(北京雅士林市場部)
設備選擇依據
存(cun)在于地球表面及大氣層空間中(zhong)的(de)(de)(de)自(zi)然環(huan)境(jing)(jing)(jing)因(yin)素和(he)(he)誘發環(huan)境(jing)(jing)(jing)因(yin)素的(de)(de)(de)種(zhong)類(lei),目前還無法統計出一個(ge)確(que)切的(de)(de)(de)數(shu)目,其中(zhong)對工程產(chan)(chan)(chan)品(pin)(pin)(pin)(設備(bei))的(de)(de)(de)使用及壽命(ming)影響較大的(de)(de)(de)因(yin)素不下(xia)十幾種(zhong)。從事工程產(chan)(chan)(chan)品(pin)(pin)(pin)環(huan)境(jing)(jing)(jing)條(tiao)件(jian)研究的(de)(de)(de)工程師們(men)將自(zi)然界存(cun)在以(yi)(yi)及人(ren)類(lei)活動所(suo)誘發的(de)(de)(de)環(huan)境(jing)(jing)(jing)條(tiao)件(jian)整理(li)歸納為一系列的(de)(de)(de)試(shi)驗(yan)(yan)(yan)標準和(he)(he)規(gui)范,用以(yi)(yi)指導(dao)工程產(chan)(chan)(chan)品(pin)(pin)(pin)的(de)(de)(de)環(huan)境(jing)(jing)(jing)及可靠(kao)性試(shi)驗(yan)(yan)(yan)。如指導(dao)軍工產(chan)(chan)(chan)品(pin)(pin)(pin)進行環(huan)境(jing)(jing)(jing)試(shi)驗(yan)(yan)(yan)GJB150――中(zhong)華人(ren)民(min)共和(he)(he)國國家軍用標準《軍用設備(bei)環(huan)境(jing)(jing)(jing)試(shi)驗(yan)(yan)(yan)方(fang)法》,指導(dao)電工電子產(chan)(chan)(chan)品(pin)(pin)(pin)進行環(huan)境(jing)(jing)(jing)試(shi)驗(yan)(yan)(yan)的(de)(de)(de)GB2423――中(zhong)華人(ren)民(min)共和(he)(he)國國家標準《電工電子產(chan)(chan)(chan)品(pin)(pin)(pin)環(huan)境(jing)(jing)(jing)試(shi)驗(yan)(yan)(yan)方(fang)法指南》等。因(yin)此,我們(men)選擇環(huan)境(jing)(jing)(jing)及可靠(kao)性試(shi)驗(yan)(yan)(yan)設備(bei)時主要的(de)(de)(de)依據是工程產(chan)(chan)(chan)品(pin)(pin)(pin)的(de)(de)(de)試(shi)驗(yan)(yan)(yan)規(gui)范和(he)(he)試(shi)驗(yan)(yan)(yan)標準。
其次,為了規范試(shi)(shi)(shi)驗(yan)(yan)(yan)設備(bei)中(zhong)環境試(shi)(shi)(shi)驗(yan)(yan)(yan)條件的容(rong)差,保(bao)證環境參數的控制(zhi)精度(du),國(guo)家技術監督(du)機(ji)構及(ji)(ji)各(ge)工業(ye)部門還制(zhi)訂(ding)了一系列的環境試(shi)(shi)(shi)驗(yan)(yan)(yan)設備(bei)及(ji)(ji)檢(jian)測儀器儀表的檢(jian)定規程(cheng)。如中(zhong)華人民(min)共和國(guo)國(guo)家標(biao)準GB5170《電工電子產品環境試(shi)(shi)(shi)驗(yan)(yan)(yan)設備(bei)基本參數檢(jian)定方法》,又如國(guo)家技術監督(du)局頒布(bu)實施的JJG190-89《電動振動試(shi)(shi)(shi)驗(yan)(yan)(yan)臺(tai)系統(tong)試(shi)(shi)(shi)行檢(jian)定規程(cheng)》等(deng)。這些(xie)檢(jian)定規程(cheng)也是(shi)選擇環境及(ji)(ji)可(ke)靠性試(shi)(shi)(shi)驗(yan)(yan)(yan)設備(bei)的重(zhong)要依據,不符合這些(xie)檢(jian)定規程(cheng)要求的試(shi)(shi)(shi)驗(yan)(yan)(yan)設備(bei)是(shi)不允(yun)許投(tou)入使用的。
設備選擇基本原則
環境(jing)及可靠性試(shi)驗設(she)備的選(xuan)擇應遵循(xun)以下五條基(ji)本原則:
1、環境條件的再(zai)現性
在(zai)試(shi)驗室內完整而(er)精(jing)確地(di)再現自(zi)然界(jie)存在(zai)的(de)(de)(de)環(huan)(huan)境條(tiao)件(jian)是(shi)(shi)可(ke)望而(er)不(bu)可(ke)及(ji)的(de)(de)(de)事情。但是(shi)(shi),在(zai)一定的(de)(de)(de)容差范圍(wei)之內,人們完全可(ke)以正確而(er)近似地(di)模(mo)擬工程產(chan)品(pin)(pin)在(zai)使(shi)用(yong)、貯(zhu)存、運輸等過程中(zhong)所經受的(de)(de)(de)外(wai)界(jie)環(huan)(huan)境條(tiao)件(jian)。這段話用(yong)工程的(de)(de)(de)語言概括(kuo),就是(shi)(shi)“試(shi)驗設備(bei)所創(chuang)造的(de)(de)(de)圍(wei)繞被(bei)試(shi)產(chan)品(pin)(pin)周邊的(de)(de)(de)環(huan)(huan)境條(tiao)件(jian)(含平臺環(huan)(huan)境)應該滿(man)足(zu)產(chan)品(pin)(pin)試(shi)驗規范所規定的(de)(de)(de)環(huan)(huan)境條(tiao)件(jian)及(ji)其容差的(de)(de)(de)要求”。如(ru)用(yong)于軍工產(chan)品(pin)(pin)試(shi)驗的(de)(de)(de)溫度箱不(bu)僅要滿(man)足(zu)國軍標(biao)GJB150.3-86、GJB150.4-86中(zhong)根(gen)據(ju)不(bu)同(tong)的(de)(de)(de)均勻性和溫度控(kong)制精(jing)度的(de)(de)(de)要求。只有這樣,才能保證在(zai)環(huan)(huan)境試(shi)驗中(zhong)環(huan)(huan)境條(tiao)件(jian)的(de)(de)(de)再現性。
2、環(huan)境條件的(de)可重復性
一(yi)臺環(huan)境試(shi)(shi)驗(yan)(yan)(yan)(yan)設(she)(she)備可能用(yong)于同一(yi)類型產品的(de)(de)(de)多次(ci)試(shi)(shi)驗(yan)(yan)(yan)(yan),而(er)一(yi)臺被試(shi)(shi)的(de)(de)(de)工程產品也(ye)可能在不同的(de)(de)(de)環(huan)境試(shi)(shi)驗(yan)(yan)(yan)(yan)設(she)(she)備中進行試(shi)(shi)驗(yan)(yan)(yan)(yan),為了保證同一(yi)臺產品在同一(yi)試(shi)(shi)驗(yan)(yan)(yan)(yan)規(gui)范所規(gui)定(ding)的(de)(de)(de)環(huan)境試(shi)(shi)驗(yan)(yan)(yan)(yan)條件下所得試(shi)(shi)驗(yan)(yan)(yan)(yan)結果(guo)的(de)(de)(de)可比較性,必然要求環(huan)境試(shi)(shi)驗(yan)(yan)(yan)(yan)設(she)(she)備所提供的(de)(de)(de)環(huan)境條件具有可重(zhong)復性。這也(ye)就(jiu)是(shi)(shi)說,環(huan)境試(shi)(shi)驗(yan)(yan)(yan)(yan)設(she)(she)備施用(yong)于被試(shi)(shi)驗(yan)(yan)(yan)(yan)產品的(de)(de)(de)應力水平(如(ru)熱應力、振動應力、電應力等)對于同一(yi)試(shi)(shi)驗(yan)(yan)(yan)(yan)規(gui)范的(de)(de)(de)要求是(shi)(shi)一(yi)致(zhi)的(de)(de)(de)。
環(huan)境(jing)(jing)試驗(yan)設備(bei)所提供環(huan)境(jing)(jing)條件的(de)可重復性(xing)是由國家計量檢(jian)定(ding)部門(men)依據國家技術(shu)(shu)監督(du)機構所制定(ding)的(de)檢(jian)定(ding)規程檢(jian)定(ding)合(he)格后提供保證。為(wei)此,必須要(yao)求環(huan)境(jing)(jing)試驗(yan)設備(bei)能滿足檢(jian)定(ding)規程中的(de)各項(xiang)技術(shu)(shu)指標(biao)及精(jing)(jing)度(du)(du)指標(biao)的(de)要(yao)求,并(bing)且(qie)(qie)在使(shi)用時(shi)(shi)間上(shang)不超過(guo)檢(jian)定(ding)周期所規定(ding)的(de)時(shi)(shi)限(xian)。如(ru)使(shi)用非(fei)常普遍的(de)電(dian)動振動臺除滿足激振力、頻率范圍、負載能力等技術(shu)(shu)指標(biao)外,還必須滿足檢(jian)定(ding)規程中規定(ding)的(de)橫向振動比、臺面(mian)加速度(du)(du)均(jun)勻性(xing)、諧波失真度(du)(du)等精(jing)(jing)度(du)(du)指標(biao)的(de)要(yao)求,而且(qie)(qie)每次檢(jian)定(ding)后的(de)使(shi)用周期為(wei)二(er)年(nian),超過(guo)二(er)年(nian)必須重新檢(jian)定(ding)合(he)格后才能投入使(shi)用。
3、環境(jing)條件參數的可測(ce)控性
任何一(yi)臺環境(jing)試(shi)驗(yan)設備(bei)所提供的(de)(de)(de)(de)(de)環境(jing)條件(jian)(jian)必須(xu)是可觀(guan)測的(de)(de)(de)(de)(de)和(he)可控制(zhi)的(de)(de)(de)(de)(de),這(zhe)不僅是為了使環境(jing)參(can)數(shu)限制(zhi)在一(yi)定的(de)(de)(de)(de)(de)容(rong)差范(fan)圍之內,保(bao)證試(shi)驗(yan)條件(jian)(jian)的(de)(de)(de)(de)(de)再現性(xing)和(he)重復性(xing)的(de)(de)(de)(de)(de)要求,而(er)且從產品(pin)(pin)試(shi)驗(yan)的(de)(de)(de)(de)(de)安全(quan)出發(fa)也是必須(xu)的(de)(de)(de)(de)(de),以(yi)便防止環境(jing)條件(jian)(jian)失控導致被試(shi)產品(pin)(pin)的(de)(de)(de)(de)(de)損壞,帶來不必要的(de)(de)(de)(de)(de)損失。目前各種(zhong)試(shi)驗(yan)規范(fan)中大體要求參(can)數(shu)測試(shi)的(de)(de)(de)(de)(de)精(jing)度不應低于(yu)試(shi)驗(yan)條件(jian)(jian)允許的(de)(de)(de)(de)(de)誤(wu)差的(de)(de)(de)(de)(de)三分之一(yi)。
4、環境試驗條件的排它性
每一(yi)(yi)次進(jin)行環境(jing)(jing)或可靠(kao)性試(shi)(shi)驗(yan),對環境(jing)(jing)因素的(de)(de)(de)類別、量(liang)值及容差都(dou)有(you)嚴格的(de)(de)(de)規定(ding),并排除非(fei)試(shi)(shi)驗(yan)所(suo)(suo)需的(de)(de)(de)環境(jing)(jing)因素滲(shen)透其(qi)中(zhong),以便在試(shi)(shi)驗(yan)中(zhong)或試(shi)(shi)驗(yan)結束(shu)后判斷和分析產品失效(xiao)與故障模式時,提(ti)供(gong)確切(qie)的(de)(de)(de)依據,故要求環境(jing)(jing)試(shi)(shi)驗(yan)設備除提(ti)供(gong)所(suo)(suo)規定(ding)的(de)(de)(de)環境(jing)(jing)條件(jian)外(wai),不允許對被(bei)試(shi)(shi)產品附加其(qi)它的(de)(de)(de)環境(jing)(jing)應力干擾。如(ru)電動振動臺檢定(ding)規程中(zhong)所(suo)(suo)限定(ding)的(de)(de)(de)臺面漏磁,加速度信噪比(bi)(bi)、帶內帶外(wai)加速度總均(jun)方根值比(bi)(bi)。隨機信號的(de)(de)(de)檢驗(yan)、諧波(bo)失真(zhen)度等(deng)精度指(zhi)標都(dou)是為了保證環境(jing)(jing)試(shi)(shi)驗(yan)條件(jian)的(de)(de)(de)唯一(yi)(yi)性而制定(ding)的(de)(de)(de)檢定(ding)項目。
5、試驗(yan)設備的(de)安全可靠性
環(huan)境(jing)試(shi)(shi)驗(yan)(yan)(yan)(yan),特(te)別(bie)是(shi)可靠(kao)(kao)性(xing)試(shi)(shi)驗(yan)(yan)(yan)(yan),試(shi)(shi)驗(yan)(yan)(yan)(yan)周期長(chang)(chang),試(shi)(shi)驗(yan)(yan)(yan)(yan)的對象有時是(shi)價值很高(gao)的軍工產品,試(shi)(shi)驗(yan)(yan)(yan)(yan)過程中,試(shi)(shi)驗(yan)(yan)(yan)(yan)人(ren)員經常要(yao)在現場(chang)周圍操作(zuo)巡視或測試(shi)(shi)工作(zuo),因此要(yao)求環(huan)境(jing)試(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)(bei)必須具有運行(xing)安(an)全(quan)、操作(zuo)方便、使(shi)用可靠(kao)(kao)、工作(zuo)壽命長(chang)(chang)等特(te)點,以確(que)保試(shi)(shi)驗(yan)(yan)(yan)(yan)本(ben)身的正常進(jin)行(xing)。試(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)(bei)的各種(zhong)保護、告警(jing)措施及安(an)全(quan)連鎖裝置應(ying)該完(wan)善可靠(kao)(kao),以保證試(shi)(shi)驗(yan)(yan)(yan)(yan)人(ren)員、被試(shi)(shi)產品和試(shi)(shi)驗(yan)(yan)(yan)(yan)設備(bei)(bei)本(ben)身的安(an)全(quan)可靠(kao)(kao)性(xing)。
溫濕度箱的選擇
1、容積的選擇
將被試產品(pin)(pin)(元器件、組件、部件或整機)置入氣(qi)候環(huan)境(jing)箱進(jin)行(xing)試驗(yan)時,為了(le)保證被試產品(pin)(pin)周圍氣(qi)氛能滿足(zu)試驗(yan)規(gui)(gui)范所規(gui)(gui)定的環(huan)境(jing)試驗(yan)條件,氣(qi)候箱工作尺(chi)寸與被試產品(pin)(pin)外廓(kuo)尺(chi)寸之間(jian)應遵循以下幾點規(gui)(gui)定:
a) 被試(shi)產(chan)品的體積(W×D×H)不(bu)得超過試(shi)驗箱有效(xiao)工(gong)作空間的(20~35)%(推薦選(xuan)用20%)。對于在(zai)試(shi)驗中發熱(re)的產(chan)品推薦選(xuan)用不(bu)大于10%。
b) 被試產品的迎風斷面積(ji)與該斷面上試驗箱工(gong)作(zuo)室總面積(ji)之比不大于(35~50)%(推(tui)薦選用35%)。
c) 被試(shi)產品(pin)外廓表面(mian)距試(shi)驗箱壁的距離(li)至少保持(chi)100~150mm,(推薦選用150mm)。
上述三點規定實際上是相(xiang)互依存和統(tong)一的。以(yi)1立(li)方(fang)米正方(fang)體(ti)箱(xiang)子為例,面積(ji)比(bi)(bi)為1:(0.35~0.5)相(xiang)當(dang)(dang)于(yu)體(ti)積(ji)之比(bi)(bi)為1:(0.207~0.354)。距箱(xiang)壁100~150mm相(xiang)當(dang)(dang)于(yu)體(ti)積(ji)之比(bi)(bi)為1:(0.343~0.512)。
總括上(shang)述(shu)三點(dian)規(gui)定,氣候環境試(shi)驗箱(xiang)的工作(zuo)腔(qiang)容積至(zhi)少應是被試(shi)產(chan)品外廓體積的3~5倍。作(zuo)出這種(zhong)規(gui)定的理(li)由(you)有以下幾點(dian):
1〕 被試驗(yan)(yan)件(jian)(jian)置(zhi)入(ru)箱(xiang)體(ti)后擠(ji)占(zhan)了流暢的通(tong)(tong)道,通(tong)(tong)道變(bian)窄將導致(zhi)氣(qi)流流速(su)的增加(jia)。加(jia)速(su)氣(qi)流與被試驗(yan)(yan)件(jian)(jian)之間(jian)的熱交(jiao)換。這與環(huan)境條件(jian)(jian)的再現不(bu)符,因為(wei)在有關標(biao)準(zhun)(zhun)中對涉(she)及(ji)溫度環(huan)境試驗(yan)(yan)都規(gui)定試驗(yan)(yan)箱(xiang)內(nei)試驗(yan)(yan)樣件(jian)(jian)周(zhou)圍的空氣(qi)流速(su)不(bu)應(ying)超過1.7m/s,以防止試驗(yan)(yan)樣件(jian)(jian)和周(zhou)圍氣(qi)氛產生(sheng)不(bu)符合實(shi)際的熱傳導。在空載時試驗(yan)(yan)箱(xiang)內(nei)平均風(feng)速(su)為(wei)0.6~0.8m/s,不(bu)超過1m/s,滿(man)足a)、b)兩(liang)點(dian)要(yao)求所規(gui)定的空間(jian)及(ji)面積比時,流場的風(feng)速(su)可能(neng)增大(da)(50~100)%,平均最高風(feng)速(su)為(wei)(1~1.7)m/s。滿(man)足標(biao)準(zhun)(zhun)規(gui)定的要(yao)求。如果在試驗(yan)(yan)中不(bu)加(jia)限制地加(jia)大(da)試驗(yan)(yan)件(jian)(jian)的體(ti)積或迎(ying)風(feng)斷面積,則實(shi)際試驗(yan)(yan)時氣(qi)流風(feng)速(su)將增大(da)到超出試驗(yan)(yan)標(biao)準(zhun)(zhun)所規(gui)定的最高風(feng)速(su),其試驗(yan)(yan)結(jie)果的有效(xiao)性將受(shou)到懷(huai)疑。
2〕 氣(qi)候箱(xiang)(xiang)工(gong)作腔內(nei)環(huan)境參(can)數(shu)〔如溫度(du)、濕(shi)度(du)、鹽(yan)霧沉降率等〕的(de)(de)(de)精度(du)指標(biao)都是在(zai)空(kong)載狀態下檢測(ce)的(de)(de)(de)結果,一旦置入被(bei)試驗(yan)件(jian)后,對試驗(yan)箱(xiang)(xiang)工(gong)作腔內(nei)環(huan)境參(can)數(shu)的(de)(de)(de)均勻(yun)性(xing)將產生影響(xiang),試驗(yan)件(jian)占有的(de)(de)(de)空(kong)間越大,這種影響(xiang)也(ye)就越嚴重(zhong)。實測(ce)試驗(yan)數(shu)據表明,流場(chang)中迎風面(mian)與(yu)背風面(mian)的(de)(de)(de)溫差可達(da)到(dao)3~8℃,嚴重(zhong)時可大到(dao)10℃以上。因此,必須盡(jin)量滿足a〕、b〕兩項要求,以保證(zheng)被(bei)試產品周圍環(huan)境參(can)數(shu)的(de)(de)(de)均勻(yun)性(xing)。
3〕 根據熱傳導的(de)(de)原(yuan)理,箱(xiang)(xiang)壁(bi)(bi)附(fu)(fu)近(jin)氣流(liu)的(de)(de)溫(wen)度(du)(du)通常與流(liu)場中心溫(wen)度(du)(du)相(xiang)差(cha)2~3℃,在高(gao)低溫(wen)的(de)(de)上下(xia)限時,還可能達到5℃。箱(xiang)(xiang)壁(bi)(bi)的(de)(de)溫(wen)度(du)(du)與箱(xiang)(xiang)壁(bi)(bi)附(fu)(fu)近(jin)流(liu)場的(de)(de)溫(wen)度(du)(du)又相(xiang)差(cha)2~3℃(視箱(xiang)(xiang)壁(bi)(bi)的(de)(de)結構和材料(liao)而定)試(shi)驗溫(wen)度(du)(du)與外界大(da)氣環(huan)境(jing)相(xiang)差(cha)越大(da),上述溫(wen)差(cha)也(ye)越大(da),因此(ci),距箱(xiang)(xiang)壁(bi)(bi)(100~150mm)距離內的(de)(de)空(kong)間(jian)是不(bu)可利用空(kong)間(jian)。
2、溫度范圍的選擇
目(mu)前,國(guo)外溫(wen)(wen)度試驗箱(xiang)(xiang)的(de)(de)(de)范(fan)圍大(da)體(ti)上(shang)(shang)為(wei)-73~+177℃,或-70~+180℃。國(guo)內多(duo)數(shu)廠家一般為(wei)-80~+130℃,-60~+130℃,-40~+130℃,也(ye)(ye)有(you)高溫(wen)(wen)到150℃。這些溫(wen)(wen)度范(fan)圍通常可(ke)(ke)以(yi)滿(man)足(zu)國(guo)內絕大(da)多(duo)數(shu)軍(jun)用、民用產(chan)品溫(wen)(wen)度試驗的(de)(de)(de)需要,除非(fei)確有(you)特殊需要,如(ru)安裝位置靠近(jin)發動機(ji)等(deng)熱源的(de)(de)(de)產(chan)品外,不(bu)可(ke)(ke)盲目(mu)提高溫(wen)(wen)度上(shang)(shang)限(xian)。因為(wei)上(shang)(shang)限(xian)溫(wen)(wen)度越高,箱(xiang)(xiang)體(ti)內外的(de)(de)(de)溫(wen)(wen)差(cha)越大(da),箱(xiang)(xiang)體(ti)內部流(liu)場(chang)的(de)(de)(de)均勻性(xing)也(ye)(ye)越差(cha)。可(ke)(ke)利用的(de)(de)(de)工作(zuo)(zuo)室體(ti)積也(ye)(ye)就越小(xiao)。另(ling)一方面,上(shang)(shang)限(xian)溫(wen)(wen)度值越高,對箱(xiang)(xiang)壁夾層中保溫(wen)(wen)材料(如(ru)玻璃(li)棉等(deng))的(de)(de)(de)耐熱性(xing)要求越高。箱(xiang)(xiang)體(ti)密封性(xing)的(de)(de)(de)要求也(ye)(ye)越高,使箱(xiang)(xiang)體(ti)的(de)(de)(de)制作(zuo)(zuo)成本增加。
3、濕(shi)度范圍的選擇
國內外環境試(shi)(shi)(shi)驗(yan)(yan)箱給出(chu)的(de)濕度(du)(du)指(zhi)標大都是20~98%RH或30~98%RH,如(ru)(ru)果濕熱試(shi)(shi)(shi)驗(yan)(yan)箱沒有除濕系統,則(ze)濕度(du)(du)范圍為(wei)(wei)60~98%,這一類試(shi)(shi)(shi)驗(yan)(yan)箱只能做高濕試(shi)(shi)(shi)驗(yan)(yan),但它的(de)價格低(di)得(de)多。值得(de)注意的(de)是在(zai)濕度(du)(du)指(zhi)標后面應該注明相(xiang)(xiang)(xiang)應的(de)溫度(du)(du)范圍,或給出(chu)最低(di)露(lu)點溫度(du)(du)。因為(wei)(wei)相(xiang)(xiang)(xiang)對(dui)濕度(du)(du)是與溫度(du)(du)直接相(xiang)(xiang)(xiang)關的(de),對(dui)于同(tong)樣(yang)的(de)絕(jue)對(dui)含濕量,溫度(du)(du)越高,相(xiang)(xiang)(xiang)對(dui)濕度(du)(du)就越小,如(ru)(ru)絕(jue)對(dui)含濕量為(wei)(wei)5g/Kg(指(zhi)1公斤干空氣中含有5克的(de)水蒸汽(qi)),當溫度(du)(du)為(wei)(wei)29℃時(shi),相(xiang)(xiang)(xiang)對(dui)濕度(du)(du)為(wei)(wei)20%RH,溫度(du)(du)為(wei)(wei)6℃時(shi),相(xiang)(xiang)(xiang)對(dui)濕度(du)(du)為(wei)(wei)90%RH,當溫度(du)(du)降至4℃以下(xia),相(xiang)(xiang)(xiang)對(dui)濕度(du)(du)超(chao)過100%,在(zai)箱體內會出(chu)現(xian)(xian)結露(lu)現(xian)(xian)象。
實現(xian)高溫(wen)、高濕(shi)(shi)(shi)(shi)(shi)只需要往箱體(ti)空(kong)(kong)(kong)(kong)氣(qi)中(zhong)噴水蒸汽(qi)或霧化的(de)(de)(de)水珠,進行加濕(shi)(shi)(shi)(shi)(shi)。低溫(wen)低濕(shi)(shi)(shi)(shi)(shi)則相對(dui)(dui)(dui)難(nan)于(yu)(yu)控(kong)制,因(yin)(yin)為此(ci)時(shi)(shi)的(de)(de)(de)絕(jue)對(dui)(dui)(dui)含(han)濕(shi)(shi)(shi)(shi)(shi)量很低,有時(shi)(shi)比大(da)氣(qi)中(zhong)的(de)(de)(de)絕(jue)對(dui)(dui)(dui)含(han)濕(shi)(shi)(shi)(shi)(shi)量低很多,需要對(dui)(dui)(dui)箱體(ti)內(nei)(nei)流動(dong)的(de)(de)(de)空(kong)(kong)(kong)(kong)氣(qi)除(chu)濕(shi)(shi)(shi)(shi)(shi),使空(kong)(kong)(kong)(kong)氣(qi)變(bian)得干燥。目前國內(nei)(nei)外絕(jue)大(da)多數的(de)(de)(de)溫(wen)濕(shi)(shi)(shi)(shi)(shi)度(du)箱都(dou)采用(yong)制冷(leng)除(chu)濕(shi)(shi)(shi)(shi)(shi)的(de)(de)(de)原(yuan)理(li),是在(zai)(zai)箱體(ti)的(de)(de)(de)空(kong)(kong)(kong)(kong)氣(qi)預(yu)調室內(nei)(nei)加一組制冷(leng)光(guang)(guang)管(guan)。當濕(shi)(shi)(shi)(shi)(shi)空(kong)(kong)(kong)(kong)氣(qi)經過冷(leng)管(guan)時(shi)(shi),其(qi)相對(dui)(dui)(dui)濕(shi)(shi)(shi)(shi)(shi)度(du)會達(da)(da)到(dao)(dao)100%RH,因(yin)(yin)空(kong)(kong)(kong)(kong)氣(qi)飽和(he)在(zai)(zai)光(guang)(guang)管(guan)上(shang)結露(lu),使空(kong)(kong)(kong)(kong)氣(qi)變(bian)得更干燥。這(zhe)種除(chu)濕(shi)(shi)(shi)(shi)(shi)方(fang)(fang)式(shi)理(li)論(lun)上(shang)可達(da)(da)到(dao)(dao)零度(du)以(yi)下(xia)的(de)(de)(de)露(lu)點(dian)(dian)溫(wen)度(du),但是當冷(leng)點(dian)(dian)表(biao)面(mian)溫(wen)度(du)到(dao)(dao)達(da)(da)0℃時(shi)(shi),光(guang)(guang)管(guan)表(biao)面(mian)結露(lu)的(de)(de)(de)水滴會結冰,從而(er)影響光(guang)(guang)管(guan)表(biao)面(mian)的(de)(de)(de)熱(re)交換(huan),使除(chu)濕(shi)(shi)(shi)(shi)(shi)能力(li)下(xia)降。又因(yin)(yin)為箱體(ti)不可能絕(jue)對(dui)(dui)(dui)密封,大(da)氣(qi)中(zhong)的(de)(de)(de)濕(shi)(shi)(shi)(shi)(shi)空(kong)(kong)(kong)(kong)氣(qi)會滲入(ru)到(dao)(dao)箱體(ti)內(nei)(nei),使露(lu)點(dian)(dian)溫(wen)度(du)回升。另一方(fang)(fang)面(mian),在(zai)(zai)光(guang)(guang)管(guan)間流動(dong)的(de)(de)(de)濕(shi)(shi)(shi)(shi)(shi)空(kong)(kong)(kong)(kong)氣(qi)只是在(zai)(zai)和(he)光(guang)(guang)管(guan)(冷(leng)點(dian)(dian))接觸(chu)的(de)(de)(de)瞬間達(da)(da)到(dao)(dao)飽和(he)狀態而(er)析出水蒸汽(qi),因(yin)(yin)此(ci)這(zhe)種除(chu)濕(shi)(shi)(shi)(shi)(shi)方(fang)(fang)法很難(nan)使箱體(ti)內(nei)(nei)的(de)(de)(de)露(lu)點(dian)(dian)溫(wen)度(du)在(zai)(zai)到(dao)(dao)0℃以(yi)下(xia)。實際所達(da)(da)到(dao)(dao)的(de)(de)(de)最低露(lu)點(dian)(dian)溫(wen)度(du)為5~7℃。露(lu)點(dian)(dian)溫(wen)度(du)5℃相當于(yu)(yu)絕(jue)對(dui)(dui)(dui)含(han)濕(shi)(shi)(shi)(shi)(shi)量為0.0055g/Kg,對(dui)(dui)(dui)應相對(dui)(dui)(dui)濕(shi)(shi)(shi)(shi)(shi)度(du)20%RH的(de)(de)(de)溫(wen)度(du)為30℃。如果要求溫(wen)度(du)20℃進相對(dui)(dui)(dui)濕(shi)(shi)(shi)(shi)(shi)度(du)達(da)(da)到(dao)(dao)20%RH,此(ci)時(shi)(shi)的(de)(de)(de)露(lu)點(dian)(dian)溫(wen)度(du)為-3℃,采用(yong)致(zhi)冷(leng)方(fang)(fang)式(shi)除(chu)濕(shi)(shi)(shi)(shi)(shi)是很困難(nan)的(de)(de)(de),必須(xu)選(xuan)用(yong)空(kong)(kong)(kong)(kong)氣(qi)干燥系統才能實現(xian)不銹(xiu)鋼焊(han)條。
4、控制方式的(de)選擇
溫度、濕度試(shi)驗(yan)箱(xiang)(xiang)有恒定試(shi)驗(yan)箱(xiang)(xiang)、交變(bian)試(shi)驗(yan)箱(xiang)(xiang)兩種情(qing)況。
普通的(de)(de)高(gao)(gao)低(di)溫(wen)(wen)(wen)(wen)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)一(yi)般指的(de)(de)是恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)高(gao)(gao)低(di)溫(wen)(wen)(wen)(wen)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang),其控(kong)制(zhi)方(fang)式為:設(she)定(ding)(ding)(ding)(ding)(ding)一(yi)個目(mu)標溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du),試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)具(ju)有(you)自(zi)動(dong)恒(heng)(heng)溫(wen)(wen)(wen)(wen)到目(mu)標溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)點的(de)(de)能(neng)力。恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)溫(wen)(wen)(wen)(wen)濕(shi)度(du)(du)(du)(du)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)控(kong)制(zhi)控(kong)制(zhi)方(fang)式也類(lei)似,設(she)定(ding)(ding)(ding)(ding)(ding)一(yi)個目(mu)標溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)、濕(shi)度(du)(du)(du)(du)點,試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)具(ju)有(you)自(zi)動(dong)恒(heng)(heng)溫(wen)(wen)(wen)(wen)到目(mu)標溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)、濕(shi)度(du)(du)(du)(du)點的(de)(de)能(neng)力。高(gao)(gao)、低(di)溫(wen)(wen)(wen)(wen)交變(bian)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)具(ju)有(you)設(she)定(ding)(ding)(ding)(ding)(ding)一(yi)條或者多條高(gao)(gao)低(di)溫(wen)(wen)(wen)(wen)變(bian)化(hua)、循環的(de)(de)程(cheng)序(xu),試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)有(you)能(neng)力根(gen)據(ju)預(yu)(yu)置(zhi)的(de)(de)曲(qu)(qu)線(xian)完成試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)過程(cheng),并且可以(yi)在(zai)最大升(sheng)溫(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)速率能(neng)力的(de)(de)范圍內(nei)(nei),精確(que)控(kong)制(zhi)升(sheng)溫(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)的(de)(de)速率,即(ji)可以(yi)根(gen)據(ju)設(she)定(ding)(ding)(ding)(ding)(ding)的(de)(de)曲(qu)(qu)線(xian)的(de)(de)斜率控(kong)制(zhi)升(sheng)溫(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)速率。同樣,高(gao)(gao)低(di)溫(wen)(wen)(wen)(wen)交變(bian)濕(shi)熱試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)也具(ju)有(you)預(yu)(yu)置(zhi)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)、濕(shi)度(du)(du)(du)(du)曲(qu)(qu)線(xian),并且根(gen)據(ju)預(yu)(yu)置(zhi)進行控(kong)制(zhi)的(de)(de)能(neng)力。當(dang)然,交變(bian)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)都具(ju)有(you)恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)功能(neng),但(dan)交變(bian)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)制(zhi)造成本(ben)較高(gao)(gao),因(yin)為交變(bian)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)需(xu)配置(zhi)有(you)曲(qu)(qu)線(xian)自(zi)動(dong)記錄(lu)裝置(zhi)、程(cheng)序(xu)控(kong)制(zhi)儀,還須解決試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)在(zai)工(gong)作(zuo)室內(nei)(nei)溫(wen)(wen)(wen)(wen)度(du)(du)(du)(du)較高(gao)(gao)的(de)(de)情(qing)況下(xia)開啟(qi)制(zhi)冷機等問題,因(yin)此(ci)(ci),交變(bian)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)價(jia)格(ge)比恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)的(de)(de)價(jia)格(ge)一(yi)般要高(gao)(gao)20%以(yi)上。因(yin)此(ci)(ci),我們應當(dang)實(shi)事求(qiu)是的(de)(de)以(yi)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)方(fang)法(fa)的(de)(de)需(xu)要為出發(fa)點,選(xuan)用恒(heng)(heng)定(ding)(ding)(ding)(ding)(ding)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)或者是交變(bian)試(shi)(shi)(shi)驗(yan)(yan)(yan)(yan)箱(xiang)(xiang)(xiang)(xiang)(xiang)(xiang)。
5、變溫速率的選擇
普通的(de)高低溫(wen)(wen)(wen)(wen)(wen)試(shi)(shi)驗(yan)(yan)箱沒有降溫(wen)(wen)(wen)(wen)(wen)速(su)(su)度(du)(du)的(de)指標(biao),從環境溫(wen)(wen)(wen)(wen)(wen)度(du)(du)降溫(wen)(wen)(wen)(wen)(wen)到(dao)標(biao)稱的(de)最低溫(wen)(wen)(wen)(wen)(wen)度(du)(du)的(de)時間(jian)一般(ban)為(wei)90~120min。高低溫(wen)(wen)(wen)(wen)(wen)交變(bian)(bian)(bian)試(shi)(shi)驗(yan)(yan)箱、高低溫(wen)(wen)(wen)(wen)(wen)交變(bian)(bian)(bian)濕熱試(shi)(shi)驗(yan)(yan)箱都有變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)速(su)(su)度(du)(du)的(de)要求,其變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)速(su)(su)率(lv)一般(ban)要求1℃/min,在(zai)此(ci)速(su)(su)率(lv)的(de)范圍內(nei)速(su)(su)度(du)(du)可調。而(er)快速(su)(su)溫(wen)(wen)(wen)(wen)(wen)度(du)(du)變(bian)(bian)(bian)化試(shi)(shi)驗(yan)(yan)箱的(de)變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)(wen)速(su)(su)率(lv)較快,升溫(wen)(wen)(wen)(wen)(wen)、降溫(wen)(wen)(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)(wen)(wen)度(du)(du)段升溫(wen)(wen)(wen)(wen)(wen)、降溫(wen)(wen)(wen)(wen)(wen)速(su)(su)率(lv)甚(shen)至可以達(da)到(dao)30℃/min以上。
各(ge)種(zhong)規格、速(su)度的(de)(de)快速(su)溫(wen)(wen)(wen)度變化試驗(yan)(yan)箱的(de)(de)溫(wen)(wen)(wen)度范圍(wei)一般(ban)都(dou)是相同的(de)(de),即-60~+130℃,但(dan)考核降溫(wen)(wen)(wen)速(su)度的(de)(de)變溫(wen)(wen)(wen)范圍(wei)卻不盡(jin)相同,根據試驗(yan)(yan)不同的(de)(de)試驗(yan)(yan)要求(qiu),快速(su)溫(wen)(wen)(wen)度變化試驗(yan)(yan)箱變溫(wen)(wen)(wen)范圍(wei)有的(de)(de)是-55~+80℃,而有的(de)(de)是-40~+80℃。
關于快(kuai)速(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)度(du)(du)(du)變(bian)(bian)(bian)化試(shi)驗(yan)(yan)箱(xiang)的(de)(de)(de)變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)率(lv)有兩種提(ti)法,一(yi)種是(shi)(shi)全程平(ping)均(jun)(jun)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du),一(yi)種是(shi)(shi)線(xian)(xian)形(xing)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)(實際(ji)上(shang)(shang)是(shi)(shi)每(mei)(mei)(mei)5 min平(ping)均(jun)(jun)速(su)(su)(su)(su)度(du)(du)(du))。全程平(ping)均(jun)(jun)速(su)(su)(su)(su)度(du)(du)(du)是(shi)(shi)指(zhi)(zhi)在試(shi)驗(yan)(yan)箱(xiang)的(de)(de)(de)變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)范(fan)圍內(nei),最(zui)(zui)高溫(wen)(wen)(wen)(wen)度(du)(du)(du)與最(zui)(zui)低(di)溫(wen)(wen)(wen)(wen)度(du)(du)(du)之差值與時(shi)間之比。目(mu)前國(guo)外各環境(jing)試(shi)驗(yan)(yan)設(she)備(bei)生產廠家提(ti)供的(de)(de)(de)變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)率(lv)的(de)(de)(de)技術參數都是(shi)(shi)指(zhi)(zhi)的(de)(de)(de)全程平(ping)均(jun)(jun)速(su)(su)(su)(su)率(lv)。線(xian)(xian)形(xing)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)指(zhi)(zhi)在任意(yi)的(de)(de)(de)每(mei)(mei)(mei)5 min時(shi)間段(duan)內(nei),能夠保證的(de)(de)(de)變(bian)(bian)(bian)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)率(lv)。而實際(ji)上(shang)(shang)對于快(kuai)速(su)(su)(su)(su)溫(wen)(wen)(wen)(wen)度(du)(du)(du)變(bian)(bian)(bian)化試(shi)驗(yan)(yan)箱(xiang)來說(shuo),保證線(xian)(xian)形(xing)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)的(de)(de)(de)難度(du)(du)(du)最(zui)(zui)大、最(zui)(zui)關鍵的(de)(de)(de)一(yi)段(duan)是(shi)(shi),在降(jiang)(jiang)溫(wen)(wen)(wen)(wen)段(duan)最(zui)(zui)后的(de)(de)(de)一(yi)個5 min的(de)(de)(de)時(shi)間段(duan)內(nei),試(shi)驗(yan)(yan)箱(xiang)可以達到的(de)(de)(de)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)率(lv)。從某種角度(du)(du)(du)講,線(xian)(xian)形(xing)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)(每(mei)(mei)(mei)5 min平(ping)均(jun)(jun)速(su)(su)(su)(su)度(du)(du)(du))更科學。因(yin)此(ci)試(shi)驗(yan)(yan)設(she)備(bei)最(zui)(zui)好具(ju)有全程平(ping)均(jun)(jun)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)和線(xian)(xian)形(xing)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)(每(mei)(mei)(mei)5 min平(ping)均(jun)(jun)速(su)(su)(su)(su)度(du)(du)(du))這兩個參數。一(yi)般(ban)來說(shuo),線(xian)(xian)形(xing)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)(每(mei)(mei)(mei)5 min平(ping)均(jun)(jun)速(su)(su)(su)(su)度(du)(du)(du))是(shi)(shi)全程平(ping)均(jun)(jun)升(sheng)降(jiang)(jiang)溫(wen)(wen)(wen)(wen)速(su)(su)(su)(su)度(du)(du)(du)的(de)(de)(de)1/2。
6、風速
有關標準(zhun)規定(ding),進行環(huan)境試(shi)驗(yan)(yan)(yan)時溫(wen)濕箱(xiang)(xiang)(xiang)內(nei)的(de)(de)(de)(de)風(feng)(feng)速應小于1.7m/s,對于試(shi)驗(yan)(yan)(yan)本身(shen)來說(shuo),風(feng)(feng)速越(yue)(yue)小越(yue)(yue)好,風(feng)(feng)速過大會加速試(shi)驗(yan)(yan)(yan)件表(biao)面與箱(xiang)(xiang)(xiang)體內(nei)流動(dong)氣(qi)流的(de)(de)(de)(de)熱交換(huan),于試(shi)驗(yan)(yan)(yan)的(de)(de)(de)(de)真實性(xing)不利(li)。但(dan)為了保證試(shi)驗(yan)(yan)(yan)箱(xiang)(xiang)(xiang)工作室(shi)內(nei)的(de)(de)(de)(de)均勻(yun)性(xing),試(shi)驗(yan)(yan)(yan)箱(xiang)(xiang)(xiang)內(nei)具有循環(huan)風(feng)(feng)是(shi)必(bi)需的(de)(de)(de)(de)。但(dan)是(shi)快速溫(wen)度(du)變化試(shi)驗(yan)(yan)(yan)箱(xiang)(xiang)(xiang)以及溫(wen)度(du)、濕度(du)、振動(dong)等多因(yin)素綜合環(huan)境試(shi)驗(yan)(yan)(yan)箱(xiang)(xiang)(xiang),為追求變溫(wen)速率(lv),必(bi)須加快箱(xiang)(xiang)(xiang)體內(nei)循環(huan)氣(qi)流的(de)(de)(de)(de)流速,風(feng)(feng)速通(tong)常在2~3m/s。因(yin)此,對于不同的(de)(de)(de)(de)使(shi)用目的(de)(de)(de)(de),風(feng)(feng)速的(de)(de)(de)(de)限(xian)制是(shi)不一樣的(de)(de)(de)(de)。
7、溫度波動度
溫度波動是一(yi)個(ge)比較容(rong)易實(shi)現的(de)參數,所有(you)環境試驗設備廠家生產的(de)多數的(de)試驗箱(xiang)實(shi)際的(de)溫度波動都可(ke)以(yi)控(kong)制在±0.3℃的(de)范圍以(yi)內(nei)。
8、溫(wen)度(du)場(chang)均勻度(du)
為了更正確地模擬產品在(zai)(zai)自然界(jie)所遭受的(de)實際環境(jing)狀況,在(zai)(zai)環境(jing)試(shi)(shi)驗(yan)中(zhong)必(bi)須保證被試(shi)(shi)產品的(de)周(zhou)邊處(chu)在(zai)(zai)同一溫度(du)環境(jing)條(tiao)件下,為此(ci),必(bi)須對試(shi)(shi)驗(yan)箱(xiang)內(nei)的(de)溫度(du)梯度(du)和溫度(du)的(de)波(bo)動度(du)加以(yi)限制(zhi)。在(zai)(zai)國軍(jun)標GJB150.1-86軍(jun)用設備環境(jing)試(shi)(shi)驗(yan)方法總則中(zhong)明(ming)確規定“試(shi)(shi)驗(yan)樣品附近測量系統(tong)的(de)溫度(du)應在(zai)(zai)試(shi)(shi)驗(yan)溫度(du)的(de)±2℃以(yi)內(nei),其溫度(du)工(gong)不超過(guo)1℃/m或(huo)總的(de)最大值(zhi)為2.2℃(試(shi)(shi)驗(yan)樣品不工(gong)作)”。
9、濕度(du)的(de)精度(du)控(kong)制
環境(jing)試(shi)驗箱中測(ce)量濕度(du)(du)多數是采用干濕球法,環境(jing)試(shi)驗設備的(de)制(zhi)造標準GB10586要求(qiu),相(xiang)對濕度(du)(du)偏差應(ying)在±23%RH。為滿足(zu)濕度(du)(du)控制(zhi)精(jing)(jing)度(du)(du)的(de)要求(qiu),濕度(du)(du)試(shi)驗箱的(de)溫度(du)(du)控制(zhi)精(jing)(jing)度(du)(du)較高,溫度(du)(du)波動一般小于±0.2℃。否則很難達到濕度(du)(du)控制(zhi)精(jing)(jing)度(du)(du)的(de)要求(qiu)。
10、冷卻方式(shi)選擇(ze)
試驗(yan)箱(xiang)如果帶有制冷系統,制冷系統需要進(jin)行冷卻。試驗(yan)箱(xiang)有風(feng)冷、水(shui)冷兩種形(xing)式。 |