These are the vacuum pressure ranges as measured in Torr (or fractions of 1 Torr). This is where vacuum lifting equipment and numerous other industrial applications operate. The vacuum range that can be measured in units of mercury (Hg) is called the rough vacuum range. Vacuum quality is subsequently divided into ranges that are somewhat arbitrary but primarily based on the equipment needed to achieve or measure it. What is Considered a High Vacuum?Īny negative pressure significantly below standard atmospheric pressure (760 Torr/mmHg, 29.9 inHg or 14.7 PSI) is considered a vacuum. A perfect vacuum (100%) as measured in all units including PSI, mmHg, Torr, mbar or inHg, is 0. A perfect vacuum is nevertheless an inevitable theoretical reference point that we, for example, use when determining and comparing percentages of vacuum. Outer space comes close with just a few hydrogen atoms per cubic meter, but it never reaches zero and the same is true even in the most technically advanced vacuum systems on Earth.Īlthough a small volume may contain no particles for a very brief moment, there would still be quantum phenomena such as photons.
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A perfect vacuum, which can also be referred to as full vacuum or absolute vacuum, would be a volume that contains no matter whatsoever. For example, a vacuum lifting system may operate at around 60% of a total vacuum. In the so-called rough vacuum range, from atmospheric pressure down to 25 Torr, it is also common (and more practical) to define vacuum as a percentage of a full vacuum. Pascal (as in kilopascal/kPa) is the metric standard unit for pressure and is normally the unit used in scientific and technical papers. Outside of North America, the more common units are negative millibar and/or kPa (often both are used on gauges). In North America, it’s common to use inHg in the rough vacuum range, Torr in higher vacuum ranges, and microns (thousands of a Torr) for pressures reached by backing pumps.
1 Torr equals 1 mmHg and 760 Torr/mmHg equals atmospheric pressure (1 atm). Millimeters of mercury or mmHg (Hg being mercury in the periodic table of elements) is also a basis for the Torr (after Torricelli) unit of vacuum measurement. Millimeters or inches of mercury are still used for measuring pressure in vacuum systems. Vacuum lifters are used to enable efficient and safe handling of heavy goods.