Pressure Instruments – Manometers

A manometer is a U-shaped tube filled with a liquid, usually mercury or water. A differential pressure will cause the column on the high-pressure side to fall and the column on the low-pressure side to rise. The value of the differential pressure equals the difference in hydrostatic head between the two columns of liquid. Manometers are used to indicate low pressures, such as furnace drafts, and to calibrate low-pressure instruments.