RE: [TCML] HV Panel Meters

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

I tried something similar to read the current from the secondary base.  Trouble is, with a static gap being so chaotic, the reading varied all over the map.  One would need something with a much longer thermal time constant than a bulb filament to achieve a stable reading.

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of William Noble
> Sent: Thursday, June 26, 2008 1:01 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] HV Panel Meters
>
>
> you may wish to consider a very crude but effective way to measure irregular
> currents in the analog domain - the old fashioned light bulb -
>
> put a bulb whose current rating is consistant with what you want to see (say a type
> 47 for a small NST) in series with one lead.  Put the bulb in an enclosure with a
> plastic light pipe (acrylic works well) - you can do this by just wrapping with tape -
> bring the fiber to your panel - color and brightness indicate current.  if you want to
> have a meter do the indicating, shine the fiber onto a
> photocell/photoresistor/phototransistor and use that to drive a meter of your choice
> - take some measurements to calibrate it and you are good to go.  This is the same
> principle used on many true RMS meters in the past, just done in the "crude and
> simple" way.  If you want more accuracy, an air gap of 6 inches with the bulb at one
> end and the photocell at the other, and a photodetectorthat is sensitive in IR will
> improve accuracy - a glass tube with the bulb at one end and the detector at the
> other, painted black and wrapped with tape will do the trick.> From:
> Gary.Lau@xxxxxx> To: tesla@xxxxxxxxxx> Date: Thu, 26 Jun 2008 14:54:37
> +0000> Subject: RE: [TCML] HV Panel Meters> CC: > > You can use a standard
> AC analog meter, but here's a couple things to think about.> > 1) You'd have to
> take special precautions to ensure that all parts of the meter are thoroughly
> insulated from a panel and contact with people. It's probably not advisable to mount
> it permanently on a panel.> > 2) AC meters are calibrated to read RMS current, and
> assume that the input waveform is a sine wave. The current drawn from an NST
> into an operating Tesla coil does not remotely resemble a sine wave and I can't
> offer any sort of conversion factor. So you might benefit form seeing a relative
> indication, but the actual current value would be unknown. To get a useful RMS
> current reading, you would need a true RMS meter, which typically being digital, is
> subject to haywire behavior anywhere near a Tesla coil.> > Regards, Gary Lau>
> MA, USA> > > -----Original Message-----> > From: tesla-bounces@xxxxxxxxxx
> [mailto:tesla-bounces@xxxxxxxxxx] On> > Behalf Of Phillip Slawinski> > Sent:
> Thursday, June 26, 2008 8:26 AM> > To: Tesla Coil Mailing List> > Subject:
> [TCML] HV Panel Meters> >> > I'd like to set up some some meters to measure the
> secondary side of my> > transformer [directly]. My question is if a standard shunted
> mA current> > meter would be okay for this, or would I have to get a special high
> voltage> > model?> > _______________________________________________>
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