Which instrument measures pressures below atmospheric pressure?

A vacuum gauge is specifically designed to measure pressures that are lower than atmospheric pressure, effectively allowing for the assessment of vacuum levels in various applications. These instruments can accurately track the amount of vacuum present in a system, which is crucial in processes where maintaining a low-pressure environment is essential, such as in certain chemical reactions or in the packaging industry.

Vacuum gauges typically operate using different principles to measure pressure, such as the change in capacitance, piezoelectric effects, or mechanical displacement. Each of these methods allows for precise readings of sub-atmospheric pressures, which is critical in ensuring the appropriate conditions are maintained in processes that rely on vacuum levels.

In contrast, pressure gauges and Bourdon tubes are generally used to measure pressures above atmospheric levels. While a diaphragm can indeed be involved in pressure measurement, it does not specifically target measurements below atmospheric pressure like a vacuum gauge does.