The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly 1760 of a standard atmosphere (101325 Pa). Thus one torr is exactly 101325760 pascals (≈ 133.32 Pa).

0 Torr

There can be no such thing as negative pressure; it is always a positive pressure but lower than atmospheric pressure. Generally expressing everything in terms of pressure is preferred. Fig. 5 mBar and torr scales.

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.

Both bar and torr are the units of pressure. 1 torr = 1mm. 1 bar = 760 torr. …

A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly 133.322387415 pascals. It is denoted mmHg or mm Hg.

Low vacuum is often measured in millimeters of mercury (mmHg) or pascals (Pa) below standard atmospheric pressure. “Below atmospheric” means that the absolute pressure is equal to the current atmospheric pressure. In other words, most low vacuum gauges that read, for example 50.79 Torr.

MmHg means millimetres of mercury (Hg = mercury) and is used in EU member states and Switzerland to measure the pressure of body fluids, such as eg blood pressure. It goes back to a time when pressure was measured by means of a mercury column.

Practically, it is impossible to make a perfect vacuum. A perfect vacuum is defined as a region in space without any particles. The problem is that to maintain a vacuum in a region you have to shield it from the environment. It is not difficult to make a container that would prevent atoms from entering the region.