Absolute Pressure Explanation

Absolute pressure is one which is measured relative to a perfect vacuum.

A good example of a pressure which is measured with an absolute reference is atmospheric or barometric pressure. This pressure is always measured with reference to absolute vacuum.

In order to produce an absolute pressure sensing instrument the manufacturer will seal a high vacuum behind the sensing diaphragm so that the total pressure can be measured on the positive side of the diaphragm.

Therefore if you leave open the pressure connection of an absolute pressure sensor to ambient air pressure it will measure the barometric pressure.

Absolute pressure is measured in many applications where the changes in atmospheric pressure have no influence on the measurements.

For example when leak testing a solid walled vessel over a long period of time the total pressure inside should remain constant independent of the changing atmospheric pressure outside the vessel. Therefore a pressure sensor or instrument with an absolute pressure reference would be the most appropriate choice for leak testing purposes.

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Site Last Updated: 12/05/08

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