Re: health question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FIFTYGUY@xxxxxxx 

In a message dated 2/4/06 6:14:42 PM Eastern Standard Time, 
tesla@xxxxxxxxxx writes:

>Bottom line though is that the 25"/Hg that your vacuum pump can attain is
>only slightly below ambient atmospheric pressure.

    Most vacuum gauges I have seen read "backwards", i.e., in units 
of "vacuum", not "pressure". "Zero" on a vacuum gauge is ambient 
atomspheric, and "30" (or thereabouts) is full vacuum.
    OTOH, "Torr" gauges tend to read as "zero" as perfect vacuum.
    A bit confusing, because folks who want to achieve a good vacuum 
might not only want "more than 29 inches of vacuum", but also want 
"less than two Torr [of pressure]" (for example).
    My experience has been with industrial vacuum packaging, where a 
final vacuum of 1 Torr was (thankfully) pretty darn good, especially 
on a high-speed production line. It's hard to find vacuum leaks 
(nothing blows out or leaks out to show the leak), and even the 
tiniest leak in a big system can cost you several Torr.

-Phil LaBudde