Again and again, we have been asked the question about the difference between an absolute 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 really a pressure that is relative to the zero pressure in the empty, air-free space of the universe. ไดอะแฟรม ซีล may be the ideal or absolute vacuum. It is denoted with the subscript ?abs?: Pabs.
Definition of gauge pressure
The gauge pressure means 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 will always be the difference from the existing ambient pressure that is measured. However, this pressure changes with the weather and the height above sea level. A complete pressure measurement measures the difference from the perfect or absolute vacuum. This is exactly why this measurement is independent of environmental influences such as for example weather or altitude. Which measurement is currently the right one?
In practice, both measurements can be differentiated the following: generally, the measuring task is to determine the gauge pressure. That is why this kind of sensor is hottest. However, in case a gauge pressure sensor can be used in an application where the actual measuring task is to gauge the absolute pressure, the next additional errors must be expected:
+/- 30 mbar due to changes in weather
around 200 mbar when changing the location (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 selection of 1 bar) or negligible (in hydraulics at 400 bar).
Note
In case you are uncertain whether your measuring task needs an absolute pressure or gauge pressure measurement, simply contact us ? we?ll be glad to assist you.