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Re: Testing Caps




From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Thursday, November 27, 1997 1:26 AM
To: 	Tesla List
Subject: 	Re: Testing Caps

Tesla List wrote:
> 
> From:   Matthew Mills[SMTP:megavolt-at-usa-dot-net]
> Reply To:       megavolt-at-usa-dot-net
> Sent:   Wednesday, November 26, 1997 1:01 PM
> To:     Tesla List
> Subject:        Testing Caps
> 
> Hi, I'm still in the process of building my first coil.  I have aquired
> 2x 15kv 30ma neons and am starting off with saltcaps and vertically
> stacked caps, my question is,
> Is there a way to see how well the caps work without having them
> connected to a coil? (I have wound a secondary but have no primary coil
> yet.)
> 
> I have got a 15inch high by 10 inch round lidded polyethylene tub which
> I am using to test individual salt water capacitor bottles
> 
> The bottles I am testing at the moment are 1/2 gallon chemical bottles.
> The straight side is 7 inches high, they are 6 inches in diameter and
> the glass is 3.5mm thick (approx 1/8inch)
> now I tried working out the expected capacitance on paper (very hard)
> with no calculator and got around .0017µF which seems low. So 6 bottles
> would be .0102µF
> 
> Am I right?
> 
> Im wanting to see how well these work without frying my neons.
> 
> Thanks,
> 
> Matt.
> 
> PS I havent got a Capacitance meter or a multimeter yet (blew the last
> one)

Matt,

The value you calculated sounds to be in the ballpark if you assumed a
dielectric constant of about 6 for the glass. The actual k is very
dependent upon the type of glass, but for typical soda-silica glass is
in the range of about 6 to 18 depending on the percentage of Na2O to
SiO2.
"Ballpark" your design so that you can tune the primary for to handle
from at least 75% of the calculated cap value and you should be OK. If
you actually have too large a cap you can always decrease the number of
bottles or tap at fewer primary turns.

Safe cappin' to you, Matt!

-- Bert --