siphon barometer

A siphon barometer is the term sometimes applied to the simplest of mercury barometers.

Siphon barometers are still produced as precision instruments.

S1200 Siphon barometer Mercury barometer in which the tube is U-shaped and has the same diameter at the levels of the two free mercury surfaces.

F0520 Float barograph Recording siphon barometer in which the movement of a float resting on the lower mercury surface is magnified and transmitted to a recording pen.

When used to measure pressures other than atmospheric pressure, a siphon barometer is sometimes called a siphon gauge; these are not siphons but follow a standard 'U'-shaped design leading to the term.