Re: VOLTS PER MM

To: tesla-at-pupman-dot-com
Subject: Re: VOLTS PER MM
From: Jim Lux <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Fri, 18 Sep 1998 03:27:01 -0600
Approved: terryf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: Cabbott Sanders <cabbott-at-cyberis-dot-net>
> 
> Hi, I need to make a safety gap for my cap..... If i want to set it to 40
kv,
> how far apart is that????  does anyone have a volts per distance table of
> air at
> sea level?? a formula perhaps?

For uniform field gaps (i.e. between spheres much larger in diameter
than the gap) figure 30 kV/cm (or 3 kV/mm). For needle points, the
distance is typically 3-4 times bigger, but depends a LOT on the points.

I have a whole bunch more on spark gap voltages on my web page at
http://home.earthlink-dot-net/~jimlux/hv/sphgap.htm for sphere gaps....

There is actually a lot more. Take a look at 
http://home.earthlink-dot-net/~jimlux/hv/hvmain.htm

There is a discussion of breakdown voltage vs pressure (density), etc.
and also correction factors for humidity and so forth.