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 can help to look at the definition of gauge pressure and absolute pressure. Mesmerizing between the two measurements is then explained relatively simply and therefore also the decision of the appropriate measurement.
Definition 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 may be 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 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, this pressure changes with the weather and the height above sea level. A complete pressure measurement measures the difference from the ideal or absolute vacuum. This is the reason this measurement is independent of environmental influences such as for example weather or altitude. Which Supported is now the right one?
In practice, the two measurements could be differentiated the following: typically, the measuring task would be to determine the gauge pressure. Because of this , this type of sensor is most widely used. However, if 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 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 can 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 work with you.g