Homebrew PCBs

In a message dated 5/6/2005 1:21:48 A.M. Eastern Daylight Time,  
robert.hedan@... writes:

How can  you pull the vacuum down 2 atmospheres?  Assuming I am at  1
atmosphere, isn't 0 a vacuum?  Or did I miss something and you can a  bigger
vacuum?  Huh?  How can you go to negative  atmosphere?  I thought atmospheres
were mostly used for pressure  chambers.

I often see reference to 0-30Hg for vacuum chambers,  something about mercury
level.  I figure I'll see where the vacuum  dial sits at rest, and where it
goes as air is pumped out is the vacuum  side.

Robert
:)



Most vacuum is measured in HG which is mercury. being so heavy  you can use a 
much smaller scale! Now if I remember my old school books normal  atmosphere 
at sea level is about 15lb's per sq inch. Now 2 Ats. would be 30lbs  per sq 
inch. No go to vacuum and the same applies but in the opposite. So 30HG  vacuum 
would be 2 Ats. When I do A/C work this is the standard test we do. Draw  down 
to as close to -30 hg and cap it off. wait 1 hour and see if we have any  
leaks then charge the system.
If I did not get any of the math right I am sure someone will  jump in and 
correct it! High school was a long time ago! LOL
Just putting the mold under 1 At or -15lbs  of vacuum  will do the job you 
need to do!
 
Ray Russell
NMRA-40609
General Contractor
Norfolk &  Western Railroad
Pocahontas Division
Circa 1958
Visit The "NEW"  Pocahontas Website at:_ Click here: N  & W Pocahontas  
Division_ (http://members.aol.com/rruss45826/public_html/index.html) 
http://members.aol.com/rruss45826/public_html/index.html

OR_ Click here:  Pocahontas Home_ 
(http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm)  
For the old website!  
http://milliron.home.sprynet.com/Pocahontas/Pocahontas1.htm


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