1151系列電容式變送器有一個可變電容的傳感組件, 稱為“δ”室。該傳感器是一個完全封閉的組件。過程壓力、差壓通過隔離膜片和灌充液硅油傳到傳感膜片引起位移, 傳感膜片和兩電容極板之間的電容差由電子部件轉換成( 4~20)mA的兩線制輸出的電信號。jRq壓力(li)變(bian)送器_差壓變(bian)送器_液位變(bian)送器_溫度(du)變(bian)送器
1151電容式壓力變送器的故障部位一般分為兩類: 傳感器故障和電子檢測及放大轉換故障。傳感器一般不易出現問題, 在按上述方法檢測正常的情況下, 一般不用懷疑。應重點檢測電路部分。1151電容式差壓變送器的故障現象主要有以下幾種:jRq壓力變(bian)送器(qi)_差壓變(bian)送器(qi)_液(ye)位變(bian)送器(qi)_溫度變(bian)送器(qi)
1.輸出過大jRq壓力變(bian)送器(qi)_差壓變(bian)送器(qi)_液位變(bian)送器(qi)_溫度變(bian)送器(qi)
在沒有壓力( 差壓) 的情況下, 變送器輸出電流(mA)數過大, 有時超量程, 調整零點及量程電位器不起作用。出現此故障的電路部分較多, 且經常損壞的是電路的后極, 即電流控制放大器到電流控制輸出部分。其結構如圖2所示jRq壓力變(bian)(bian)送器_差壓變(bian)(bian)送器_液位變(bian)(bian)送器_溫度變(bian)(bian)送器
jRq壓力變送器_差壓變送器_液位變送器_溫度變送器
IC3 為電壓放大器經V17 轉換為mA輸出。用萬用表直流電壓擋測IC3 的3腳電位值, 調節量程或零點, 3腳電壓應有變化, 說明前極回路正常。同時測量6腳輸出應有放大的電壓信號輸出。從而判斷IC3 及外圍偏置回路是否正常。若6腳電壓始終很高( 接近電源電壓) , 則可判斷為IC3 損壞, 更換同型號LM308即可。若IC3 正常, 則用萬用表測量V17、V18 是否擊穿。在實際檢測中, 經常遇到V17、V18擊穿致使輸出過大。jRq壓力變送(song)器(qi)_差壓變送(song)器(qi)_液位變送(song)器(qi)_溫度(du)變送(song)器(qi)
2.輸出過小或無輸出jRq壓(ya)力變(bian)(bian)送(song)(song)器(qi)_差壓(ya)變(bian)(bian)送(song)(song)器(qi)_液位變(bian)(bian)送(song)(song)器(qi)_溫度變(bian)(bian)送(song)(song)器(qi)
檢查加到變壓器兩端的電壓是否正常; 集成運算放大器兩端電壓是否正常; 判斷振蕩電路是否起振; 量程、零點、電位器調節電壓是否變化及15Ω量程負載電阻是否損壞。用檢測輸出過大的方法檢測后極電路, 判斷后極電路是否正常。jRq壓(ya)力變(bian)送(song)器(qi)_差壓(ya)變(bian)送(song)器(qi)_液(ye)位變(bian)送(song)器(qi)_溫(wen)度(du)變(bian)送(song)器(qi)
3.輸出不穩定jRq壓力變送(song)器_差壓變送(song)器_液位變送(song)器_溫度(du)變送(song)器
檢查變壓器是否有間歇性的短路、開路和多點接地的現象; 檢查加到變壓器的電壓是否穩定正常; 穩壓電路是否正常; 檢測各個穩壓二極管、測試振蕩頻率是否穩定; 電路板有無虛焊。jRq壓力變(bian)送(song)器(qi)_差壓變(bian)送(song)器(qi)_液(ye)位變(bian)送(song)器(qi)_溫度變(bian)送(song)器(qi)
4.輸出非線性jRq壓力(li)變(bian)送(song)(song)器(qi)_差壓變(bian)送(song)(song)器(qi)_液位變(bian)送(song)(song)器(qi)_溫度變(bian)送(song)(song)器(qi)
此類故障出現的相對多一些且檢測難度大, 電路中各個部分參數變差都可能引起此類故障。但其主要出現在非線性調整電路部分。其電路如圖3所示。jRq壓(ya)力(li)變送(song)(song)器(qi)(qi)_差壓(ya)變送(song)(song)器(qi)(qi)_液位(wei)變送(song)(song)器(qi)(qi)_溫度(du)變送(song)(song)器(qi)(qi)
jRq壓力變送器_差壓變送器_液位(wei)變送器_溫度(du)變送器
用萬用表電阻擋檢測二極管V9、V10、線形電位器R24、電阻R23、R22 及C3、C6、C4 是否正常, 調節R24 輸出是否有相應變化, 以上元件的損壞經常引起線性不好。jRq壓(ya)力變送(song)器(qi)_差壓(ya)變送(song)器(qi)_液位變送(song)器(qi)_溫度變送(song)器(qi)
1151系列電容式壓力、差壓變送器在長期的運行工作中, 出現的故障五花八門。在處理故障時應通過周密細致的觀察、分析, 確定故障的大體位置及解決步驟, 再動手調試及檢測, 這樣就可以取得事半功倍的效果。此外, 在此提醒使用單位注意, 儀表在維修后一定要經過調校和檢定合格后, 才可投入正常的使用。jRq壓力變(bian)送(song)(song)器(qi)_差壓變(bian)送(song)(song)器(qi)_液位變(bian)送(song)(song)器(qi)_溫度(du)變(bian)送(song)(song)器(qi)
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