A U-tube manometer is a simple device used to measure the pressure of gases or liquids. It consists of a U-shaped tube filled with a liquid, usually water or mercury. When pressure is applied to one side of the tube, the liquid level changes, allowing for the measurement of pressure differences. These manometers are commonly used in laboratories and industrial applications to monitor pressure in systems like HVAC or gas pipelines. The height difference between the two liquid columns in the U-tube indicates the pressure difference, which can be easily read and calculated.