Again and again, digital pressure gauge are asked the question concerning the difference between an absolute pressure measurement and a gauge pressure measurement. To answer this question it can help to look at this is of gauge pressure and absolute pressure. The difference between your two measurements is then explained relatively simply and thus also the choice of the correct measurement.
Definition of absolute pressure
Absolute pressure is really 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.
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 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 elements and the height above sea level. An absolute pressure measurement measures the difference from the ideal or absolute vacuum. diaphragm seal is the reason this measurement is independent of environmental influences such as weather or altitude. Which measurement is currently the right one?
In practice, the two measurements can be differentiated the following: typically, the measuring task is to determine the gauge pressure. For this reason this type of sensor is hottest. However, in case a gauge pressure sensor is used in an application in which the actual measuring task is to gauge the absolute pressure, the following additional errors should be expected:
+/- 30 mbar due to changes in weather
up to 200 mbar when changing the location (e.g. from sea level to 2,000 m)
Depending on 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
When you are uncertain whether your measuring task needs a complete pressure or gauge pressure measurement, simply contact us ? we?ll be glad to assist you.