What is Absolute & Ultimate Vacuum?

Absolute Vacuum: Absolute vacuum refers to the complete absence of matter, including air and all other gases. In practice, achieving absolute vacuum is impossible because there will always be trace amounts of gas present. Absolute vacuum is often considered as a theoretical reference point, represented by zero pressure on the absolute pressure scale. On the practical side, the lowest achievable pressure in a vacuum system is typically expressed relative to atmospheric pressure.

 Ultimate Vacuum: Ultimate vacuum, on the other hand, is a more practical and achievable measure in vacuum systems. It is the lowest pressure that can be attained in a vacuum system under specific conditions. Ultimate vacuum is usually expressed as a pressure value relative to atmospheric pressure, such as millimeters of mercury (mmHg), torr, millibar, pascals (Pa), or other pressure units.

For example, if a vacuum system achieves an ultimate vacuum of 1 mbar, it means that the pressure in the system is equivalent to 1 mbar above absolute vacuum or nearly a complete vacuum. Ultimate vacuum is a critical specification for vacuum systems, as it indicates the system's ability to remove gases and create a low-pressure environment.

It's important to note that achieving a perfect vacuum (absolute vacuum) is practically unattainable, and ultimate vacuum values are influenced by factors like the design of the vacuum system, the quality of vacuum pumps, and the presence of any leaks or contaminants in the system.

Another important factor is that the term "ultimate vacuum" refers to the lowest pressure that a vacuum pump can achieve under ideal conditions. In practical applications, the achieved vacuum level may vary due to factors such as the type of pump, the presence of leaks, and the specific conditions of the vacuum system.

In summary, a vacuum pump with a specified ultimate vacuum of 100 mbar is capable of creating a vacuum with a pressure as low as 100 millibars, indicating effective performance for applications requiring a moderate level of vacuum.