Leybold vacuum measurement and control solutions

With a wide range of vacuum systems and processes comes a need to measure the vacuum performance.
The instruments used for measuring the pressure within this wide range are called vacuum gauges and measure from above atmospheric pressure (~ 2000 mbar (1500 Torr)) down to 10-12 mbar/torr. No single sensor technology is capable of measuring across this range.
Therefore, a variety of different vacuum gauges are available, each with their own characteristics and ability to measure over multiple decades of vacuum. In order to widen the measurement range, it is now common to combine multiple technologies into a single gauge to reduce the connections needed in a system.

A main way to differentiate vacuum gauge types is by how they measure the gas: direct or indirect pressure measurements.

In the case of direct (or gas independent) pressure measurements, the readings obtained through the vacuum gauge are independent of the type of gas and the pressure given is always the true pressure of the system. Often relying on a mechanical deflection of a membrane, these are capable of measuring from above atmospheric pressure down to 10-4 mbar/torr. These gauge types will give you high accuracy over a short range and are typically very robust.
In the case of indirect pressure measurements, the pressure is determined as a function of a pressure dependent property of the gas (thermal conductivity, ionization probability, for example). These properties do not only depend on the pressure, but also on the molar mass of the gases. Therefore, these are also known as gas dependent. The readings usually relate to air or nitrogen as the measurement gas. For the measurement of other vapors or gases the corresponding correction factors must be applied for the true pressure of the system. These gauges are capable of pressure measurement over a much wider range (atmospheric pressure to 10 x 10-12 mbar dependent on type/combination), with the tradeoff being a lower level of accuracy.