What instrument is typically used to measure atmospheric pressure?

The barometer is the instrument specifically designed to measure atmospheric pressure. It operates on the principle of using a column of liquid, typically mercury, or other mechanisms, to determine the weight of the atmosphere pressing down. Changes in atmospheric pressure can be detected as variations in the liquid level, which is crucial for meteorology and understanding weather patterns.

In contrast, other instruments mentioned serve different purposes. A voltmeter measures electrical potential difference, a thermometer measures temperature, and a manometer is used to measure the pressure of gases in closed systems rather than atmospheric pressure. Understanding the distinct functions of these instruments helps clarify why the barometer is the appropriate answer in this context.