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 the definition of gauge pressure and absolute pressure. The difference between the two measurements is then explained relatively simply and therefore also the decision of the correct measurement.
Beating 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. It really 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 is denoted with the subscript ?e?: Devastating and is calculated the following: Pe = Pabs ? Pamb.
Lying between the two measurements is relatively easily clarified: in a gauge pressure measurement, it is always 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. Because of this , this measurement is independent of environmental influences such as weather or altitude. Which measurement is now the right one?
In practice, both measurements could be differentiated as follows: in most cases, the measuring task is to determine the gauge pressure. This is why this kind of sensor is hottest. However, in case a gauge pressure sensor can be used in an application in which the actual measuring task is to measure the absolute pressure, the following additional errors should be expected:
+/- 30 mbar caused by 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 could be substantial (e.g. in pneumatics at a measuring range of 1 bar) or negligible (in hydraulics at 400 bar).
Note
For anyone who is uncertain whether your measuring task needs a complete pressure or gauge pressure measurement, simply contact us ? we?ll be glad to assist you.