一、電阻的種類有哪些
1、按伏安特性分類
可分為線性(xing)電(dian)阻(zu)和非線性(xing)電(dian)阻(zu)。對大多(duo)數導體來說,在一定的溫度下,其電(dian)阻(zu)幾乎維持(chi)不(bu)變(bian)而(er)為一定值,這類電(dian)阻(zu)稱為線性(xing)電(dian)阻(zu)。
有(you)些(xie)材(cai)料的(de)電(dian)(dian)(dian)阻(zu)(zu)(zu)明顯(xian)地隨(sui)著電(dian)(dian)(dian)流(或(huo)電(dian)(dian)(dian)壓(ya))而(er)變(bian)化(hua),其伏(fu)安特(te)(te)(te)性是一條曲線(xian)(xian)(xian),這類電(dian)(dian)(dian)阻(zu)(zu)(zu)稱為非線(xian)(xian)(xian)性電(dian)(dian)(dian)阻(zu)(zu)(zu)。非線(xian)(xian)(xian)性電(dian)(dian)(dian)阻(zu)(zu)(zu)在某(mou)一給(gei)定(ding)的(de)電(dian)(dian)(dian)壓(ya)(或(huo)電(dian)(dian)(dian)流)作用下(xia),電(dian)(dian)(dian)壓(ya)與電(dian)(dian)(dian)流的(de)比(bi)值為在該(gai)工作點下(xia)的(de)靜(jing)態電(dian)(dian)(dian)阻(zu)(zu)(zu),伏(fu)安特(te)(te)(te)性曲線(xian)(xian)(xian)上的(de)斜率為動態電(dian)(dian)(dian)阻(zu)(zu)(zu)。表達非線(xian)(xian)(xian)性電(dian)(dian)(dian)阻(zu)(zu)(zu)特(te)(te)(te)性的(de)方(fang)式比(bi)較(jiao)復雜,但這些(xie)非線(xian)(xian)(xian)性關系在電(dian)(dian)(dian)子電(dian)(dian)(dian)路(lu)中得到了廣泛的(de)應用。
2、按材料分類
a.線(xian)繞(rao)(rao)電(dian)阻器由電(dian)阻線(xian)繞(rao)(rao)成電(dian)阻器,用高阻合金線(xian)繞(rao)(rao)在絕(jue)緣骨(gu)架上制成,外面涂有耐(nai)熱(re)的釉絕(jue)緣層或絕(jue)緣漆。繞(rao)(rao)線(xian)電(dian)阻具有較低(di)的溫(wen)度系數(shu),阻值(zhi)精度高,穩定(ding)性好,耐(nai)熱(re)耐(nai)腐(fu)蝕(shi),主要(yao)做精密大(da)功率(lv)電(dian)阻使用,缺點是高頻性能差,時間常數(shu)大(da)。
b.碳合成(cheng)(cheng)電(dian)阻器由(you)碳及合成(cheng)(cheng)塑(su)膠壓制成(cheng)(cheng)而成(cheng)(cheng)。
c.碳(tan)膜電(dian)阻(zu)器在瓷(ci)管上鍍(du)上一層碳(tan)而成,將(jiang)結晶(jing)碳(tan)沉積在陶(tao)瓷(ci)棒骨架(jia)上制成。碳(tan)膜電(dian)阻(zu)器成本低、性能穩定(ding)、阻(zu)值范(fan)圍寬、溫度系(xi)數和(he)電(dian)壓系(xi)數低,是目前(qian)應用最(zui)廣泛(fan)的電(dian)阻(zu)器。
d.金(jin)屬膜(mo)電阻(zu)器(qi)在瓷管上(shang)鍍(du)上(shang)一層金(jin)屬而成,用(yong)真(zhen)空蒸發的(de)方(fang)法將合(he)金(jin)材料蒸鍍(du)于陶瓷棒骨架表面。金(jin)屬膜(mo)電阻(zu)比碳膜(mo)電阻(zu)的(de)精(jing)度高(gao),穩定性好,噪聲,溫度系數小。在儀(yi)器(qi)儀(yi)表及通訊設備中大量采用(yong)。
e.金(jin)屬氧化膜(mo)電阻(zu)器在瓷管上鍍(du)上一層(ceng)氧化錫而成,在絕緣棒上沉積一層(ceng)金(jin)屬氧化物(wu)。由(you)于(yu)其本身即是氧化物(wu),所以高(gao)溫(wen)下穩定,耐熱沖擊,負載能(neng)力強。按用(yong)途分,有通用(yong)、精密、高(gao)頻、高(gao)壓、高(gao)阻(zu)、大功率和電阻(zu)網絡(luo)等。
3、特殊電阻器
a.保(bao)(bao)險電(dian)(dian)(dian)阻(zu):又叫熔斷電(dian)(dian)(dian)阻(zu)器,在(zai)正常情況下(xia)起著電(dian)(dian)(dian)阻(zu)和保(bao)(bao)險絲(si)(si)的雙重作用(yong)(yong),當電(dian)(dian)(dian)路(lu)出現(xian)故障而使其(qi)功(gong)率超過額定功(gong)率時,它會像保(bao)(bao)險絲(si)(si)一樣熔斷使連(lian)接電(dian)(dian)(dian)路(lu)斷開(kai)。保(bao)(bao)險絲(si)(si)電(dian)(dian)(dian)阻(zu)一般電(dian)(dian)(dian)阻(zu)值都小(0.33Ω~10KΩ),功(gong)率也較(jiao)小。保(bao)(bao)險絲(si)(si)電(dian)(dian)(dian)阻(zu)器常用(yong)(yong)型(xing)(xing)(xing)號有:RF10型(xing)(xing)(xing)、RF111-5保(bao)(bao)險絲(si)(si)電(dian)(dian)(dian)阻(zu)器的符號型(xing)(xing)(xing)、RRD0910型(xing)(xing)(xing)、RRD0911型(xing)(xing)(xing)等。
b.敏(min)(min)感(gan)電(dian)阻器:是(shi)指(zhi)其(qi)電(dian)阻值(zhi)對(dui)于某種物(wu)(wu)理(li)量(liang)(liang)(如溫度、濕度、光照、電(dian)壓(ya)、機(ji)械力(li)、以及氣(qi)體濃度等(deng))具有敏(min)(min)感(gan)特性,當這些(xie)物(wu)(wu)理(li)量(liang)(liang)發(fa)生變(bian)化時(shi),敏(min)(min)感(gan)電(dian)阻的(de)阻值(zhi)就(jiu)會隨物(wu)(wu)理(li)量(liang)(liang)變(bian)化而(er)發(fa)生改變(bian),呈現不(bu)同的(de)電(dian)阻值(zhi)。根據對(dui)不(bu)同物(wu)(wu)理(li)量(liang)(liang)敏(min)(min)感(gan),敏(min)(min)感(gan)電(dian)阻器可分為熱(re)敏(min)(min)、濕敏(min)(min)、光敏(min)(min)、壓(ya)敏(min)(min)、力(li)敏(min)(min)、磁敏(min)(min)和氣(qi)敏(min)(min)等(deng)類型敏(min)(min)感(gan)電(dian)阻。敏(min)(min)感(gan)電(dian)阻器所用的(de)材料幾乎都是(shi)半導體材料,這類電(dian)阻器也稱為半導體電(dian)阻器。
c.熱(re)敏(min)電(dian)(dian)阻(zu)(zu)(zu)的(de)(de)阻(zu)(zu)(zu)值隨(sui)溫(wen)(wen)度(du)(du)變(bian)化(hua)而(er)變(bian)化(hua),溫(wen)(wen)度(du)(du)升高阻(zu)(zu)(zu)為負(fu)溫(wen)(wen)度(du)(du)系(xi)數(shu)(NTC)熱(re)敏(min)電(dian)(dian)阻(zu)(zu)(zu)。應(ying)用較多的(de)(de)是負(fu)溫(wen)(wen)度(du)(du)系(xi)數(shu)熱(re)敏(min)電(dian)(dian)阻(zu)(zu)(zu),又可分為普通型負(fu)溫(wen)(wen)度(du)(du)系(xi)數(shu)熱(re)敏(min)電(dian)(dian)阻(zu)(zu)(zu);穩壓型負(fu)溫(wen)(wen)度(du)(du)系(xi)數(shu)熱(re)敏(min)電(dian)(dian)阻(zu)(zu)(zu);測溫(wen)(wen)型負(fu)溫(wen)(wen)度(du)(du)系(xi)數(shu)熱(re)敏(min)電(dian)(dian)阻(zu)(zu)(zu)等。光(guang)敏(min)電(dian)(dian)阻(zu)(zu)(zu)是電(dian)(dian)阻(zu)(zu)(zu)的(de)(de)阻(zu)(zu)(zu)值隨(sui)入(ru)射光(guang)的(de)(de)強弱變(bian)化(hua)而(er)改變(bian),當入(ru)射光(guang)增強時,光(guang)敏(min)電(dian)(dian)阻(zu)(zu)(zu)的(de)(de)減小,入(ru)射光(guang)減弱時電(dian)(dian)阻(zu)(zu)(zu)值增大。
二、電阻器選用的方法
1、固定電阻器的選用
固定電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)有多種(zhong)類(lei)型,選擇哪一種(zhong)材料和(he)(he)結構的(de)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),應根據應用(yong)電(dian)(dian)(dian)(dian)路的(de)具(ju)體(ti)要求而定。高頻電(dian)(dian)(dian)(dian)路應選用(yong)分(fen)布(bu)電(dian)(dian)(dian)(dian)感和(he)(he)分(fen)布(bu)電(dian)(dian)(dian)(dian)容小的(de)非(fei)線繞電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),例(li)如(ru)碳(tan)膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)、金屬電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)和(he)(he)金屬氧化膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),薄膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),厚膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),合(he)金電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),防腐蝕鍍膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)等。高增益小信號放大(da)電(dian)(dian)(dian)(dian)路應選用(yong)低噪聲電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),例(li)如(ru)金屬膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)、碳(tan)膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)和(he)(he)線繞電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi),而不能使用(yong)噪聲較(jiao)大(da)的(de)合(he)成碳(tan)膜(mo)電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)和(he)(he)有機(ji)實(shi)心電(dian)(dian)(dian)(dian)阻器(qi)(qi)(qi)(qi)。
所(suo)選(xuan)(xuan)電(dian)(dian)(dian)阻(zu)器(qi)(qi)的(de)電(dian)(dian)(dian)阻(zu)值(zhi)應接近應用(yong)電(dian)(dian)(dian)路(lu)中計算值(zhi)的(de)一個標稱值(zhi),應優先選(xuan)(xuan)用(yong)標準系列的(de)電(dian)(dian)(dian)阻(zu)器(qi)(qi)。一般電(dian)(dian)(dian)路(lu)使用(yong)的(de)電(dian)(dian)(dian)阻(zu)器(qi)(qi)允(yun)許誤差為±5%~±10%。精密(mi)儀器(qi)(qi)及特殊電(dian)(dian)(dian)路(lu)中使用(yong)的(de)電(dian)(dian)(dian)阻(zu)器(qi)(qi),應選(xuan)(xuan)用(yong)精密(mi)電(dian)(dian)(dian)阻(zu)器(qi)(qi),對精密(mi)度為1%以內(nei)的(de)電(dian)(dian)(dian)阻(zu),如0.01%,0.1%,0.5%這(zhe)些量(liang)(liang)級的(de)電(dian)(dian)(dian)阻(zu)應采用(yong)捷比信電(dian)(dian)(dian)阻(zu)。所(suo)選(xuan)(xuan)電(dian)(dian)(dian)阻(zu)器(qi)(qi)的(de)額(e)定功率,要(yao)符(fu)合(he)應用(yong)電(dian)(dian)(dian)路(lu)中對電(dian)(dian)(dian)阻(zu)器(qi)(qi)功率容量(liang)(liang)的(de)要(yao)求,一般不(bu)應隨意加大或減小電(dian)(dian)(dian)阻(zu)器(qi)(qi)的(de)功率。
若電(dian)路(lu)要求是功(gong)率(lv)型(xing)電(dian)阻器(qi),則其額定功(gong)率(lv)可(ke)高于實際應用電(dian)路(lu)要求功(gong)率(lv)的1~2倍。
2、熔斷電阻器的選用
熔(rong)斷電阻器(qi)具有保(bao)(bao)護功(gong)能(neng)的(de)電阻器(qi)。選用(yong)時應考慮其(qi)雙(shuang)重性(xing)能(neng),根據電路的(de)具體要求選擇其(qi)阻值和功(gong)率(lv)(lv)等(deng)參(can)數。既(ji)要保(bao)(bao)證它(ta)(ta)在過負荷時能(neng)快速熔(rong)斷,又要保(bao)(bao)證它(ta)(ta)在正(zheng)常條件(jian)下能(neng)長期穩定的(de)工作。電阻值過大或功(gong)率(lv)(lv)過大,均不(bu)能(neng)起到保(bao)(bao)護作用(yong)。
三、電阻器選用的基本原則
1、選擇通過認(ren)證機構(gou)認(ren)證的(de)(de)生產(chan)線制(zhi)造(zao)出的(de)(de)執(zhi)行高(gao)水平(ping)標準的(de)(de)電(dian)阻器(qi)。
2、選擇(ze)具(ju)備功(gong)能(neng)優(you)(you)勢、質量優(you)(you)勢、效率(lv)優(you)(you)勢、功(gong)能(neng)價格比優(you)(you)勢、服務(wu)優(you)(you)勢的(de)(de)制造商生產的(de)(de)電阻(zu)器(qi)。
3、選擇能滿足上述要求的上型號目錄的制造商,并向其直接訂購電阻器。