熱電偶安裝不當引起的誤差
熱電偶anzhuangdeweizhijicharushendubunengfanyinglutangdezhenshiwendudeng,huanjuhuashuo,redianoubuyingzhuangzaitaikaojinmenhejiarededifang,charudeshenduzhishaoyingweibaohuguanzhijingde8~10倍;redianoudebaohutaoguanyubijiandejiangeweitianjuerewuzhizhishiluneireyichuhuolengkongqiqinru,yinciredianoubaohuguanhelubikongzhijiandekongxiyingyongnaihuonihuoshimianshengdengjuerewuzhidusaiyimianlengrekongqiduiliueryingxiangcewendezhunquexing;熱電偶冷端太靠近爐體使溫度超過100℃;熱電偶的安裝應盡可能避開強磁場和強電場,所以不應把熱電偶和動力電纜線裝在同一根導管內以免引入幹擾造成誤差;熱re電dian偶ou不bu能neng安an裝zhuang在zai被bei測ce介jie質zhi很hen少shao流liu動dong的de區qu域yu內nei,當dang用yong熱re電dian偶ou測ce量liang管guan內nei氣qi體ti溫wen度du時shi,必bi須xu使shi熱re電dian偶ou逆ni著zhe流liu速su方fang向xiang安an裝zhuang,而er且qie充chong分fen與yu氣qi體ti接jie觸chu。
熱電偶絕緣變差而引起的誤差
如(ru)熱(re)電(dian)偶(ou)絕(jue)緣(yuan)了(le),保(bao)護(hu)管(guan)和(he)拉(la)線(xian)板(ban)汙(wu)垢(gou)或(huo)鹽(yan)渣(zha)過(guo)多(duo)致(zhi)使(shi)熱(re)電(dian)偶(ou)極(ji)間(jian)與(yu)爐(lu)壁(bi)間(jian)絕(jue)緣(yuan)不(bu)良(liang),在(zai)高(gao)溫(wen)下(xia)更(geng)為(wei)嚴(yan)重(zhong),這(zhe)不(bu)僅(jin)會(hui)引(yin)起(qi)熱(re)電(dian)勢(shi)的(de)損(sun)耗(hao)而(er)且(qie)還(hai)會(hui)引(yin)入(ru)幹(gan)擾(rao),由(you)此(ci)引(yin)起(qi)的(de)誤(wu)差(cha)有(you)時(shi)可(ke)達(da)上(shang)百(bai)度(du)。
熱電偶熱惰性引起的誤差
由於熱電偶的熱惰性使儀表的指示值落後於被測溫度的變化,在進行快速測量時這種影響尤為突出。所以應盡可能采用熱電極較細、保bao護hu管guan直zhi徑jing較jiao小xiao的de熱re電dian偶ou。測ce溫wen環huan境jing許xu可ke時shi,甚shen至zhi可ke將jiang保bao護hu管guan取qu去qu。由you於yu存cun在zai測ce量liang滯zhi後hou,用yong熱re電dian偶ou檢jian測ce出chu的de溫wen度du波bo動dong的de振zhen幅fu較jiao爐lu溫wen波bo動dong的de振zhen幅fu小xiao。測ce量liang滯zhi後hou越yue大da,熱re電dian偶ou波bo動dong的de振zhen幅fu就jiu越yue小xiao,與yu實shi際ji爐lu溫wen的de差cha別bie也ye就jiu越yue大da。當dang用yong時shi間jian常chang數shu大da的de熱re電dian偶ou測ce溫wen或huo控kong溫wen時shi,儀yi表biao顯xian示shi的de溫wen度du雖sui然ran波bo動dong很hen小xiao,但dan實shi際ji爐lu溫wen的de波bo動dong可ke能neng很hen大da。為wei了le準zhun確que的de測ce量liang溫wen度du,應ying當dang選xuan擇ze時shi間jian常chang數shu小xiao的de熱re電dian偶ou。時shi間jian常chang數shu與yu傳chuan熱re係xi數shu成cheng反fan比bi,與yu熱re電dian偶ou熱re端duan的de直zhi徑jing、材料的密度及比熱成正比,如要減小時間常數,除增加傳熱係數以外,最有效的辦法是盡量減小熱端的尺寸。