Vacuum (original) (raw)

Vacuum is defined as air pressure below atmospheric pressure.

• Convert between vacuum units - torr, mm Mercury and psi

The vacuum level is the difference in pressure between atmospheric pressure and pressure in the evacuated system:

• 0% vacuum = 760 torr = 14.7 psia = 29.92 inc mercury abs = 101.4 kPa abs
• 50% vacuum = 380 torr = 7.3 psia = 15 inc mercury abs = 50.8 kPa abs
• 99.9% vacuum = 1 torr = 0.01934 psia = 0.03937 inc mercury abs = 1.3 kPa abs

For perfect vacuum (100%) - the pressure is 0 torr, 0 psia or 0 Pa abs.

Vacuum versus Absolute Air Pressure

Example - Vacuum

If the absolute pressure is 60 kPa the vacuum according the diagram above is approximately 40 % - or approximately 450 Torr.

Vacuum Ranges

• atmospheric pressure - 760 torr
• low vacuum - 760 to 25 torr
• medium vacuum - 25 to 10-3 torr
• high vacuum - 10-3 to 10-9torr
• ultra high vacuum - 10-9to 10-12 torr
• extremely high vacuum - < 10-12 torr
• perfect vacuum - 0 torr <

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