鎧裝熱電偶是(shi)(shi)溫(wen)(wen)度測(ce)量中(zhong)應(ying)用(yong)最廣泛(fan)的(de)(de)(de)溫(wen)(wen)度器件，他的(de)(de)(de)主要特點就是(shi)(shi)測(ce)溫(wen)(wen)范(fan)圍寬(kuan)，性能(neng)比較穩(wen)定，同(tong)(tong)(tong)時結(jie)構簡單，動(dong)態響應(ying)好，更能(neng)夠遠傳4-20mA電(dian)(dian)(dian)(dian)信號，便(bian)于自動(dong)控(kong)制和集中(zhong)控(kong)制。熱(re)電(dian)(dian)(dian)(dian)偶的(de)(de)(de)測(ce)溫(wen)(wen)原理是(shi)(shi)基于熱(re)電(dian)(dian)(dian)(dian)效(xiao)應(ying)。將兩(liang)種不同(tong)(tong)(tong)的(de)(de)(de)導(dao)(dao)(dao)體(ti)或(huo)半導(dao)(dao)(dao)體(ti)連接(jie)成(cheng)閉合回路，當(dang)兩(liang)個接(jie)點處的(de)(de)(de)溫(wen)(wen)度不同(tong)(tong)(tong)時，回路中(zhong)將產(chan)生(sheng)熱(re)電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)，這種現象稱為熱(re)電(dian)(dian)(dian)(dian)效(xiao)應(ying)，又(you)稱為塞貝克效(xiao)應(ying)。。溫(wen)(wen)差電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)是(shi)(shi)指同(tong)(tong)(tong)一導(dao)(dao)(dao)體(ti)的(de)(de)(de)兩(liang)端因溫(wen)(wen)度不同(tong)(tong)(tong)而產(chan)生(sheng)的(de)(de)(de)電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)，不同(tong)(tong)(tong)的(de)(de)(de)導(dao)(dao)(dao)體(ti)具有不同(tong)(tong)(tong)的(de)(de)(de)電(dian)(dian)(dian)(dian)子(zi)(zi)密(mi)度，所(suo)(suo)以他們(men)(men)產(chan)生(sheng)的(de)(de)(de)電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)也不相同(tong)(tong)(tong)，而接(jie)觸(chu)(chu)電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)顧名思義就是(shi)(shi)指兩(liang)種不同(tong)(tong)(tong)的(de)(de)(de)導(dao)(dao)(dao)體(ti)相接(jie)觸(chu)(chu)時，因為他們(men)(men)的(de)(de)(de)電(dian)(dian)(dian)(dian)子(zi)(zi)密(mi)度不同(tong)(tong)(tong)所(suo)(suo)以產(chan)生(sheng)一定的(de)(de)(de)電(dian)(dian)(dian)(dian)子(zi)(zi)擴散，當(dang)他們(men)(men)達(da)到一定的(de)(de)(de)平衡后所(suo)(suo)形成(cheng)的(de)(de)(de)電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)，接(jie)觸(chu)(chu)電(dian)(dian)(dian)(dian)勢(shi)(shi)(shi)的(de)(de)(de)大小取決(jue)于兩(liang)種不同(tong)(tong)(tong)導(dao)(dao)(dao)體(ti)的(de)(de)(de)材料(liao)性質以及他們(men)(men)接(jie)觸(chu)(chu)點的(de)(de)(de)溫(wen)(wen)度。

國際上應用的熱電偶具有一個標準規范，國際上規定熱電偶分為八個不同的分度，分別為B，R，S，K，N，E，J和T，其測量溫度的最低可測零下270攝氏度，最高可達1800攝氏度，其中B，R，S屬于鉑系列的熱補償導線。不同(tong)(tong)的(de)熱(re)(re)(re)電(dian)偶需(xu)要(yao)不同(tong)(tong)的(de)補(bu)(bu)(bu)(bu)償導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)，其主要(yao)作用(yong)(yong)就是(shi)與熱(re)(re)(re)電(dian)偶連接(jie)，使熱(re)(re)(re)電(dian)偶的(de)參(can)比(bi)端遠離電(dian)源，從(cong)而使參(can)比(bi)端溫度(du)穩定。補(bu)(bu)(bu)(bu)償導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)又分(fen)為補(bu)(bu)(bu)(bu)償型和(he)延長(chang)型兩種，延長(chang)導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)的(de)化學成分(fen)與被補(bu)(bu)(bu)(bu)償的(de)熱(re)(re)(re)電(dian)偶相同(tong)(tong)，但(dan)是(shi)實(shi)際中，延長(chang)型的(de)導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)也并不是(shi)用(yong)(yong)和(he)熱(re)(re)(re)電(dian)偶相同(tong)(tong)材(cai)質的(de)金屬，一(yi)般采用(yong)(yong)和(he)熱(re)(re)(re)電(dian)偶具(ju)有相同(tong)(tong)電(dian)子密度(du)的(de)導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)代替。補(bu)(bu)(bu)(bu)償導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)的(de)與熱(re)(re)(re)電(dian)偶的(de)連線(xian)(xian)(xian)(xian)一(yi)般都是(shi)很明了，熱(re)(re)(re)電(dian)偶的(de)正極(ji)連接(jie)補(bu)(bu)(bu)(bu)償導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)的(de)紅色(se)(se)線(xian)(xian)(xian)(xian)，而負極(ji)則(ze)連接(jie)剩下的(de)顏色(se)(se)。一(yi)般的(de)補(bu)(bu)(bu)(bu)償導(dao)(dao)(dao)線(xian)(xian)(xian)(xian)的(de)材(cai)質大部分(fen)都采用(yong)(yong)合金。