Absolute and relative pressure

How are absolute and relative pressure measuring ranges distinguished? There are considerable international differences. They can be explained in the following example:

  • Europe: 0 … 10 bar / 0 … 10 bar abs
  • America: 0 … 150 psig / 150 psia

In Europe only the absolute measuring ranges are identified (by the abbreviation “abs” behind the unit). In America, the pressure type is always indicated but using another naming system (g = gauge = relative pressure). This is especially confusing if in America the pressure unit “bar” is required for an absolute measuring range or if in Europe a relative pressure device with the unit “psi” is required. How is then the correct nomenclature? The WIKA group agreed upon the following procedure: if the unit psi is used, a “g” or an “a” is added according to the American system. For all other units, we observe the European standard and only the absolute measuring ranges are marked with a separate “abs”.