What instrument is typically used to measure gas pressure?

The instrument that is typically used to measure gas pressure is a manometer. A manometer consists of a U-shaped tube filled with a liquid, usually mercury or water, allowing for the measurement of pressure by observing the height difference between the two columns of liquid. It provides a direct reading of the pressure exerted by the gas in question.

While a pressure gauge is also commonly used for measuring gas pressure, particularly in industrial applications, it typically operates with a spring mechanism or diaphragm and is often calibrated for specific units (such as psi or Pa). However, manometers are fundamentally designed for measuring differential pressure and can be more sensitive and precise in certain applications.

Thermometers and barometers serve different functions; thermometers measure temperature and barometers measure atmospheric pressure, respectively. Thus, in the context of measuring gas pressure, the manometer is the most suitable and direct answer.