Pressure Modes

Absolute Pressure

Pressure that is measured relative to (referenced to) absolute zero pressure.

Gauge Pressure

Pressure that is measured relative to (referenced to) atmospheric pressure.

Barometric Pressure

An absolute pressure that measures atmospheric pressure.

Vacuum Pressure

A gauge pressure that is expressed as a positive value below atmospheric pressure. Example: 29 inches of mercury vacuum.

Bidirectional Pressure

A gauge pressure with a span below and above atmospheric pressure.  Example: -15 to +15 psi, -10 to 100 psi etc.

Sealed Gauge Pressure

A pressure that is referenced to a fixed sealed reference, usually standard atmospheric pressure.

Differential Pressure

Pressure that represents the difference between two arbitrary pressures