Measuring Pressure

From Chemepedia

5 Types of Pressure

Barometric Pressure
This is the absolute pressure of the current atmospheric pressure at a specific location. The typical barometric pressure is around 101.325 Pa which is also equal to 1 atm and 14.696 psi absolute.

Vacuum Pressure
Vacuum pressure is a gauge pressure with which is below the current atmospheric pressure and is often indicated as a negative gauge pressure. The term vacuum simply refers to a pressure that is below atmospheric pressure.

Gauge Pressure
Gauge pressure is always compared to the current atmospheric pressure. Therefore, if where the pressure is being measured is exposed to the atmosphere, the gauge will read 0.

Absolute Pressure
This is the pressure that is compared to an absolute vacuum. An absolute vacuum occurs when the vacuum does not contain any air molecules, resulting in there being no pressure. Vacuum pressure is also always a positive value, hence it being an absolute value.

Differential Pressure
This is the difference between two different pressures of which can be positive, negative, or a value of 0.