On 7 March 2018 at 06:29, Andre <an...@lanoe.net> wrote:

> Please be VERY VERY careful. To be honest its far safer to use CCFL
> drivers and rectify them with camera diodes in series and the absolute
> minimum capacitance for the job, shunted with a high value resistor.

The problem with 2.2 nF is it is difficult to know what voltage is on the
capacitor at any time, since with a 10 M ohm multimeter, the time constant
is 22 ms. I have a high voltage probe around somewhere, which probably has
a 100 M ohm input impedance, but that would still only give a time constant
of 220 ms, which is too short to measure easily.

I have 47 uF @ 650 V (or it might have been 550 V) capacitor on order, but
I might go to something a bit lower capacitance if the charge storage is
not required.

I would like to know where the energy comes from to move the leaf. I wonder
if any is taken from the capacitor. In the gold leaf electrometer, with no
internal supply, it is clear the energy much come from the charge on the
plates. But when there's an electric field, that might not be the case. I
was thinking of sticking a 50 uA FSD meter inside, to see if any current is
take from the capacitor, but I don't know if 50 uA would be sufficiently
sensitive to deflect.

Clearly having an electrometer here would be useful for these sorts of
experiments, but I don't have one. I see a reference on here recently to
the Keithley 642 being one of the best, but whilst the basic meters are not
that expensive, the test head and cable are much rarer, so attract a much
higher price.

In any case, there's not a single half-decent electrometer on eBay in the
UK at the minute, and I need it before Monday.

> I have a few inverters , 10M resistor packs and diode strips here if
> anyone has a use on the understanding they are only to be used at your own
> risk, and for the intended purpose.
> Microwave capacitors can be deadly (you could DIE!) under the wrong
> circumstances, fibrillation can occur even with quite small shocks down to
> <8J if you get hit badly or have an undetected problem. I don't want to
> scare people but it is a serious risk.

It's fairly obvious to me, based on a few quick experiements last night,
that kV is not needed for this. Whilst I'm not doubting one could make an
electrometer (electroscope???) of greater sensitivity using a higher
electric field, this is good enough for a demonstration, and to learn a
bit. For quantitative measurements, I will look for a Keithley
electrometer, at a later date.

> -A

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