Howdy Jens-
If you've got any kind of spark coil, you don't need a vacuum
gauge. The color of the discharge in the gas remaining in the tube
will tell you the vacuum.
You'll really need a 2-stage pump to attain enough vacuum (i've been
using an old Welch for 15 years)..
Once the pump has gotten to the maximum ( about .01 torr) , there
will be no glow in the tube at all- just a vague blue from the glass.
This is called 'blackout'- anything else ( a higher pressure) is
just not enough.
I've made 95% of my bulbs and tubes without any kind of vacuum
gauge, except this method.
A manometer with the oil from your vacuum pump will work fine- you
won't need mercury. (except to add to the nixies later to prevent
sputtering)
To really get the tubes to last 10,000 hours or more, you'll need
to 'bake' them. That is, to run your vacuum manifold partially under/
into a kiln..
This video will give you some ideas/info.
http://www.youtube.com/watch?v=8n4WVRKkmww
Cheers-
-Dylan
On Jan 14, 3:23 am, jb-electronics <webmas...@jb-electronics.de>
wrote:
> Hi folks,
>
> as you know, I am currently trying to build Nixie tubes. I am making
> some progress, but I still need to figure out the vacuum part. Here is
> where I am so far:
>
> I use a reasonably priced (100EUR) 1-stage rotary vane pump that has a
> stated final pressure of 0.05mbar. Realistically, let's say it will end
> up at 1mbar. Now I have a three-way valve where one end is connected to
> the vacuum pump and a vacuum meter, the other one to my glass bulb (i.e.
> the Nixie tube in sp ), and the third to my Penning mixture (2% Ar in
> Ne, 1bar).
>
> I evacuate the bulb as far as possible (to about 1mbar I guess) and then
> wash it with my Penning mixture for some time (i.e. leave the vacuum
> pump running while feeding my Penning mixture to the bulb. After some
> time (what time exactly? 10s or 1 minute?) I disconnect the vacuum pump
> and feed some more Penning mixture to the glass bulb until the final
> pressure of about 30 Torr (i.e. 40mbar) is reached.
>
> Then I heat the glass bulb at the pump port and disconnect it from the
> system.
>
> -----
>
> So those are my first ideas, my questions are:
>
> 1) What could I use as a vacuum gauge? I need to have a resolution of
> about .1mbar, and a range of 1bar down to 1mbar or so. Does anyone know
> where to buy those at a reasonable price?
>
> 2) The vacuum pump I am considering to purchase is a pump that is used
> in refrigeration technique. Is it essential to use a 2-stage pump? I
> have no experiences in this area, that is why I ask. I just assume that
> with washing the tube I can make up for some of it.
>
> 3) Any comments? Suggestions?
>
> Thanks for your time,
> and may the glow be with you,
> Jens
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