一、 設備選擇依據

    存(cun)在于地球表(biao)面及(ji)大氣層空(kong)間中(zhong)的(de)(de)(de)(de)自然(ran)環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)因(yin)素和(he)誘(you)發環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)因(yin)素的(de)(de)(de)(de)種類(lei)(lei)，目(mu)前還無法(fa)(fa)統計出一(yi)個確切的(de)(de)(de)(de)數(shu)目(mu)，其中(zhong)對(dui)工(gong)(gong)程(cheng)產(chan)(chan)品(pin)（設備(bei)）的(de)(de)(de)(de)使(shi)用(yong)(yong)及(ji)壽(shou)命影響較大的(de)(de)(de)(de)因(yin)素不(bu)下十幾(ji)種。從事工(gong)(gong)程(cheng)產(chan)(chan)品(pin)環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)條件研究的(de)(de)(de)(de)工(gong)(gong)程(cheng)師(shi)們將(jiang)自然(ran)界存(cun)在以及(ji)人類(lei)(lei)活動(dong)所(suo)誘(you)發的(de)(de)(de)(de)環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)條件整理(li)歸納(na)為一(yi)系列的(de)(de)(de)(de)試驗(yan)(yan)標準(zhun)和(he)規(gui)范(fan)(fan)，用(yong)(yong)以指(zhi)導(dao)工(gong)(gong)程(cheng)產(chan)(chan)品(pin)的(de)(de)(de)(de)環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)及(ji)可靠性(xing)試驗(yan)(yan)。如(ru)指(zhi)導(dao)產(chan)(chan)品(pin)進行環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)試驗(yan)(yan)GJB150――中(zhong)華人民(min)共和(he)國(guo)國(guo)家軍用(yong)(yong)標準(zhun)《軍用(yong)(yong)設備(bei)環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)試驗(yan)(yan)方法(fa)(fa)》，指(zhi)導(dao)電(dian)工(gong)(gong)電(dian)子(zi)產(chan)(chan)品(pin)進行環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)試驗(yan)(yan)的(de)(de)(de)(de)GB2423――中(zhong)華人民(min)共和(he)國(guo)國(guo)家標準(zhun)《電(dian)工(gong)(gong)電(dian)子(zi)產(chan)(chan)品(pin)環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)試驗(yan)(yan)方法(fa)(fa)指(zhi)南(nan)》等。因(yin)此，我們選擇環(huan)(huan)(huan)(huan)境(jing)(jing)(jing)(jing)及(ji)可靠性(xing)試驗(yan)(yan)設備(bei)時(shi)主要的(de)(de)(de)(de)依據是工(gong)(gong)程(cheng)產(chan)(chan)品(pin)的(de)(de)(de)(de)試驗(yan)(yan)規(gui)范(fan)(fan)和(he)試驗(yan)(yan)標準(zhun)。

    其次，為了規范試(shi)驗(yan)設(she)備(bei)(bei)中(zhong)環(huan)(huan)境(jing)試(shi)驗(yan)條(tiao)件的(de)容差，保證環(huan)(huan)境(jing)參數(shu)的(de)控制精度，國(guo)家技(ji)術(shu)監(jian)督(du)機構及(ji)各(ge)工業部門還制訂了一系列的(de)環(huan)(huan)境(jing)試(shi)驗(yan)設(she)備(bei)(bei)及(ji)檢測儀器儀表的(de)檢定(ding)規程。如中(zhong)華人民共和國(guo)國(guo)家標準GB5170《電工電子(zi)產(chan)品環(huan)(huan)境(jing)試(shi)驗(yan)設(she)備(bei)(bei)基本(ben)參數(shu)檢定(ding)方(fang)法》，又如國(guo)家技(ji)術(shu)監(jian)督(du)局頒布實施的(de)JJG190－89《電動振動試(shi)驗(yan)臺(tai)系統試(shi)行檢定(ding)規程》等(deng)。這(zhe)些檢定(ding)規程也是選(xuan)擇環(huan)(huan)境(jing)及(ji)可靠性試(shi)驗(yan)設(she)備(bei)(bei)的(de)重要依據，不符合這(zhe)些檢定(ding)規程要求的(de)試(shi)驗(yan)設(she)備(bei)(bei)是不允(yun)許(xu)投入使(shi)用(yong)的(de)。

二、 設備選擇基本原則

環境(jing)及可靠性試驗(yan)設備的選擇(ze)應遵(zun)循以下五條基(ji)本原則：

1、環境(jing)條件的再現性

    在試(shi)驗(yan)室內完整(zheng)而(er)地(di)再現(xian)自然(ran)界存在的(de)(de)(de)環(huan)(huan)境(jing)(jing)條件是(shi)可望而(er)不(bu)可及(ji)的(de)(de)(de)事情(qing)。但(dan)是(shi)，在一定的(de)(de)(de)容差范圍之內，人們*可以正(zheng)確而(er)近似地(di)模擬(ni)工程產(chan)(chan)(chan)品(pin)在使用、貯(zhu)存、運輸等(deng)過程中(zhong)所(suo)經受的(de)(de)(de)外界環(huan)(huan)境(jing)(jing)條件。這段話用工程的(de)(de)(de)語言概括，就是(shi)“試(shi)驗(yan)設備所(suo)創造的(de)(de)(de)圍繞(rao)被試(shi)產(chan)(chan)(chan)品(pin)周邊的(de)(de)(de)環(huan)(huan)境(jing)(jing)條件（含平(ping)臺環(huan)(huan)境(jing)(jing)）應該滿足(zu)產(chan)(chan)(chan)品(pin)試(shi)驗(yan)規范所(suo)規定的(de)(de)(de)環(huan)(huan)境(jing)(jing)條件及(ji)其容差的(de)(de)(de)要求(qiu)”。如用于產(chan)(chan)(chan)品(pin)試(shi)驗(yan)的(de)(de)(de)溫度箱不(bu)僅要滿足(zu)國軍標GJB150.3－86、GJB150.4－86中(zhong)根(gen)據不(bu)同的(de)(de)(de)均勻性和(he)溫度控(kong)制精度的(de)(de)(de)要求(qiu)。只有這樣，才能保證在環(huan)(huan)境(jing)(jing)試(shi)驗(yan)中(zhong)環(huan)(huan)境(jing)(jing)條件的(de)(de)(de)再現(xian)性。

2、環境(jing)條件的可重(zhong)復性

    一(yi)(yi)(yi)臺(tai)環(huan)(huan)境(jing)(jing)試(shi)驗(yan)(yan)設(she)備(bei)(bei)可(ke)能(neng)(neng)用于(yu)(yu)同(tong)(tong)(tong)一(yi)(yi)(yi)類型產(chan)品(pin)(pin)(pin)的(de)多次試(shi)驗(yan)(yan)，而(er)一(yi)(yi)(yi)臺(tai)被試(shi)的(de)工程產(chan)品(pin)(pin)(pin)也可(ke)能(neng)(neng)在不同(tong)(tong)(tong)的(de)環(huan)(huan)境(jing)(jing)試(shi)驗(yan)(yan)設(she)備(bei)(bei)中進(jin)行試(shi)驗(yan)(yan)，為了保(bao)證同(tong)(tong)(tong)一(yi)(yi)(yi)臺(tai)產(chan)品(pin)(pin)(pin)在同(tong)(tong)(tong)一(yi)(yi)(yi)試(shi)驗(yan)(yan)規范所(suo)規定(ding)的(de)環(huan)(huan)境(jing)(jing)試(shi)驗(yan)(yan)條件(jian)下(xia)所(suo)得試(shi)驗(yan)(yan)結(jie)果(guo)的(de)可(ke)比較性，必(bi)然要求環(huan)(huan)境(jing)(jing)試(shi)驗(yan)(yan)設(she)備(bei)(bei)所(suo)提供的(de)環(huan)(huan)境(jing)(jing)條件(jian)具有可(ke)重(zhong)復性。這也就是(shi)說(shuo)，環(huan)(huan)境(jing)(jing)試(shi)驗(yan)(yan)設(she)備(bei)(bei)施用于(yu)(yu)被試(shi)驗(yan)(yan)產(chan)品(pin)(pin)(pin)的(de)應(ying)(ying)力(li)(li)(li)(li)水平（如熱(re)應(ying)(ying)力(li)(li)(li)(li)、振動應(ying)(ying)力(li)(li)(li)(li)、電(dian)應(ying)(ying)力(li)(li)(li)(li)等）對于(yu)(yu)同(tong)(tong)(tong)一(yi)(yi)(yi)試(shi)驗(yan)(yan)規范的(de)要求是(shi)一(yi)(yi)(yi)致的(de)。

    環(huan)境(jing)(jing)(jing)試驗設(she)備(bei)所(suo)提供環(huan)境(jing)(jing)(jing)條件的(de)可重(zhong)(zhong)復性是由(you)國家計量檢(jian)(jian)定(ding)部門依(yi)據國家技術(shu)監督機構(gou)所(suo)制(zhi)定(ding)的(de)檢(jian)(jian)定(ding)規(gui)(gui)(gui)程檢(jian)(jian)定(ding)合(he)格后(hou)(hou)提供保證。為此，必須要(yao)(yao)求環(huan)境(jing)(jing)(jing)試驗設(she)備(bei)能(neng)滿足檢(jian)(jian)定(ding)規(gui)(gui)(gui)程中的(de)各(ge)項技術(shu)指(zhi)標(biao)及(ji)精(jing)度指(zhi)標(biao)的(de)要(yao)(yao)求，并且在(zai)使用(yong)時間(jian)上不超過(guo)(guo)檢(jian)(jian)定(ding)周(zhou)期所(suo)規(gui)(gui)(gui)定(ding)的(de)時限。如使用(yong)非(fei)常普遍(bian)的(de)電動(dong)(dong)振(zhen)動(dong)(dong)臺(tai)(tai)除滿足激(ji)振(zhen)力、頻率范圍、負(fu)載能(neng)力等(deng)技術(shu)指(zhi)標(biao)外，還必須滿足檢(jian)(jian)定(ding)規(gui)(gui)(gui)程中規(gui)(gui)(gui)定(ding)的(de)橫向振(zhen)動(dong)(dong)比、臺(tai)(tai)面加速度均勻(yun)性、諧波失(shi)真度等(deng)精(jing)度指(zhi)標(biao)的(de)要(yao)(yao)求，而且每次檢(jian)(jian)定(ding)后(hou)(hou)的(de)使用(yong)周(zhou)期為二(er)年，超過(guo)(guo)二(er)年必須重(zhong)(zhong)新檢(jian)(jian)定(ding)合(he)格后(hou)(hou)才能(neng)投入使用(yong)。

3、環境條(tiao)件參(can)數的可測控性

    任何一臺環(huan)境(jing)(jing)試(shi)(shi)驗(yan)(yan)(yan)設(she)備所提供的(de)環(huan)境(jing)(jing)條件(jian)必(bi)須(xu)是(shi)可(ke)觀(guan)測的(de)和(he)可(ke)控(kong)制的(de)，這不(bu)僅是(shi)為了使(shi)環(huan)境(jing)(jing)參(can)數限制在一定(ding)的(de)容(rong)差范圍之內，保證試(shi)(shi)驗(yan)(yan)(yan)條件(jian)的(de)再現性和(he)重復(fu)性的(de)要(yao)求，而(er)且從產品試(shi)(shi)驗(yan)(yan)(yan)的(de)安全出發(fa)也(ye)是(shi)必(bi)須(xu)的(de)，以便防止環(huan)境(jing)(jing)條件(jian)失(shi)控(kong)導致被試(shi)(shi)產品的(de)損壞，帶來不(bu)必(bi)要(yao)的(de)損失(shi)。目前各種試(shi)(shi)驗(yan)(yan)(yan)規范中大體要(yao)求參(can)數測試(shi)(shi)的(de)精(jing)度不(bu)應低(di)于試(shi)(shi)驗(yan)(yan)(yan)條件(jian)允許的(de)誤差的(de)三分之一。

4、環境試驗條(tiao)件的排它性(xing)

    每一次進行環(huan)境(jing)(jing)或可靠性試驗(yan)，對環(huan)境(jing)(jing)因(yin)素的(de)(de)(de)類別、量值及容差都(dou)有嚴格的(de)(de)(de)規定，并排除非試驗(yan)所需(xu)的(de)(de)(de)環(huan)境(jing)(jing)因(yin)素滲透其(qi)中(zhong)(zhong)，以(yi)便(bian)在試驗(yan)中(zhong)(zhong)或試驗(yan)結束(shu)后判斷和分析產品失效與故(gu)(gu)障(zhang)模式時，提(ti)供(gong)確切的(de)(de)(de)依據，故(gu)(gu)要求環(huan)境(jing)(jing)試驗(yan)設備除提(ti)供(gong)所規定的(de)(de)(de)環(huan)境(jing)(jing)條件(jian)外，不允(yun)許對被試產品附加其(qi)它的(de)(de)(de)環(huan)境(jing)(jing)應力干(gan)擾。如電動振動臺檢定規程(cheng)中(zhong)(zhong)所限定的(de)(de)(de)臺面(mian)漏磁，加速度信噪比、帶(dai)內(nei)帶(dai)外加速度總均方根值比。隨機(ji)信號(hao)的(de)(de)(de)檢驗(yan)、諧波失真度等精度指標都(dou)是(shi)為了(le)保證環(huan)境(jing)(jing)試驗(yan)條件(jian)的(de)(de)(de)*性而制定的(de)(de)(de)檢定項目(mu)。

5、試(shi)驗設備的安全可靠性

    環境(jing)試(shi)(shi)(shi)驗(yan)(yan)，特別是可靠性試(shi)(shi)(shi)驗(yan)(yan)，試(shi)(shi)(shi)驗(yan)(yan)周(zhou)期長，試(shi)(shi)(shi)驗(yan)(yan)的對象(xiang)有時(shi)是價值很高的產(chan)品(pin)，試(shi)(shi)(shi)驗(yan)(yan)過程中，試(shi)(shi)(shi)驗(yan)(yan)人員經常要在(zai)現場周(zhou)圍操作(zuo)(zuo)巡視或測試(shi)(shi)(shi)工作(zuo)(zuo)，因此要求環境(jing)試(shi)(shi)(shi)驗(yan)(yan)設備必(bi)須具(ju)有運(yun)行(xing)安全、操作(zuo)(zuo)方便、使用可靠、工作(zuo)(zuo)壽命(ming)長等特點，以確保(bao)試(shi)(shi)(shi)驗(yan)(yan)本身的正常進行(xing)。試(shi)(shi)(shi)驗(yan)(yan)設備的各種保(bao)護、告警措(cuo)施及安全連鎖裝置(zhi)應該完善可靠，以保(bao)證試(shi)(shi)(shi)驗(yan)(yan)人員、被試(shi)(shi)(shi)產(chan)品(pin)和試(shi)(shi)(shi)驗(yan)(yan)設備本身的安全可靠性。

三、 溫(wen)濕度箱的(de)選擇(ze)

1、容積(ji)的選擇

    將被(bei)試(shi)(shi)(shi)(shi)產品(pin)（元(yuan)器件、組件、部(bu)件或整機）置入(ru)氣候環(huan)(huan)境(jing)箱(xiang)進行試(shi)(shi)(shi)(shi)驗(yan)(yan)時，為了保證被(bei)試(shi)(shi)(shi)(shi)產品(pin)周圍氣氛能滿足試(shi)(shi)(shi)(shi)驗(yan)(yan)規(gui)范所規(gui)定的環(huan)(huan)境(jing)試(shi)(shi)(shi)(shi)驗(yan)(yan)條件，氣候箱(xiang)工作尺寸(cun)與被(bei)試(shi)(shi)(shi)(shi)產品(pin)外廓(kuo)尺寸(cun)之(zhi)間應遵循以下(xia)幾點規(gui)定：

    a） 被試產品的(de)體積（W×D×H）不得超過試驗箱有效工(gong)作空(kong)間(jian)的(de)（20～35）％（推薦選(xuan)用20％）。對于在試驗中發(fa)熱的(de)產品推薦選(xuan)用不大(da)于10％。

    b） 被試(shi)產品的迎(ying)風斷面積與(yu)該斷面上試(shi)驗箱工(gong)作室(shi)總(zong)面積之比不大于（35～50）％（推(tui)薦(jian)選用(yong)35％）。

    c） 被試產(chan)品外廓(kuo)表(biao)面距(ju)試驗箱壁的距(ju)離至少保持100～150mm，（推薦(jian)選用150mm）。

    上(shang)述三點(dian)規定實際上(shang)是相(xiang)(xiang)互依存和統一的。以1立方米正方體(ti)箱(xiang)子為(wei)例，面(mian)積(ji)比為(wei)1：（0.35～0.5）相(xiang)(xiang)當于體(ti)積(ji)之比為(wei)1：（0.207～0.354）。距箱(xiang)壁100～150mm相(xiang)(xiang)當于體(ti)積(ji)之比為(wei)1：（0.343～0.512）。

總(zong)括(kuo)上(shang)述三(san)點規(gui)定(ding)，氣候環境(jing)試(shi)驗箱的(de)工作(zuo)腔容積至少應是被(bei)試(shi)產品(pin)外廓(kuo)體積的(de)3～5倍。作(zuo)出這(zhe)種規(gui)定(ding)的(de)理由(you)有以(yi)下幾點：

    1〕 被試(shi)驗(yan)(yan)(yan)件(jian)置入箱(xiang)體后擠占了流(liu)(liu)暢的通道，通道變窄將(jiang)導致氣(qi)流(liu)(liu)流(liu)(liu)速(su)(su)的增加。加速(su)(su)氣(qi)流(liu)(liu)與(yu)被試(shi)驗(yan)(yan)(yan)件(jian)之(zhi)間的熱(re)交換(huan)。這與(yu)環境(jing)(jing)條件(jian)的再(zai)現不(bu)(bu)符(fu)，因為(wei)在有關標(biao)準(zhun)中對涉及溫度(du)環境(jing)(jing)試(shi)驗(yan)(yan)(yan)都規定(ding)試(shi)驗(yan)(yan)(yan)箱(xiang)內試(shi)驗(yan)(yan)(yan)樣(yang)件(jian)周圍的空氣(qi)流(liu)(liu)速(su)(su)不(bu)(bu)應超過(guo)1.7m/s，以防止試(shi)驗(yan)(yan)(yan)樣(yang)件(jian)和(he)周圍氣(qi)氛產生(sheng)不(bu)(bu)符(fu)合實(shi)際的熱(re)傳導。在空載時(shi)試(shi)驗(yan)(yan)(yan)箱(xiang)內平(ping)均(jun)風(feng)(feng)速(su)(su)為(wei)0.6～0.8m/s，不(bu)(bu)超過(guo)1m/s，滿(man)足(zu)a）、b）兩點要求所(suo)規定(ding)的空間及面積比(bi)時(shi)，流(liu)(liu)場的風(feng)(feng)速(su)(su)可能增大(da)（50～100）％，平(ping)均(jun)zui高風(feng)(feng)速(su)(su)為(wei)（1～1.7）m/s。滿(man)足(zu)標(biao)準(zhun)規定(ding)的要求。如果(guo)在試(shi)驗(yan)(yan)(yan)中不(bu)(bu)加限制地加大(da)試(shi)驗(yan)(yan)(yan)件(jian)的體積或迎風(feng)(feng)斷(duan)面積，則實(shi)際試(shi)驗(yan)(yan)(yan)時(shi)氣(qi)流(liu)(liu)風(feng)(feng)速(su)(su)將(jiang)增大(da)到(dao)超出試(shi)驗(yan)(yan)(yan)標(biao)準(zhun)所(suo)規定(ding)的zui高風(feng)(feng)速(su)(su)，其試(shi)驗(yan)(yan)(yan)結(jie)果(guo)的有效性將(jiang)受到(dao)懷疑。

    2〕 氣候箱(xiang)工作腔內環(huan)(huan)境參(can)(can)數〔如(ru)溫度、濕度、鹽(yan)霧沉降(jiang)率等〕的(de)精度指標都是(shi)在空載狀(zhuang)態下檢(jian)測(ce)的(de)結(jie)果，一(yi)旦(dan)置入(ru)被試(shi)(shi)驗件后，對試(shi)(shi)驗箱(xiang)工作腔內環(huan)(huan)境參(can)(can)數的(de)均勻性將產生影響，試(shi)(shi)驗件占有的(de)空間越(yue)大，這(zhe)種影響也就越(yue)嚴重。實測(ce)試(shi)(shi)驗數據表(biao)明，流場中迎風面(mian)與背風面(mian)的(de)溫差可達到3～8℃，嚴重時可大到10℃以上。因此，必須盡量(liang)滿足a〕、b〕兩項要求，以保證被試(shi)(shi)產品周圍環(huan)(huan)境參(can)(can)數的(de)均勻性。

    3〕 根據(ju)熱(re)傳導的(de)原理(li)，箱壁(bi)附近(jin)氣(qi)流的(de)溫度通常與(yu)(yu)流場中心溫度相差2～3℃，在高(gao)低(di)溫的(de)上下*，還(huan)可能達(da)到5℃。箱壁(bi)的(de)溫度與(yu)(yu)箱壁(bi)附近(jin)流場的(de)溫度又相差2～3℃（視(shi)箱壁(bi)的(de)結構和材(cai)料而(er)定）試驗溫度與(yu)(yu)外界大(da)氣(qi)環(huan)境相差越大(da)，上述溫差也越大(da)，因(yin)此(ci)，距(ju)箱壁(bi)（100～150mm）距(ju)離內的(de)空(kong)間是不(bu)可利(li)用(yong)空(kong)間。

2、溫(wen)度范圍的選擇

    目前，國外(wai)(wai)溫(wen)(wen)(wen)(wen)度試驗箱(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)(de)范(fan)圍大(da)體(ti)上(shang)為(wei)(wei)－73～＋177℃，或－70～＋180℃。國內多(duo)數(shu)廠家一(yi)般為(wei)(wei)－80～＋130℃，－60～＋130℃，－40～＋130℃，也有高(gao)(gao)(gao)溫(wen)(wen)(wen)(wen)到150℃。這些溫(wen)(wen)(wen)(wen)度范(fan)圍通(tong)常可以(yi)滿足國內絕大(da)多(duo)數(shu)軍(jun)用、民用產品溫(wen)(wen)(wen)(wen)度試驗的(de)(de)(de)需(xu)要，除非確有特殊(shu)需(xu)要，如(ru)安裝(zhuang)位置靠近發動機等熱源的(de)(de)(de)產品外(wai)(wai)，不可盲目提高(gao)(gao)(gao)溫(wen)(wen)(wen)(wen)度上(shang)限(xian)(xian)。因(yin)為(wei)(wei)上(shang)限(xian)(xian)溫(wen)(wen)(wen)(wen)度越高(gao)(gao)(gao)，箱(xiang)(xiang)(xiang)(xiang)(xiang)體(ti)內外(wai)(wai)的(de)(de)(de)溫(wen)(wen)(wen)(wen)差越大(da)，箱(xiang)(xiang)(xiang)(xiang)(xiang)體(ti)內部流場的(de)(de)(de)均(jun)勻性也越差。可利(li)用的(de)(de)(de)工作室體(ti)積也就越小(xiao)。另(ling)一(yi)方面，上(shang)限(xian)(xian)溫(wen)(wen)(wen)(wen)度值越高(gao)(gao)(gao)，對箱(xiang)(xiang)(xiang)(xiang)(xiang)壁(bi)夾(jia)層中保溫(wen)(wen)(wen)(wen)材(cai)料(liao)（如(ru)玻璃(li)棉等 ）的(de)(de)(de)耐熱性要求越高(gao)(gao)(gao)。箱(xiang)(xiang)(xiang)(xiang)(xiang)體(ti)密(mi)封性的(de)(de)(de)要求也越高(gao)(gao)(gao)，使箱(xiang)(xiang)(xiang)(xiang)(xiang)體(ti)的(de)(de)(de)制作成本增加。

3、濕(shi)度范圍的選擇(ze)

    國內外(wai)環(huan)境(jing)試(shi)驗箱(xiang)(xiang)給出(chu)的(de)濕(shi)度(du)(du)(du)指(zhi)標大都(dou)是(shi)20～98％RH或30～98％RH，如(ru)果濕(shi)熱試(shi)驗箱(xiang)(xiang)沒有(you)除濕(shi)系統，則濕(shi)度(du)(du)(du)范(fan)圍為(wei)(wei)60～98％，這(zhe)一(yi)類試(shi)驗箱(xiang)(xiang)只能做高(gao)濕(shi)試(shi)驗，但它的(de)價(jia)格低得(de)多。值得(de)注意(yi)的(de)是(shi)在濕(shi)度(du)(du)(du)指(zhi)標后(hou)面應該注明相(xiang)(xiang)應的(de)溫(wen)(wen)度(du)(du)(du)范(fan)圍，或給出(chu)zui低露點溫(wen)(wen)度(du)(du)(du)。因為(wei)(wei)相(xiang)(xiang)對濕(shi)度(du)(du)(du)是(shi)與溫(wen)(wen)度(du)(du)(du)直接(jie)相(xiang)(xiang)關的(de)，對于同(tong)樣的(de)含(han)(han)濕(shi)量(liang)，溫(wen)(wen)度(du)(du)(du)越高(gao)，相(xiang)(xiang)對濕(shi)度(du)(du)(du)就越小，如(ru)含(han)(han)濕(shi)量(liang)為(wei)(wei)5g/Kg（指(zhi)1公斤干(gan)空氣中(zhong)含(han)(han)有(you)5克的(de)水蒸汽），當(dang)溫(wen)(wen)度(du)(du)(du)為(wei)(wei)29℃時，相(xiang)(xiang)對濕(shi)度(du)(du)(du)為(wei)(wei)20％RH，溫(wen)(wen)度(du)(du)(du)為(wei)(wei)6℃時，相(xiang)(xiang)對濕(shi)度(du)(du)(du)為(wei)(wei)90％RH，當(dang)溫(wen)(wen)度(du)(du)(du)降(jiang)至4℃以下，相(xiang)(xiang)對濕(shi)度(du)(du)(du)超(chao)過(guo)100％，在箱(xiang)(xiang)體內會出(chu)現結露現象。

    實(shi)(shi)現(xian)高溫(wen)(wen)(wen)(wen)(wen)、高濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)只需(xu)要往箱(xiang)(xiang)體(ti)空氣(qi)中(zhong)(zhong)噴水蒸(zheng)汽(qi)或霧化(hua)的(de)(de)(de)水珠，進(jin)(jin)行加濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)。低(di)(di)溫(wen)(wen)(wen)(wen)(wen)低(di)(di)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)則相(xiang)(xiang)對(dui)(dui)(dui)難(nan)于控(kong)制(zhi)，因(yin)為(wei)此(ci)時的(de)(de)(de)含(han)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)量(liang)很低(di)(di)，有時比大(da)氣(qi)中(zhong)(zhong)的(de)(de)(de)含(han)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)量(liang)低(di)(di)很多(duo)，需(xu)要對(dui)(dui)(dui)箱(xiang)(xiang)體(ti)內流動(dong)的(de)(de)(de)空氣(qi)除(chu)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)，使空氣(qi)變得(de)(de)干燥。目前國內外絕大(da)多(duo)數的(de)(de)(de)溫(wen)(wen)(wen)(wen)(wen)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)度(du)(du)(du)(du)(du)(du)箱(xiang)(xiang)都(dou)采(cai)(cai)用制(zhi)冷除(chu)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)的(de)(de)(de)原理(li)，是(shi)在(zai)箱(xiang)(xiang)體(ti)的(de)(de)(de)空氣(qi)預調室內加一(yi)組制(zhi)冷光管。當(dang)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)空氣(qi)經過冷管時，其相(xiang)(xiang)對(dui)(dui)(dui)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)度(du)(du)(du)(du)(du)(du)會(hui)達(da)(da)到(dao)100％RH，因(yin)空氣(qi)飽(bao)和(he)在(zai)光管上結露(lu)，使空氣(qi)變得(de)(de)更干燥。這種(zhong)除(chu)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)方(fang)式理(li)論上可達(da)(da)到(dao)零度(du)(du)(du)(du)(du)(du)以下的(de)(de)(de)露(lu)點(dian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)，但是(shi)當(dang)冷點(dian)表面溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)到(dao)達(da)(da)0℃時，光管表面結露(lu)的(de)(de)(de)水滴會(hui)結冰，從而影(ying)響光管表面的(de)(de)(de)熱交換，使除(chu)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)能(neng)(neng)力(li)下降(jiang)。又因(yin)為(wei)箱(xiang)(xiang)體(ti)不可能(neng)(neng)密封，大(da)氣(qi)中(zhong)(zhong)的(de)(de)(de)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)空氣(qi)會(hui)滲入(ru)到(dao)箱(xiang)(xiang)體(ti)內，使露(lu)點(dian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)回升。另一(yi)方(fang)面，在(zai)光管間流動(dong)的(de)(de)(de)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)空氣(qi)只是(shi)在(zai)和(he)光管（冷點(dian)）接觸的(de)(de)(de)瞬間達(da)(da)到(dao)飽(bao)和(he)狀態(tai)而析出水蒸(zheng)汽(qi)，因(yin)此(ci)這種(zhong)除(chu)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)方(fang)法(fa)很難(nan)使箱(xiang)(xiang)體(ti)內的(de)(de)(de)露(lu)點(dian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)在(zai)到(dao)0℃以下。實(shi)(shi)際(ji)所達(da)(da)到(dao)的(de)(de)(de)zui低(di)(di)露(lu)點(dian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)為(wei)5～7℃。露(lu)點(dian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)5℃相(xiang)(xiang)當(dang)于含(han)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)量(liang)為(wei)0.0055g/Kg，對(dui)(dui)(dui)應相(xiang)(xiang)對(dui)(dui)(dui)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)度(du)(du)(du)(du)(du)(du)20％RH的(de)(de)(de)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)為(wei)30℃。如(ru)果要求溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)20℃進(jin)(jin)相(xiang)(xiang)對(dui)(dui)(dui)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)度(du)(du)(du)(du)(du)(du)達(da)(da)到(dao)20％RH，此(ci)時的(de)(de)(de)露(lu)點(dian)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)(du)(du)(du)(du)為(wei)－3℃，采(cai)(cai)用致(zhi)冷方(fang)式除(chu)濕(shi)(shi)(shi)(shi)(shi)(shi)(shi)是(shi)很困難(nan)的(de)(de)(de)，必須(xu)選用空氣(qi)干燥系統才能(neng)(neng)實(shi)(shi)現(xian)。

4、控制方式的選擇

    溫度(du)、濕度(du)試驗(yan)箱(xiang)有恒定試驗(yan)箱(xiang)、交變試驗(yan)箱(xiang)兩種情況(kuang)。

普(pu)通的(de)高(gao)(gao)(gao)低(di)(di)溫(wen)(wen)(wen)(wen)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)一(yi)(yi)般指(zhi)的(de)是(shi)恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)高(gao)(gao)(gao)低(di)(di)溫(wen)(wen)(wen)(wen)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)，其控(kong)(kong)制(zhi)(zhi)(zhi)方(fang)式為：設定(ding)(ding)(ding)(ding)(ding)一(yi)(yi)個目標溫(wen)(wen)(wen)(wen)度(du)(du)(du)，試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)具(ju)有(you)自動恒(heng)(heng)溫(wen)(wen)(wen)(wen)到目標溫(wen)(wen)(wen)(wen)度(du)(du)(du)點(dian)的(de)能(neng)(neng)(neng)(neng)力(li)(li)。恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)溫(wen)(wen)(wen)(wen)濕度(du)(du)(du)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)的(de)控(kong)(kong)制(zhi)(zhi)(zhi)控(kong)(kong)制(zhi)(zhi)(zhi)方(fang)式也類似，設定(ding)(ding)(ding)(ding)(ding)一(yi)(yi)個目標溫(wen)(wen)(wen)(wen)度(du)(du)(du)、濕度(du)(du)(du)點(dian)，試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)具(ju)有(you)自動恒(heng)(heng)溫(wen)(wen)(wen)(wen)到目標溫(wen)(wen)(wen)(wen)度(du)(du)(du)、濕度(du)(du)(du)點(dian)的(de)能(neng)(neng)(neng)(neng)力(li)(li)。高(gao)(gao)(gao)、低(di)(di)溫(wen)(wen)(wen)(wen)交(jiao)變試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)具(ju)有(you)設定(ding)(ding)(ding)(ding)(ding)一(yi)(yi)條(tiao)或(huo)者(zhe)多條(tiao)高(gao)(gao)(gao)低(di)(di)溫(wen)(wen)(wen)(wen)變化、循環的(de)程(cheng)序(xu)，試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)有(you)能(neng)(neng)(neng)(neng)力(li)(li)根據預置(zhi)的(de)曲(qu)(qu)線完成試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)過程(cheng)，并且可(ke)以(yi)在(zai)zui大升溫(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)速(su)率能(neng)(neng)(neng)(neng)力(li)(li)的(de)范圍內，控(kong)(kong)制(zhi)(zhi)(zhi)升溫(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)的(de)速(su)率，即可(ke)以(yi)根據設定(ding)(ding)(ding)(ding)(ding)的(de)曲(qu)(qu)線的(de)斜率控(kong)(kong)制(zhi)(zhi)(zhi)升溫(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)速(su)率。同樣，高(gao)(gao)(gao)低(di)(di)溫(wen)(wen)(wen)(wen)交(jiao)變濕熱試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)也具(ju)有(you)預置(zhi)溫(wen)(wen)(wen)(wen)度(du)(du)(du)、濕度(du)(du)(du)曲(qu)(qu)線，并且根據預置(zhi)進(jin)行(xing)控(kong)(kong)制(zhi)(zhi)(zhi)的(de)能(neng)(neng)(neng)(neng)力(li)(li)。當(dang)然，交(jiao)變試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)都具(ju)有(you)恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)的(de)功(gong)能(neng)(neng)(neng)(neng)，但交(jiao)變試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)的(de)制(zhi)(zhi)(zhi)造成本(ben)較(jiao)(jiao)高(gao)(gao)(gao)，因為交(jiao)變試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)需(xu)配置(zhi)有(you)曲(qu)(qu)線自動記錄裝置(zhi)、程(cheng)序(xu)控(kong)(kong)制(zhi)(zhi)(zhi)儀，還須解決試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)在(zai)工作室內溫(wen)(wen)(wen)(wen)度(du)(du)(du)較(jiao)(jiao)高(gao)(gao)(gao)的(de)情況下(xia)開啟(qi)制(zhi)(zhi)(zhi)冷(leng)機等問題(ti)，因此(ci)，交(jiao)變試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)的(de)價格比恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)的(de)價格一(yi)(yi)般要高(gao)(gao)(gao)20%以(yi)上(shang)。因此(ci)，我(wo)們(men)應當(dang)實事求是(shi)的(de)以(yi)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)方(fang)法的(de)需(xu)要為出發(fa)點(dian)，選用恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)或(huo)者(zhe)是(shi)交(jiao)變試(shi)(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)(yan)箱(xiang)。

5、變溫(wen)速率(lv)的選擇

    普通的(de)(de)高(gao)(gao)低溫(wen)(wen)(wen)試(shi)驗箱(xiang)沒(mei)有降溫(wen)(wen)(wen)速(su)(su)度(du)(du)的(de)(de)指標(biao)，從環(huan)境溫(wen)(wen)(wen)度(du)(du)降溫(wen)(wen)(wen)到(dao)標(biao)稱的(de)(de)zui低溫(wen)(wen)(wen)度(du)(du)的(de)(de)時間一(yi)般為90～120min。高(gao)(gao)低溫(wen)(wen)(wen)交(jiao)變(bian)(bian)試(shi)驗箱(xiang)、高(gao)(gao)低溫(wen)(wen)(wen)交(jiao)變(bian)(bian)濕熱試(shi)驗箱(xiang)都有變(bian)(bian)溫(wen)(wen)(wen)速(su)(su)度(du)(du)的(de)(de)要求，其變(bian)(bian)溫(wen)(wen)(wen)速(su)(su)率(lv)一(yi)般要求1℃/min，在(zai)此速(su)(su)率(lv)的(de)(de)范圍(wei)內速(su)(su)度(du)(du)可調。而快速(su)(su)溫(wen)(wen)(wen)度(du)(du)變(bian)(bian)化試(shi)驗箱(xiang)的(de)(de)變(bian)(bian)溫(wen)(wen)(wen)速(su)(su)率(lv)較快，升溫(wen)(wen)(wen)、降溫(wen)(wen)(wen)速(su)(su)率(lv)可以達(da)到(dao)3℃/min～15℃/min，在(zai)某些溫(wen)(wen)(wen)度(du)(du)段升溫(wen)(wen)(wen)、降溫(wen)(wen)(wen)速(su)(su)率(lv)甚(shen)至可以達(da)到(dao)30℃/min以上(shang)。

    各種(zhong)規格、速(su)度(du)的(de)快速(su)溫(wen)(wen)度(du)變(bian)(bian)(bian)化(hua)(hua)試(shi)(shi)驗(yan)箱的(de)溫(wen)(wen)度(du)范(fan)圍(wei)一般(ban)都是(shi)(shi)相(xiang)(xiang)同(tong)的(de)，即－60～＋130℃，但考核降溫(wen)(wen)速(su)度(du)的(de)變(bian)(bian)(bian)溫(wen)(wen)范(fan)圍(wei)卻不盡相(xiang)(xiang)同(tong)，根據(ju)試(shi)(shi)驗(yan)不同(tong)的(de)試(shi)(shi)驗(yan)要求，快速(su)溫(wen)(wen)度(du)變(bian)(bian)(bian)化(hua)(hua)試(shi)(shi)驗(yan)箱變(bian)(bian)(bian)溫(wen)(wen)范(fan)圍(wei)有的(de)是(shi)(shi)－55～＋80℃，而有的(de)是(shi)(shi)－40～＋80℃。

    關于(yu)快速(su)(su)(su)溫(wen)(wen)(wen)度(du)(du)(du)(du)變(bian)(bian)化試驗(yan)箱(xiang)的(de)(de)變(bian)(bian)溫(wen)(wen)(wen)速(su)(su)(su)率(lv)有(you)兩種提(ti)法(fa)，一種是(shi)全程(cheng)平(ping)均(jun)(jun)(jun)升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)，一種是(shi)線(xian)(xian)形升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)（實(shi)際上是(shi)每(mei)5 min平(ping)均(jun)(jun)(jun)速(su)(su)(su)度(du)(du)(du)(du)）。全程(cheng)平(ping)均(jun)(jun)(jun)速(su)(su)(su)度(du)(du)(du)(du)是(shi)指(zhi)在試驗(yan)箱(xiang)的(de)(de)變(bian)(bian)溫(wen)(wen)(wen)范(fan)圍內，zui高溫(wen)(wen)(wen)度(du)(du)(du)(du)與zui低溫(wen)(wen)(wen)度(du)(du)(du)(du)之差值(zhi)與時(shi)間(jian)(jian)之比。目前國外各(ge)環境試驗(yan)設(she)(she)備生(sheng)產廠家提(ti)供的(de)(de)變(bian)(bian)溫(wen)(wen)(wen)速(su)(su)(su)率(lv)的(de)(de)技術參(can)數都是(shi)指(zhi)的(de)(de)全程(cheng)平(ping)均(jun)(jun)(jun)速(su)(su)(su)率(lv)。線(xian)(xian)形升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)指(zhi)在任(ren)意的(de)(de)每(mei)5 min時(shi)間(jian)(jian)段內，能夠保證的(de)(de)變(bian)(bian)溫(wen)(wen)(wen)速(su)(su)(su)率(lv)。而實(shi)際上對于(yu)快速(su)(su)(su)溫(wen)(wen)(wen)度(du)(du)(du)(du)變(bian)(bian)化試驗(yan)箱(xiang)來說，保證線(xian)(xian)形升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)的(de)(de)難(nan)度(du)(du)(du)(du)zui大、zui關鍵的(de)(de)一段是(shi)，在降(jiang)溫(wen)(wen)(wen)段zui后的(de)(de)一個5 min的(de)(de)時(shi)間(jian)(jian)段內，試驗(yan)箱(xiang)可以達到的(de)(de)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)率(lv)。從(cong)某種角度(du)(du)(du)(du)講(jiang)，線(xian)(xian)形升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)（每(mei)5 min平(ping)均(jun)(jun)(jun)速(su)(su)(su)度(du)(du)(du)(du)）更(geng)科學。因此試驗(yan)設(she)(she)備具有(you)全程(cheng)平(ping)均(jun)(jun)(jun)升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)和線(xian)(xian)形升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)（每(mei)5 min平(ping)均(jun)(jun)(jun)速(su)(su)(su)度(du)(du)(du)(du)）這(zhe)兩個參(can)數。一般來說，線(xian)(xian)形升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)（每(mei)5 min平(ping)均(jun)(jun)(jun)速(su)(su)(su)度(du)(du)(du)(du)）是(shi)全程(cheng)平(ping)均(jun)(jun)(jun)升(sheng)(sheng)降(jiang)溫(wen)(wen)(wen)速(su)(su)(su)度(du)(du)(du)(du)的(de)(de)1/2。

6、風速

    有關標(biao)準(zhun)規定，進行環境試(shi)(shi)驗時溫濕箱(xiang)內(nei)(nei)的(de)風速(su)(su)(su)應小于1.7m/s，對于試(shi)(shi)驗本身來說，風速(su)(su)(su)越(yue)小越(yue)好，風速(su)(su)(su)過大會加速(su)(su)(su)試(shi)(shi)驗件表(biao)面(mian)與箱(xiang)體內(nei)(nei)流(liu)動氣流(liu)的(de)熱交換，于試(shi)(shi)驗的(de)真實性不(bu)利。但為了保證試(shi)(shi)驗箱(xiang)工作室內(nei)(nei)的(de)均勻(yun)性，試(shi)(shi)驗箱(xiang)內(nei)(nei)具有循環風是(shi)必(bi)需的(de)。但是(shi)快速(su)(su)(su)溫度變(bian)化試(shi)(shi)驗箱(xiang)以及溫度、濕度、振(zhen)動等多因素綜(zong)合(he)環境試(shi)(shi)驗箱(xiang)，為追(zhui)求變(bian)溫速(su)(su)(su)率，必(bi)須加快箱(xiang)體內(nei)(nei)循環氣流(liu)的(de)流(liu)速(su)(su)(su)，風速(su)(su)(su)通常在2～3m/s。因此，對于不(bu)同的(de)使(shi)用目的(de)，風速(su)(su)(su)的(de)限制是(shi)不(bu)一(yi)樣的(de)。

7、溫(wen)度波動度

    溫(wen)度(du)波動是(shi)一個比較容易實現的參數，所(suo)有環(huan)境試(shi)驗(yan)設備廠家(jia)生產的多數的試(shi)驗(yan)箱實際的溫(wen)度(du)波動都可以(yi)控制在±0.3℃的范(fan)圍以(yi)內。

8、溫(wen)度(du)場(chang)均勻度(du)

    為了(le)更正(zheng)確地(di)模擬產(chan)品(pin)在(zai)自然界(jie)所遭受(shou)的實(shi)際環(huan)境(jing)(jing)(jing)狀況，在(zai)環(huan)境(jing)(jing)(jing)試(shi)驗(yan)(yan)中必(bi)須(xu)保證被試(shi)產(chan)品(pin)的周邊處在(zai)同一溫(wen)(wen)度(du)(du)環(huan)境(jing)(jing)(jing)條件下(xia)，為此，必(bi)須(xu)對試(shi)驗(yan)(yan)箱內的溫(wen)(wen)度(du)(du)梯(ti)度(du)(du)和溫(wen)(wen)度(du)(du)的波動度(du)(du)加(jia)以限(xian)制。在(zai)國軍標GJB150.1－86軍用設備環(huan)境(jing)(jing)(jing)試(shi)驗(yan)(yan)方法總則中明確規定“試(shi)驗(yan)(yan)樣品(pin)附近測(ce)量系統的溫(wen)(wen)度(du)(du)應在(zai)試(shi)驗(yan)(yan)溫(wen)(wen)度(du)(du)的±2℃以內，其溫(wen)(wen)度(du)(du)工(gong)不超過1℃/m或總的zui大(da)值為2.2℃（試(shi)驗(yan)(yan)樣品(pin)不工(gong)作）”。

9、濕(shi)度(du)的精度(du)控制

    環(huan)境試驗(yan)箱中測量濕度多數是(shi)采用(yong)干濕球法，環(huan)境試驗(yan)設備的(de)制造標(biao)準GB10586要(yao)求(qiu)，相對濕度偏差應在(zai)±２３％RH。為(wei)滿足濕度控制精度的(de)要(yao)求(qiu)，濕度試驗(yan)箱的(de)溫度控制精度較高，溫度波動一般小于±0.2℃。否則很難達到濕度控制精度的(de)要(yao)求(qiu)。