Again and again, we are asked the question concerning the difference between a complete pressure measurement and a gauge pressure measurement. To answer this question it can help to look at the definition of gauge pressure and absolute pressure. The difference between the two measurements is then explained relatively simply and thus also the decision 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. Brazen is denoted with the subscript ?abs?: Pabs.
Definition of gauge pressure
The gauge pressure means 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 the two measurements is relatively easily clarified: in a gauge pressure measurement, it is usually the difference from the current ambient pressure that is measured. However, this pressure changes with the elements and the height above sea level. An absolute pressure measurement measures the difference from the perfect or absolute vacuum. That is why this measurement is independent of environmental influences such as weather or altitude. Which measurement is currently the right one?
In Trapped , both measurements could be differentiated the following: normally, the measuring task is to determine the gauge pressure. Because of this , this kind of sensor is most widely used. However, if a gauge pressure sensor can be used in an application where the actual measuring task is to measure the absolute pressure, the following 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)
With regards to the measuring range, these errors could be substantial (e.g. in pneumatics at a measuring range of 1 bar) or negligible (in hydraulics at 400 bar).
Note
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