熱電偶溫度計故障分析維修技巧

        熱(re)(re)電偶(ou)在測溫(wen)過(guo)程中的電位——溫(wen)度非線性特性，需要(yao)補(bu)償導線將熱(re)(re)電偶(ou)熱(re)(re)端(duan)的熱(re)(re)點電位傳輸到二次(ci)儀表或恒溫(wen)控制室，然后通過(guo)最后的輔(fu)助(zhu)儀表。冷端(duan)溫(wen)度補(bu)償后，顯示現場熱(re)(re)電偶(ou)熱(re)(re)端(duan)溫(wen)度，即被測點的過(guo)程介(jie)質溫(wen)度。
        溫(wen)(wen)(wen)度(du)(du)補償(chang)是(shi)通(tong)(tong)過二(er)次(ci)表(biao)或控制系統內置的(de)(de)(de)熱(re)(re)點電(dian)(dian)(dian)位-溫(wen)(wen)(wen)度(du)(du)對照表(biao)中的(de)(de)(de)軟件，二(er)次(ci)表(biao)采集補償(chang)導線末端的(de)(de)(de)熱(re)(re)點電(dian)(dian)(dian)位，然(ran)后(hou)計(ji)算出檢測(ce)到的(de)(de)(de)冷(leng)端溫(wen)(wen)(wen)度(du)(du)。儀表(biao)本(ben)身（兩(liang)個第二(er)個儀表(biao)是(shi)安裝位置的(de)(de)(de)環(huan)境溫(wen)(wen)(wen)度(du)(du)），這(zhe)個溫(wen)(wen)(wen)度(du)(du)檢測(ce)儀表(biao)可(ke)以是(shi)熱(re)(re)電(dian)(dian)(dian)偶或熱(re)(re)電(dian)(dian)(dian)阻(zu)（由(you)于(yu)環(huan)境溫(wen)(wen)(wen)度(du)(du)低，大多使(shi)用PT100熱(re)(re)電(dian)(dian)(dian)阻(zu)）來(lai)測(ce)量溫(wen)(wen)(wen)度(du)(du)，然(ran)后(hou)查看軟件中的(de)(de)(de)表(biao)格，得(de)到模型(xing)（連接儀表(biao)的(de)(de)(de)熱(re)(re)電(dian)(dian)(dian)偶模型(xing)）的(de)(de)(de)熱(re)(re)點電(dian)(dian)(dian)位，然(ran)后(hou)通(tong)(tong)過加(jia)法(fa)器將采集到的(de)(de)(de)熱(re)(re)點電(dian)(dian)(dian)位和(he)轉換后(hou)的(de)(de)(de)熱(re)(re)點電(dian)(dian)(dian)位相加(jia)，得(de)到查表(biao)對應的(de)(de)(de)溫(wen)(wen)(wen)度(du)(du)，顯示(shi)為當場被(bei)測(ce)點 得(de)到溫(wen)(wen)(wen)度(du)(du)。
        從熱(re)電(dian)偶和二次表(biao)(biao)測(ce)溫原理可以看出，要得(de)到現(xian)(xian)場實(shi)測(ce)點的(de)溫度(du)(du)，最重(zhong)要的(de)是熱(re)點電(dian)位-溫度(du)(du)對(dui)照(zhao)表(biao)(biao)。只(zhi)有(you)(you)(you)有(you)(you)(you)了這個對(dui)照(zhao)表(biao)(biao)，我們才能(neng)得(de)到電(dian)位-溫度(du)(du)的(de)對(dui)應(ying)關系(xi)。如果技(ji)術人(ren)員(yuan)(yuan)懷疑現(xian)(xian)場測(ce)量的(de)溫度(du)(du)不(bu)(bu)允(yun)許通知儀(yi)表(biao)(biao)人(ren)員(yuan)(yuan)維修(xiu)，儀(yi)表(biao)(biao)人(ren)員(yuan)(yuan)還必須有(you)(you)(you)相應(ying)型(xing)號的(de)熱(re)電(dian)勢(shi)-溫度(du)(du)對(dui)應(ying)關系(xi)，才能(neng)知道(dao)現(xian)(xian)場熱(re)電(dian)偶是否正常(chang)，因此電(dian)勢(shi)-溫度(du)(du)對(dui)照(zhao)表(biao)(biao)很重(zhong)要，但(dan)現(xian)(xian)實(shi)情況 國內很多儀(yi)器維修(xiu)人(ren)員(yuan)(yuan)沒(mei)有(you)(you)(you)對(dui)照(zhao)表(biao)(biao)，或者維修(xiu)時(shi)不(bu)(bu)隨身(shen)攜帶。在這種情況下，找對(dui)照(zhao)表(biao)(biao)后修(xiu)理熱(re)電(dian)偶，不(bu)(bu)僅浪費時(shi)間，而且影(ying)響(xiang)生產(chan)。
        通過多年的(de)(de)維護工作，即使在(zai)現(xian)場維修熱(re)電(dian)(dian)偶(ou)(ou)時，也能快速處理故(gu)障，無需對(dui)照表。石化(hua)行業zui常(chang)用的(de)(de)熱(re)電(dian)(dian)偶(ou)(ou)是(shi)(shi)K型(xing)和E型(xing)熱(re)電(dian)(dian)偶(ou)(ou)。看對(dui)比(bi)表發(fa)現(xian)，雖(sui)然熱(re)點電(dian)(dian)位-溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)不是(shi)(shi)線性的(de)(de)，但大部分能與(yu)電(dian)(dian)位和溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)相(xiang)關的(de)(de)E型(xing)熱(re)電(dian)(dian)偶(ou)(ou)對(dui)應(ying)10度(du)(du)(du)(du)(du)。 0.6mv，K型(xing)為10度(du)(du)(du)(du)(du)對(dui)應(ying)0.4mv，所以(yi)只(zhi)要在(zai)現(xian)場用萬用表檢測(ce)熱(re)電(dian)(dian)偶(ou)(ou)端子的(de)(de)熱(re)點電(dian)(dian)位，除以(yi)0.6或(huo)0.4后(hou)(hou)乘(cheng)以(yi)熱(re)電(dian)(dian)偶(ou)(ou)測(ce)得的(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)10.由于(yu)沒有(you)冷端補償，溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)低(di)于(yu)實際溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)，與(yu)環境(jing)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)一樣低(di)。該環境(jing)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)可(ke)以(yi)粗略估(gu)計。求出，再將轉換后(hou)(hou)的(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)與(yu)環境(jing)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)相(xiang)加，粗略得到被測(ce)點的(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)。這個(ge)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)可(ke)以(yi)和控制室的(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)對(dui)比(bi)，就知道熱(re)電(dian)(dian)偶(ou)(ou)顯示是(shi)(shi)否正(zheng)常(chang)。
       ; 由于(yu)熱(re)點電位(wei)與溫(wen)度(du)不是線性關系，估計(ji)溫(wen)度(du)誤差(cha)較大(da)，但(dan)維修時(shi)(shi)，技術人(ren)員懷疑溫(wen)度(du)不準時(shi)(shi)應(ying)該與顯示溫(wen)度(du)相差(cha)很大(da)，不是1度(du)和2度(du)。因(yin)此，這種方法(fa)是可行的。通過這種方法(fa)，可以直(zhi)接知道是現場熱(re)電偶還是補償導線故障。
        通(tong)過這種方法(fa)判斷(duan)后，如果(guo)還沒有找到(dao)故(gu)障原因(yin)，可(ke)以(yi)拔出熱(re)電(dian)(dian)(dian)(dian)偶(ou)芯(xin)。如果(guo)是正(zheng)常的(de)保護(hu)套，檢(jian)查保護(hu)套是否完好，內(nei)部是否有水和濕氣，有無碰撞現象。 , 熱(re)電(dian)(dian)(dian)(dian)偶(ou)與(yu)接(jie)線(xian)(xian)端子接(jie)觸是否良好，熱(re)電(dian)(dian)(dian)(dian)偶(ou)如果(guo)長時間運(yun)行，一(yi)般(ban)時間不(bu)夠長，安裝型號(hao)不(bu)正(zheng)確，補償線(xian)(xian)不(bu)匹配(pei)。最多的(de)問題(ti)是進水、松動(dong)和接(jie)觸。電(dian)(dian)(dian)(dian)阻大、接(jie)線(xian)(xian)松動(dong)或外殼漏電(dian)(dian)(dian)(dian)，這些(xie)問題(ti)可(ke)以(yi)通(tong)過使用萬用表和檢(jian)查熱(re)電(dian)(dian)(dian)(dian)偶(ou)芯(xin)來判斷(duan)和解決。
        因此，該方法(fa)對于現場(chang)熱(re)電偶顯示低（與真值相差大）、顯示波動、顯示高、溫度(du)不穩定的判(pan)斷非常(chang)實用和方便，加快了維修(xiu)速度(du)和效率。