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Pressure Units of Measure

There are various units of pressure used widely unlike units other dimensions.  The most widely used unit of pressure is atmosphere.  It is the measure of typical air pressure on earth at average sea level.  As mentioned above since pressure is a force exerted, this force can cause displacement of a liquid in a tube and this property is used to measure pressures.  
The tubes often glass tubes which are transparent are marked and filled with liquids, which are resistant to other effects and the magnitude of pressure is measured by the displacement of these liquids caused by the force exerted.  One of these liquids is mercury and hence it is used to measure pressure at a particular place.  The instruments solder are called as manometers solder the normal atmospheric pressure can be defined at which the Hg in a column is displaced by 760 millimeter.


Units


While atmosphere is used as the unit of pressure in gas law calculation such as earlier gas law or gas constants e.t.c.  The standard SI unit for pressure is Pascal.  Pascal is the measure of force of one Newton exerted per square meter; hence it can be shown as N⁄M2


The name Pascal is in mark of the scientist called Pascal, the other units which are being used are Barr or Torr or Kilopascal.  The co-relationships between kilopascal, Torr, Barr are given as under

1 torr="0.1333" kPa
1 atm="101.325" kPa="760" mm
1 atm = 760 torr
1 Atm = 14.6959488 Psi  
1 bar =100kPa

Variation of units

Unlike other dimension like temperature which are generally only three units like Celsius or Fahrenheit or Kelvin the pressure is measured in number of units on the back of what because it facilitates the same.  The national institute of standards and technology in the United States of America has devised rules for use of units of measures of pressure.