Absolute Pressure Pressure measured relative to high vacuum, often measured in PSIA(Pound per Square Inch, Absolute), or in Torr. Full vacuum is 0 PSIA or 0 Torr, atmosphere is about 14.7 PSIA or 760 Torr.
Barometric pressure Atmosphere pressure measured relative to high vacuum, often measured in millibars. Atmosphere is about 1013 mbar.
Differential Pressure Pressure measured relative to a reference side, often measured in PSID(Pound per Square Inch, Differential), inch of water column or in Pascal.
Gage Pressure Pressure measured relative to ambient atmosphere pressure, often measured in PSIG (Pound per Square Inch, Gage), or in Pascal.
Vacuum Pressure Pressure measured relative to ambient atmosphere pressure, often measured in PSIV (Pound per Square Inch, Vacuum). Atmosphere is 0 PSIV, full vacuum is about 14.7 PSIV.
Pressure Transducer A pressure sensing device with voltage output.
Pressure Transmitter A pressure sensing device with current output. The typical output range is 4 to 20 mA.
Accuracy Combined error of non-linearity, hysteresis and non-repeatability. Often use RSS (Root Sum of the Squares) method.
Hysteresis The maximum output difference at any pressure point, when the point was reached first by increasing pressure and then by decreasing pressure.
Non-linearity Sometimes referred to as linearity. It is the maximum deviation of the output at any pressure points comparing with a straight line.
Non-repeatability Sometimes referred to as repeatability. It is the maximum output difference at any pressure point, when the pressure is applied under the same condition.