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)都是(shi)接(jie)線(xian)使用的(de),壓力變(bian)送(song)器的(de)接(jie)線(xian)一(yi)般有(you)三種:兩線(xian)制(zhi)、三線(xian)制(zhi)、四線(xian)制(zhi),壓力變(bian)送(song)器需(xu)要連(lian)接(jie)的(de)連(lian)線(xian)有(you)幾根連(lian)線(xian),就是(shi)幾線(xian)制(zhi)的(de)接(jie)法:
1、兩線制
兩線制壓(ya)(ya)力變送(song)器是(shi)(shi)最常(chang)用(yong)的(de)(de)(de)(de),兩根(gen)線組(zu)成一條回路(lu),這條回路(lu)既(ji)是(shi)(shi)為壓(ya)(ya)力變送(song)器提供電(dian)(dian)(dian)(dian)(dian)源支持(chi)的(de)(de)(de)(de)回路(lu),也是(shi)(shi)傳輸(shu)電(dian)(dian)(dian)(dian)(dian)流(liu)信號(hao)的(de)(de)(de)(de)回路(lu)。也就是(shi)(shi)說在(zai)兩線制接線中,壓(ya)(ya)力變送(song)器的(de)(de)(de)(de)輸(shu)出(chu)的(de)(de)(de)(de)負載和電(dian)(dian)(dian)(dian)(dian)源是(shi)(shi)被串(chuan)聯在(zai)一起(qi)的(de)(de)(de)(de)。使用(yong)這種連接方式的(de)(de)(de)(de)通常(chang)都是(shi)(shi)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)信號(hao)的(de)(de)(de)(de)壓(ya)(ya)力變送(song)器,如4~20mA的(de)(de)(de)(de)標準電(dian)(dian)(dian)(dian)(dian)控信號(hao),當二線制需要輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)值時,可以通過串(chuan)聯電(dian)(dian)(dian)(dian)(dian)阻的(de)(de)(de)(de)方式取壓(ya)(ya)測得,如4-20mA電(dian)(dian)(dian)(dian)(dian)流(liu)電(dian)(dian)(dian)(dian)(dian)路(lu)中串(chuan)聯250Ω電(dian)(dian)(dian)(dian)(dian)阻。
2、三線制
三(san)線制壓(ya)力(li)變送(song)(song)器(qi)將電源正端和信號輸出的正端分(fen)離,但(dan)它們另一(yi)個(ge)接線端子卻是用(yong)同一(yi)根線連接的。在這種情況下,電流實際的通(tong)路(lu)還(huan)是由電源正負(fu)極的連線所組(zu)成的回,信號正端的電流接近為0,只能(neng)傳遞電位電壓(ya),可以理解為萬用(yong)表的電壓(ya)檔,負(fu)載(zai)無(wu)限大(da)近似(si)斷(duan)路(lu)。使(shi)用(yong)這種連接方(fang)式的都是輸出電壓(ya)信號的壓(ya)力(li)變送(song)(song)器(qi)1~10V,1~5V,0~5V等標準控制信號。
3、四線制
四線(xian)(xian)(xian)制不(bu)同于(yu)二(er)線(xian)(xian)(xian)制與(yu)三線(xian)(xian)(xian)制,它由兩個獨立(li)的回路(lu)組成,彼此互不(bu)干(gan)擾(rao)。因為(wei)輸出電路(lu)的獨立(li),使得(de)它無論式(shi)輸出電壓信號還是電流(liu)信號都可以做到。
二、壓力變送器接線怎么接
壓(ya)力變(bian)送器接線制不同,接線方法(fa)也有所不同:
1、二(er)線(xian)制(zhi)的(de)(de)壓力變送器(qi),+極出來接PLC AI 模(mo)塊的(de)(de)-;-極出來接PLC AI 模(mo)塊的(de)(de)+。
2、三線制的(de)壓力(li)變(bian)送(song)器,信號+出來接(jie)(jie)PLC AI 模塊(kuai)的(de)+;公用(yong)-出來接(jie)(jie)PLC AI 模塊(kuai)的(de)-;剩下的(de)24dc+接(jie)(jie)24v電源(yuan)+。
3、四線制的壓力變送器,信(xin)號(hao)+出來(lai)接(jie)(jie)PLC AI 模塊的+;信(xin)號(hao)-出來(lai)接(jie)(jie)PLC AI 模塊的-;剩下(xia)的24dc+接(jie)(jie)24v電源+;24dc-接(jie)(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)(dian)源(yuan)(yuan)有(you)交流和(he)直(zhi)(zhi)流之分,交流分為(wei)220V和(he)110V兩(liang)種,直(zhi)(zhi)流分為(wei)固定電(dian)(dian)(dian)(dian)壓(ya)和(he)寬電(dian)(dian)(dian)(dian)壓(ya)之分,固定電(dian)(dian)(dian)(dian)壓(ya)比如5V、10V、12V、24V等(deng)固定電(dian)(dian)(dian)(dian)壓(ya)這(zhe)樣的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)選(xuan)擇(ze)電(dian)(dian)(dian)(dian)源(yuan)(yuan)時,一(yi)定要(yao)(yao)按照標(biao)稱電(dian)(dian)(dian)(dian)壓(ya)來選(xuan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)。寬電(dian)(dian)(dian)(dian)壓(ya)比如3-36V、5-24V等(deng)這(zhe)樣的(de)(de)(de)標(biao)稱,電(dian)(dian)(dian)(dian)源(yuan)(yuan)選(xuan)擇(ze)在這(zhe)個范圍內的(de)(de)(de)就(jiu)可(ke)以了,接(jie)線(xian)時注意(yi)電(dian)(dian)(dian)(dian)壓(ya)等(deng)級,直(zhi)(zhi)流電(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)正負極不要(yao)(yao)接(jie)錯。系統中如果有(you)兩(liang)塊不同電(dian)(dian)(dian)(dian)壓(ya)電(dian)(dian)(dian)(dian)源(yuan)(yuan)注意(yi)電(dian)(dian)(dian)(dian)源(yuan)(yuan)共問(wen)題,就(jiu)是(shi)兩(liang)個電(dian)(dian)(dian)(dian)源(yuan)(yuan)負極要(yao)(yao)接(jie)在一(yi)起。