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)(jie)線(xian)(xian)(xian)(xian)使用(yong)的，壓力變送器的接(jie)(jie)線(xian)(xian)(xian)(xian)一般有三種：兩線(xian)(xian)(xian)(xian)制、三線(xian)(xian)(xian)(xian)制、四線(xian)(xian)(xian)(xian)制，壓力變送器需要連接(jie)(jie)的連線(xian)(xian)(xian)(xian)有幾(ji)根(gen)連線(xian)(xian)(xian)(xian)，就是幾(ji)線(xian)(xian)(xian)(xian)制的接(jie)(jie)法(fa)：

1、兩線制

兩(liang)(liang)線(xian)(xian)制壓(ya)(ya)(ya)力(li)變(bian)送(song)器(qi)是(shi)(shi)最(zui)常用(yong)的(de)(de)(de)，兩(liang)(liang)根線(xian)(xian)組成一條(tiao)回(hui)(hui)路，這條(tiao)回(hui)(hui)路既是(shi)(shi)為壓(ya)(ya)(ya)力(li)變(bian)送(song)器(qi)提(ti)供電(dian)源(yuan)支持的(de)(de)(de)回(hui)(hui)路，也(ye)是(shi)(shi)傳輸(shu)(shu)電(dian)流信號(hao)的(de)(de)(de)回(hui)(hui)路。也(ye)就是(shi)(shi)說在兩(liang)(liang)線(xian)(xian)制接(jie)(jie)線(xian)(xian)中，壓(ya)(ya)(ya)力(li)變(bian)送(song)器(qi)的(de)(de)(de)輸(shu)(shu)出(chu)的(de)(de)(de)負載和電(dian)源(yuan)是(shi)(shi)被串(chuan)(chuan)聯在一起(qi)的(de)(de)(de)。使用(yong)這種(zhong)連接(jie)(jie)方(fang)式的(de)(de)(de)通(tong)常都是(shi)(shi)輸(shu)(shu)出(chu)電(dian)流信號(hao)的(de)(de)(de)壓(ya)(ya)(ya)力(li)變(bian)送(song)器(qi)，如(ru)4~20mA的(de)(de)(de)標準電(dian)控信號(hao)，當(dang)二線(xian)(xian)制需要輸(shu)(shu)出(chu)電(dian)壓(ya)(ya)(ya)值時，可(ke)以通(tong)過(guo)串(chuan)(chuan)聯電(dian)阻的(de)(de)(de)方(fang)式取壓(ya)(ya)(ya)測(ce)得(de)，如(ru)4-20mA電(dian)流電(dian)路中串(chuan)(chuan)聯250Ω電(dian)阻。

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2、三線制

三線(xian)(xian)(xian)制(zhi)壓(ya)(ya)力變送器將電(dian)源正端和信號(hao)(hao)輸出(chu)的(de)(de)(de)正端分離，但(dan)它們另一個接線(xian)(xian)(xian)端子卻是用同一根線(xian)(xian)(xian)連(lian)接的(de)(de)(de)。在(zai)這(zhe)(zhe)種(zhong)(zhong)情況下，電(dian)流(liu)實際的(de)(de)(de)通(tong)路還是由電(dian)源正負極的(de)(de)(de)連(lian)線(xian)(xian)(xian)所組成的(de)(de)(de)回，信號(hao)(hao)正端的(de)(de)(de)電(dian)流(liu)接近為(wei)0，只(zhi)能傳遞電(dian)位電(dian)壓(ya)(ya)，可以理解(jie)為(wei)萬用表的(de)(de)(de)電(dian)壓(ya)(ya)檔，負載無限大近似斷路。使用這(zhe)(zhe)種(zhong)(zhong)連(lian)接方式的(de)(de)(de)都是輸出(chu)電(dian)壓(ya)(ya)信號(hao)(hao)的(de)(de)(de)壓(ya)(ya)力變送器1~10V，1~5V，0~5V等標準控制(zhi)信號(hao)(hao)。

3、四線制

四線(xian)(xian)制(zhi)不同于二(er)線(xian)(xian)制(zhi)與三線(xian)(xian)制(zhi)，它由(you)兩個獨立(li)的回路組成，彼此互不干擾。因為輸(shu)出(chu)電路的獨立(li)，使得(de)它無論式輸(shu)出(chu)電壓信(xin)號還(huan)是電流信(xin)號都可以做到。

二、壓力變送器接線怎么接

壓力變送器接(jie)線(xian)制不(bu)同，接(jie)線(xian)方法也有所不(bu)同：

1、二線制的壓力變送(song)器，+極(ji)(ji)出(chu)來(lai)接PLC AI 模塊的-；-極(ji)(ji)出(chu)來(lai)接PLC AI 模塊的+。

2、三線(xian)制的(de)壓力(li)變送(song)器，信(xin)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電源(yuan)+。

3、四線制(zhi)的(de)壓力變(bian)送器(qi)，信(xin)號(hao)+出(chu)來(lai)接(jie)PLC AI 模(mo)塊的(de)+；信(xin)號(hao)-出(chu)來(lai)接(jie)PLC AI 模(mo)塊的(de)-；剩下的(de)24dc+接(jie)24v電源(yuan)(yuan)+；24dc-接(jie)24v電源(yuan)(yuan)-。

三、壓力變送器接線注意事項

壓力變送器電(dian)(dian)(dian)(dian)源(yuan)(yuan)有交流和(he)直(zhi)(zhi)流之分(fen)，交流分(fen)為220V和(he)110V兩(liang)種，直(zhi)(zhi)流分(fen)為固(gu)定(ding)(ding)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)和(he)寬電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)之分(fen)，固(gu)定(ding)(ding)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)如5V、10V、12V、24V等固(gu)定(ding)(ding)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)這樣(yang)的(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)選擇電(dian)(dian)(dian)(dian)源(yuan)(yuan)時，一(yi)定(ding)(ding)要按照(zhao)標(biao)稱(cheng)(cheng)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)來選電(dian)(dian)(dian)(dian)源(yuan)(yuan)。寬電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)如3-36V、5-24V等這樣(yang)的(de)標(biao)稱(cheng)(cheng)，電(dian)(dian)(dian)(dian)源(yuan)(yuan)選擇在(zai)這個(ge)范(fan)圍內的(de)就可(ke)以(yi)了，接線時注(zhu)意電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)等級，直(zhi)(zhi)流電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)正負極不要接錯(cuo)。系統中如果有兩(liang)塊不同電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)源(yuan)(yuan)注(zhu)意電(dian)(dian)(dian)(dian)源(yuan)(yuan)共問題，就是(shi)兩(liang)個(ge)電(dian)(dian)(dian)(dian)源(yuan)(yuan)負極要接在(zai)一(yi)起。