壓力(li)(li)變(bian)送器是工(gong)業(ye)(ye)(ye)實踐中常用(yong)(yong)的(de)一種傳感器，其廣泛(fan)應用(yong)(yong)于(yu)各(ge)種工(gong)業(ye)(ye)(ye)自控(kong)環境，涉及水(shui)(shui)利水(shui)(shui)電、鐵路交通(tong)、智(zhi)能(neng)建筑、生(sheng)產自控(kong)、航空航天(tian)、軍工(gong)、石化(hua)、油井、電力(li)(li)、船舶(bo)、機床、管道等眾多行業(ye)(ye)(ye)。下面就(jiu)簡單(dan)介紹一些常用(yong)(yong)壓力(li)(li)變(bian)送器的(de)原(yuan)理(li)及其應用(yong)(yong)、壓力(li)(li)變(bian)送器是用(yong)(yong)于(yu)測(ce)量液(ye)體(ti)、氣體(ti)或蒸汽的(de)液(ye)位、密度和壓力(li)(li)，然后將壓力(li)(li)信號轉變(bian)成4～20mA DC信號輸出。
壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)主(zhu)要有電容式壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)和(he)擴散硅壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)，陶(tao)瓷壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)，應變(bian)(bian)(bian)式壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)等。壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)根據(ju)測(ce)壓(ya)(ya)范(fan)圍可(ke)分成一般壓(ya)(ya)力(li)(li)變(bian)(bian)(bian)送(song)(song)(song)器(qi)（0.001MPa～35MPa）和(he)微差壓(ya)(ya)變(bian)(bian)(bian)送(song)(song)(song)器(qi)（0～1.5kPa），負壓(ya)(ya)變(bian)(bian)(bian)送(song)(song)(song)器(qi)三種。
壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)變(bian)(bian)送(song)器的(de)(de)(de)主要作用把壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)信(xin)號傳到(dao)電(dian)子(zi)設備，進而在計算機顯示(shi)壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)其(qi)原理大(da)致是：將(jiang)水壓(ya)(ya)(ya)(ya)(ya)這種壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)的(de)(de)(de)力(li)(li)(li)學信(xin)號轉變(bian)(bian)成電(dian)流(liu)（4-20mA）這樣(yang)的(de)(de)(de)電(dian)子(zi)信(xin)號壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)和(he)電(dian)壓(ya)(ya)(ya)(ya)(ya)或(huo)電(dian)流(liu)大(da)小成線性關系(xi)，一般是正比(bi)關系(xi)。所以(yi)，變(bian)(bian)送(song)器輸出(chu)的(de)(de)(de)電(dian)壓(ya)(ya)(ya)(ya)(ya)或(huo)電(dian)流(liu)隨壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)增大(da)而增大(da)由此(ci)得出(chu)一個壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)和(he)電(dian)壓(ya)(ya)(ya)(ya)(ya)或(huo)電(dian)流(liu)的(de)(de)(de)關系(xi)式壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)變(bian)(bian)送(song)器的(de)(de)(de)被測介質的(de)(de)(de)兩(liang)(liang)種壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)通入(ru)高、低(di)兩(liang)(liang)壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)室，低(di)壓(ya)(ya)(ya)(ya)(ya)室壓(ya)(ya)(ya)(ya)(ya)力(li)(li)(li)采用大(da)氣壓(ya)(ya)(ya)(ya)(ya)或(huo)真(zhen)空，作用在δ元（即敏感(gan)元件）的(de)(de)(de)兩(liang)(liang)側隔離膜(mo)片上，通過隔離片和(he)元件內的(de)(de)(de)填充液傳送(song)到(dao)測量膜(mo)片兩(liang)(liang)側。
壓(ya)力變送器(qi)是(shi)由測量膜片與兩(liang)側(ce)絕緣片上(shang)的電(dian)(dian)極各組成一個電(dian)(dian)容器(qi)。當兩(liang)側(ce)壓(ya)力不(bu)一致時(shi)，致使測量膜片產生位(wei)(wei)移，其位(wei)(wei)移量和壓(ya)力差成正比，故兩(liang)側(ce)電(dian)(dian)容量就不(bu)等，通過(guo)振蕩和解調環節。
