Pressure standards

In metrological terms, pressure is a unit derived from the International System, based on mass, length and time. The SI unit of pressure is the pascal (Pa), which is the pressure generated by a force of one newton uniformly distributed over a surface area of one square metre. From this definition, we can see that the pascal is a very small unit: atmospheric pressure, with which we are very familiar, has around 100,000 pascal at sea level. The more common units, which are tending to become the kilopascal (kPa) and the megapascal (MPa), are the millibar (mbar, 1 mbar = 0.1 kPa) and the bar (bar, 1 bar = 0.1 MPa).

After a review of the various techniques used to create a static pressure standard, the methods used to disseminate the pressure unit throughout the industrial field from a few pascals to 1 GPa (or 10,000 bar) are described.

This dissemination is expressed in terms of calibration means and methods. It is approached from the angle of the calibration chain, the aim of which is to demonstrate an uninterrupted link to national and international standards. The methods described focus on the various components that enable calibration uncertainty to be propagated to uncertainty of use.