EMI: negative values of conductivity?

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LisaStahl
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EMI: negative values of conductivity?

Post by LisaStahl »

As a student, can you explain to me why there can also be negative values in electromagnetic induction measurements? I do not understand the physical background of negative conductivity... I didn't find anything when googling either...

Thank you very much
Lisa

kaminae
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Re: EMI: negative values of conductivity?

Post by kaminae »

There is no such a term as "Negative conductivity" in EM.
"Apparent conductivity" can be negative for some reasons. "Complex conductivity" theoretically can give negative effect in some cases,
but there is no "Negative conductivity" in geophysics.

LisaStahl
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Re: EMI: negative values of conductivity?

Post by LisaStahl »

thanks a lot for your answer. I am currently making a few test measurements with the CMD Miniexplorer and this device gives me many negative values for the apparent conductivity. Obviously no matter what underground. I would like to understand why. The device is properly calibrated, I guess.

LisaStahl
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Re: EMI: negative values of conductivity?

Post by LisaStahl »

Hmm, was that a stupid question I asked? Or has no one thought about it yet? I'd just like to understand how the negative values arise... By the way, two fellow students also want to... Please answer honestly, don't keep silent. Thanks

markg21ca
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Re: EMI: negative values of conductivity?

Post by markg21ca »

This has been a topic of discussion in the time domain airborne EM world for years where negative transients have been attributed to IP effects under certain conditions. If this is in line with what you are seeing, I suggest you perform a literature search. Here is an example of a simple summary with a few references: http://ip.geosciences.mines-paristech.fr/s2_macnae1 .

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