測(ce)溫原理是基于(yu)(yu)導體(ti)或(huo)半(ban)導體(ti)的電(dian)阻值隨著溫度(du)(du)的變(bian)化(hua)而變(bian)化(hua)的特性(xing)。其優點(dian)也(ye)很(hen)多(duo)，也(ye)可以(yi)(yi)遠傳電(dian)信號，靈敏度(du)(du)高，穩定(ding)(ding)性(xing)強，互換性(xing)以(yi)(yi)及準確性(xing)都比較好，但是需要電(dian)源激(ji)勵，不(bu)能夠瞬時測(ce)量溫度(du)(du)的變(bian)化(hua)。不(bu)同的導體(ti)具有不(bu)同的電(dian)子(zi)(zi)密度(du)(du)，因為(wei)他(ta)(ta)們的電(dian)子(zi)(zi)密度(du)(du)不(bu)同所以(yi)(yi)產生一定(ding)(ding)的電(dian)子(zi)(zi)擴散，當他(ta)(ta)們達到一定(ding)(ding)的平衡后所形成(cheng)的電(dian)勢(shi)，接觸電(dian)勢(shi)的大小(xiao)取決(jue)于(yu)(yu)兩種(zhong)不(bu)同導體(ti)的材(cai)料性(xing)質以(yi)(yi)及他(ta)(ta)們接觸點(dian)的溫度(du)(du)。 耐磨熱電(dian)(dian)(dian)阻(zu)(zu)(zu)采用三線(xian)(xian)制是為了(le)消除連(lian)接(jie)導(dao)線(xian)(xian)電(dian)(dian)(dian)阻(zu)(zu)(zu)引起(qi)的(de)(de)測量誤(wu)差(cha)。這(zhe)是因(yin)為測量熱電(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)(de)電(dian)(dian)(dian)路一(yi)般是不平衡電(dian)(dian)(dian)橋(qiao)(qiao)。熱電(dian)(dian)(dian)阻(zu)(zu)(zu)作(zuo)為電(dian)(dian)(dian)橋(qiao)(qiao)的(de)(de)一(yi)個橋(qiao)(qiao)臂(bei)電(dian)(dian)(dian)阻(zu)(zu)(zu)，其連(lian)接(jie)導(dao)線(xian)(xian)（從熱電(dian)(dian)(dian)阻(zu)(zu)(zu)到(dao)中控室）也(ye)成為橋(qiao)(qiao)臂(bei)電(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)(de)一(yi)部分，這(zhe)一(yi)部分電(dian)(dian)(dian)阻(zu)(zu)(zu)是未知的(de)(de)且隨(sui)環境溫(wen)度變化(hua)，造成測量誤(wu)差(cha)。采用三線(xian)(xian)制，將(jiang)導(dao)線(xian)(xian)一(yi)根接(jie)到(dao)電(dian)(dian)(dian)橋(qiao)(qiao)的(de)(de)電(dian)(dian)(dian)源端(duan)，其余(yu)兩根分別接(jie)到(dao)熱電(dian)(dian)(dian)阻(zu)(zu)(zu)所(suo)在的(de)(de)橋(qiao)(qiao)臂(bei)及與其相(xiang)鄰的(de)(de)橋(qiao)(qiao)臂(bei)上，這(zhe)樣消除了(le)導(dao)線(xian)(xian)線(xian)(xian)路電(dian)(dian)(dian)阻(zu)(zu)(zu)帶來的(de)(de)測量誤(wu)差(cha)。
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