What is vacuum?
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Vacuum- literally
translated, the word describes the volume from which all the air has
been totally removed. However, so far nobody has succeeded in
achieving such a condition. Scientifically the highest vacuum yet
reached is in the range of 10-14 torr. This result has
been achieved during a test by IBM Thomas J. Watson Research Center,
New York, USA, October 1976, in a cryogene system where the
temperature dropped to minus 269 °C. Even at this low pressure
thousands of gas molecules were detected per cm3. Also
far out in space the presence of gas has been measured. Consequently
the word vacuum is used to define pressure below normal atmospheric
pressure, which is usually denoted as 760 mmHg or 1013 mbar. By
normal air pressure the molecular density is 1023 per cm3
air.
Conversion Chart between
the unit measures
| Unit |
N·m-2,
Pa |
mbar |
bar |
Torr |
| 1 N·m-2 (= 1 Pa) |
1 |
1·10-2 |
1·10-5 |
7,5·10-3 |
| 1 mbar |
100 |
1 |
1·10-3 |
0,75 |
| 1 bar |
1·105 |
1·103 |
1 |
750 |
| 1 Torr |
133 |
1,33 |
1·33·10-3 |
1 |
A vacuum pump is used to create vacuum. During the
removal of air there will gradually be less molecules to collide
with the walls of the vacuum chamber, thus giving lower pressure.
Vacuum has many practical applications from which we all benefit in
everyday life. The vacuum cleaner works by means of air pressure
pushing air molecules into the machine through a vacuum hose. Dust
and dirt are being entrained with the air.
Very good insulation is achieved with vacuum, therefore, there is
vacuum between the inner and outer wall of a thermos flask. Vacuum
is produced by means of a vacuum source. Vacuum sources are
pneumatic ejectors, steam ejectors, and vacuum pumps.
Vacuum can be used in transportation systems, e.g.
pneumatic transportation, where the vacuum source is a roots blower.
Vacuum can also be used to hold and lift materials with the use of
vacuum cups.
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Conversion of
pressure between 0 and 1013 mbar
| mbar |
N·m-2 (Pa) |
Torr |
bar |
atm |
at |
%Vak. |
mm WS |
| 1013 |
101300 |
760,00 |
1,01 |
1,0 |
1,03 |
0 |
1,03 · 104 |
| 1000 |
100000 |
750,00 |
1,00 |
0,987 |
1,02 |
1,3 |
1,02 · 104 |
| 981 |
98100 |
735,75 |
0,981 |
0,968 |
1 |
3,2 |
104 |
| 900 |
90000 |
675,00 |
0,90 |
0,888 |
0,918 |
11,1 |
9177 |
| 800 |
80000 |
600,00 |
0,80 |
0,789 |
0,816 |
21,0 |
8157 |
| 700 |
70000 |
525,00 |
0,70 |
0,691 |
0,714 |
30,9 |
7137 |
| 600 |
60000 |
450,00 |
0,60 |
0,592 |
0,612 |
40,8 |
6118 |
| 500 |
50000 |
375,00 |
0,50 |
0,494 |
0,510 |
50,6 |
5098 |
| 400 |
40000 |
300,00 |
0,40 |
0,395 |
0,408 |
60,5 |
4078 |
| 300 |
30000 |
225,00 |
0,30 |
0,296 |
0,306 |
70,4 |
3059 |
| 200 |
20000 |
150,00 |
0,20 |
0,197 |
0,204 |
80,2 |
2039 |
| 100 |
10000 |
75,00 |
0,10 |
0,099 |
0,102 |
90,1 |
1019 |
| 90 |
9000 |
67,50 |
0,09 |
0,089 |
0,092 |
91,1 |
918 |
| 80 |
8000 |
60,00 |
0,08 |
0,079 |
0,082 |
92,1 |
816 |
| 70 |
7000 |
52,50 |
0,07 |
0,069 |
0,071 |
93,1 |
714 |
| 60 |
6000 |
45,00 |
0,06 |
0,059 |
0,061 |
94,1 |
612 |
| 50 |
5000 |
37,50 |
0,05 |
0,049
|
0,051 |
95,1 |
510 |
| 40 |
4000 |
30,00 |
0,04 |
0,040 |
0,041 |
96,1 |
408 |
| 30 |
3000 |
22,50 |
0,03 |
0,030 |
0,031 |
97,0 |
306 |
| 20 |
2000 |
15,00 |
0,02 |
0,020 |
0,020 |
98,0 |
204 |
| 10 |
1000 |
7,50 |
0,01 |
0,010 |
0,010 |
99,0 |
102 |
| 5 |
500 |
3,75 |
0,005 |
0,005 |
0,005 |
99,5 |
51 |
| 1 |
100 |
0,75 |
0,001 |
0,001 |
0,001 |
99,9 |
10 |
| 0,5 |
50 |
0,375 |
5 · 10-4 |
5 · 10-4 |
5 · 10-4 |
99,9 |
5 |
| 0,1 |
10 |
0,075 |
1 · 10-4 |
1 · 10-4 |
1 · 10-4 |
99,99 |
1 |
| 1 · 10-2 |
1 |
7,5 · 10-3 |
1 · 10-5 |
1 · 10-5 |
1 · 10-5 |
99,99 |
0,1 |
| 1 · 10-n |
1 · 10-(n+2) |
7,5 · 10-(n+1) |
1 · 10-(n+3) |
1 · 10-(n+3) |
1 · 10-(n+3) |
|
1 · 10-(n-1) |
| 0 |
0 |
0 |
0 |
0 |
0 |
100 |
0 |
|
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©2000-2002 Dr.-Ing.
K. Busch GmbH |
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