一、壓力變送器是幾線制
壓力變送器是將壓力信號轉換為模擬量信號或者數字量信號的轉換設備,一般除無線壓力變送器外,其他的都是接(jie)線(xian)使用的,壓(ya)力(li)變(bian)送(song)器(qi)的接(jie)線(xian)一般有(you)三種:兩(liang)線(xian)制(zhi)(zhi)(zhi)、三線(xian)制(zhi)(zhi)(zhi)、四線(xian)制(zhi)(zhi)(zhi),壓(ya)力(li)變(bian)送(song)器(qi)需要連(lian)(lian)接(jie)的連(lian)(lian)線(xian)有(you)幾根連(lian)(lian)線(xian),就是幾線(xian)制(zhi)(zhi)(zhi)的接(jie)法(fa):
1、兩線制
兩(liang)(liang)線(xian)(xian)制(zhi)壓力變(bian)(bian)送(song)器(qi)是(shi)最常用的(de)(de),兩(liang)(liang)根(gen)線(xian)(xian)組成一條回路(lu),這條回路(lu)既是(shi)為壓力變(bian)(bian)送(song)器(qi)提供電(dian)源支持的(de)(de)回路(lu),也是(shi)傳輸電(dian)流(liu)信(xin)(xin)號(hao)的(de)(de)回路(lu)。也就是(shi)說在兩(liang)(liang)線(xian)(xian)制(zhi)接線(xian)(xian)中(zhong),壓力變(bian)(bian)送(song)器(qi)的(de)(de)輸出的(de)(de)負載(zai)和電(dian)源是(shi)被串(chuan)聯在一起的(de)(de)。使用這種連接方(fang)式的(de)(de)通常都是(shi)輸出電(dian)流(liu)信(xin)(xin)號(hao)的(de)(de)壓力變(bian)(bian)送(song)器(qi),如(ru)(ru)4~20mA的(de)(de)標(biao)準電(dian)控信(xin)(xin)號(hao),當二線(xian)(xian)制(zhi)需要輸出電(dian)壓值時,可以(yi)通過串(chuan)聯電(dian)阻的(de)(de)方(fang)式取壓測得,如(ru)(ru)4-20mA電(dian)流(liu)電(dian)路(lu)中(zhong)串(chuan)聯250Ω電(dian)阻。
2、三線制
三線(xian)(xian)制(zhi)(zhi)壓力變送(song)器將電(dian)(dian)(dian)(dian)源正(zheng)端(duan)和(he)信(xin)號輸出的(de)(de)正(zheng)端(duan)分離,但它們(men)另一(yi)個接(jie)線(xian)(xian)端(duan)子卻是用同一(yi)根線(xian)(xian)連(lian)接(jie)的(de)(de)。在這種(zhong)情(qing)況(kuang)下,電(dian)(dian)(dian)(dian)流(liu)實際的(de)(de)通路還是由電(dian)(dian)(dian)(dian)源正(zheng)負(fu)極的(de)(de)連(lian)線(xian)(xian)所組(zu)成的(de)(de)回(hui),信(xin)號正(zheng)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)流(liu)接(jie)近(jin)為(wei)0,只能(neng)傳遞(di)電(dian)(dian)(dian)(dian)位電(dian)(dian)(dian)(dian)壓,可(ke)以理解為(wei)萬用表的(de)(de)電(dian)(dian)(dian)(dian)壓檔(dang),負(fu)載無(wu)限大近(jin)似斷路。使用這種(zhong)連(lian)接(jie)方(fang)式的(de)(de)都是輸出電(dian)(dian)(dian)(dian)壓信(xin)號的(de)(de)壓力變送(song)器1~10V,1~5V,0~5V等標準(zhun)控制(zhi)(zhi)信(xin)號。
3、四線制
四線(xian)制(zhi)不(bu)同于二(er)線(xian)制(zhi)與(yu)三線(xian)制(zhi),它由兩個獨立(li)的回路組成,彼此(ci)互(hu)不(bu)干(gan)擾。因(yin)為(wei)輸出(chu)(chu)電路的獨立(li),使得它無(wu)論(lun)式輸出(chu)(chu)電壓信號還(huan)是電流信號都(dou)可以做到。
二、壓力變送器接線怎么接
壓力變(bian)送(song)器接(jie)線制不(bu)同(tong),接(jie)線方法(fa)也有所不(bu)同(tong):
1、二線制的(de)壓力變送器(qi),+極出來(lai)接PLC AI 模塊的(de)-;-極出來(lai)接PLC AI 模塊的(de)+。
2、三(san)線制(zhi)的(de)壓力變送(song)器,信號+出(chu)來接PLC AI 模(mo)塊的(de)+;公用-出(chu)來接PLC AI 模(mo)塊的(de)-;剩(sheng)下的(de)24dc+接24v電(dian)源+。
3、四線制的壓力變送器,信號+出來接PLC AI 模塊的+;信號-出來接PLC AI 模塊的-;剩下的24dc+接24v電源+;24dc-接24v電源-。
三、壓力變送器接線注意事項
壓力變送器電(dian)(dian)(dian)(dian)(dian)源(yuan)有(you)交流(liu)(liu)和(he)直流(liu)(liu)之分,交流(liu)(liu)分為(wei)(wei)220V和(he)110V兩(liang)種(zhong),直流(liu)(liu)分為(wei)(wei)固定(ding)(ding)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)和(he)寬電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)之分,固定(ding)(ding)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)比如5V、10V、12V、24V等(deng)(deng)固定(ding)(ding)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)這(zhe)樣的電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)選(xuan)擇(ze)電(dian)(dian)(dian)(dian)(dian)源(yuan)時(shi),一定(ding)(ding)要按(an)照標(biao)稱電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)來選(xuan)電(dian)(dian)(dian)(dian)(dian)源(yuan)。寬電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)比如3-36V、5-24V等(deng)(deng)這(zhe)樣的標(biao)稱,電(dian)(dian)(dian)(dian)(dian)源(yuan)選(xuan)擇(ze)在這(zhe)個(ge)(ge)范(fan)圍內的就(jiu)可以了(le),接(jie)線時(shi)注(zhu)意電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)等(deng)(deng)級,直流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)源(yuan)的正負極(ji)不要接(jie)錯。系統中如果有(you)兩(liang)塊不同(tong)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)源(yuan)注(zhu)意電(dian)(dian)(dian)(dian)(dian)源(yuan)共問(wen)題,就(jiu)是兩(liang)個(ge)(ge)電(dian)(dian)(dian)(dian)(dian)源(yuan)負極(ji)要接(jie)在一起。