Re: Measuring E-fields?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Steve,

Maybe this would work:

http://hot-streamer.com/TeslaCoils/MyPapers/planant/waveant3.html

http://hot-streamer.com/temp/PlaneWave.pdf

If you put the output into a very high impedance load (like a JFET 
OP-AMP) the frequency response will go will into the mHz or almost 
DC.  Mostly depends on the leakage of the insulators.  Mine 
calibrates well ;-))

http://hot-streamer.com/temp/PlaneWaveTest.gif

The layout and all can be changed to suit your needs.  Nothing is 
very critical.

Cheers,

        Terry


At 06:21 AM 8/14/2005, you wrote:
> Hi all,
>
> In some experiments I've been doing recently, I've felt the need for 
> a meter that I can hold in mid-air and have it read out the peak 
> value of the alternating E-field produced by a nearby Tesla coil.
>
> I have no problem with the measuring electronics, but I can't 
> imagine what sort of antenna I would need, or how to calculate the 
> calibration. (ie how many volts I get out the antenna for "X" volts 
> per meter of electric field in the immediate neighbourhood of it)
>
> As far as I understand, if I put say two small spheres 10cm apart, 
> and connect them to an amplifier with very high input resistance and 
> very low capacitance, I could just read the field directly? So if it 
> was 1kV per meter, 100v would appear between the spheres? Is this 
> correct? Or is there a less naive way to do it that works better?
>
> On a related note, if I can't get the capacitance of the amplifier 
> small enough to be "negligible", is there a way of taking it into 
> account in the calibration?
>
> Steve Conner