RE: [TCML] HV Panel Meters

[William Noble <william_b_noble@xxxxxxx>]

you have some choices when you pick the bulb that can affect the thermal time constant, and if you then use a photodetector, you can add a lowpass to smooth the measurement using any time constant you wish - personally, I'd use a bulb with a short time constant and then apply smoothing electronically - it just takes one capacitor added to your op amp circuit.> From: Gary.Lau@xxxxxx> To: tesla@xxxxxxxxxx> Date: Thu, 26 Jun 2008 17:13:26 +0000> Subject: RE: [TCML] HV Panel Meters> CC: > > 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?> > _______________________________________________>> > Tesla mailing list> Tesla@xxxxxxxxxxxxxx>> > http://www.pupman.com/mailman/listinfo/tesla______________________________> > _________________> > Tesla mailing list> > Tesla@xxxxxxxxxxxxxx> > http://www.pupman.com/mailman/listinfo/tesla> _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxx> http://www.pupman.com/mailman/listinfo/tesla_______________________________________________
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