Why do I get DC resistance between two disconnected coils?

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  • Last Post 14 February 2023
AlteredUnity posted this 14 February 2023

My question is with a set of coils I made a long time ago on a ferrite core.  135 turns of 20awg wire i think, I believe both wires are exactly the same length because of how OCD I am. 
This is the only setup I get the effect with, as I have 3 other cores of same type wound the same way, but different lengths, turns, and guage of wire, though don't get the same result.
With 2 separate coils, I connect a multimeter on one end of each coil, the other ends are open. I have a variety of meters, and all give same reading, when testing resistance using DC. Below are some pictures of the setup testing with DC for resistance,  and showing the capacitance at 10khz

You can see as I move the open ends of the wires farther apart the resistance drops. Same with the capacitance between the coils.

It probably has something to do with parasitic capacitance, or the capacitance between the coils, tho has anyone else seen this with any of their setups? I will be moving back to working with these coils till I can wind new ones on my AMCC core. Thanks for any help.

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AlteredUnity posted this 14 February 2023

My question is with a set of coils I made a long time ago on a ferrite core.  135 turns of 20awg wire i think, I believe both wires are exactly the same length because of how OCD I am. 
This is the only setup I get the effect with, as I have 3 other cores of same type wound the same way, but different lengths, turns, and guage of wire, though don't get the same result.
With 2 separate coils, I connect a multimeter on one end of each coil, the other ends are open. I have a variety of meters, and all give same reading, when testing resistance using DC. Below are some pictures of the setup testing with DC for resistance,  and showing the capacitance at 10khz

You can see as I move the open ends of the wires farther apart the resistance drops. Same with the capacitance between the coils.

It probably has something to do with parasitic capacitance, or the capacitance between the coils, tho has anyone else seen this with any of their setups? I will be moving back to working with these coils till I can wind new ones on my AMCC core. Thanks for any help.

cd_sharp posted this 14 February 2023

It looks like the core is electrically conductive and the wire insulation is damaged.

If you know how to build such a device and you're not sharing, you're a schmuck! - Graham Gunderson

AlteredUnity posted this 14 February 2023

Thanks cd_sharp. I will test the resistance of the wires separately, there is a very good possibility that is the case. Turns out your correct my coil is shorting out somewhere, thanks CD.

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