水中各種溶解性鹽類都以離子狀態存在，均具有導電能力，水中溶解的鹽類越多，離子也越多，水的電導率就越大。因此，根據水的電導率的大小，可以間接表示水中溶解固體的多少。作為反映水質狀況的一個重要指標，通過電導率的(de)大小能夠初步確定水(shui)質(zhi)狀況(kuang)。

但是(shi)(shi)純(chun)(chun)凈的(de)水是(shi)(shi)不(bu)能(neng)(neng)導(dao)電(dian)(dian)(dian)(dian)的(de)，但是(shi)(shi)也基本不(bu)存在百(bai)分之(zhi)分純(chun)(chun)凈的(de)水，水之(zhi)所(suo)以(yi)(yi)(yi)可以(yi)(yi)(yi)導(dao)電(dian)(dian)(dian)(dian)是(shi)(shi)因為其中(zhong)含(han)有某些鹽等電(dian)(dian)(dian)(dian)解質(zhi)，許多物(wu)質(zhi)溶(rong)于水時會形成離(li)(li)子，電(dian)(dian)(dian)(dian)解質(zhi)又(you)分為強電(dian)(dian)(dian)(dian)解質(zhi)和弱(ruo)(ruo)電(dian)(dian)(dian)(dian)解質(zhi)。弱(ruo)(ruo)電(dian)(dian)(dian)(dian)解質(zhi)的(de)電(dian)(dian)(dian)(dian)離(li)(li)與平衡常(chang)數、濃(nong)度(du)、電(dian)(dian)(dian)(dian)離(li)(li)度(du)均(jun)有關系(xi)；同樣的(de)，對于強電(dian)(dian)(dian)(dian)解質(zhi)，溶(rong)液電(dian)(dian)(dian)(dian)導(dao)率也與濃(nong)度(du)相關。所(suo)以(yi)(yi)(yi)，通(tong)過測量(liang)電(dian)(dian)(dian)(dian)導(dao)率的(de)大小，可以(yi)(yi)(yi)間(jian)接計算出溶(rong)液中(zhong)所(suo)含(han)電(dian)(dian)(dian)(dian)解質(zhi)的(de)濃(nong)度(du)，了解水中(zhong)電(dian)(dian)(dian)(dian)解質(zhi)的(de)含(han)量(liang)。因此，電(dian)(dian)(dian)(dian)導(dao)率是(shi)(shi)表示物(wu)質(zhi)傳(chuan)輸電(dian)(dian)(dian)(dian)流能(neng)(neng)力(li)強弱(ruo)(ruo)的(de)一種測量(liang)值。

水(shui)質(zhi)電(dian)(dian)導(dao)(dao)率(lv)(lv)檢測(ce)時(shi)，當施(shi)加電(dian)(dian)壓(ya)于導(dao)(dao)體的(de)兩端時(shi)，其電(dian)(dian)荷(he)載(zai)子(zi)會(hui)(hui)呈(cheng)現朝某方向流(liu)動的(de)行為(wei)，因而(er)產生(sheng)電(dian)(dian)流(liu)，用電(dian)(dian)流(liu)和(he)電(dian)(dian)壓(ya)測(ce)量(liang)(liang)值計(ji)算電(dian)(dian)導(dao)(dao)率(lv)(lv)。水(shui)溶液的(de)電(dian)(dian)導(dao)(dao)率(lv)(lv)高低(di)相(xiang)依于其內含(han)溶質(zhi)鹽的(de)濃度，或(huo)其它(ta)會(hui)(hui)分(fen)解(jie)為(wei)電(dian)(dian)解(jie)質(zhi)的(de)化(hua)學雜質(zhi)。水(shui)的(de)電(dian)(dian)導(dao)(dao)率(lv)(lv)是(shi)測(ce)量(liang)(liang)水(shui)的(de)含(han)鹽成(cheng)分(fen)、含(han)離子(zi)成(cheng)分(fen)、含(han)雜質(zhi)成(cheng)分(fen)等等的(de)重(zhong)要指標。水(shui)越(yue)(yue)純凈，電(dian)(dian)導(dao)(dao)率(lv)(lv)越(yue)(yue)低(di)，水(shui)中雜質(zhi)越(yue)(yue)多，電(dian)(dian)導(dao)(dao)率(lv)(lv)越(yue)(yue)高。所以(yi)根據測(ce)量(liang)(liang)電(dian)(dian)導(dao)(dao)率(lv)(lv)的(de)大小(xiao)，就可以(yi)基本判定水(shui)中雜質(zhi)含(han)量(liang)(liang)。

自然界的水體有很多種，不同的水體電解質含量各不相同，因此不同水體的電導率是不一樣的，通過電導率的數據，就可以很快速的鑒別各種不同的水類別。比如海水、自來水、鍋爐水、純凈水及超純水等，根據電導率的測定(ding)就(jiu)可(ke)以分辨出不(bu)同的水質，更(geng)好的服務于人類生活及工業應用。