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 helps 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 appropriate measurement.
Definition of absolute pressure
Absolute pressure is a pressure that is in accordance with 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.
pressure gauge น้ำมัน 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 the two measurements is relatively easily clarified: in a gauge pressure measurement, it will always be the difference from the existing ambient pressure that’s measured. However, this pressure changes with the elements and the height above sea level. An absolute pressure measurement measures the difference from the ideal 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, the two measurements could be differentiated as follows: usually, the measuring task is to determine the gauge pressure. This is why this sort of sensor is hottest. However, if a gauge pressure sensor can be used in an application where the actual measuring task is to gauge the absolute pressure, the following additional errors must be expected:
+/- 30 mbar due to changes in weather
around 200 mbar when changing the positioning (e.g. from sea level to 2,000 m)
According 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
Should you be uncertain whether your measuring task needs an absolute pressure or gauge pressure measurement, simply contact us ? we?ll be glad to work with you.