Two-liquid manometer

Japanese: 二液マノメーター - にえきマノメーター（英語表記）two‐liquid manometer

A type of liquid column manometer, this instrument measures minute pressure differences by using the difference in the liquid columns of a U-shaped connecting tube containing two liquids with a small density difference. Two liquids with different densities that do not mix are placed at the same height on both sides in a U-shaped tube with a liquid reservoir at the top that has a larger cross-sectional area than the narrow tube section (Figure). If pressures of p ₁ and p ₂ are applied to both sides of the reservoir, the interface between the two liquids will move up and down until the weight of the liquid columns balances the pressure difference. If the difference in height of the interface at this time is h , the pressure difference is given by p ₁ - p ₂ = {(ρ ₁ -ρ ₂ ) + ( a / A )ρ ₂ } h g.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

液柱型圧力計の一種で，密度の差が小さい2種の液体を入れたU字管型連通管の液柱差を利用して，微小な圧力差を測る計器。細管部に比べて大きな断面積の液だめを上部にもつU字管内に，互いに混合しないで，かつ密度の異なる2種の液体を両側で同じ高さになるように入れる(図)。いま液だめの両側にp₁,p₂の圧力を加えると，液柱の重量が圧力差とつり合うまで2液の境界面が上下に移動する。このときの境界面の高さの差をhとすれば，圧力差は，　p₁－p₂＝｛(ρ₁－ρ₂)＋(a/A)ρ₂｝hgで与えられる。

出典　株式会社平凡社世界大百科事典第２版について　情報

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