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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