恒電(dian)(dian)(dian)位(wei)儀(yi)整體說是一(yi)個負(fu)反饋放大(da)——輸出系統，與被保護物（如埋地管道）構成(cheng)閉環調(diao)節(jie)，通過參比電(dian)(dian)(dian)極測(ce)量通電(dian)(dian)(dian)點電(dian)(dian)(dian)位(wei)，作為取樣信(xin)號(hao)與控制信(xin)號(hao)進行(xing)比較，實現(xian)控制并調(diao)節(jie)極化電(dian)(dian)(dian)流輸出，使通電(dian)(dian)(dian)點電(dian)(dian)(dian)位(wei)得以保持在設定的控制電(dian)(dian)(dian)位(wei)上。

　其過(guo)程是(shi)：不管什(shen)么(me)原(yuan)(yuan)因(yin)——供電(dian)(dian)(dian)(dian)系統電(dian)(dian)(dian)(dian)壓波動，環境介質(zhi)導(dao)電(dian)(dian)(dian)(dian)性變化(hua)(hua)，或電(dian)(dian)(dian)(dian)路參(can)數(shu)漂(piao)移——使(shi)輸出(chu)(chu)增(zeng)大(da)(da)(da)，導(dao)致通電(dian)(dian)(dian)(dian)點(dian)(dian)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)上(shang)升(sheng)，則(ze)取樣(yang)信號(hao)增(zeng)大(da)(da)(da)，取樣(yang)信號(hao)是(shi)加在恒(heng)(heng)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)儀(yi)比較(jiao)(jiao)放(fang)(fang)大(da)(da)(da)的反相輸入端，與接在正相輸入端控(kong)制(zhi)(zhi)信號(hao)比較(jiao)(jiao)后使(shi)放(fang)(fang)大(da)(da)(da)器放(fang)(fang)大(da)(da)(da)倍數(shu)下降，控(kong)制(zhi)(zhi)極(ji)化(hua)(hua)電(dian)(dian)(dian)(dian)源(yuan)輸出(chu)(chu)減小，使(shi)通電(dian)(dian)(dian)(dian)點(dian)(dian)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)下降，回復到(dao)原(yuan)(yuan)設(she)定的控(kong)制(zhi)(zhi)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)值上(shang)；同樣(yang)，如(ru)果什(shen)么(me)原(yuan)(yuan)因(yin)使(shi)通電(dian)(dian)(dian)(dian)點(dian)(dian)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)下降，參(can)比電(dian)(dian)(dian)(dian)極(ji)得到(dao)的取樣(yang)信號(hao)下降，經過(guo)與控(kong)制(zhi)(zhi)信號(hao)比較(jiao)(jiao)使(shi)放(fang)(fang)大(da)(da)(da)器放(fang)(fang)大(da)(da)(da)倍數(shu)上(shang)升(sheng)，控(kong)制(zhi)(zhi)極(ji)化(hua)(hua)電(dian)(dian)(dian)(dian)源(yuan)輸出(chu)(chu)增(zeng)大(da)(da)(da)，通電(dian)(dian)(dian)(dian)點(dian)(dian)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)上(shang)升(sheng)，回復到(dao)原(yuan)(yuan)設(she)定的控(kong)制(zhi)(zhi)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)值上(shang)。也就是(shi)當外部或內部任(ren)何原(yuan)(yuan)因(yin)造成被保護物對地電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)變化(hua)(hua)時，恒(heng)(heng)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)儀(yi)都能(neng)相應地增(zeng)大(da)(da)(da)或減小輸出(chu)(chu)把變化(hua)(hua)的電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)拉回來，使(shi)通電(dian)(dian)(dian)(dian)點(dian)(dian)電(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)保持不變。

只要儀(yi)(yi)器的(de)放大倍數計算設計得正(zheng)確，取(qu)樣信(xin)號特性與儀(yi)(yi)器輸(shu)入輸(shu)出特性有足夠(gou)的(de)線(xian)性一(yi)致，并且調整良好(hao)，恒電位(wei)儀(yi)(yi)在額定工作范圍內可使被(bei)保護物通電點(dian)的(de)電位(wei)與設定的(de)控制電位(wei)一(yi)致，誤差一(yi)般在5mV以下(xia)。正(zheng)因其有使通電點(dian)電位(wei)保持近于恒定的(de)性質，因此稱為恒電位(wei)儀(yi)(yi)。

恒電(dian)(dian)位儀的核(he)心是比較(jiao)放大(da)器，由(you)深(shen)度負反饋的差(cha)動放大(da)器構成，現(xian)在(zai)一般采用性能優良的集(ji)成運算放大(da)器擔任，其輸入是控制(zhi)和參(can)比（取(qu)樣）電(dian)(dian)路，輸出(chu)到(dao)跟隨放大(da)、控制(zhi)移相、振蕩等電(dian)(dian)路生成觸發(fa)脈(mo)沖，極(ji)化電(dian)(dian)源由(you)晶閘管整流電(dian)(dian)路構成，通(tong)過改變導通(tong)角實現(xian)調節輸出(chu)。

恒(heng)電(dian)(dian)位(wei)(wei)(wei)(wei)儀(yi)的(de)接(jie)(jie)線不復雜，一般由4條(tiao)電(dian)(dian)纜組成（不考慮誤(wu)差、故障(zhang)報警(jing)等附屬(shu)電(dian)(dian)路(lu)可引出(chu)(chu)的(de)信號接(jie)(jie)線），分別接(jie)(jie)于(yu)：輸(shu)(shu)出(chu)(chu)陰(yin)極(ji)(ji)(ji)、輸(shu)(shu)出(chu)(chu)陽極(ji)(ji)(ji)、零(ling)位(wei)(wei)(wei)(wei)接(jie)(jie)陰(yin)、參(can)(can)比電(dian)(dian)極(ji)(ji)(ji)。輸(shu)(shu)出(chu)(chu)陰(yin)極(ji)(ji)(ji)是(shi)恒(heng)電(dian)(dian)位(wei)(wei)(wei)(wei)儀(yi)輸(shu)(shu)出(chu)(chu)的(de)負端子，接(jie)(jie)至(zhi)被保護物的(de)通(tong)電(dian)(dian)點，輸(shu)(shu)出(chu)(chu)陽極(ji)(ji)(ji)是(shi)恒(heng)電(dian)(dian)位(wei)(wei)(wei)(wei)儀(yi)的(de)正端子，接(jie)(jie)至(zhi)輔助陽極(ji)(ji)(ji)（地床或深井陽極(ji)(ji)(ji)）；零(ling)位(wei)(wei)(wei)(wei)接(jie)(jie)陰(yin)是(shi)儀(yi)器電(dian)(dian)路(lu)的(de)地端，接(jie)(jie)于(yu)被保護物通(tong)電(dian)(dian)點附近，參(can)(can)比電(dian)(dian)極(ji)(ji)(ji)即(ji)取樣信號輸(shu)(shu)入端，接(jie)(jie)埋設在通(tong)電(dian)(dian)點附近的(de)參(can)(can)比電(dian)(dian)極(ji)(ji)(ji)。輸(shu)(shu)出(chu)(chu)陰(yin)極(ji)(ji)(ji)和(he)輸(shu)(shu)出(chu)(chu)陽極(ji)(ji)(ji)電(dian)(dian)纜要有足(zu)(zu)夠(gou)(gou)的(de)截面積，一般不應小于(yu)10 mm2；零(ling)位(wei)(wei)(wei)(wei)接(jie)(jie)陰(yin)和(he)參(can)(can)比電(dian)(dian)極(ji)(ji)(ji)對(dui)電(dian)(dian)纜截面無(wu)要求，只考慮足(zu)(zu)夠(gou)(gou)強度(du)即(ji)可。恒(heng)電(dian)(dian)位(wei)(wei)(wei)(wei)儀(yi)的(de)接(jie)(jie)線都應該是(shi)銅線，遠端并(bing)應焊(han)接(jie)(jie)。

　　值得說(shuo)明的是(shi)零(ling)位接陰(yin)是(shi)接于(yu)通電(dian)點幾乎同一點（以電(dian)的概(gai)念解釋就是(shi)同一點，施工時應該離開(kai)50～100mm，避開(kai)電(dian)流涌(yong)入），但是(shi)必須用單(dan)獨接線(xian)，因(yin)為零(ling)位接陰(yin)是(shi)整個儀器(qi)電(dian)路(lu)的地，這個“地”必須建立在被(bei)保護(hu)物（管道）上，才能實現正確控制，因(yin)此絕不能使(shi)用短(duan)線(xian)把零(ling)位接陰(yin)與輸(shu)出陰(yin)極(ji)接在一起，雖(sui)然(ran)那(nei)按電(dian)的概(gai)念也是(shi)同一點。

　　zui后說(shuo)明一下，恒(heng)電位(wei)(wei)儀是(shi)電化學研究、應(ying)用方面(mian)的(de)重要儀器，有很多(duo)種類，上面(mian)說(shuo)的(de)是(shi)用于陰(yin)極(ji)保護(hu)的(de)恒(heng)電位(wei)(wei)儀的(de)基本方面(mian)。