🚀 go-pugleaf

In article <10390@inews.intel.com> bhoughto@hopi.intel.com (Blair P. Houghton) writes:
>In article <1992Apr10.085039.10688@dxcern.cern.ch> jeroen@dxcern.cern.ch (Jeroen Belleman) writes:
>>Can anyone suggest a method to measure the output voltage? I do not
>>think suitable probes exist.
>
>There isn't really an "output voltage."  The potential on
>the sphere is a function of the charge it holds and the
>capacitance between it and the grounds around the room.
>

So? Can anyone suggest a way to measure the potential of the sphere?
The capacitance of the sphere is hardly affected by any grounds around
the room. The nearest ground is about 70cm away, normally.

>>So far, I get fat sparks from a polished 4cm diameter metal pipe over
>>a little more than 10cm. The more diffuse sparks from the pipe's end
>>easily exceed 50cm. You can make you own voltage estimates from that.
>
>Drat.  I forgot the breakdown voltages for air.  The
>potential at the time of the spark is of course just the
>distance (cm) times the breakdown voltage (KV/cm).
>

No sir, it's electric field strength that gives the breakdown voltage
between two electrodes, not simply their potential difference and
distance. For a given distance, sharp electrodes will cause
breakdown for much lower potential differences than blunt ones.
Besides, the capacitance change caused by a small nearby electrode
is negligible. ('Small', that is to say, compared to the size of
the high voltage electrode.)

>As you can see, by varying the capacitance (a smooth surface
>nearby; a sharp surface at a greater distance) your generator
>can operate at different potentials.
>
>If you integrate the charging current to get the charge you
>can determine the capacitance.
>

The charging current is constant and independent of the terminal
voltage. (Excuse me, potential.) It's breakdown of the air
insulation that limits the potential. The relatively simple
geometry of the setup enables me to calculate the capacitance.
It's about 18pF. If I integrate the 9uA charging current over
the time it takes to get the first discharge (about 1 second),
that gives me a peak potential of 500kV. I don't really believe
that. That's why I'm looking for a different way to measure it.

Jeroen Belleman (Getting a sore throat from breathing too much ozone)
jeroen@dxcern.cern.ch
jeroen@cernvax.cern.ch