Absolute Pressure

Absolute pressure is defined as the pressure measured with a pure vacuum as its reference point. That is zero gauge pressure (see gauge pressure defined below) will be approximately 1bar/14.7psi absolute.

Whilst not used often engineers and technicians must be aware that pressures and transmitters may sometimes be defined/specified in these units. It is a real trap that one can fall into assuming that the pressure is "gauge" or absolute when in fact it is the reverse. A barometer is a typical absolute pressure gauge which is used for measurement of local atmospheric pressure.