Cause of phase shift?

[goldjackal]

In an induction balance metal detector, what particular property of a material is it that causes the phase shift between the transmit and receive channels?

Is the the magnetic permeability of the material being detected? The resistivity? A combination of the two? Or does it involve some other electromagnetic principle? Does the size of the object have any influence?

Basically I'm asking, because I want to be able to more acurately gauge detection on the device I'm building, but I've come to realize that most of the theory sources I've obtained my information from thus far fail to explain exactly how to correlate a phase shift to a particular material.

I look forward to any information you all can provide. Metal detection technology is thrilling stuff to research. I've got a long way still to go in my studies, but this has REALLY gotten me interested in electromagnetics in general. I'm even testing for an amateur radio licence next month, I've gotten so interested.

Thanks,

- Jack

[ivconic]

Permeability.

[Qiaozhi]

In an induction balance metal detector, what particular property of a material is it that causes the phase shift between the transmit and receive channels?

Is the the magnetic permeability of the material being detected? The resistivity? A combination of the two? Or does it involve some other electromagnetic principle? Does the size of the object have any influence?

Basically I'm asking, because I want to be able to more acurately gauge detection on the device I'm building, but I've come to realize that most of the theory sources I've obtained my information from thus far fail to explain exactly how to correlate a phase shift to a particular material.

I look forward to any information you all can provide. Metal detection technology is thrilling stuff to research. I've got a long way still to go in my studies, but this has REALLY gotten me interested in electromagnetics in general. I'm even testing for an amateur radio licence next month, I've gotten so interested.

Thanks,

- Jack

Eddy currents generated in a conductive target produce their own electromagnetic field, which is phase-shifted (or time-delayed) when compared to the transmitted signal. Non-conductive objects with a permeability greater than air produce a similar imbalance by concentrating the magnetic field within their internal volume, but there is no phase-shift.
Hope this clears up any confusion.

[Max]

Hi,
...now to put some more gasoline on fire...

What about magnetic hysteresys and viscosity ? Are permeability and viscosity effects somehow involved in phase shifts or not when e.g. ferromagnetic oxides are in soil ?

What would be the cause of the ideal -90° degree X (pure mineral) deviation if not ?

What do you think ?

Best regards,
Max

[ivconic]

Hysteresys...! I hate that woman!

[goldjackal]

Hi,
...now to put some more gasoline on fire...

What about magnetic hysteresis and viscosity ? Are permeability and viscosity effects somehow involved in phase shifts or not when e.g. ferromagnetic oxides are in soil ?

What would be the cause of the ideal -90° degree X (pure mineral) deviation if not ?

What do you think ?

Best regards,
Max

Yeah, this is why I was asking in the first place. There are so many aspects of magnetism, I wasn't sure exactly what to look for.