G01L7/00—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements
G01L7/18—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements using liquid as the pressure-sensitive medium, e.g. liquid-column gauges
G01L7/24—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements using liquid as the pressure-sensitive medium, e.g. liquid-column gauges involving balances in the form of rings partly filled with liquid