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RE: [TCML] DANGER Ground wire question
I think that this is a very difficult topic to discuss quantitatively, as I'm not aware of anyone ever having actually measured secondary base voltages. While the DC resistance from the secondary base to the ground rod may be close to zero Ohms, there is likely a significant inductance, and a significant voltage would appear across that inductance at TC frequencies. It's clear that a simple voltmeter cannot be used, as the waveform is just low duty cycle HV transients, not a steady state sine wave. Probably not something that you can reliably feel, but something that would still wreak havoc if applied to electronic devices.
I think the resistance from one ground rod to another is not close to zero Ohms. For my RF ground I buried a long copper pipe horizontally at the base of a concrete foundation, but if I Ohm from that pipe to my houses 3rd wire ground (connected to a different ground rod), the Ohmmeter shows an open circuit. I think that for a TC RF ground, it's not the DC resistance to the earth that matters as much as the capacitance to the earth. Which is why a counterpoise is often suggested as an alternative.
I realize that I'm using the phrase "I think" a lot in this post. This is a topic that there's not a lot of authoritative data on.
Regards, Gary Lau
MA, USA
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Tim Wenzel
> Sent: Saturday, February 13, 2010 6:21 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] DANGER Ground wire question
>
> I think this is somewhat related to the last string I chimed in on and got
> shot down. I am prepared to get corrected again on this one, but would not
> be commenting if I thought otherwise.
>
> I believe the voltages in question would be based on point of reference. If
> I ohm out my ground rod with the reference of another ground rod or the
> bottom of my secondary, with my coil running full or shut down, it measures
> 0 Ohms. When I measure voltage for the same reference points under the same
> conditions, there is 0 Volts.
>
> So, when I touch the ground rod of my coil while it is running full out,
> whether I am firmly grounded or not, I feel nothing because there is
> nothing. If you have a floating ground, vis-a-vis a counterpoise, which is
> not grounded to mother earth there may well be a price to pay.
>
> If your ground is hot while your coil is running, you had better have it
> isolated from your power grid through the use of filtering equipment. But I
> think the wisest thing to do is make sure you reference earth ground in all
> operations, unless you are running your own power grid at your house with
> an isolated grounding system.
>
> ----- Original Message -----
> From: "Bert Hickman" <bert.hickman@xxxxxxxxxx>
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Sent: Saturday, February 13, 2010 10:45 AM
> Subject: Re: [TCML] DANGER Ground wire question
>
>
> > Chris Arielles wrote:
> >> Is the ground wire and ground rod of a Tesla coil dangerous. If someone
> >> were to touch it during coil operation that is? Sorry im a noob.
> >> _______________________________________________
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> >>
> >
> > Chris,
> >
> > Depending on the power level of the coil and how well it's grounded, the
> > base of the secondary will typically have voltage peaks from hundreds to
> > thousands of volts. Although the ground rod itself will have less, it is
> > not wise to touch either while running your coil. =<:o
> >
> > Bert
> > --
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