二線(xian)(xian)(xian)制:在熱電阻(zu)的(de)(de)(de)兩端各連接一根導(dao)線(xian)(xian)(xian)來(lai)引出(chu)電阻(zu)信號的(de)(de)(de)方式(shi)(shi)叫(jiao)二線(xian)(xian)(xian)制:這種(zhong)引線(xian)(xian)(xian)方法(fa)很(hen)簡單,但由(you)于(yu)連接導(dao)線(xian)(xian)(xian)必然存在引線(xian)(xian)(xian)電阻(zu)r,r大小(xiao)與導(dao)線(xian)(xian)(xian)的(de)(de)(de)材(cai)質和長度的(de)(de)(de)因素有關,因此這種(zhong)引線(xian)(xian)(xian)方式(shi)(shi)只(zhi)適用于(yu)測量精(jing)度較(jiao)低的(de)(de)(de)場合
三(san)線(xian)制:在熱電(dian)(dian)阻的(de)根(gen)(gen)部的(de)一(yi)端連接一(yi)根(gen)(gen)引(yin)(yin)(yin)線(xian),另一(yi)端連接兩根(gen)(gen)引(yin)(yin)(yin)線(xian)的(de)方式稱為三(san)線(xian)制,這種方式通常(chang)(chang)與(yu)電(dian)(dian)橋配套使用,可以(yi)較(jiao)好的(de)消(xiao)除(chu)引(yin)(yin)(yin)線(xian)電(dian)(dian)阻的(de)影(ying)響,是工業過程控(kong)制中(zhong)的(de)常(chang)(chang)用的(de)。
四線(xian)(xian)制(zhi):在熱(re)電(dian)(dian)阻(zu)的(de)(de)根部兩(liang)端各連接兩(liang)根導線(xian)(xian)的(de)(de)方(fang)式(shi)稱為四線(xian)(xian)制(zhi),其中兩(liang)根引線(xian)(xian)為熱(re)電(dian)(dian)阻(zu)提供恒定電(dian)(dian)流I,把(ba)R轉換成電(dian)(dian)壓信號(hao)U,再通過另兩(liang)根引線(xian)(xian)把(ba)U引至二次儀表(biao)。可(ke)見(jian)這(zhe)種引線(xian)(xian)方(fang)式(shi)可(ke)消除(chu)引線(xian)(xian)的(de)(de)電(dian)(dian)阻(zu)影響,主要(yao)用于高(gao)精度(du)的(de)(de)溫度(du)檢(jian)測(ce)。
熱(re)電(dian)(dian)阻(zu)采用(yong)(yong)三(san)線(xian)(xian)制接法(fa)。采用(yong)(yong)三(san)線(xian)(xian)制是(shi)為了消除(chu)連(lian)接導線(xian)(xian)電(dian)(dian)阻(zu)引起(qi)的(de)(de)(de)(de)測量(liang)(liang)(liang)誤(wu)(wu)差(cha)。這是(shi)因(yin)為測量(liang)(liang)(liang)熱(re)電(dian)(dian)阻(zu)的(de)(de)(de)(de)電(dian)(dian)路一般是(shi)不平衡(heng)電(dian)(dian)橋。熱(re)電(dian)(dian)阻(zu)作(zuo)為電(dian)(dian)橋的(de)(de)(de)(de)一個橋臂電(dian)(dian)阻(zu),其連(lian)接導線(xian)(xian)(從(cong)熱(re)電(dian)(dian)阻(zu)到(dao)(dao)中控室(shi))也成為橋臂電(dian)(dian)阻(zu)的(de)(de)(de)(de)一部分(fen),這一部分(fen)電(dian)(dian)阻(zu)是(shi)未(wei)知的(de)(de)(de)(de)且隨環境溫度變化,造成測量(liang)(liang)(liang)誤(wu)(wu)差(cha)。采用(yong)(yong)三(san)線(xian)(xian)制,將導線(xian)(xian)一根接到(dao)(dao)電(dian)(dian)橋的(de)(de)(de)(de)電(dian)(dian)源(yuan)端,其余兩根分(fen)別(bie)接到(dao)(dao)熱(re)電(dian)(dian)阻(zu)所在的(de)(de)(de)(de)橋臂及與其相(xiang)鄰的(de)(de)(de)(de)橋臂上(shang),這樣(yang)消除(chu)了導線(xian)(xian)線(xian)(xian)路電(dian)(dian)阻(zu)帶(dai)來的(de)(de)(de)(de)測量(liang)(liang)(liang)誤(wu)(wu)差(cha)。
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