A manometer is a pressure measuring device consisting of a clear tube connected to a liquid reservoir. When pressure is applied to the reservoir, the liquid rises in the tube to a height that is proportional to the pressure applied.

The sensitivity of a manometer can be increased by placing the tube in a nearly horizontal position so that a small change in pressure produces a large, mostly horizontal movement of the liquid inside the tube. The more sensitive type of manometer is called an incline manometer.

See also Digital manometer, PEI/RP300.