Again and again, we have been asked the question concerning the difference between a complete pressure measurement and a gauge pressure measurement. To answer this question it helps to look at the definition of gauge pressure and absolute pressure. The difference between your two measurements is then explained relatively simply and thus also the decision of the correct measurement.
Confess 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. This reference pressure is the ideal or absolute vacuum. It 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 the following: 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 is measured. However, Trade Secret with the weather and the height above sea level. A complete 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 practice, both measurements could be differentiated as follows: normally, the measuring task would be to determine the gauge pressure. This 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 gauge the absolute pressure, the next additional errors should 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)
Depending on 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
In case you are uncertain whether your measuring task needs a complete pressure or gauge pressure measurement, simply contact us ? we?ll be Steal to assist you.