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(de)都(dou)是接(jie)線(xian)(xian)使用的(de)，壓力變(bian)送(song)器的(de)接(jie)線(xian)(xian)一(yi)般(ban)有三(san)種：兩線(xian)(xian)制、三(san)線(xian)(xian)制、四(si)線(xian)(xian)制，壓力變(bian)送(song)器需要連(lian)接(jie)的(de)連(lian)線(xian)(xian)有幾根連(lian)線(xian)(xian)，就(jiu)是幾線(xian)(xian)制的(de)接(jie)法：

1、兩線制

兩(liang)線制壓(ya)(ya)力變(bian)送器(qi)(qi)是(shi)(shi)最(zui)常用(yong)的(de)，兩(liang)根線組(zu)成一(yi)條(tiao)(tiao)回(hui)(hui)路(lu)，這(zhe)條(tiao)(tiao)回(hui)(hui)路(lu)既(ji)是(shi)(shi)為壓(ya)(ya)力變(bian)送器(qi)(qi)提供(gong)電(dian)(dian)源支持(chi)的(de)回(hui)(hui)路(lu)，也是(shi)(shi)傳輸電(dian)(dian)流信號的(de)回(hui)(hui)路(lu)。也就是(shi)(shi)說在兩(liang)線制接(jie)線中，壓(ya)(ya)力變(bian)送器(qi)(qi)的(de)輸出(chu)的(de)負載和電(dian)(dian)源是(shi)(shi)被(bei)串(chuan)(chuan)聯(lian)(lian)在一(yi)起的(de)。使用(yong)這(zhe)種連接(jie)方式(shi)(shi)的(de)通常都(dou)是(shi)(shi)輸出(chu)電(dian)(dian)流信號的(de)壓(ya)(ya)力變(bian)送器(qi)(qi)，如4~20mA的(de)標準電(dian)(dian)控信號，當二線制需要輸出(chu)電(dian)(dian)壓(ya)(ya)值時，可以通過串(chuan)(chuan)聯(lian)(lian)電(dian)(dian)阻(zu)的(de)方式(shi)(shi)取壓(ya)(ya)測得(de)，如4-20mA電(dian)(dian)流電(dian)(dian)路(lu)中串(chuan)(chuan)聯(lian)(lian)250Ω電(dian)(dian)阻(zu)。

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2、三線制

三線(xian)制壓(ya)(ya)(ya)力(li)變送器(qi)將電(dian)(dian)源正(zheng)(zheng)端和(he)信號輸(shu)出的(de)(de)(de)(de)正(zheng)(zheng)端分(fen)離，但它們(men)另一(yi)個接線(xian)端子卻是(shi)用(yong)(yong)同一(yi)根線(xian)連(lian)接的(de)(de)(de)(de)。在這種情況下，電(dian)(dian)流(liu)實際的(de)(de)(de)(de)通路還是(shi)由電(dian)(dian)源正(zheng)(zheng)負(fu)極的(de)(de)(de)(de)連(lian)線(xian)所組成的(de)(de)(de)(de)回，信號正(zheng)(zheng)端的(de)(de)(de)(de)電(dian)(dian)流(liu)接近(jin)為(wei)0，只(zhi)能傳(chuan)遞電(dian)(dian)位(wei)電(dian)(dian)壓(ya)(ya)(ya)，可以理解為(wei)萬(wan)用(yong)(yong)表(biao)的(de)(de)(de)(de)電(dian)(dian)壓(ya)(ya)(ya)檔(dang)，負(fu)載(zai)無限大近(jin)似斷(duan)路。使用(yong)(yong)這種連(lian)接方式的(de)(de)(de)(de)都(dou)是(shi)輸(shu)出電(dian)(dian)壓(ya)(ya)(ya)信號的(de)(de)(de)(de)壓(ya)(ya)(ya)力(li)變送器(qi)1~10V，1~5V，0~5V等標準(zhun)控(kong)制信號。

3、四線制

四線(xian)制(zhi)不(bu)同(tong)于二線(xian)制(zhi)與三線(xian)制(zhi)，它(ta)由兩個獨(du)立的(de)回路(lu)(lu)組成，彼此互不(bu)干擾。因為輸出電(dian)(dian)(dian)路(lu)(lu)的(de)獨(du)立，使得它(ta)無論式輸出電(dian)(dian)(dian)壓(ya)信號還是電(dian)(dian)(dian)流信號都可以(yi)做到。

二、壓力變送器接線怎么接

壓(ya)力變送器接線(xian)制不(bu)同，接線(xian)方法也有所不(bu)同：

1、二線制的(de)壓(ya)力變送器，+極(ji)出來接PLC AI 模塊的(de)-；-極(ji)出來接PLC AI 模塊的(de)+。

2、三線制的(de)壓力變送器，信號+出來接PLC AI 模(mo)塊的(de)+；公用-出來接PLC AI 模(mo)塊的(de)-；剩(sheng)下的(de)24dc+接24v電(dian)源+。

3、四線制的(de)壓力(li)變送器(qi)，信號(hao)+出來(lai)接(jie)PLC AI 模塊的(de)+；信號(hao)-出來(lai)接(jie)PLC AI 模塊的(de)-；剩下的(de)24dc+接(jie)24v電源+；24dc-接(jie)24v電源-。

三、壓力變送器接線注意事項

壓力變送器電(dian)(dian)(dian)源(yuan)(yuan)有交流和(he)直(zhi)流之分(fen)，交流分(fen)為220V和(he)110V兩種，直(zhi)流分(fen)為固(gu)定電(dian)(dian)(dian)壓(ya)(ya)(ya)和(he)寬電(dian)(dian)(dian)壓(ya)(ya)(ya)之分(fen)，固(gu)定電(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)(bi)如5V、10V、12V、24V等固(gu)定電(dian)(dian)(dian)壓(ya)(ya)(ya)這(zhe)樣(yang)的(de)電(dian)(dian)(dian)壓(ya)(ya)(ya)選擇(ze)電(dian)(dian)(dian)源(yuan)(yuan)時，一定要(yao)按照標稱電(dian)(dian)(dian)壓(ya)(ya)(ya)來選電(dian)(dian)(dian)源(yuan)(yuan)。寬電(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)(bi)如3-36V、5-24V等這(zhe)樣(yang)的(de)標稱，電(dian)(dian)(dian)源(yuan)(yuan)選擇(ze)在這(zhe)個范圍內的(de)就可以了，接線時注意電(dian)(dian)(dian)壓(ya)(ya)(ya)等級，直(zhi)流電(dian)(dian)(dian)源(yuan)(yuan)的(de)正負極不要(yao)接錯。系統中如果有兩塊不同電(dian)(dian)(dian)壓(ya)(ya)(ya)電(dian)(dian)(dian)源(yuan)(yuan)注意電(dian)(dian)(dian)源(yuan)(yuan)共(gong)問題，就是兩個電(dian)(dian)(dian)源(yuan)(yuan)負極要(yao)接在一起。