Pressure Measurement. Gas pressure can be monitored directly or indirectly by the use of vacuum gauges. The output of the vacuum gauges is often used to control various aspects of PVD processing such as when to “crossover” from roughing to high vacuum pumping and when to begin thermal evaporation.
What is a vacuum Gage?
A vacuum gauge measures pressure below the atmospheric pressure. Normally the atmospheric pressure is set as zero and the vacuum pressure is given in negative values, so -1 barg (-15 psig) means complete vacuum.
Which pressure gauge can be used for vacuum measurement?
Therefore only gauge pressure ranges that include a negative pressure range will be suitable for measuring a vacuum pressure. For example a 0 to -1 bar or -15 to 0 psi gauge range will cover the entire range of vacuums, and is a popular range offered by manufacturers.