What are the Vacuum Measurement Units?

vacuum measurement units

If you find yourself bewildered by the different units used in vacuum measurement when selecting a vacuum pump, fear not! Let’s clarify the most important vacuum measurement units, making it easier for you to understand their significance and make an informed choice.

In the realm of vacuum industry, several units are widely employed for measuring pressure, including torr, mbar (millibar), pascal, and micron. These vacuum measurement units exhibit regional preferences: torr finds common usage in America, mbar is the favored unit in Europe, while pascal enjoys popularity in Asia.

‣ Torr

Tracing its origins back to 1643, the Italian physicist Evangelista Torricelli introduced the maiden barometer – a glass tube replete with mercury. Torricelli’s experimentation with mercury, symbolized chemically as Hg, aimed to gauge the presence of air. As a tribute to Torricelli, the millimeter of mercury underwent a rechristening to become the Torr in the 1970s. Notably, one millimeter of Hg roughly corresponds to one Torr.

‣ Mbar

Across Europe, metric units predominantly govern measurements. The millibar, denoted as mbar, reigns as the prevailing vacuum measurement unit. Vilhelm Bjerknes, a Norwegian meteorologist, introduced the millibar as an offshoot of the bar unit. One mbar equates to 0.75 Torr or 100 pascals (Pa).

‣ Pascal

Bestowed with the name of the distinguished French mathematician and physicist Blaise Pascal, the pascal unit (symbol: Pa) was ushered in. In 1646, Pascal replicated Torricelli’s experiment on an elevated terrain, unveiling distinct fluctuations in the height of the mercury column. Approximately, one Torr translates to 133 pascals.

‣ Micron

Within certain vacuum industries, the micron unit holds sway. The millimeter of mercury was fractionated into a thousand minuscule parts, termed as microns. A micron signifies one-millionth of a meter. One millimeter of Hg or one Torr corresponds to 1,000 microns. Similarly, one pascal is tantamount to 7.5 microns.

Understanding vacuum levels

When encountering descriptions like “deep vacuum of 150 Micron,” it’s essential to pay attention and understand the corresponding values. In this case, it equals 20 Pa or 0.2 mbar, classified as a rough vacuum level. Such a vacuum can be achieved by using a single-stage pump. However, in some situations, you might come across 2 Pa instead of 20 Pa. As an end user, you don’t necessarily need to grasp the intricacies between partial and total ultimate pressure. Just remember that reading 2 Pa can be misleading, as you don’t truly have it. The figure for partial ultimate pressure is significantly smaller but doesn’t hold practical significance.

Similarly, the level of a dual-stage pump can be considered as a medium vacuum, while the real vacuum it provides is 2 Pa or 0.02 mbar, which is equivalent to 15 Micron. 

By understanding these values, you can better assess the performance of vacuum pumps and make informed decisions.

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