Difference between gauge pressure and absolute pressure measurement

Again and again, we have been asked the question about the difference between a complete pressure measurement and a gauge pressure measurement. To answer this question it can help to look at this is of gauge pressure and absolute pressure. The difference between the two measurements is then explained relatively simply and therefore also the choice of the appropriate measurement.
Definition of absolute pressure
Absolute pressure is a pressure that is in accordance with the zero pressure in the empty, air-free space of the universe. This reference pressure may be the ideal or absolute vacuum. Battle is denoted with the subscript ?abs?: Pabs.
Definition of gauge pressure
The gauge pressure is defined as the difference between a complete pressure (Pabs) and the prevailing atmospheric pressure (Pamb). It really is denoted with the subscript ?e?: Pe and is calculated as follows: Pe = Pabs ? Pamb.
Absolute vs gauge pressure measurement
The difference between your two measurements is relatively easily clarified: in a gauge pressure measurement, it is usually the difference from the existing ambient pressure that’s measured. However, this pressure changes with the weather and the height above sea level. A complete pressure measurement measures the difference from the ideal or absolute vacuum. That is why this measurement is independent of environmental influences such as for example weather or altitude. Which measurement is now the right one?
In practice, both measurements can be differentiated as follows: normally, the measuring task would be to determine the gauge pressure. That is why this type of sensor is hottest. However, in case a gauge pressure sensor is used in an application in which the actual measuring task would be to measure the absolute pressure, the following additional errors should be expected:
+/- 30 mbar due to changes in weather
up to 200 mbar when changing the location (e.g. from sea level to 2,000 m)
With respect to the measuring range, these errors can be substantial (e.g. in pneumatics at a measuring selection of 1 bar) or negligible (in hydraulics at 400 bar).
Note
When you are uncertain whether your measuring task needs a complete pressure or gauge pressure measurement, simply e mail us ? we?ll be glad to work with you.

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