What does negative gauge pressure measure?

Negative gauge pressure measures vacuum pressure. Gauge pressure is defined as the pressure relative to the atmospheric pressure. When gauge pressure is negative, it indicates that the pressure in a system is lower than the atmospheric pressure. This is typically encountered in vacuum systems where the pressure is decreased to below atmospheric levels.

In vacuum applications, the readings are often expressed in negative terms to indicate how much lower than atmospheric the internal pressure is. For example, a negative gauge pressure of -10 psi means that the pressure is 10 psi below atmospheric pressure. Understanding this concept is crucial in various industrial applications where maintaining the proper vacuum levels is necessary for processes such as chemical reactions, material handling, and equipment efficiency.

In contrast, atmospheric pressure is the baseline pressure at sea level and does not apply when talking about negative figures, while absolute pressure measures the total pressure including atmospheric pressure, and fluid pressure generally refers to the pressure exerted by fluids in a system without regard to atmospheric conditions.