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怎樣區別熱電偶和熱電阻

時間：2018-10-23 17:23:47 點擊：次

首先(xian)，介紹一下熱電偶(ou)，熱(re)電偶(ou)是溫(wen)度(du)測量中應用最廣泛的(de)溫(wen)度(du)器件，他的(de)主要特點(dian)就(jiu)是測量范圍(wei)寬，性能比(bi)較(jiao)穩定(ding)，同(tong)時(shi)結構(gou)簡單，動(dong)態響應好，更(geng)能夠(gou)遠傳4-20mA電信號，便(bian)于自動(dong)控制(zhi)和集中控制(zhi)。
熱(re)電偶的(de)(de)(de)測溫(wen)(wen)原理是基于熱電(dian)(dian)效(xiao)應(ying)。將(jiang)兩(liang)種(zhong)(zhong)(zhong)不(bu)同(tong)(tong)(tong)的(de)(de)(de)導體或半導體連(lian)接(jie)(jie)成閉合回路(lu)(lu)，當(dang)兩(liang)個(ge)接(jie)(jie)點處的(de)(de)(de)溫(wen)(wen)度(du)不(bu)同(tong)(tong)(tong)時，回路(lu)(lu)中將(jiang)產(chan)(chan)生(sheng)(sheng)熱電(dian)(dian)勢(shi)(shi)(shi)，這種(zhong)(zhong)(zhong)現象稱為熱電(dian)(dian)效(xiao)應(ying)，又稱為塞(sai)貝克效(xiao)應(ying)。閉合回路(lu)(lu)中產(chan)(chan)生(sheng)(sheng)的(de)(de)(de)熱電(dian)(dian)勢(shi)(shi)(shi)有(you)兩(liang)種(zhong)(zhong)(zhong)電(dian)(dian)勢(shi)(shi)(shi)組成；溫(wen)(wen)差(cha)電(dian)(dian)勢(shi)(shi)(shi)和接(jie)(jie)觸電(dian)(dian)勢(shi)(shi)(shi)。溫(wen)(wen)差(cha)電(dian)(dian)勢(shi)(shi)(shi)是指(zhi)同(tong)(tong)(tong)一(yi)(yi)導體的(de)(de)(de)兩(liang)端因溫(wen)(wen)度(du)不(bu)同(tong)(tong)(tong)而產(chan)(chan)生(sheng)(sheng)的(de)(de)(de)電(dian)(dian)勢(shi)(shi)(shi)，不(bu)同(tong)(tong)(tong)的(de)(de)(de)導體具有(you)不(bu)同(tong)(tong)(tong)的(de)(de)(de)電(dian)(dian)子(zi)密(mi)度(du)，所以他(ta)們(men)產(chan)(chan)生(sheng)(sheng)的(de)(de)(de)電(dian)(dian)勢(shi)(shi)(shi)也不(bu)相同(tong)(tong)(tong)，而接(jie)(jie)觸電(dian)(dian)勢(shi)(shi)(shi)顧名思義就是指(zhi)兩(liang)種(zhong)(zhong)(zhong)不(bu)同(tong)(tong)(tong)的(de)(de)(de)導體相接(jie)(jie)觸時，因為他(ta)們(men)的(de)(de)(de)電(dian)(dian)子(zi)密(mi)度(du)不(bu)同(tong)(tong)(tong)所以產(chan)(chan)生(sheng)(sheng)一(yi)(yi)定的(de)(de)(de)電(dian)(dian)子(zi)擴散，當(dang)他(ta)們(men)達到一(yi)(yi)定的(de)(de)(de)平(ping)衡后(hou)所形(xing)成的(de)(de)(de)電(dian)(dian)勢(shi)(shi)(shi)，接(jie)(jie)觸電(dian)(dian)勢(shi)(shi)(shi)的(de)(de)(de)大小取決于兩(liang)種(zhong)(zhong)(zhong)不(bu)同(tong)(tong)(tong)導體的(de)(de)(de)材料性質以及他(ta)們(men)接(jie)(jie)觸點的(de)(de)(de)溫(wen)(wen)度(du)。
目前(qian)國際(ji)(ji)上應用的熱(re)電偶(ou)(ou)(ou)具有一(yi)(yi)個(ge)(ge)標準規范，國際(ji)(ji)上規定熱(re)電偶(ou)(ou)(ou)分為(wei)(wei)八個(ge)(ge)不同的分度，分別(bie)為(wei)(wei)B、R、S、K、N、E、J和T，其(qi)測(ce)量溫度最低(di)可測(ce)零下(xia)270攝氏(shi)度，最高可達1800攝氏(shi)度，其(qi)中B、R、S屬(shu)于鉑(bo)系列熱(re)電偶(ou)(ou)(ou)，由于鉑(bo)屬(shu)于貴重金(jin)屬(shu)，所以又被稱為(wei)(wei)貴金(jin)屬(shu)熱(re)電偶(ou)(ou)(ou)。而(er)(er)剩下(xia)的則稱為(wei)(wei)廉(lian)價金(jin)屬(shu)熱(re)電偶(ou)(ou)(ou)。熱(re)電偶(ou)(ou)(ou)的結構有兩種：普通型(xing)(xing)(xing)和鎧裝型(xing)(xing)(xing)。普通型(xing)(xing)(xing)熱(re)電偶(ou)(ou)(ou)一(yi)(yi)般由熱(re)電極、絕(jue)緣管(guan)、保護(hu)套管(guan)和接線盒(he)等部分組成。而(er)(er)鎧裝型(xing)(xing)(xing)熱(re)電偶(ou)(ou)(ou)則是將熱(re)電偶(ou)(ou)(ou)絲、絕(jue)緣材料和金(jin)屬(shu)保護(hu)套管(guan)三者組合裝配后，經過拉伸(shen)加工而(er)(er)成的一(yi)(yi)種堅實的組合體(ti)。
但是(shi)熱(re)(re)(re)電(dian)(dian)偶(ou)的(de)(de)(de)電(dian)(dian)信號卻需要(yao)(yao)一(yi)(yi)種(zhong)特(te)殊的(de)(de)(de)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)來進行傳遞，這種(zhong)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)我們稱為補(bu)(bu)償(chang)(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)。不(bu)同(tong)的(de)(de)(de)熱(re)(re)(re)電(dian)(dian)偶(ou)需要(yao)(yao)不(bu)同(tong)的(de)(de)(de)補(bu)(bu)償(chang)(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)，其主要(yao)(yao)作用(yong)(yong)就(jiu)是(shi)與(yu)熱(re)(re)(re)電(dian)(dian)偶(ou)連(lian)(lian)接(jie)，使熱(re)(re)(re)電(dian)(dian)偶(ou)的(de)(de)(de)參比端(duan)遠離電(dian)(dian)源，從而使參比端(duan)溫度穩(wen)定。補(bu)(bu)償(chang)(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)又分為補(bu)(bu)償(chang)(chang)型和(he)延(yan)(yan)長(chang)型兩種(zhong)，延(yan)(yan)長(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)的(de)(de)(de)化學(xue)成(cheng)分與(yu)被補(bu)(bu)償(chang)(chang)的(de)(de)(de)熱(re)(re)(re)電(dian)(dian)偶(ou)相同(tong)，但是(shi)實際中(zhong)，延(yan)(yan)長(chang)型的(de)(de)(de)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)也并不(bu)是(shi)用(yong)(yong)和(he)熱(re)(re)(re)電(dian)(dian)偶(ou)相同(tong)材質的(de)(de)(de)金(jin)屬，一(yi)(yi)般(ban)采(cai)用(yong)(yong)和(he)熱(re)(re)(re)電(dian)(dian)偶(ou)具有相同(tong)電(dian)(dian)子密度的(de)(de)(de)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)代替(ti)。補(bu)(bu)償(chang)(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)的(de)(de)(de)與(yu)熱(re)(re)(re)電(dian)(dian)偶(ou)的(de)(de)(de)連(lian)(lian)線(xian)(xian)(xian)一(yi)(yi)般(ban)都是(shi)很明了(le)，熱(re)(re)(re)電(dian)(dian)偶(ou)的(de)(de)(de)正極連(lian)(lian)接(jie)補(bu)(bu)償(chang)(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)的(de)(de)(de)紅色線(xian)(xian)(xian)，而負(fu)極則連(lian)(lian)接(jie)剩下的(de)(de)(de)顏色。一(yi)(yi)般(ban)補(bu)(bu)償(chang)(chang)導(dao)(dao)(dao)(dao)線(xian)(xian)(xian)的(de)(de)(de)材質大(da)部(bu)分都采(cai)用(yong)(yong)銅鎳合金(jin)。
其次我們介紹一(yi)下熱電(dian)阻，熱電(dian)阻雖然在工(gong)業中應用(yong)也比較(jiao)廣泛(fan)，但是(shi)由于(yu)他的(de)(de)測溫(wen)范圍使他的(de)(de)應用(yong)受到了一定(ding)的(de)(de)限制，熱電(dian)阻的(de)(de)測溫(wen)原(yuan)理是(shi)基于(yu)導體(ti)或(huo)半導體(ti)的(de)(de)電(dian)阻值隨著溫(wen)度的(de)(de)變(bian)化(hua)而變(bian)化(hua)的(de)(de)特性(xing)(xing)。其優點也很多，也可以遠傳電(dian)信號，靈敏度高、穩定(ding)性(xing)(xing)強、互換性(xing)(xing)以及準確性(xing)(xing)都比較(jiao)好(hao)，但是(shi)需要電(dian)源激勵(li)，不能夠瞬(shun)時測量溫(wen)度的(de)(de)變(bian)化(hua)。工(gong)業用(yong)熱電(dian)阻一般采用(yong)Pt100,Pt10,Cu50,Cu100。鉑(bo)熱電(dian)阻的(de)(de)(de)測溫的(de)(de)(de)范圍一(yi)般為(wei)零下200-800攝氏(shi)度(du)，銅熱(re)(re)電(dian)阻為(wei)零下40到140攝氏(shi)度(du)。熱(re)(re)電(dian)阻和熱(re)(re)電(dian)偶一(yi)樣的(de)(de)(de)區(qu)分類型，但是(shi)他卻不需要(yao)補償導(dao)線，而(er)且比(bi)熱(re)(re)電(dian)偶便(bian)宜(yi)。

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