恒電(dian)位(wei)儀(yi)整體說是一個負(fu)反饋放大——輸出系統，與被(bei)保護(hu)物(wu)（如埋地管道）構成閉環調節，通過參比電(dian)極測量通電(dian)點(dian)電(dian)位(wei)，作(zuo)為取樣信號與控(kong)制(zhi)信號進行比較，實(shi)現(xian)控(kong)制(zhi)并調節極化(hua)電(dian)流輸出，使通電(dian)點(dian)電(dian)位(wei)得(de)以保持(chi)在設定的控(kong)制(zhi)電(dian)位(wei)上。

　其(qi)過(guo)程是(shi)(shi)：不管什么原(yuan)因——供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)系(xi)統電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓波動，環境介質導電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)性變(bian)化(hua)，或電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路參(can)數(shu)漂(piao)移(yi)——使(shi)輸出增(zeng)大(da)(da)，導致(zhi)通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)點電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)上(shang)升(sheng)，則取(qu)(qu)(qu)樣信(xin)(xin)號(hao)增(zeng)大(da)(da)，取(qu)(qu)(qu)樣信(xin)(xin)號(hao)是(shi)(shi)加在(zai)恒電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)儀比較(jiao)(jiao)放大(da)(da)的(de)反(fan)相輸入(ru)端，與接(jie)在(zai)正相輸入(ru)端控制(zhi)信(xin)(xin)號(hao)比較(jiao)(jiao)后使(shi)放大(da)(da)器(qi)放大(da)(da)倍數(shu)下降，控制(zhi)極(ji)化(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源輸出減小(xiao)，使(shi)通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)點電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)下降，回復到原(yuan)設(she)定(ding)的(de)控制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)值上(shang)；同樣，如果什么原(yuan)因使(shi)通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)點電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)下降，參(can)比電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極(ji)得(de)到的(de)取(qu)(qu)(qu)樣信(xin)(xin)號(hao)下降，經過(guo)與控制(zhi)信(xin)(xin)號(hao)比較(jiao)(jiao)使(shi)放大(da)(da)器(qi)放大(da)(da)倍數(shu)上(shang)升(sheng)，控制(zhi)極(ji)化(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源輸出增(zeng)大(da)(da)，通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)點電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)上(shang)升(sheng)，回復到原(yuan)設(she)定(ding)的(de)控制(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)值上(shang)。也就(jiu)是(shi)(shi)當外部或內部任何原(yuan)因造成被(bei)保護物對(dui)地(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)變(bian)化(hua)時，恒電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)儀都能(neng)相應地(di)增(zeng)大(da)(da)或減小(xiao)輸出把(ba)變(bian)化(hua)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)拉回來，使(shi)通電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)點電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)(wei)(wei)(wei)(wei)(wei)保持不變(bian)。

只要儀器的放大(da)倍數(shu)計算設(she)(she)計得正確，取樣(yang)信號(hao)特性(xing)與儀器輸入輸出特性(xing)有(you)(you)足(zu)夠(gou)的線性(xing)一致，并(bing)且(qie)調整良好(hao)，恒(heng)電(dian)位儀在額定工(gong)作范圍內(nei)可(ke)使(shi)被(bei)保護(hu)物通(tong)電(dian)點(dian)的電(dian)位與設(she)(she)定的控制電(dian)位一致，誤差一般在5mV以(yi)下。正因其(qi)有(you)(you)使(shi)通(tong)電(dian)點(dian)電(dian)位保持近于恒(heng)定的性(xing)質，因此稱為(wei)恒(heng)電(dian)位儀。

恒(heng)電(dian)位儀(yi)的核心是(shi)比較(jiao)放(fang)大(da)(da)器(qi)，由深度負反饋(kui)的差動放(fang)大(da)(da)器(qi)構成(cheng)，現(xian)在一般采用性能優(you)良(liang)的集成(cheng)運算放(fang)大(da)(da)器(qi)擔任(ren)，其(qi)輸入是(shi)控(kong)制(zhi)(zhi)和參(can)比（取樣(yang)）電(dian)路(lu)，輸出(chu)到跟隨放(fang)大(da)(da)、控(kong)制(zhi)(zhi)移相、振蕩等電(dian)路(lu)生成(cheng)觸發脈沖，極(ji)化電(dian)源由晶閘(zha)管整(zheng)流電(dian)路(lu)構成(cheng)，通過(guo)改變導通角實現(xian)調節輸出(chu)。

恒電(dian)(dian)(dian)(dian)位(wei)儀(yi)(yi)的接(jie)(jie)線(xian)(xian)不復雜，一般由4條(tiao)電(dian)(dian)(dian)(dian)纜組成(cheng)（不考(kao)慮誤差、故障(zhang)報(bao)警等附屬(shu)電(dian)(dian)(dian)(dian)路(lu)可(ke)引出(chu)的信號接(jie)(jie)線(xian)(xian)），分別接(jie)(jie)于(yu)：輸(shu)出(chu)陰(yin)(yin)極(ji)(ji)(ji)(ji)、輸(shu)出(chu)陽(yang)極(ji)(ji)(ji)(ji)、零位(wei)接(jie)(jie)陰(yin)(yin)、參(can)比(bi)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)。輸(shu)出(chu)陰(yin)(yin)極(ji)(ji)(ji)(ji)是恒電(dian)(dian)(dian)(dian)位(wei)儀(yi)(yi)輸(shu)出(chu)的負(fu)端子，接(jie)(jie)至(zhi)被(bei)保護物的通(tong)電(dian)(dian)(dian)(dian)點(dian)，輸(shu)出(chu)陽(yang)極(ji)(ji)(ji)(ji)是恒電(dian)(dian)(dian)(dian)位(wei)儀(yi)(yi)的正(zheng)端子，接(jie)(jie)至(zhi)輔助陽(yang)極(ji)(ji)(ji)(ji)（地床或深(shen)井陽(yang)極(ji)(ji)(ji)(ji)）；零位(wei)接(jie)(jie)陰(yin)(yin)是儀(yi)(yi)器電(dian)(dian)(dian)(dian)路(lu)的地端，接(jie)(jie)于(yu)被(bei)保護物通(tong)電(dian)(dian)(dian)(dian)點(dian)附近(jin)，參(can)比(bi)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)即取樣信號輸(shu)入端，接(jie)(jie)埋設(she)在通(tong)電(dian)(dian)(dian)(dian)點(dian)附近(jin)的參(can)比(bi)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)。輸(shu)出(chu)陰(yin)(yin)極(ji)(ji)(ji)(ji)和(he)輸(shu)出(chu)陽(yang)極(ji)(ji)(ji)(ji)電(dian)(dian)(dian)(dian)纜要(yao)有足夠(gou)的截(jie)面(mian)積，一般不應(ying)小(xiao)于(yu)10 mm2；零位(wei)接(jie)(jie)陰(yin)(yin)和(he)參(can)比(bi)電(dian)(dian)(dian)(dian)極(ji)(ji)(ji)(ji)對電(dian)(dian)(dian)(dian)纜截(jie)面(mian)無要(yao)求，只(zhi)考(kao)慮足夠(gou)強度即可(ke)。恒電(dian)(dian)(dian)(dian)位(wei)儀(yi)(yi)的接(jie)(jie)線(xian)(xian)都應(ying)該是銅線(xian)(xian)，遠端并應(ying)焊(han)接(jie)(jie)。

　　值(zhi)得(de)說明(ming)的是(shi)零(ling)(ling)位接(jie)(jie)陰是(shi)接(jie)(jie)于(yu)通電點(dian)幾乎同一(yi)點(dian)（以電的概念解(jie)釋(shi)就是(shi)同一(yi)點(dian)，施工時應該(gai)離(li)開50～100mm，避開電流(liu)涌(yong)入(ru)），但是(shi)必須(xu)(xu)用單獨接(jie)(jie)線(xian)，因(yin)為零(ling)(ling)位接(jie)(jie)陰是(shi)整(zheng)個儀器電路的地，這個“地”必須(xu)(xu)建立在(zai)(zai)被保護物（管道）上，才能(neng)實現(xian)正確(que)控(kong)制，因(yin)此絕不能(neng)使用短(duan)線(xian)把零(ling)(ling)位接(jie)(jie)陰與輸(shu)出陰極接(jie)(jie)在(zai)(zai)一(yi)起(qi)，雖然(ran)那按電的概念也是(shi)同一(yi)點(dian)。

　　zui后說明一下，恒電(dian)位儀(yi)是電(dian)化學研究(jiu)、應用方(fang)面的(de)重(zhong)要儀(yi)器，有(you)很多種類，上(shang)面說的(de)是用于陰極保(bao)護(hu)的(de)恒電(dian)位儀(yi)的(de)基本方(fang)面。