Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

What are the key differences between Gauge pressure and absolute pressure?

Are there any other forms of pressure?

share|improve this question

closed as off topic by Sklivvz, Manishearth Dec 22 '12 at 21:55

Questions on Physics Stack Exchange are expected to relate to physics within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.If this question can be reworded to fit the rules in the help center, please edit the question.

6 Answers 6

up vote 6 down vote accepted

just wiki it. Anyways I will give you a oneliner from wiki itself-

  • Absolute pressure is zero-referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure.

  • Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. Negative signs are usually omitted.

  • Differential pressure is the difference in pressure between two points.

share|improve this answer
    
negative gauge pressure (w/o the sign) is called vacuum pressure. –  mythealias Nov 16 '12 at 13:47
    
Haha. –  Dimensio1n0 Aug 29 '13 at 15:46

Assuming you are in air at sea level and you have an open container the pressure inside and outside will be the same - so a pressure gauge will read zero. That's gauge pressure PSIG

But there is 1 atmosphere of pressure inside the container - so 1atm of absolute pressure.

Now pump the air out of the container to give a vacuum, you have zero absolute pressure and -1 atmosphere of gauge pressure. Although negative gauge pressures are rarely used as they are confusing

share|improve this answer

It's just a matter of defining your 'zero point'.

In a real, actual gauge, pressure is measured relative to the atmospheric pressure. If there was 1 atmosphere of pressure inside a container (so it's the same pressure inside the container as it is outside it), the gauge will not read 1 atm, but rather 0 atm, as the pressure inside the container would just be the same as the pressure outside. Relative to the outside world there would be no pressure in the container. This is gauge pressure.

Absolute pressure is technically what we think of when we say pressure - the force that the gas is applying per unit area of the container.

If the gas is applying 101,300 Newtons per square meter, then the absolute pressure would be 101.3 kPa. On the other hand, the gauge pressure would be 0 kPa, as 101.3 kPa also happens to be the pressure of the atmosphere outside the container.

share|improve this answer

absolute pressure= pressure thats actually inside the vessel on which a gauge is fitted.

gauge pressure= pressure shown by gauge which will be <<1 atm>> lesser than actual pressure as atmosphere exerts 1 atm pressure on the gauge.

vacuum pressure= pressure less than atmospheric pressure.

share|improve this answer

the pressure which is measured above atmospheric pressure is called gauge pressure. the pressure which is measured above vaccum is called-absolute pressure.

share|improve this answer
2  
There's nothing new in here, could you possibly elaborate so that it has info not in the other answers? –  Manishearth Dec 2 '12 at 2:04
    
This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient reputation you will be able to comment on any post. –  Sklivvz Dec 9 '12 at 12:01

Pressure above atmospheric pressure is gauge pressure. If atmospheric pressure is 1 then gauge pressure will be 0. Vacuum pressure is pressure less than 1 atm. absolute pressure=gauge pressure+atmospheric pressure while pressure absolute=atmospheric-vacuum pressure.

share|improve this answer
1  
This answer can be improved a lot by using proper interpunction and spelling for better readibility. Also, I think there is not a lot different with the accepted answer? –  Bernhard Nov 4 '12 at 10:37

Not the answer you're looking for? Browse other questions tagged or ask your own question.