Gauge and Absolute pressure manometers

[skiprat]

Hi Guys, Here is a pic of two similar dial gauges ( or manometers if you prefer)
The reason I'm showing them is to show the difference between Absolute pressure and Gauge pressure.
Both of these gauges have a full scale of 14 Bar ( 200psi ) but look closer at the smaller one. This one reads Absolute pressure and is calibrated to show normal atmospheric pressure as Zero. (Technically this is untrue - but don't worry about it.) The big one reads Gauge pressure.
The point is, if you use the small one, you can use it for vacuuming and pressurising without fear of damaging it. Both of these are made by USG ( US Gauge ) and are really quite cheap.
If you find a good stockist of these, they will even make up one with a dial that reads from -1bar to 0bar to +6bar, which is perfect for our needs. Although this one is fine and will be fitted to my new pot in the morning

 

[stevers]

Steve, be sure and post your set up when you are done. I'd like to see what you decide on.

 

[Tea Clipper]

With respect to Skiprat, I would like to clarify a point:

Atmospheric pressure is approximately 14.7 psi; any gage that reads '0' at this point is reading the relative pressure differential and not absolute pressure. The gage on the left is called a compound gage because it can measure both pressure and vacuum. Note the scale is in pounds per square inch for readings above zero (atmosphere) and inches of mercury for pressures less than atmosphere (aka vacuum).

I'll agree with Skiprat in that a compound gage would certainly simplify paint pot setups. []

 

[skiprat]

Ron, you are perfectly correct of course, I just didn't want to complicate the issue. I tried to qualify my statement a bit though.[]
Here is a pic of a true absolute gauge. The reading with no additional external influence on it shows atmospheric pressure. If you connect this to a vac pump and achieve a good vac it will read zero. Same result as my small gauge, but just different scaling on the dial.

<br />

and here is a couple more that the company I work for gets custom made for the various gas insulated switchgear. The units of measure have been left off so as not to confuse things. If the needle is not in the green zone then the device it is monitoring is not safe to use. The one on the right is the same as the small one above but does not have the same range.

<br />