RE: [TCML] Panel Meters

["Lau, Gary" <Gary.Lau@xxxxxx>]

My earlier comments about current meters presuming a sine wave to read the RMS value apply equally to voltmeters as well.  The voltage waveform of an NST in an operating Tesla coil is not remotely sinusoidal.  Of course since you're providing your own series scaling resistor, you can make it read anything you choose.  But if you read the open-circuit sine wave NST voltage and calibrate the resistor so the meter reads 15kV (assuming that's what the NST is), the reading obtained when the gap is firing and no longer sinusoidal will be meaningless.  Useful for a qualitative indication, but nothing more.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of DC Cox
> Sent: Thursday, June 26, 2008 2:38 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Panel Meters
>
> They don't have to withstand any high voltage.  That's what the divider or
> series hi-meg resistors do.  With the anti-parallel diodes the max voltage
> across the meter is less than 10 Volts.
>
> In summary, the DC mA meter, when used in series with a high-meg value
> resistor, is shorting the HV to ground thru the meter movement.  Under these
> short circuit conditions, with a current limiting xmfr such as a nst, there
> is no voltage rise due to the short.  only a few Volts develop across the
> meter.
>
> Any standard DC mA meter works fine --- use diodes for rectification or use
> an AC mA meter.
>
> Dr. Resonance
>
>
>
>
> On Wed, Jun 25, 2008 at 7:49 PM, Phillip Slawinski <pslawinski@xxxxxxxxx>
> wrote:
>
> > Will these current meters withstand several kV?
> >
> > On Wed, Jun 25, 2008 at 8:18 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
> >
> > > And yes, shunts can be home-brewed easily. I did this with a couple
> > meters
> > > that required external shunts. I used thin brass sheets and drilled two
> > > holes to match the meter bolts. I then used scissors to cut out the
> > shunts.
> > > I measured current with a digital meter on a load and then hooked up the
> > > meter with the homebrew shunt and cut and filed away at the strip of
> > brass
> > > sheeting until the current matched the meter. Pretty easy to do.
> > >
> > > Take care,
> > > Bart
> > >
> > >
> > > William Noble wrote:
> > >
> > >> I have a pile in my garage - if you can make your own shunts/dividers I
> > >> may be able to help - contact me off the list> Date: Tue, 24 Jun 2008
> > >> 23:53:28 -0500> From: pslawinski@xxxxxxxxx> To: tesla@xxxxxxxxxx> CC:
> >
> > >> Subject: [TCML] Panel Meters> > Does anyone know a good source for
> > >> [analogue] panel meters?>
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