一、什么是熱敏電阻

熱敏電阻器是敏(min)(min)感元(yuan)件的(de)一類(lei)，按照溫(wen)(wen)(wen)度(du)(du)系數(shu)(shu)不(bu)同(tong)(tong)分為(wei)正溫(wen)(wen)(wen)度(du)(du)系數(shu)(shu)熱(re)(re)敏(min)(min)電(dian)阻(zu)(zu)(zu)(zu)器(qi)(qi)(qi)（PTC）和負溫(wen)(wen)(wen)度(du)(du)系數(shu)(shu)熱(re)(re)敏(min)(min)電(dian)阻(zu)(zu)(zu)(zu)器(qi)(qi)(qi)（NTC）。熱(re)(re)敏(min)(min)電(dian)阻(zu)(zu)(zu)(zu)器(qi)(qi)(qi)的(de)典(dian)型(xing)特點是對溫(wen)(wen)(wen)度(du)(du)敏(min)(min)感，不(bu)同(tong)(tong)的(de)溫(wen)(wen)(wen)度(du)(du)下表現出不(bu)同(tong)(tong)的(de)電(dian)阻(zu)(zu)(zu)(zu)值。正溫(wen)(wen)(wen)度(du)(du)系數(shu)(shu)熱(re)(re)敏(min)(min)電(dian)阻(zu)(zu)(zu)(zu)器(qi)(qi)(qi)（PTC）在溫(wen)(wen)(wen)度(du)(du)越(yue)(yue)高(gao)時(shi)電(dian)阻(zu)(zu)(zu)(zu)值越(yue)(yue)大，負溫(wen)(wen)(wen)度(du)(du)系數(shu)(shu)熱(re)(re)敏(min)(min)電(dian)阻(zu)(zu)(zu)(zu)器(qi)(qi)(qi)（NTC）在溫(wen)(wen)(wen)度(du)(du)越(yue)(yue)高(gao)時(shi)電(dian)阻(zu)(zu)(zu)(zu)值越(yue)(yue)低，它(ta)們同(tong)(tong)屬于(yu)半導體(ti)器(qi)(qi)(qi)件。

二、熱敏電阻的工作原理

熱(re)敏電(dian)(dian)(dian)阻(zu)(zu)(zu)是一種傳感器(qi)電(dian)(dian)(dian)阻(zu)(zu)(zu)，熱(re)敏電(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)阻(zu)(zu)(zu)值(zhi)(zhi)，隨(sui)著溫度(du)的(de)(de)(de)(de)(de)變(bian)(bian)化(hua)而改(gai)變(bian)(bian)，與(yu)一般(ban)的(de)(de)(de)(de)(de)固定電(dian)(dian)(dian)阻(zu)(zu)(zu)不同。金屬(shu)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)阻(zu)(zu)(zu)值(zhi)(zhi)隨(sui)植度(du)的(de)(de)(de)(de)(de)升高而增(zeng)大(da)，但半(ban)(ban)導(dao)體(ti)則相反，它(ta)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)阻(zu)(zu)(zu)值(zhi)(zhi)隨(sui)溫度(du)的(de)(de)(de)(de)(de)升高而急劇(ju)減小，并呈現非線性。在溫度(du)變(bian)(bian)化(hua)相同時，熱(re)敏電(dian)(dian)(dian)阻(zu)(zu)(zu)器(qi)的(de)(de)(de)(de)(de)阻(zu)(zu)(zu)值(zhi)(zhi)變(bian)(bian)化(hua)約為(wei)鉛熱(re)電(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)(de)(de)(de)(de)10倍，因此可以(yi)說(shuo)，熱(re)敏電(dian)(dian)(dian)阻(zu)(zu)(zu)器(qi)對(dui)溫度(du)的(de)(de)(de)(de)(de)變(bian)(bian)化(hua)特(te)別(bie)敏感。半(ban)(ban)導(dao)體(ti)的(de)(de)(de)(de)(de)這種溫度(du)特(te)性.是因為(wei)半(ban)(ban)導(dao)體(ti)的(de)(de)(de)(de)(de)導(dao)電(dian)(dian)(dian)方(fang)式是載流(liu)(liu)子(zi)（電(dian)(dian)(dian)子(zi)、空(kong)穴）導(dao)電(dian)(dian)(dian)。由于半(ban)(ban)導(dao)體(ti)中載流(liu)(liu)子(zi)的(de)(de)(de)(de)(de)數(shu)(shu)目(mu)遠比金屬(shu)中的(de)(de)(de)(de)(de)自由電(dian)(dian)(dian)子(zi)少得多(duo)，所以(yi)它(ta)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)阻(zu)(zu)(zu)率很大(da)。隨(sui)著溫度(du)的(de)(de)(de)(de)(de)升高，半(ban)(ban)導(dao)體(ti)中參加(jia)導(dao)電(dian)(dian)(dian)的(de)(de)(de)(de)(de)載流(liu)(liu)子(zi)數(shu)(shu)目(mu)就(jiu)會(hui)增(zeng)多(duo)，故半(ban)(ban)導(dao)體(ti)導(dao)電(dian)(dian)(dian)率就(jiu)增(zeng)加(jia)，它(ta)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)阻(zu)(zu)(zu)率也(ye)就(jiu)降(jiang)低了(le)。

熱敏電阻(zu)(zu)器正是利用半導體的(de)(de)(de)電阻(zu)(zu)值隨溫(wen)度(du)顯著(zhu)變(bian)化(hua)這一(yi)(yi)特性制成的(de)(de)(de)熱敏元(yuan)件(jian)。它(ta)是由(you)某些(xie)金屬氧化(hua)物按不同的(de)(de)(de)配方(fang)制成的(de)(de)(de)。在一(yi)(yi)定(ding)的(de)(de)(de)溫(wen)度(du)范圍內，根據測(ce)量熱敏電阻(zu)(zu)阻(zu)(zu)值的(de)(de)(de)變(bian)化(hua)，便可知(zhi)被測(ce)介質的(de)(de)(de)溫(wen)度(du)變(bian)化(hua)。

將熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)安裝在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中使用(yong)時(shi)(shi)，熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)在環境溫(wen)(wen)度(du)相(xiang)同(tong)時(shi)(shi)，動(dong)作時(shi)(shi)間(jian)(jian)隨著(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的增(zeng)(zeng)加而急劇縮短(duan);熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)在環境溫(wen)(wen)度(du)相(xiang)對較高時(shi)(shi)具有(you)更短(duan)的動(dong)作時(shi)(shi)間(jian)(jian)和較小(xiao)(xiao)(xiao)的維持電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)及動(dong)作電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)正常工(gong)作時(shi)(shi)，熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)溫(wen)(wen)度(du)與室溫(wen)(wen)相(xiang)近、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)很小(xiao)(xiao)(xiao)，串聯在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)中不會(hui)阻(zu)(zu)礙電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)通(tong)過(guo)(guo);而當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)因(yin)故障(zhang)而出(chu)現過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)時(shi)(shi)，熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)由于發熱(re)(re)功率增(zeng)(zeng)加導致溫(wen)(wen)度(du)上(shang)升，當溫(wen)(wen)度(du)超過(guo)(guo)開關溫(wen)(wen)度(du)時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)瞬間(jian)(jian)會(hui)劇增(zeng)(zeng)，回路(lu)中的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)迅速減小(xiao)(xiao)(xiao)到(dao)安全值。

該圖片由注冊用戶"天空之城"提供，版權聲明反饋

三、熱敏電阻的作用

1、測(ce)溫。作為測(ce)量溫度的熱敏電(dian)阻傳感器(qi)一(yi)般結構(gou)較簡(jian)單，價(jia)格較低(di)廉;

2、溫度補(bu)償。熱敏電(dian)阻傳感(gan)器可在一定的溫度范(fan)圍(wei)內對某(mou)些元器件濕度進(jin)行(xing)補(bu)償;

3、過熱(re)保護。當溫度大(da)于突變(bian)點時(shi)，電路中的電流可以內十(shi)分之幾毫安突變(bian)為幾十(shi)毫安，因此繼電器動作，從(cong)而實(shi)現過熱(re)保護;

4、液面測量。

四、熱敏電阻型號

熱敏電(dian)阻分別有(you)三(san)種(zhong)型號：

1、PTC是(shi)指在某一溫(wen)度(du)下電(dian)阻急劇增加、具有正溫(wen)度(du)系數(shu)的熱(re)敏電(dian)阻現象或材料。

2、NTC是指(zhi)隨溫(wen)度上升電(dian)阻呈指(zhi)數關(guan)系減小、具有負溫(wen)度系數的熱敏(min)電(dian)阻現(xian)象和材料。

3、CTR（臨(lin)界溫(wen)度(du)熱敏電阻(zu)(zu)）具(ju)有(you)負電阻(zu)(zu)突(tu)變(bian)特(te)性。

五、熱敏電阻參數

1、標稱阻值Rc：一般指環(huan)境溫度為25℃時(shi)熱敏(min)電阻器(qi)的實際電阻值。

2、實際阻值RT：在一定的溫度條(tiao)件(jian)下(xia)所測(ce)得的電(dian)阻值。

3、材(cai)料常(chang)數：它是(shi)一個(ge)描述熱(re)敏電阻材(cai)料物(wu)理特性的參(can)數，也是(shi)熱(re)靈(ling)敏度指標，B值(zhi)越大(da)，表(biao)示熱(re)敏電阻器的靈(ling)敏度越高。應注(zhu)意的是(shi)，在實際工(gong)作(zuo)時，B值(zhi)并非一個(ge)常(chang)數，而是(shi)隨溫(wen)度的升高略有增加(jia)。

4、電阻溫度(du)(du)系數(shu)αT：它(ta)表(biao)示溫度(du)(du)變化(hua)1℃時的阻值變化(hua)率，單位為%/℃。

5、時(shi)間常(chang)數τ：熱(re)(re)敏(min)電阻器是有熱(re)(re)慣性的，時(shi)間常(chang)數，就是一(yi)個(ge)描(miao)述熱(re)(re)敏(min)電阻器熱(re)(re)慣性的參數。它(ta)的定(ding)(ding)義(yi)為，在無功(gong)耗(hao)的狀態下(xia)，當環境溫度(du)由一(yi)個(ge)特(te)定(ding)(ding)溫度(du)向另一(yi)個(ge)特(te)定(ding)(ding)溫度(du)突然(ran)改變(bian)時(shi)，熱(re)(re)敏(min)電阻體的溫度(du)變(bian)化了兩個(ge)特(te)定(ding)(ding)溫度(du)之差的63.2%所需的時(shi)間。τ越小，表(biao)明熱(re)(re)敏(min)電阻器的熱(re)(re)慣性越小。

6、額(e)定(ding)功率PM：在(zai)規定(ding)的技術(shu)條件下，熱(re)敏電阻器長期連續負載所(suo)允許的耗散功率。在(zai)實際使用(yong)時不得超過額(e)定(ding)功率。若熱(re)敏電阻器工(gong)作的環境溫度超過25℃，則(ze)必須相應降(jiang)低其負載。

7、額定工作電(dian)流(liu)IM：熱敏(min)電(dian)阻器在(zai)工作狀態下規(gui)定的(de)名義電(dian)流(liu)值。

8、測量功率Pc：在規(gui)定的環境(jing)溫(wen)度(du)下，熱敏(min)電阻體受測試(shi)電流加熱而引起的阻值變(bian)化不(bu)超(chao)過0.1%時所消耗的電功率。

9、最大電(dian)(dian)(dian)壓：對(dui)于NTC熱敏(min)電(dian)(dian)(dian)阻(zu)器，是指在規(gui)定的環(huan)境溫度下(xia)，不使熱敏(min)電(dian)(dian)(dian)阻(zu)器引起熱失(shi)控所允許連續施(shi)加的最大直流電(dian)(dian)(dian)壓；對(dui)于PTC熱敏(min)電(dian)(dian)(dian)阻(zu)器，是指在規(gui)定的環(huan)境溫度和靜止空氣(qi)中(zhong)，允許連續施(shi)加到熱敏(min)電(dian)(dian)(dian)阻(zu)器上并保證熱敏(min)電(dian)(dian)(dian)阻(zu)器正常工作在PTC特性部分的最大直流電(dian)(dian)(dian)壓。

10、最高工(gong)作溫度Tmax：在規(gui)定(ding)的技術條件(jian)下，熱敏電阻器(qi)長(chang)期(qi)連續工(gong)作所允許的最高溫度。

11、開關溫(wen)度tb:PTC熱(re)敏(min)電(dian)阻(zu)(zu)器的電(dian)阻(zu)(zu)值開始發生(sheng)躍(yue)增時的溫(wen)度。

12、耗散系數H：溫度增加1℃時，熱敏電阻器所耗散(san)的功率，單位為(wei)mW/℃。