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UNITS FOR VACUUM MEASUREMENT

According to SI (abbreviation from French Le Système. International d'Unités), the official unit for measurement of vacuum gas pressure is pascal (symbol: Pa). Other commonly used pressure units for stating the vacuum gas pressure are torr, micron and mbar.

Use of vacuum pressure units have regional, applicational and industry preference: torr is commonly used in the United States, while mbar the preferred unit of measure in Europe. Pascal is commonly used in Asia.

Torr vacuum pressure unit

One torr (symbol: Torr) is approximately equal to one millimeter of mercury in a manometer at 0 °C. The unit micron can be found in the vacuum industry and its derived from the unit torr where one milliTorr is equal to one micron. 

The unit torr is named after the Italian physicist Evangelista Torricelli and the unit torr is not an SI unit.

mbar vacuum pressure unit

The European vacuum industry prefers the metric millibar (symbol: mbar) unit for vacuum pressure. Millibar is derived from the bar unit and the two units were originally introduced by the Norwegian meteorologist Vilhelm Bjerknes. One mbar is equal to 100 Pa or one hPa.

In meteorology mbar was previously the preferred unit for atmospheric pressure level, but today the SI unit Hectopascal is the official unit for meteorology science and weather forecasts.

Pa vacuum pressure unit

Pascal is the official SI unit for vacuum pressure and consequently widely used in physical sciences. One pascal is the force of one Newton per square meter acting perpendicular on a surface. Pascal is named after the French mathematician, physicist and inventor Blaise Pascal.