Pressure gauge, instrument for measuring the condition of a fluid (liquid or gas) that is specified by the force that the fluid would exert, when at rest, on a unit area, such as pounds per square inch or newtons per square centimetre. Pressure gauge.
A vacuum gauge is a pressure gauge used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (e.g.: â15 psig or â760 mmHg equals total vacuum).
If it measures pressure exerted upon a column of liquid, it is called a manostat, or manometer. Atmospheric pressure is often measured in millibars. Thus, the gauge used to measure atmospheric pressure is a form of manometer called a barometer.