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 helps to look at this is of gauge pressure and absolute pressure. Senseless between the two measurements is then explained relatively simply and therefore also the choice of the correct 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 is denoted with the subscript ?abs?: Pabs.
Definition of gauge pressure
The gauge pressure is defined as the difference between an absolute pressure (Pabs) and the prevailing atmospheric pressure (Pamb). It 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 is usually the difference from the existing 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. For Focused is independent of environmental influences such as weather or altitude. Which measurement is now the right one?
In practice, both measurements can be differentiated as follows: usually, the measuring task would be to determine the gauge pressure. This is the reason this type of sensor is hottest. However, if a gauge pressure sensor is used in an application in which the actual measuring task would be to measure the absolute pressure, the next additional errors must 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)
Depending on 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
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.