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[TCML] Re: Pratical measurement of voltages and current on TCs

Hi Paul,
 
Interesting!
 
Pearson curent probes are fully shileded but the sheid acts as a shorted turn near the primary.  All that 90 degree stuff is really imprortant near the primary.  I think remote location is a big help for those new people that not brave (stupid enough :D ) to locate scope probes near coils.
 
I love E-field probes.  They just work!  I just had to whip up another for myself since all the folks I lend them to never bring them back :D
 
https://ibb.co/YL99n1H
 
Good thought about field probe interference.  I don't think most folks who care much about fine details.  But for true science it would me a major factor.
 
Who would ever waist time on dividers!!!!
 
LOLZZZZ
 
https://ibb.co/v3CdbZj
 
Best Regards,
 
Terry
 
 

Sent: Sunday, December 05, 2021 at 11:34 PM
From: "paul" <tcml88@xxxxxxxxxxx>
To: tcml@xxxxxxxxxxxxxxx
Subject: [TCML] Re: Pratical measurement of voltages and current on TCs
Hi Terry,

> Do you think it matters ... if the current transformer is
> located right near the base of the coil ...

The current transformer will be a toroid, so a fairly tight
magnetic circuit, but not perfect. Keeping it away from
the mag field of the system will reduce spurious response
via the CT's leakage field.

So I would move it away for that reason. Otherwise, not too
difficult to shield from discharges and electric field effects.
If running a ground plane/counterpoise, run the sec base wire
away under the GP, or use a coax.

But too long a wire and you have to account for the shunt C
of the wire to ground (thus bypassing the CT primary).

Others mentioned E-field probes. Easy to calibrate, and easy
to model too if you have a nice shape to the probe such as
a sphere, disc, or toroid. It may be preferable to operate
the E probe grounded and measure or record (via a CT or shunt)
the current flowing in that ground. Then your instruments are
more isolated.

Trouble with E probes is they respond to the field of the whole
system, not just the topload (which is the waveform you really
want to capture).

Seem to remember us discussing dividers a long time ago and
not coming up with any really great solution.

--
Paul Nicholson
--
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