W0UN--Signal Hill Ranch wrote:
> The leaks I have seen (maybe a dozen out of the 100+ vacuum
> caps I own) have all been due to failures in the bellows as far as
> I can tell. Don't know if it is harder on the bellows to store them
> at minimum capacitance (maximum compression of the bellows)
> or not--but I always store mine at maximum capacitance (minimum
> compression).
Interesting point, since I suppose vacuum caps are of ten stored for years.
Have
you ever checked if Jennings recommends one or the other?
>
>
> My sample is not that big--but all of mine have been either good or
> grossly bad, I just haven't seen any with a little bit of a leak--but
> guess it could happen.
>
> I recall a UV test setup (for an OSO satellite in the mid-60s) that
> consisted of a vacuum chamber with a HOLE in it to allow UV
> light to enter. With a big vacuum pump followed by an oil
> diffusion pump and then a titanium sublimation pump we were
> able to keep a pretty hard vacuum in the chamber even with
> the UV hole in it.
Interesting. I have encountered the same situation; a vacuum specimen chamber
on
the business end of a van de Graaf accelerator with a hole in it to allow a
beam of
low energy electrons to exit with minimum energy dispersion. This was pumped
with a
backed-up turbomolecular pump, and it worked. Maybe not applicable to vacuum
variables though.
Bert, VE3QAA
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|