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Re: [TCML] Voltage Question



What about Terry Fritz' plane wave antenna method? Wasn't that shown to be fairly accurate? Similar idea...

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-----Original message-----
From: Ed Phillips <evp@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tue, Jan 24, 2012 02:01:07 GMT+00:00
Subject: Re: [TCML] Voltage Question

The 'before streamers' bit is all important of course. Once streamers form I would expect the peak voltage to drop because of the extra loading from spark to spark.

Ed

Antonio Carlos M. de Queiroz wrote:

On 16:59, Charles Van Neste wrote:

Hi Everyone,

I have been trying to quantify the Tesla coil I recently made and >> I've
had some issues trying to calculate the voltage of the top >> terminal (I think it is normally called the Top load - but I think >> that is a terrible description). Anyway, measuring the E field is >> straight forward. I typically put mini-grabber clips on a pole and >> elevate it to the same
height of the top terminal.  The clips are connected to a coax cable
which goes to a grounded oscilloscope - making sure this E-field >>
"probe" is far enough away not to disturb the system. Of course the >> E field is not the actual voltage of the top terminal. The only way >> I've been able to estimate it is to slowly turn the input voltage up >> until streamers form at the top (then I know the top terminal voltage >> is near 30kV - since that is the breakdown voltage in air, again this >> still assumes a gap of 1cm and the top terminal is with respect to >> ground so the voltage may be much higher than 30kV)

This can be wrong by an order of magnitude. 30 kV would cause > breakdown
in air in a sphere with 1 cm of radius, not on a large toroid.

. You can't bring a probe near the terminal or you change >> everything.
I need to know the top voltage so I can get an accurate >> measurement of the voltage gain of the system (from input to output - >> output being the top terminal). I would think there is a way to >> calculate the voltage by taking measurements of the E-field (since >> voltage should be related to the electric field)? How do you guys >> figure out your top terminal voltage?

Connect a signal generator between the top terminal and ground with >
known amplitude, as large as possible, and frequency close to the > resonance frequency of the secondary coil. See then what the > oscilloscope measures. You have then the ratio between actual terminal > voltage and the measurement, that shall be the same with the coil in > operation, before streamers form at least.

Antonio Carlos M. de Queiroz

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