Liquid level gauge

Japanese: 液面計 - えきめんけい（英語表記）liquid-level gauge

An indicator of the liquid level in a tank. In order to automatically adjust the liquid level, it is often linked to the start relay of the liquid pump, but there are many different ideas. (1) Float method Usually, a float is attached to a string, which is guided outside the tank with a pulley system and balanced with the float with a suitable weight, and the liquid level is measured by its up and down. In some cases, a magnet is attached to the float so that it moves up and down along the tank wall, and the liquid level is measured by the position of the iron piece outside the tank. (2) Glass gauge Branch pipes are extended from both the top and bottom of the tank, and graduated glass tubes are connected to them to guide the liquid and read the liquid level. (3) Hydraulic pressure method Air is sent through a tube that reaches the bottom of the tank, and the air pressure when bubbles start to appear is measured with a pressure gauge to measure the liquid level. This is also used in tide gauges, etc. (4) Ultrasonic method Based on the same principle as acoustic sounding, there are two types: an ultrasonic transmitter and receiver is installed at the bottom of the tank, and a method of placing it on the top of the tank. The former measures the liquid level itself, while the latter measures the height of the air column to the liquid surface. It is the most precise and is suitable for remote indication and continuous recording. There are many other types, such as the capacitor method, in which two concentric cylindrical capacitor plates are partially immersed in the liquid and the liquid level is determined by the change in electrical capacitance; the platinum resistance thermometer method, in which a platinum wire is partially immersed in the liquid, an electric current is passed through it, and the immersed part is cooled to reduce resistance, thereby determining the liquid level by the change in resistance; and the radiation method, in which the liquid level is determined by the change in radiation absorption by the liquid.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

槽内の液面の高さの指示計。液高を自動調整するために，液ポンプの始動用継電器と連動するようにした場合が多いが，非常に多くの考案がある。 (1) 浮き子法　通常は浮き子に糸をつけてこれを滑車装置で槽外に導き，適当なおもりで浮き子と平衡させ，その上下で液高を知る。場合によれば浮き子に磁石をつけて槽壁に沿って上下するようにし，槽外の鉄片の位置で液高を知る方法もある。 (2) ガラスゲージ　槽の上下両端から支管を出し，これに目盛りつきガラス管を連結して液を導き，液高を読取る。 (3) 液圧法　槽底に届く管から空気を送り，泡の出始めるときの空気圧を圧力計ではかって液高を知る。これは潮汐計などにも利用されている。 (4) 超音波法　音響測深と同原理で，超音波送受波器を槽底に設置する方式と槽の頂上に置く方式とがある。前者は液高そのものをはかるが，後者は液面までの空気柱の高さをはかる。最も精密で遠隔指示や連続記録に適する。その他，2枚の同心円筒形蓄電器極板をなかば液に浸し，電気容量変化で液面の高下を知る蓄電器法，白金線をなかば液に浸して電流を通じ，浸された部分の冷却による抵抗減少を利用して，抵抗変化で液高を知る白金抵抗温度計法，放射線の液による吸収変化で液高を知る放射線法など，多くの種類がある。

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