Re: Voltagee measurement

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Matthew Smith by way of Terry Fritz <twftesla-at-qwest-dot-net>" <matt-at-kbc-dot-net.au>

Hi

Someone stop me if I'm making a daft suggestion but: how about series
resistance and a voltmeter?  

Example (not yours - easy figures!):  If we assume a maximum voltage to
be measured of 10kV and your DMM is rated up 1kV AC, we can use your
meter provided that we divide the voltage to be measured by 10.  We
connect 10 x 50MOhm resistors in series, giving an overall resistance of
500MOhm.  (Determine resistor power rating by V^2/R =
100,000,000/50,000,000 = 2W; higher powered resistors would probably be
better because their chunkiness would reduce the risk of flashover) 
With ten series resistors of equal value, the voltage across each will
be one tenth of the voltage across the whole string.  So, whatever you
read on your DMM should be multiplied by ten to get the input voltage.

Although I might try this on an NST or the like, I don't think that I'd
fancy hooking this up on the secondary of a Telsa coil; there
could come a point when the resistors would flash over, unless they are
specifically designed for EHT use, or are in an oil bath, etc.

Cheers

Matthew


Tesla list wrote:
> 
> Original poster: "Kamil Kompa by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<tcmail-at-poczta.fm>
> 
> Hi !
> 
> I have a trouble with a transformer. I don't know it's parameters, so I
> want to measure voltage
> of the transformer (i think 5 to 20 kV). How can I do this?
> I found that spark apears between the electrodes connected to the
> transformer when the gap is about 15mm (between sharp nails) and about 6mm
> gap is required when electrotes are two spheres (no sharp edges).
> I know that breakdown in air is about 30V per 0.025mm, but which distance
> schould I use for accountings (6mm or 15mm)?
> I also noticed that when nails aore little wider than 15mm on the top of
> one of them appears corona. (sparks striking to the air in the direction of
> the other nail). There is no corona when I use spheres separated with more
> than 6mm of air.
> Could you tell me something about the output voltage of my transformer
> having this data?
> Thanks for all answers.
> 
> Kamil Kompa