壓力(li)變送(song)(song)器是工(gong)業(ye)實踐中常用(yong)(yong)的(de)一種傳感器，其廣泛(fan)應(ying)(ying)用(yong)(yong)于各種工(gong)業(ye)自控環(huan)境，涉(she)及水(shui)利水(shui)電、鐵路交通、智能建筑、生產自控、航(hang)(hang)空航(hang)(hang)天、軍工(gong)、石(shi)化、油井、電力(li)、船(chuan)舶、機床(chuang)、管道等眾多(duo)行業(ye)。下面(mian)就簡單介紹一些常用(yong)(yong)壓力(li)變送(song)(song)器的(de)原理及其應(ying)(ying)用(yong)(yong)、壓力(li)變送(song)(song)器是用(yong)(yong)于測量液體、氣(qi)體或蒸(zheng)汽的(de)液位(wei)、密度和壓力(li)，然后將壓力(li)信號轉(zhuan)變成4～20mA DC信號輸(shu)出。
壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)主要有(you)電(dian)容式(shi)壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)和(he)擴(kuo)散(san)硅壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)，陶瓷(ci)壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)，應變(bian)式(shi)壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)等。壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)根據測壓(ya)(ya)(ya)范圍可分(fen)成一般壓(ya)(ya)(ya)力(li)(li)變(bian)送器(qi)(qi)（0.001MPa～35MPa）和(he)微差壓(ya)(ya)(ya)變(bian)送器(qi)(qi)（0～1.5kPa），負壓(ya)(ya)(ya)變(bian)送器(qi)(qi)三種(zhong)。
壓(ya)(ya)力(li)(li)(li)(li)變(bian)送器(qi)的(de)主要作用把壓(ya)(ya)力(li)(li)(li)(li)信(xin)號(hao)傳(chuan)(chuan)到(dao)(dao)電(dian)子(zi)設(she)備，進而(er)在(zai)計算機顯示壓(ya)(ya)力(li)(li)(li)(li)其(qi)原理大致是(shi)：將水(shui)壓(ya)(ya)這種壓(ya)(ya)力(li)(li)(li)(li)的(de)力(li)(li)(li)(li)學(xue)信(xin)號(hao)轉(zhuan)變(bian)成電(dian)流（4-20mA）這樣的(de)電(dian)子(zi)信(xin)號(hao)壓(ya)(ya)力(li)(li)(li)(li)和電(dian)壓(ya)(ya)或(huo)電(dian)流大小成線(xian)性關(guan)系(xi)，一般是(shi)正比關(guan)系(xi)。所以，變(bian)送器(qi)輸出的(de)電(dian)壓(ya)(ya)或(huo)電(dian)流隨壓(ya)(ya)力(li)(li)(li)(li)增大而(er)增大由(you)此得出一個壓(ya)(ya)力(li)(li)(li)(li)和電(dian)壓(ya)(ya)或(huo)電(dian)流的(de)關(guan)系(xi)式壓(ya)(ya)力(li)(li)(li)(li)變(bian)送器(qi)的(de)被測介質的(de)兩(liang)(liang)種壓(ya)(ya)力(li)(li)(li)(li)通入高、低(di)兩(liang)(liang)壓(ya)(ya)力(li)(li)(li)(li)室，低(di)壓(ya)(ya)室壓(ya)(ya)力(li)(li)(li)(li)采用大氣壓(ya)(ya)或(huo)真空，作用在(zai)δ元(yuan)（即敏感元(yuan)件）的(de)兩(liang)(liang)側隔離膜片(pian)(pian)上，通過(guo)隔離片(pian)(pian)和元(yuan)件內(nei)的(de)填充液傳(chuan)(chuan)送到(dao)(dao)測量膜片(pian)(pian)兩(liang)(liang)側。
壓(ya)力變送器(qi)是由測量(liang)膜片與兩側(ce)(ce)絕緣片上的(de)電極各(ge)組成一(yi)個(ge)電容器(qi)。當兩側(ce)(ce)壓(ya)力不一(yi)致時，致使(shi)測量(liang)膜片產生位移，其位移量(liang)和壓(ya)力差成正比，故兩側(ce)(ce)電容量(liang)就(jiu)不等，通(tong)過振蕩和解調環(huan)節。
