The atmospheric pressure is the standard pressure at sea level and is 101.325 kPa. It is more common to express pressure in bar or psi. Vacuum pressure (Pvac) is expressed in a negative value with respect to the atmospheric pressure.
How does a vacuum pressure gauge work?
Most pressure gauges make use of a bended tube. This tube is called a Bourdon tube. The tube deflects slightly under a pressure differential between the medium and the atmosphere. The tube deflection is converted via a mechanism to a needle position on the dial.
This design principle is in fact the same for normal and vacuum pressure gauges. If you want to learn more about the design principles, you can read our full article about pressure gauges.
Most gauges are available with bottom connection or back connection (panel mount). Gauges are available with plastic casing or stainless steel. Plastic is cheaper and corrosion-resistant, but is more sensitive to impact. They can be analog gauges like a bourdon tube pressure gauge or digital pressure gauges.
Pressure gauges for absolute pressure
It is important to note that vacuum pressure gauges and absolute pressure gauges are not the same thing. Normal vacuum pressure gauges measure against the atmospheric pressure, while absolute pressure gauges measure with reference to the absolute zero point. In order to do so, these gauges contain a reference chamber with a near full vacuum. These are high end products that are for example used to monitor vacuum pumps or vacuum packaging machines.
For other pressure gauges, see our bellows pressure gauge or our diaphragm pressure gauge articles. For tips on selecting the right pressure gauge for your application read our pressure gauge selection guide.