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Pa<br />
bar<br />
mbar<br />
μbar<br />
Torr<br />
micron<br />
atm<br />
at<br />
mm WC<br />
psi<br />
psf<br />
www.pfeiffer-vacuum.net<br />
1<br />
Pa = N / m 2<br />
1 . 10 5<br />
100<br />
0.1<br />
1.33 . 10 2<br />
0.133<br />
1.01 . 10 5<br />
9.81 . 10 4<br />
9.81<br />
6.89 . 10 3<br />
47.8<br />
The pressure range of vacuum comprises the interval of 0 – 1 bar. A distinction is made<br />
between the following pressure ranges:<br />
Table 1.2: Pressure ranges / Molecular number density<br />
Pressure Range<br />
Low vacuum<br />
Medium vacuum<br />
High vacuum<br />
Ultra high vacuum<br />
Pressure / mbar<br />
10 3 – 10 0<br />
10 0 - 3 – 10<br />
10 - 3 - 7 – 10<br />
10 - 7 - 12 – 10<br />
Molecular Number<br />
Density / cm -3<br />
2.65 . 1019 – 2.65 . 10 16<br />
2.65 . 1016 – 2.65 . 10 13<br />
2.65 . 1013 – 2.65 . 10 9<br />
2.65 . 109 – 2.65 . 10 4<br />
In accordance with Formula 1-3 for pressure definition, the SI unit Pa = N / m² will be used<br />
for this purpose. Also customary in actual practice are the units of pressure shown in the<br />
conversion table below. It is very customary to use mbar as a unit of pressure.<br />
Table 1.3: Conversion table for units of pressure<br />
bar<br />
1 . - 5 10<br />
1<br />
1 . - 3 10<br />
1 . - 6 10<br />
1.33 . - 3 10<br />
1.33 . - 6 10<br />
1.013<br />
0.981<br />
9.81 . - 5 10<br />
6.89 . - 2 10<br />
4.78 . - 4 10<br />
mbar<br />
1 . - 2 10<br />
1 . 10 3<br />
1<br />
1 . - 3 10<br />
1.33<br />
1.33 . - 3 10<br />
1,013<br />
981<br />
9.81 . - 2 10<br />
68.9<br />
0.478<br />
10<br />
μbar = dyn / cm 2<br />
1 . 10 6<br />
1,000<br />
1<br />
1,330<br />
1.33<br />
1.01 . 10 6<br />
9.81 . 10 5<br />
98.1<br />
6.89 . 10 4<br />
478<br />
Torr = mm Hg<br />
7.5 . - 3 10<br />
750<br />
0.75<br />
7.5 . - 4 10<br />
1<br />
1 . - 3 10<br />
760<br />
735.6<br />
7.36 . - 2 10<br />
51.71<br />
0.359<br />
7.5<br />
micron μ = mTorr<br />
7.5 . 10 5<br />
750<br />
0.75<br />
1,000<br />
1<br />
7.6 . 10 5<br />
7.36 . 10 5<br />
73.6<br />
5.17 . 10 4<br />
359<br />
atm<br />
9.87 . - 6 10<br />
0.987<br />
9.87 . - 4 10<br />
9.87 . - 7 10<br />
1.32 . - 3 10<br />
1.32 . - 6 10<br />
1<br />
0.968<br />
9.68 . - 5 10<br />
6.8 . - 2 10<br />
4.72 . - 4 10<br />
at<br />
1.02 . - 5 10<br />
1.02<br />
1.02 . - 3 10<br />
1.02 . - 6 10<br />
1.36 . - 3 10<br />
1.36 . - 6 10<br />
1.03<br />
1<br />
1 . - 4 10<br />
7.02 . - 2 10<br />
4.87 . - 4 10<br />
mm WS<br />
0.102<br />
1.02 . 10 4<br />
10.2<br />
1.02 . - 2 10<br />
13.6<br />
1.36 . - 2 10<br />
1.03 . 10 4<br />
1 . - 4 10<br />
1<br />
702<br />
4.87<br />
psi = lbf / inch 2<br />
1.45 . - 4 10<br />
14.5<br />
1.45 . - 2 10<br />
1.45 . - 5 10<br />
1.93 . - 2 10<br />
1.93 . - 5 10<br />
14.7<br />
14.2<br />
1.42 . - 3 10<br />
1<br />
6.94 . - 3 10<br />
psf = lbf / ft 2<br />
2.09 . - 2 10<br />
2.09 . 10 3<br />
2.09<br />
2.09 . - 3 10<br />
2.78<br />
2.78 . - 3 10<br />
2.12 . 10 3<br />
2.04 . 10 3<br />
0.204<br />
144<br />
1<br />
Page 11<br />
<strong>Vacuum</strong><br />
<strong>Technology</strong>
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