中國(guo)計量科學研(yan)究院在(zai)建(jian)立我(wo)國(guo)961.78℃以(yi)上溫區國(guo)際溫標(ITS-90)的基礎上,研(yan)制了用作(zuo)溫標傳遞標準及精(jing)密(mi)測溫的新型精(jing)密(mi)光電(dian)高溫計。
鑒(jian)于(yu)鎢帶(dai)燈和黑體爐在(zai)溫標傳遞中的重要地位,新型光(guang)電高(gao)(gao)溫計(ji)(ji)(ji)具備測(ce)量(liang)目標小(xiao)和輻(fu)射源尺寸效(xiao)應(Size-of-sourceeffect)小(xiao)的特點。新基(ji)準(zhun)(zhun)光(guang)電溫度比較儀(yi)在(zai)設(she)計(ji)(ji)(ji)時使其主要參(can)數(shu)(shu)與(yu)(yu)國(guo)際(ji)建(jian)議(yi)一致;同樣,新光(guang)電高(gao)(gao)溫計(ji)(ji)(ji)在(zai)被測(ce)目標形狀、面積、受光(guang)立體角、儀(yi)器(qi)(qi)光(guang)譜(pu)帶(dai)寬等參(can)數(shu)(shu)及儀(yi)器(qi)(qi)結構(gou)上與(yu)(yu)國(guo)家(jia)基(ji)準(zhun)(zhun)比較儀(yi)保(bao)持基(ji)本(ben)一致,以避免因基(ji)準(zhun)(zhun)和標準(zhun)(zhun)儀(yi)器(qi)(qi)的差異在(zai)溫度量(liang)值(zhi)傳遞的過程(cheng)中產生顯著的系(xi)統誤差。由于(yu)該高(gao)(gao)溫計(ji)(ji)(ji)的光(guang)電探(tan)測(ce)器(qi)(qi)輸(shu)出與(yu)(yu)被測(ce)目標的光(guang)譜(pu)輻(fu)射亮度呈現很好的線性關系(xi),并在(zai)我(wo)國(guo)首(shou)次將原地測(ce)量(liang)有效(xiao)波長(chang)方(fang)法應用于(yu)傳遞溫標的高(gao)(gao)溫計(ji)(ji)(ji),因此,可直接由內部(bu)微控制器(qi)(qi)依(yi)據(ju)普朗(lang)克(ke)定律(lv)計(ji)(ji)(ji)算(suan)被測(ce)溫度;具有數(shu)(shu)字濾波、自動(dong)暗電流修(xiu)正及發射率(lv)修(xiu)正等功(gong)能,具備GPIB接口(kou)功(gong)能,便于(yu)組成自動(dong)化測(ce)試系(xi)統。
該高溫計(ji)在660nm波長(chang)(chang)、900℃時溫度(du)分辨率為0.01℃;在800℃~2200℃溫度(du)范圍、置信水平為0.99時,擴展不確定度(du)為1.0℃~2.4℃。精密(mi)光電高溫計(ji)的結構參數和性能適(shi)合溫度(du)精密(mi)測量并作為溫標的傳遞標準,也為高溫溫標采用(yong)多波長(chang)(chang)傳遞方法及固定點(dian)分度(du)等(deng)技術創(chuang)造了條件。
按(an)功能劃分(fen)高溫(wen)計(ji)在形式上分(fen)為(wei)兩部分(fen)。一(yi)部分(fen)為(wei)光(guang)(guang)學(xue)機械系(xi)統、光(guang)(guang)電轉換(huan)及(ji)微(wei)電流放大(da)器,另一(yi)部分(fen)為(wei)由微(wei)控(kong)制器等組成的(de)測量顯示儀表。
精密光(guang)(guang)(guang)(guang)電(dian)高(gao)溫計(ji)光(guang)(guang)(guang)(guang)學系統的(de)設計(ji),參考了復現(xian)ITS-90的(de)基(ji)準(zhun)(zhun)(zhun)光(guang)(guang)(guang)(guang)電(dian)溫度比較儀的(de)光(guang)(guang)(guang)(guang)學系統及(ji)國外同類儀器的(de)方案。高(gao)溫計(ji)光(guang)(guang)(guang)(guang)學系統布(bu)置:被測(ce)輻射(she)源經物(wu)鏡(jing)(jing)(jing)成像于(yu)視場光(guang)(guang)(guang)(guang)闌,視場光(guang)(guang)(guang)(guang)闌中心為(wei)直(zhi)徑0.2mm的(de)圓孔(kong),周圍為(wei)鏡(jing)(jing)(jing)反(fan)射(she)面,用(yong)于(yu)瞄(miao)準(zhun)(zhun)(zhun)。被測(ce)目標成像于(yu)圓孔(kong)上(shang)(shang),其(qi)輻射(she)經準(zhun)(zhun)(zhun)直(zhi)鏡(jing)(jing)(jing)、限(xian)制(zhi)光(guang)(guang)(guang)(guang)闌、干涉濾(lv)(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)、減弱(ruo)濾(lv)(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)、準(zhun)(zhun)(zhun)直(zhi)鏡(jing)(jing)(jing)后(hou)會聚(ju)到光(guang)(guang)(guang)(guang)電(dian)探(tan)測(ce)器上(shang)(shang)。限(xian)制(zhi)光(guang)(guang)(guang)(guang)闌決(jue)定高(gao)溫計(ji)的(de)孔(kong)徑比。可轉動的(de)干涉濾(lv)(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)輪上(shang)(shang)有四個安裝位置,可安裝三片(pian)不同波長的(de)干涉濾(lv)(lv)(lv)光(guang)(guang)(guang)(guang)片(pian),使光(guang)(guang)(guang)(guang)束單色化,減弱(ruo)濾(lv)(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)用(yong)于(yu)擴展測(ce)溫上(shang)(shang)限(xian)(使光(guang)(guang)(guang)(guang)電(dian)探(tan)測(ce)器工(gong)作于(yu)線性區域),為(wei)瞄(miao)準(zhun)(zhun)(zhun)系統的(de)反(fan)射(she)鏡(jing)(jing)(jing),為(wei)瞄(miao)準(zhun)(zhun)(zhun)物(wu)鏡(jing)(jing)(jing),為(wei)減光(guang)(guang)(guang)(guang)片(pian)(輪),為(wei)目鏡(jing)(jing)(jing)。
高溫(wen)計物(wu)鏡(jing)直徑(jing)為(wei)68mm,焦距140mm,最小(xiao)測量(liang)距離約(yue)0.4m,最小(xiao)測量(liang)靶(ba)面直徑(jing)小(xiao)于(yu)0.8mm,顯微物(wu)鏡(jing)和目鏡(jing)放大(da)倍數為(wei)2×15。高溫(wen)計采(cai)用干涉濾光片(pian)為(wei)單色器,其中心波長約(yue)為(wei)660nm,半寬帶(dai)約(yue)為(wei)10nm,長波截(jie)止至1200nm,830nm附(fu)近次峰透過率約(yue)為(wei)1×10-4;采(cai)用吸熱玻璃可將(jiang)次峰透過率降低1~2個(ge)數量(liang)級。根據需要可選(xuan)用900nm或950nm的紅外干涉濾光片(pian)。
雖然(ran)高溫計在(zai)小目標(biao)(biao)和窄譜(pu)帶條件下測量(liang)難度(du)增加,但(dan)在(zai)測量(liang)靶直徑為0.75mm條件下使用(yong)時,測量(liang)靶的形狀大小、有效(xiao)波長及光譜(pu)帶寬(kuan)等參(can)數(shu)(shu)與國家基(ji)準的相(xiang)應參(can)數(shu)(shu)基(ji)本一致,避免(mian)了溫度(du)基(ji)準至標(biao)(biao)準的傳遞過程(cheng)中因這些(xie)參(can)數(shu)(shu)不(bu)同(tong)引起的系統誤差(cha)。
電流放大器通常有5~6個量程,其動態范圍滿足800℃~3200℃測溫范圍探測器光電流的測量要求。放大器的輸入失調電壓的變化將導致探測器光譜響應率的變化, 必須嚴格限制。由于測量信號微弱,對光電探測器及放大器采取了嚴格的屏蔽措施。帶有微處(chu)理機的(de)測(ce)(ce)量(liang)顯(xian)(xian)示(shi)儀表(biao)的(de)組(zu)成部分:測(ce)(ce)量(liang)顯(xian)(xian)示(shi)儀表(biao)在微處(chu)理器的(de)控(kong)制(zhi)下完成對(dui)微電(dian)流(liu)放大器的(de)控(kong)制(zhi)及對(dui)放大器輸出電(dian)壓的(de)AD轉換;按放大器相(xiang)應量(liang)程增益計算(suan)光(guang)電(dian)流(liu),并根據普(pu)朗克定律計算(suan)并顯(xian)(xian)示(shi)溫度值。可(ke)通(tong)過GPIB接口接收相(xiang)應的(de)控(kong)制(zhi)命令或發(fa)送(song)測(ce)(ce)量(liang)數據、儀器狀(zhuang)態、參數等。在800℃,高溫計的(de)分辨率(lv)優于0.05℃,在900℃時分辨率(lv)優于0.01℃。
根(gen)據(ju)普(pu)朗克定(ding)(ding)律測溫(wen)(wen)的(de)(de)(de)前提之一是準確(que)(que)(que)確(que)(que)(que)定(ding)(ding)精密光(guang)(guang)(guang)(guang)電高溫(wen)(wen)計的(de)(de)(de)有(you)效波(bo)(bo)(bo)(bo)長(chang)。它是高溫(wen)(wen)計光(guang)(guang)(guang)(guang)學系統(tong)光(guang)(guang)(guang)(guang)譜透(tou)過(guo)率、光(guang)(guang)(guang)(guang)電探測器光(guang)(guang)(guang)(guang)譜響應(ying)及被(bei)測溫(wen)(wen)度(du)的(de)(de)(de)函數(shu)。其(qi)數(shu)值主要(yao)取決(jue)于干(gan)涉濾(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)的(de)(de)(de)光(guang)(guang)(guang)(guang)譜特性。干(gan)涉濾(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)具有(you)顯著的(de)(de)(de)不均勻性,必(bi)須采用原地測量(liang)方(fang)法確(que)(que)(que)定(ding)(ding)高溫(wen)(wen)計有(you)效波(bo)(bo)(bo)(bo)長(chang),以減(jian)小(xiao)(xiao)(xiao)有(you)效波(bo)(bo)(bo)(bo)長(chang)的(de)(de)(de)不確(que)(que)(que)定(ding)(ding)度(du)。由于選用的(de)(de)(de)中心波(bo)(bo)(bo)(bo)長(chang)約為(wei)660nm的(de)(de)(de)干(gan)涉濾(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)在(zai)830nm附近有(you)次(ci)峰,其(qi)峰值透(tou)過(guo)率為(wei)10-4數(shu)量(liang)級。該(gai)次(ci)峰將導致有(you)效波(bo)(bo)(bo)(bo)長(chang)在(zai)較低(di)溫(wen)(wen)度(du)時隨溫(wen)(wen)度(du)降低(di)迅速(su)增大(da)。為(wei)減(jian)小(xiao)(xiao)(xiao)次(ci)峰對有(you)效波(bo)(bo)(bo)(bo)長(chang)的(de)(de)(de)影響,在(zai)干(gan)涉濾(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)前加一吸熱玻璃,使(shi)有(you)效波(bo)(bo)(bo)(bo)長(chang)隨溫(wen)(wen)度(du)變(bian)化顯著減(jian)小(xiao)(xiao)(xiao),同時也減(jian)小(xiao)(xiao)(xiao)了(le)光(guang)(guang)(guang)(guang)電探測器光(guang)(guang)(guang)(guang)譜響應(ying)測量(liang)不確(que)(que)(que)定(ding)(ding)度(du)對有(you)效波(bo)(bo)(bo)(bo)長(chang)不確(que)(que)(que)定(ding)(ding)度(du)的(de)(de)(de)影響。加吸熱玻璃前后干(gan)涉濾(lv)(lv)光(guang)(guang)(guang)(guang)片(pian)的(de)(de)(de)光(guang)(guang)(guang)(guang)譜透(tou)過(guo)率及平均有(you)效波(bo)(bo)(bo)(bo)長(chang)計算(suan)結果。加吸熱玻璃后有(you)效波(bo)(bo)(bo)(bo)長(chang)隨溫(wen)(wen)度(du)的(de)(de)(de)變(bian)化顯著減(jian)小(xiao)(xiao)(xiao)。
用真空(kong)燈(deng)和充氣(qi)燈(deng)分度(du)高溫(wen)計的分度(du)重復性,10天內(nei)分度(du)6次。實驗時室溫(wen)控制在22℃±1℃內(nei),燈(deng)座溫(wen)度(du)控制在21℃±0.3℃內(nei)。
由于光學(xue)系統雜散光及象差等因素的影響,高溫(wen)計測(ce)量(liang)(liang)溫(wen)度一(yi)定的輻(fu)射源時(shi),測(ce)量(liang)(liang)結果(guo)與(yu)被測(ce)源形狀大小有關。高溫(wen)計在(zai)測(ce)量(liang)(liang)1000℃和2000℃的40mm面黑(hei)體時(shi),SSE的影響分(fen)別為(wei)0.13℃和0.43℃。該(gai)特性表明,用鎢帶(dai)燈分(fen)度該(gai)高溫(wen)計,在(zai)測(ce)量(liang)(liang)黑(hei)體爐時(shi),若不做SSE修正(zheng)也不致產(chan)生顯著(zhu)的誤差。
測(ce)(ce)量距(ju)離(li)不同時(shi)高溫(wen)計光(guang)學系統的(de)透過率(lv)略有變(bian)化。用鎢帶燈和黑體(ti)爐測(ce)(ce)量了高溫(wen)計放大(da)器輸出受測(ce)(ce)量距(ju)離(li)的(de)影(ying)響(xiang)(DE)。在近距(ju)離(li)測(ce)(ce)量時(shi)要(yao)注意(yi)距(ju)離(li)變(bian)化的(de)影(ying)響(xiang)。
精(jing)密光(guang)電(dian)(dian)高(gao)(gao)溫(wen)(wen)(wen)(wen)計在確定(ding)(ding)(ding)其有效(xiao)波(bo)長和放(fang)大器(qi)各(ge)量(liang)(liang)程增(zeng)益比后,僅(jin)需(xu)一(yi)個參考溫(wen)(wen)(wen)(wen)度(du)(du)(du)點分(fen)度(du)(du)(du),即可確定(ding)(ding)(ding)其溫(wen)(wen)(wen)(wen)度(du)(du)(du)量(liang)(liang)值(忽略高(gao)(gao)溫(wen)(wen)(wen)(wen)計非線性(xing)的(de)(de)(de)影響(xiang))。作為溫(wen)(wen)(wen)(wen)標(biao)(biao)(biao)的(de)(de)(de)傳遞(di)標(biao)(biao)(biao)準(zhun)時,為與(yu)現行檢定(ding)(ding)(ding)方法統一(yi),800℃~2200℃暫(zan)用工(gong)(gong)作基(ji)準(zhun)燈(deng)檢定(ding)(ding)(ding)(或檢驗)精(jing)密(標(biao)(biao)(biao)準(zhun))光(guang)電(dian)(dian)高(gao)(gao)溫(wen)(wen)(wen)(wen)計。影響(xiang)其不(bu)確定(ding)(ding)(ding)度(du)(du)(du)的(de)(de)(de)主要(yao)因(yin)素(su)為以下6項:分(fen)度(du)(du)(du)重復性(xing)標(biao)(biao)(biao)準(zhun)不(bu)確定(ding)(ding)(ding)度(du)(du)(du);標(biao)(biao)(biao)準(zhun)光(guang)電(dian)(dian)高(gao)(gao)溫(wen)(wen)(wen)(wen)計年穩(wen)定(ding)(ding)(ding)性(xing)的(de)(de)(de)標(biao)(biao)(biao)準(zhun)不(bu)確定(ding)(ding)(ding)度(du)(du)(du);工(gong)(gong)作基(ji)準(zhun)燈(deng)的(de)(de)(de)合成標(biao)(biao)(biao)準(zhun)不(bu)確定(ding)(ding)(ding)度(du)(du)(du);工(gong)(gong)作基(ji)準(zhun)燈(deng)電(dian)(dian)測設備標(biao)(biao)(biao)準(zhun)不(bu)確定(ding)(ding)(ding)度(du)(du)(du)(含標(biao)(biao)(biao)準(zhun)電(dian)(dian)阻、電(dian)(dian)壓測量(liang)(liang)儀表(biao)和穩(wen)流電(dian)(dian)源紋波(bo)的(de)(de)(de)影響(xiang));有效(xiao)波(bo)長的(de)(de)(de)標(biao)(biao)(biao)準(zhun)不(bu)確定(ding)(ding)(ding)度(du)(du)(du)(0.2nm)對鎢帶燈(deng)亮度(du)(du)(du)溫(wen)(wen)(wen)(wen)度(du)(du)(du)的(de)(de)(de)影響(xiang)u5;環境溫(wen)(wen)(wen)(wen)度(du)(du)(du)對標(biao)(biao)(biao)準(zhun)光(guang)電(dian)(dian)高(gao)(gao)溫(wen)(wen)(wen)(wen)計影響(xiang)的(de)(de)(de)標(biao)(biao)(biao)準(zhun)不(bu)確定(ding)(ding)(ding)度(du)(du)(du)。
當采用固(gu)定(ding)點(dian)(dian)作為溫(wen)(wen)度(du)參(can)考點(dian)(dian)的分(fen)度(du)方法時,參(can)考點(dian)(dian)溫(wen)(wen)度(du)不確定(ding)度(du)對(dui)各(ge)溫(wen)(wen)度(du)延伸點(dian)(dian)的影響都將(jiang)顯著減(jian)小(xiao)。由于(yu)本(ben)精密光電高溫(wen)(wen)計(ji)在設計(ji)上完全具(ju)備用單點(dian)(dian)分(fen)度(du)的技(ji)術特點(dian)(dian),因此為將(jiang)來采用新分(fen)度(du)方法傳遞溫(wen)(wen)標、減(jian)小(xiao)測溫(wen)(wen)不確定(ding)度(du)打(da)下(xia)了良好(hao)基礎。
精密(mi)光電(dian)高溫(wen)(wen)(wen)計的結構參數(shu)和性能不僅適用于溫(wen)(wen)(wen)度(du)(du)精密(mi)測量(liang),而且(qie)可作(zuo)為(wei)(wei)溫(wen)(wen)(wen)標的傳遞(di)標準。該(gai)高溫(wen)(wen)(wen)計在小目標和窄譜帶的測量(liang)條件下,具有(you)分(fen)辨率高、SSE小、自動化測量(liang)等特點。采用原地測量(liang)有(you)效波長標定(ding)技術(shu),測溫(wen)(wen)(wen)范圍(wei)為(wei)(wei)800℃~3200℃。在660nm波長下,900℃時(shi)溫(wen)(wen)(wen)度(du)(du)分(fen)辨率為(wei)(wei)0.01℃,在800℃~2200℃溫(wen)(wen)(wen)度(du)(du)范圍(wei)內,置信水平為(wei)(wei)0.99時(shi),擴(kuo)展不確定(ding)度(du)(du)為(wei)(wei)1.0℃~2.4℃。