Difference between gauge pressure and absolute pressure measurement

Again and again, we are asked the question about the difference between an absolute pressure measurement and a gauge pressure measurement. To answer this question it helps to look at this is of gauge pressure and absolute pressure. The difference between the two measurements is then explained relatively simply and thus also the choice of the correct measurement.
Definition of absolute pressure
Absolute pressure is a pressure that is relative to the zero pressure in the empty, air-free space of the universe. This reference pressure is the ideal or absolute vacuum. Popular is denoted with the subscript ?abs?: Pabs.
Definition of gauge pressure
The gauge pressure is defined as the difference between an absolute pressure (Pabs) and the prevailing atmospheric pressure (Pamb). It 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 always the difference from the current ambient pressure that is measured. However, this pressure changes with the weather and the height above sea level. An absolute pressure measurement measures the difference from the ideal or absolute vacuum. This is exactly why this measurement is independent of environmental influences such as weather or altitude. Which measurement is currently the right one?
In practice, both measurements could be differentiated the following: typically, the measuring task is to determine the gauge pressure. This is exactly why this sort of sensor is hottest. However, if a gauge pressure sensor can be used in an application where the actual measuring task would be to measure the absolute pressure, the next additional errors must be expected:
+/- 30 mbar due to changes in weather
up to 200 mbar when changing the positioning (e.g. from sea level to 2,000 m)
Based on the measuring range, these errors could 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 an absolute pressure or gauge pressure measurement, simply contact us ? we?ll be glad to work with you.

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