一、什么是熱敏電阻

熱敏電阻器是(shi)敏(min)(min)感元(yuan)件的一類(lei)，按照溫(wen)(wen)(wen)度(du)(du)(du)系(xi)(xi)(xi)數(shu)不同分為正溫(wen)(wen)(wen)度(du)(du)(du)系(xi)(xi)(xi)數(shu)熱(re)敏(min)(min)電(dian)阻(zu)器(qi)(qi)(qi)（PTC）和(he)負溫(wen)(wen)(wen)度(du)(du)(du)系(xi)(xi)(xi)數(shu)熱(re)敏(min)(min)電(dian)阻(zu)器(qi)(qi)(qi)（NTC）。熱(re)敏(min)(min)電(dian)阻(zu)器(qi)(qi)(qi)的典型特點(dian)是(shi)對溫(wen)(wen)(wen)度(du)(du)(du)敏(min)(min)感，不同的溫(wen)(wen)(wen)度(du)(du)(du)下表現(xian)出不同的電(dian)阻(zu)值(zhi)。正溫(wen)(wen)(wen)度(du)(du)(du)系(xi)(xi)(xi)數(shu)熱(re)敏(min)(min)電(dian)阻(zu)器(qi)(qi)(qi)（PTC）在溫(wen)(wen)(wen)度(du)(du)(du)越高時電(dian)阻(zu)值(zhi)越大，負溫(wen)(wen)(wen)度(du)(du)(du)系(xi)(xi)(xi)數(shu)熱(re)敏(min)(min)電(dian)阻(zu)器(qi)(qi)(qi)（NTC）在溫(wen)(wen)(wen)度(du)(du)(du)越高時電(dian)阻(zu)值(zhi)越低，它們同屬于半(ban)導體(ti)器(qi)(qi)(qi)件。

二、熱敏電阻的工作原理

熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)是一種(zhong)(zhong)傳(chuan)感器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)值(zhi)，隨(sui)著(zhu)溫(wen)度(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)變化而改變，與一般(ban)的(de)(de)(de)(de)(de)(de)固定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)不同。金屬(shu)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)值(zhi)隨(sui)植度(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)升(sheng)高而增(zeng)大，但半(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)則相反，它的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)值(zhi)隨(sui)溫(wen)度(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)升(sheng)高而急劇減(jian)小，并呈現非線(xian)性。在溫(wen)度(du)(du)(du)(du)變化相同時，熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)器的(de)(de)(de)(de)(de)(de)阻(zu)(zu)值(zhi)變化約為(wei)鉛(qian)熱(re)(re)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)的(de)(de)(de)(de)(de)(de)10倍，因(yin)此可以(yi)說，熱(re)(re)敏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)器對溫(wen)度(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)變化特(te)別(bie)敏感。半(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)的(de)(de)(de)(de)(de)(de)這種(zhong)(zhong)溫(wen)度(du)(du)(du)(du)特(te)性.是因(yin)為(wei)半(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)的(de)(de)(de)(de)(de)(de)導(dao)(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)方式(shi)是載(zai)(zai)流子（電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子、空穴）導(dao)(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。由(you)于半(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)中載(zai)(zai)流子的(de)(de)(de)(de)(de)(de)數目遠比金屬(shu)中的(de)(de)(de)(de)(de)(de)自(zi)由(you)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子少得多(duo)，所以(yi)它的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)率(lv)很(hen)大。隨(sui)著(zhu)溫(wen)度(du)(du)(du)(du)的(de)(de)(de)(de)(de)(de)升(sheng)高，半(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)中參(can)加導(dao)(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)(de)載(zai)(zai)流子數目就(jiu)會增(zeng)多(duo)，故(gu)半(ban)(ban)(ban)導(dao)(dao)(dao)體(ti)導(dao)(dao)(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)率(lv)就(jiu)增(zeng)加，它的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)率(lv)也就(jiu)降低了。

熱(re)敏(min)(min)電阻器正是利用半(ban)導體的電阻值隨溫度(du)顯著變(bian)(bian)化(hua)這(zhe)一特性制成(cheng)的熱(re)敏(min)(min)元件。它(ta)是由某些金屬氧(yang)化(hua)物按(an)不同的配(pei)方制成(cheng)的。在一定的溫度(du)范圍內(nei)，根據測量熱(re)敏(min)(min)電阻阻值的變(bian)(bian)化(hua)，便(bian)可(ke)知被測介質(zhi)的溫度(du)變(bian)(bian)化(hua)。

將熱敏(min)電(dian)(dian)阻(zu)安裝在電(dian)(dian)路(lu)中使用時(shi)(shi)，熱敏(min)電(dian)(dian)阻(zu)在環境溫度相同時(shi)(shi)，動作(zuo)時(shi)(shi)間隨著電(dian)(dian)流(liu)的(de)增(zeng)加而(er)(er)急劇縮(suo)短;熱敏(min)電(dian)(dian)阻(zu)在環境溫度相對較高時(shi)(shi)具有更短的(de)動作(zuo)時(shi)(shi)間和較小的(de)維(wei)持電(dian)(dian)流(liu)及動作(zuo)電(dian)(dian)流(liu)。當電(dian)(dian)路(lu)正常工作(zuo)時(shi)(shi)，熱敏(min)電(dian)(dian)阻(zu)溫度與室(shi)溫相近、電(dian)(dian)阻(zu)很小，串聯在電(dian)(dian)路(lu)中不會(hui)阻(zu)礙電(dian)(dian)流(liu)通過(guo)(guo);而(er)(er)當電(dian)(dian)路(lu)因故(gu)障而(er)(er)出現過(guo)(guo)電(dian)(dian)流(liu)時(shi)(shi)，熱敏(min)電(dian)(dian)阻(zu)由于發熱功率增(zeng)加導致溫度上升，當溫度超過(guo)(guo)開關溫度時(shi)(shi)，電(dian)(dian)阻(zu)瞬間會(hui)劇增(zeng)，回路(lu)中的(de)電(dian)(dian)流(liu)迅速減小到安全值。

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三、熱敏電阻的作用

1、測溫。作為測量溫度(du)的熱敏電阻傳感(gan)器一般結構(gou)較(jiao)簡單，價格較(jiao)低廉;

2、溫度(du)(du)補償。熱敏電阻傳感器(qi)可(ke)在(zai)一定的溫度(du)(du)范圍(wei)內對某些元器(qi)件濕度(du)(du)進行(xing)補償;

3、過(guo)熱(re)保護(hu)。當溫度大于突(tu)變點時(shi)，電(dian)(dian)路中的電(dian)(dian)流可(ke)以內十(shi)分之幾毫(hao)安突(tu)變為幾十(shi)毫(hao)安，因(yin)此(ci)繼電(dian)(dian)器動作，從而實現(xian)過(guo)熱(re)保護(hu);

4、液面測量。

四、熱敏電阻型號

熱敏電阻分(fen)別有三種型號：

1、PTC是指(zhi)在某一溫度下電(dian)阻(zu)(zu)急劇增加、具有(you)正溫度系數(shu)的(de)熱敏電(dian)阻(zu)(zu)現象或材料。

2、NTC是指隨溫度(du)上升電(dian)阻(zu)呈指數(shu)關(guan)系減小、具有(you)負(fu)溫度(du)系數(shu)的(de)熱敏(min)電(dian)阻(zu)現象和材料。

3、CTR（臨界溫度熱敏電阻(zu)）具(ju)有負電阻(zu)突變特(te)性。

五、熱敏電阻參數

1、標稱阻(zu)(zu)值(zhi)Rc：一(yi)般指環(huan)境(jing)溫度為25℃時熱敏電阻(zu)(zu)器(qi)的實(shi)際電阻(zu)(zu)值(zhi)。

2、實際(ji)阻值RT：在一定的溫度(du)條件下(xia)所測得的電(dian)阻值。

3、材料(liao)常數：它(ta)是(shi)一個描述(shu)熱敏電阻材料(liao)物理(li)特性(xing)的參數，也是(shi)熱靈敏度(du)指標，B值(zhi)越(yue)大(da)，表示熱敏電阻器(qi)的靈敏度(du)越(yue)高。應注(zhu)意的是(shi)，在實際工作時，B值(zhi)并非一個常數，而是(shi)隨溫度(du)的升高略(lve)有增加。

4、電阻(zu)溫度系數αT：它表示溫度變化1℃時(shi)的阻(zu)值變化率(lv)，單(dan)位為%/℃。

5、時間(jian)常(chang)數(shu)(shu)τ：熱敏電(dian)阻器(qi)是有熱慣性的，時間(jian)常(chang)數(shu)(shu)，就(jiu)是一(yi)(yi)個描述熱敏電(dian)阻器(qi)熱慣性的參數(shu)(shu)。它的定(ding)(ding)義(yi)為，在無功耗的狀態下(xia)，當(dang)環境溫度(du)由一(yi)(yi)個特(te)定(ding)(ding)溫度(du)向另一(yi)(yi)個特(te)定(ding)(ding)溫度(du)突然改變時，熱敏電(dian)阻體的溫度(du)變化了兩個特(te)定(ding)(ding)溫度(du)之差的63.2%所需的時間(jian)。τ越(yue)(yue)小(xiao)，表明熱敏電(dian)阻器(qi)的熱慣性越(yue)(yue)小(xiao)。

6、額(e)定(ding)功(gong)(gong)(gong)率(lv)(lv)PM：在(zai)規(gui)定(ding)的(de)技術條件下，熱敏電阻器(qi)長期連續負載(zai)所(suo)允許的(de)耗散功(gong)(gong)(gong)率(lv)(lv)。在(zai)實際使用時不得超(chao)過額(e)定(ding)功(gong)(gong)(gong)率(lv)(lv)。若熱敏電阻器(qi)工作的(de)環境溫度超(chao)過25℃，則必(bi)須相應降低其負載(zai)。

7、額定工(gong)作電(dian)流(liu)IM：熱(re)敏(min)電(dian)阻器在工(gong)作狀態下規定的(de)名義電(dian)流(liu)值。

8、測(ce)量功(gong)率(lv)Pc：在規定的環境溫(wen)度下，熱(re)敏電(dian)阻體受測(ce)試電(dian)流加熱(re)而引起的阻值變化不(bu)超過(guo)0.1%時所消耗的電(dian)功(gong)率(lv)。

9、最(zui)(zui)大(da)電(dian)(dian)(dian)(dian)壓：對(dui)于(yu)NTC熱敏(min)(min)電(dian)(dian)(dian)(dian)阻(zu)器，是(shi)(shi)指(zhi)(zhi)在規定的環境(jing)(jing)溫度下，不使熱敏(min)(min)電(dian)(dian)(dian)(dian)阻(zu)器引起熱失(shi)控所允許(xu)連續(xu)施(shi)(shi)加(jia)的最(zui)(zui)大(da)直流電(dian)(dian)(dian)(dian)壓；對(dui)于(yu)PTC熱敏(min)(min)電(dian)(dian)(dian)(dian)阻(zu)器，是(shi)(shi)指(zhi)(zhi)在規定的環境(jing)(jing)溫度和靜止空(kong)氣中(zhong)，允許(xu)連續(xu)施(shi)(shi)加(jia)到熱敏(min)(min)電(dian)(dian)(dian)(dian)阻(zu)器上并保證(zheng)熱敏(min)(min)電(dian)(dian)(dian)(dian)阻(zu)器正常工作在PTC特性部(bu)分的最(zui)(zui)大(da)直流電(dian)(dian)(dian)(dian)壓。

10、最高(gao)工作溫度Tmax：在(zai)規(gui)定的技(ji)術條件下，熱(re)敏(min)電阻器(qi)長期連續工作所允許的最高(gao)溫度。

11、開(kai)關溫(wen)度tb:PTC熱敏(min)電阻(zu)(zu)器的電阻(zu)(zu)值開(kai)始發(fa)生(sheng)躍增時的溫(wen)度。

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