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Vented Gauge Reference Pressure (VG)

The most used pressure reference is gauge pressure which is signified by a (g) after the pressure unit (e.g. 30 psi g), and means that the pressure measured is the total pressure minus atmospheric pressure. There are two types of gauge reference pressure which are called vented gauge (vg or g) and sealed gauge (sg).


A vented gauge pressure transmitter for example allows the outside air pressure to be exposed to the negative side of the pressure sensing diaphragm, via a vented cable or a hole on the side of the device, so that it always measures the pressure referred to the ambient barometric pressure.


Thus a vented gauge reference pressure sensor should always read zero pressure when the process pressure connection is held open to the air. This is particularly useful in low pressure ranges where output is significantly affected by atmospheric temperature changes.

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