)緣電(dian)(dian)(dian)(dian)(dian)阻(zu)的數(shu)值。當受熱和受潮(chao)時，絕(jue)緣材料便老化。其絕(jue)緣電(dian)(dian)(dian)(dian)(dian)阻(zu)便降低。從而造(zao)成(cheng)電(dian)(dian)(dian)(dian)(dian)器設備(bei)漏電(dian)(dian)(dian)(dian)(dian)或(huo)短(duan)路事(shi)故的發生。為了避免事(shi)故發生，就要(yao)求經常測量各種(zhong)電(dian)(dian)(dian)(dian)(dian)器設備(bei)的絕(jue)緣電(dian)(dian)(dian)(dian)(dian)阻(zu)。判斷其絕(jue)緣程(cheng)(cheng)度(du)是否滿(man)足(zu)設備(bei)需要(yao)。

兆歐表在工作時，自身產生高電壓，而測量對象又是(shi)電氣設備(bei)，所以必須正確使(shi)用，否則就(jiu)會造(zao)成人身或設備(bei)事故。使(shi)用前(qian)，首先要做好以下(xia)各種準備(bei)：

（1）測量前必(bi)須將被測設備電(dian)源切斷，并對地短路放電(dian)，決不允許設備帶(dai)電(dian)進行測量，以保證人身和設備的安全。

（2）對(dui)可能(neng)(neng)感應出高壓電(dian)的設備，必須消除這種可能(neng)(neng)性后，才能(neng)(neng)進行測(ce)量。

（3）被測(ce)物表面要清潔(jie)，減少接觸電阻，確保測(ce)量結果的(de)正確性。

（4）測量前要檢(jian)(jian)查兆歐(ou)表是否處于正常工作狀態，主要檢(jian)(jian)查其(qi)“0”和“∞”兩點(dian)。即搖動手柄，使電機達到(dao)額定轉速，兆歐(ou)表在(zai)短路(lu)(lu)時應指在(zai)“0”位(wei)置，開路(lu)(lu)時應指在(zai)“∞”位(wei)置。

（5）兆歐(ou)表使(shi)用(yong)時應放在平穩、牢固的地方，且遠(yuan)離大的外(wai)電流導體和外(wai)磁場。

做好上述準備(bei)工作(zuo)后就(jiu)可(ke)以進行測(ce)量了(le)，在測(ce)量時，還要注意(yi)兆(zhao)歐(ou)表(biao)的正確接線(xian)，否則將引(yin)起(qi)不必要的誤(wu)差甚至錯誤(wu)。