Wouldn't the fields from the primary canceling out be dependent on those fields being uniform though?
The primary is a spiral, so you have some non uniformity from that effect (offset circles)
But more probable is the primary inner lead, which would probably run "roughly" parallel to the wire coming from the base of the secondary.
Add on top of that the fact that primary currents are usually orders of magnitude higher than that of the secondary.
Seems reasonable to me that the proximity of the primary would be a major concern.
Perhaps you can put the current transformer inside a hunk of thick iron pipe to try and eliminate some of these magnetic effects?
Thanks,
John "Jay" Howson IV
"Why thank you, I will be happy to take those electrons off your hands."
----- Original Message -----
From: "Andreas Hahn" <andreas.hahn@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, September 1, 2012 2:58:02 PM
Subject: [TCML] Measuring Isecondary: Current transformer too close to primary?
Looking through the archives for current transformer theory, I found this:
http://www.pupman.com/listarchives/1999/February/msg00081.html
"I was using a current transformer and (this time) a usual scope 10:1
probe.
As I was about 40 cm from the primary, probably the magnetic field induced
by the primary was stronger than the field induced by the secondary base
lead passing through the same transformer.
The result was that I measured an attenuated version of the primary
current, NOT the secondary current."
Is this actually possible? Since the primary windings do not pass through
the current transformer toroid, my understanding is that any fields from
the primary would cancel out, and therefore little or no influence from
the primary should show up in the secondary of the CT.
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