真空可分为4级:
粗真空 (rv): 1000 - 1 mbar
中真空 (mv): 1 - 10-3 mbar
高真空 (hv): < 10-3 - 10-7 mbar
超高真空 (uhv): < 10-7 mbar
真空的度量单位:
国际制单位: mbar pa 1 mbar = 100 pa = 1 hpa
其它单位: n/m² 1 n/m² = 1 pa = 0,01 mbar
torr 1 torr = 1,33 mbar
mmhg 1 mmhg = 1 torr = 1,33 mbar
atmosphere 1 atm = 1013 mbar
micron 1 μ = 0,001 torr = 0,00133 mbar
psi 1 psi = 0,069 bar
% vacuum 1 % vacuum = 10 mbar