【正文】 光纖傳感法：文獻(xiàn)提出了一種光纖液位傳感器，當(dāng)液位變化時(shí)， 壓力傳感器 的敏感彈性膜片產(chǎn)生位移，帶動(dòng)反光膜移動(dòng)，使探頭感受的光強(qiáng)發(fā)生變化，從而計(jì)算出液位。核輻射液位儀采用非接觸式安裝采用點(diǎn)式放射源、探測(cè)器，測(cè)量范圍較??；采用點(diǎn)式放射源、線狀探測(cè)器，測(cè)量范圍較大；采用線狀放射源、探測(cè)器，測(cè)量范圍最大。實(shí)驗(yàn)證明，穿過物質(zhì)前后 γ射線強(qiáng)度會(huì)發(fā)生變化。伺服機(jī)構(gòu)控制振錘上下爬動(dòng)并激振，激振后的自由振動(dòng)被振動(dòng)傳感器檢測(cè)，該檢測(cè)信號(hào)經(jīng)FET 變換后得到最大功率處的頻率，最后由空罐時(shí)固有頻率／液位關(guān)系得到液位。故根據(jù)磁翻板的顏色即可確定液位。 以上 3 種方法都是通過檢測(cè)信號(hào)傳播的時(shí)間來確定液位的。則引起的液位誤差 Δh 將 超過 1 mm，由此證明，在傾斜角度 α（單位為度）較小時(shí)， Δh滿足： 雷達(dá)液位儀特別適合于高污染度或高粘度的產(chǎn)品，如瀝青等。微波速度受傳播介質(zhì)、溫度、壓力、液體介電常數(shù)的影響很小，但液體界面的波動(dòng)、液體表面的泡沫、液體介質(zhì)的介電常數(shù)對(duì)微波反射信號(hào)強(qiáng)弱有很大影響。詢問脈沖與返回脈沖之間的時(shí)間差即對(duì)應(yīng)油水界面和油氣界面的高度。 磁致伸縮法、超聲波法、調(diào)制型光學(xué)法、微波法 磁致伸縮法：該方法用于測(cè)量油罐液位中有兩個(gè)浮子，分別用來檢測(cè)油氣界面和油水界面。電容式液位儀價(jià)格較低，安裝容易，且可以應(yīng)用于高溫、高壓的場(chǎng)合。扭力管式沉筒法：扭力管芯軸的扭角發(fā)生變化，二次儀表根據(jù)扭角的變化量計(jì)算出液位 以上 5 種方法都是利用浮力原理來 工作的。浮球法主要用于測(cè)量溫度高、粘度大的液位，但量程較小。液位變化帶動(dòng)空心磁浮筒（內(nèi)藏永久磁鐵）沿套管上下移動(dòng)，并吸引套管內(nèi)的磁鐵沿套管內(nèi)壁上下移動(dòng)，二次儀器 |儀表根據(jù)磁鐵的移動(dòng)量計(jì)算出液位。如果壓力處于測(cè)量范圍下限時(shí)對(duì)應(yīng)的輸出信號(hào)大于或小于 4 mA，則都需要采用調(diào)整遷移彈簧等零點(diǎn)遷移技術(shù)，使之等于 4 mA。吹氣法適用于測(cè)量腐蝕性強(qiáng)、有懸濁物的液體，主要應(yīng)用在測(cè)量精度要求不高的場(chǎng)合。測(cè)量時(shí)，測(cè)量員把量油尺投入油品中，并在尺砣與罐底接觸時(shí)提起量油尺。玻璃板法：玻璃板可通過連通器安裝，也可在容器壁上開孔安裝，并可串聯(lián)幾段玻璃板以增 10 大量程。連續(xù)液位測(cè)量是對(duì)液位連續(xù)地進(jìn)行測(cè)量，它廣泛地應(yīng)用于石油、化工、食品加工等諸多領(lǐng)域，具有非常重要的意義。注意槽內(nèi)的攪拌，槽壁的粘附物會(huì)產(chǎn)生干擾的反射波，影響液位測(cè)量，在安裝是要選擇合適的安裝位置，以避免這些因素的干擾。雷達(dá)的發(fā)射角度比超聲波大，小容器或瘦長(zhǎng)的容器不推薦用非接觸式雷達(dá)，一般推薦導(dǎo)播雷達(dá)。電磁波在液位表面發(fā)射時(shí)，信號(hào)會(huì)衰減，當(dāng)信號(hào)衰減過小時(shí)，會(huì)導(dǎo)致雷達(dá)液位計(jì)無法測(cè)到足夠的電磁波信號(hào)，導(dǎo)電介質(zhì)能很好的反射電磁波，介電常數(shù)大于 的非導(dǎo)電介質(zhì)（空氣的介電常數(shù)為 ）也能夠保證足夠的反射波，介電常數(shù)越大，反射信號(hào)越強(qiáng)。采用調(diào)頻波技術(shù)的液位計(jì)，功耗大，須采用四線制，電子電路復(fù)雜。物料有揮發(fā)、液夾氣時(shí)，容器上由震動(dòng)（如容器上安裝有電機(jī)）不能選用超聲波液位計(jì)。 物位計(jì)發(fā)射超聲波脈沖時(shí)，不能同時(shí)檢測(cè)反射回波。 在化工過程的物位測(cè)量中，不僅有常溫、常壓，一般性介質(zhì)的液位、料位、界面的測(cè)量，而且還常常會(huì)遇到高溫、低溫（負(fù)溫）、高壓、易燃易爆。 All three methods above is through testing to determine the level of the signal propagation time. Sets the time of transmitting and receiving signals to t, h = n / 2 is empty, v for wave propagation speed. 7 6 magic flap method, the vibration method, radiation method, optical fiber sensors method Magic flap method principle: float is equipped with a set of permanent mags, with the liquid level change and move up and down, flip through magic coupling driving magic flap ponents. When the liquid level goes up, the magic flap of red face outwards。 H level. So the liquid level is measured by the static pressure P can be H. Strong method suitable for measuring the corrosive gas blowing, have suspended material content in the liquid, and is mainly used in the measurement accuracy is not high. Differential pressure method: the open container or atmospheric vessels, valves and gas phase pressure pipeline saves. Based on the relationship between differential pressure and liquid level Δ P = P2 P1 = rho gH type: Δ P positive and negative pressure chamber pressure transmitter。t use ultrasonic liquid level meter. (2) radar material level meter Radar level gauge USES launch reflection receive work mode. Radar level meter antenna emit electromagic wave, the wave reflected by the measured object surface, again by the antenna, the electromagic wave from transmitting to receiving time is proportional to the distance to the liquid surface. In practice, there are two kinds of radar level gauge means the frequency modulation continuous wave and pulse wave. Liquid level meter adopts frequency modulation wave technology, power consumption is big, the four wire system, should be used in electronic circuit is plicated. And the radar pulse wave technology level gauge, low power consumption, easy to implement essential safety, high precision, wider application scope. Radar level gauge measuring the electromagic waves can pass through a vacuum, don39。 1 附錄 C Liquid Level Measurement Chemical industry with the progress of science and technology got rapid development, in order to make the equipment safe and reliable operation, and can be utmost to improve product quantity and quality, to effectively operate automatically and process adjustment, realize the scientific management for the enterprise to provide the necessary material and energy of accurate data, must be in production in the process of pressure, flow, level, temperature, chemical position of various parameters such as timely, accurate measurement. Generally the process of containers, tanks, towers, tank of liquid surface position level, slot bucket, cans, and warehouse ChuFa solid block, the accumulation of particles, powder height and surface position is called a material level。t need a transmission medium, is not affected by air, steam, groove volatile fog effect, can be used for such as coarse benzene volatile medium level measu