一、什么是熱敏電阻

熱敏電阻器是敏(min)(min)(min)(min)感(gan)元(yuan)件的一類，按照溫(wen)(wen)度(du)系(xi)(xi)數不同分為(wei)正(zheng)溫(wen)(wen)度(du)系(xi)(xi)數熱敏(min)(min)(min)(min)電(dian)阻(zu)(zu)器(qi)(qi)（PTC）和(he)負(fu)溫(wen)(wen)度(du)系(xi)(xi)數熱敏(min)(min)(min)(min)電(dian)阻(zu)(zu)器(qi)(qi)（NTC）。熱敏(min)(min)(min)(min)電(dian)阻(zu)(zu)器(qi)(qi)的典型(xing)特點是對(dui)溫(wen)(wen)度(du)敏(min)(min)(min)(min)感(gan)，不同的溫(wen)(wen)度(du)下(xia)表現出不同的電(dian)阻(zu)(zu)值(zhi)。正(zheng)溫(wen)(wen)度(du)系(xi)(xi)數熱敏(min)(min)(min)(min)電(dian)阻(zu)(zu)器(qi)(qi)（PTC）在(zai)溫(wen)(wen)度(du)越高(gao)(gao)時電(dian)阻(zu)(zu)值(zhi)越大，負(fu)溫(wen)(wen)度(du)系(xi)(xi)數熱敏(min)(min)(min)(min)電(dian)阻(zu)(zu)器(qi)(qi)（NTC）在(zai)溫(wen)(wen)度(du)越高(gao)(gao)時電(dian)阻(zu)(zu)值(zhi)越低，它們同屬于半導體(ti)器(qi)(qi)件。

二、熱敏電阻的工作原理

熱(re)(re)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)是一種傳感(gan)器電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)，熱(re)(re)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)值，隨著溫(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)變化而改(gai)變，與一般的(de)(de)(de)(de)(de)(de)固定電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)不同。金屬的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)值隨植度(du)(du)的(de)(de)(de)(de)(de)(de)升高而增(zeng)大(da)，但(dan)半(ban)(ban)導體(ti)(ti)則相(xiang)反，它(ta)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)值隨溫(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)升高而急劇(ju)減小(xiao)，并呈現非線性。在溫(wen)度(du)(du)變化相(xiang)同時，熱(re)(re)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)器的(de)(de)(de)(de)(de)(de)阻(zu)(zu)(zu)(zu)(zu)值變化約為鉛熱(re)(re)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)的(de)(de)(de)(de)(de)(de)10倍(bei)，因此可以說，熱(re)(re)敏(min)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)器對溫(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)變化特(te)(te)別敏(min)感(gan)。半(ban)(ban)導體(ti)(ti)的(de)(de)(de)(de)(de)(de)這種溫(wen)度(du)(du)特(te)(te)性.是因為半(ban)(ban)導體(ti)(ti)的(de)(de)(de)(de)(de)(de)導電(dian)(dian)(dian)(dian)(dian)(dian)方式是載(zai)(zai)流子（電(dian)(dian)(dian)(dian)(dian)(dian)子、空穴）導電(dian)(dian)(dian)(dian)(dian)(dian)。由于半(ban)(ban)導體(ti)(ti)中載(zai)(zai)流子的(de)(de)(de)(de)(de)(de)數目遠比金屬中的(de)(de)(de)(de)(de)(de)自由電(dian)(dian)(dian)(dian)(dian)(dian)子少得多，所以它(ta)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)率很大(da)。隨著溫(wen)度(du)(du)的(de)(de)(de)(de)(de)(de)升高，半(ban)(ban)導體(ti)(ti)中參加導電(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，故半(ban)(ban)導體(ti)(ti)導電(dian)(dian)(dian)(dian)(dian)(dian)率就(jiu)增(zeng)加，它(ta)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)(zu)(zu)率也就(jiu)降低了。

熱(re)(re)敏電阻(zu)器正是利用半(ban)導體(ti)的(de)電阻(zu)值隨溫(wen)度(du)顯著變(bian)化這(zhe)一(yi)特性制成的(de)熱(re)(re)敏元件。它是由(you)某些金屬氧化物按不同的(de)配方制成的(de)。在一(yi)定的(de)溫(wen)度(du)范圍內(nei)，根據測(ce)(ce)量熱(re)(re)敏電阻(zu)阻(zu)值的(de)變(bian)化，便可知被測(ce)(ce)介質(zhi)的(de)溫(wen)度(du)變(bian)化。

將熱(re)敏電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)安裝(zhuang)在(zai)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中使用時(shi)，熱(re)敏電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)在(zai)環(huan)境溫度相同(tong)時(shi)，動(dong)作(zuo)時(shi)間隨著(zhu)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)增(zeng)加(jia)而急劇(ju)縮短;熱(re)敏電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)在(zai)環(huan)境溫度相對(dui)較高時(shi)具有更短的(de)動(dong)作(zuo)時(shi)間和較小的(de)維持電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)及動(dong)作(zuo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。當(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)正常工作(zuo)時(shi)，熱(re)敏電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)溫度與(yu)室溫相近、電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)很小，串聯在(zai)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)中不會(hui)阻(zu)(zu)礙電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通過;而當(dang)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)因(yin)故障而出現過電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)時(shi)，熱(re)敏電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)由于(yu)發熱(re)功率增(zeng)加(jia)導致溫度上(shang)升，當(dang)溫度超(chao)過開關(guan)溫度時(shi)，電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)瞬間會(hui)劇(ju)增(zeng)，回路(lu)(lu)中的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)迅速(su)減小到(dao)安全(quan)值。

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三、熱敏電阻的作用

1、測溫。作(zuo)為測量(liang)溫度的熱敏電阻傳感器一般結構較簡單，價格較低廉(lian);

2、溫(wen)度補(bu)償。熱敏電阻傳感(gan)器可(ke)在一定的溫(wen)度范圍內對某些元(yuan)器件濕度進行補(bu)償;

3、過熱(re)保護。當溫度(du)大于突變點時，電路中的電流可以內十分之幾毫安突變為幾十毫安，因此繼(ji)電器動(dong)作，從(cong)而實現過熱(re)保護;

4、液面測量。

四、熱敏電阻型號

熱(re)敏電阻(zu)分別有(you)三(san)種(zhong)型(xing)號：

1、PTC是指(zhi)在某一溫度(du)下電(dian)(dian)阻急劇增加(jia)、具有正溫度(du)系數的熱敏電(dian)(dian)阻現象(xiang)或(huo)材(cai)料。

2、NTC是(shi)指(zhi)隨溫度上升電阻呈指(zhi)數關(guan)系減(jian)小(xiao)、具(ju)有負(fu)溫度系數的熱(re)敏電阻現象(xiang)和材料。

3、CTR（臨(lin)界溫(wen)度熱敏電阻(zu)）具有負電阻(zu)突變特性。

五、熱敏電阻參數

1、標稱阻(zu)值(zhi)Rc：一(yi)般(ban)指環境溫(wen)度為25℃時熱敏電阻(zu)器的實(shi)際(ji)電阻(zu)值(zhi)。

2、實際阻值RT：在一(yi)定的(de)溫度條件下所(suo)測(ce)得的(de)電(dian)阻值。

3、材(cai)料(liao)常數：它是(shi)(shi)(shi)一個描(miao)述熱敏(min)(min)電阻材(cai)料(liao)物理(li)特性的參數，也是(shi)(shi)(shi)熱靈(ling)敏(min)(min)度(du)指標，B值(zhi)越(yue)大(da)，表(biao)示熱敏(min)(min)電阻器的靈(ling)敏(min)(min)度(du)越(yue)高。應注(zhu)意(yi)的是(shi)(shi)(shi)，在實(shi)際工作時，B值(zhi)并非一個常數，而是(shi)(shi)(shi)隨溫度(du)的升高略有增加。

4、電阻溫度(du)系數(shu)αT：它表示溫度(du)變化1℃時的(de)阻值變化率，單(dan)位為%/℃。

5、時(shi)間(jian)常數(shu)τ：熱(re)(re)(re)敏電阻器是有熱(re)(re)(re)慣性的(de)，時(shi)間(jian)常數(shu)，就是一(yi)(yi)個(ge)(ge)描(miao)述熱(re)(re)(re)敏電阻器熱(re)(re)(re)慣性的(de)參數(shu)。它的(de)定義為，在(zai)無功耗的(de)狀態下(xia)，當環境溫度(du)由一(yi)(yi)個(ge)(ge)特定溫度(du)向(xiang)另一(yi)(yi)個(ge)(ge)特定溫度(du)突然改變(bian)時(shi)，熱(re)(re)(re)敏電阻體的(de)溫度(du)變(bian)化了兩個(ge)(ge)特定溫度(du)之(zhi)差的(de)63.2%所需的(de)時(shi)間(jian)。τ越(yue)小(xiao)，表明熱(re)(re)(re)敏電阻器的(de)熱(re)(re)(re)慣性越(yue)小(xiao)。

6、額定(ding)(ding)功率(lv)(lv)PM：在規定(ding)(ding)的技術條(tiao)件下，熱敏(min)電阻器長期連續負載(zai)(zai)所允許的耗散功率(lv)(lv)。在實(shi)際使用時不得超(chao)過(guo)額定(ding)(ding)功率(lv)(lv)。若(ruo)熱敏(min)電阻器工作的環境溫度超(chao)過(guo)25℃，則(ze)必須(xu)相應降(jiang)低其負載(zai)(zai)。

7、額(e)定(ding)工作(zuo)電流IM：熱敏電阻器在工作(zuo)狀態(tai)下規定(ding)的(de)名義電流值(zhi)。

8、測(ce)量功率Pc：在(zai)規定的環境溫度下，熱(re)敏電阻(zu)體受(shou)測(ce)試(shi)電流加熱(re)而(er)引起的阻(zu)值變(bian)化不超過0.1%時所消耗(hao)的電功率。

9、最大(da)電(dian)壓：對于NTC熱(re)(re)(re)敏(min)電(dian)阻(zu)器(qi)，是(shi)指(zhi)在規定的(de)環境溫(wen)度(du)下，不(bu)使熱(re)(re)(re)敏(min)電(dian)阻(zu)器(qi)引(yin)起熱(re)(re)(re)失(shi)控所允許連續施加的(de)最大(da)直流電(dian)壓；對于PTC熱(re)(re)(re)敏(min)電(dian)阻(zu)器(qi)，是(shi)指(zhi)在規定的(de)環境溫(wen)度(du)和(he)靜止空氣中(zhong)，允許連續施加到熱(re)(re)(re)敏(min)電(dian)阻(zu)器(qi)上并保證熱(re)(re)(re)敏(min)電(dian)阻(zu)器(qi)正(zheng)常工(gong)作在PTC特性部(bu)分的(de)最大(da)直流電(dian)壓。

10、最高(gao)工(gong)作溫(wen)度Tmax：在(zai)規定的技術條件下，熱敏電阻器長期(qi)連續工(gong)作所允許的最高(gao)溫(wen)度。

11、開關(guan)溫(wen)度tb:PTC熱敏(min)電阻器的(de)電阻值開始發生躍增時的(de)溫(wen)度。

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