Coil resistance

[pito]

this is for ferrite, 0.8 deg

[Sergey_P]

Ferrite is a ferromagnetic material similar to iron. It generates a magnetic field due to its magnetizing properties. This magnetic component is the reactive component of the secondary field.
Energy is not wasted because, due to the dielectric properties of ferrite, no current flows through the target, meaning the active component tends to zero.
At the receiving end, you should observe a phase similar to that of the ferromagnetic target and an active component close to zero.
This is what I demonstrated in post #26. This is the target's response to the pulse, which is independent of phase coordinate rotation, since synchronization occurs from the leading edge of the pulse in time.

[Carl-NC]

The phase response of ferrite depends on how much hysteresis is in the BH curve:



An ideal ferrite has no hysteresis and the loss angle is 0°. The hysteresis in a lossy ferrite will elevate the loss angle; the one shown might be 10-15° which is rather extreme for a ferrite. A lossy ferrite still has near-zero conductivity but the hysteresis causes a real power loss as energy is needed to overcome the coercivity. Iron targets tend to have a decent amount of hysteresis, plus conductivity that creates an eddy component, so there are two response mechanisms happening at the same time.

[Sergey_P]

Hi, Carl-NC
Specifically, this hysteresis causes the response from the iron target in the device's hodograph to become broader in phase than the response from the non-ferrous target when the sensor is moved over the target.

[Carl-NC]

Yes, and the combination of magnetic response and eddy response can send the hodograph all over the place. Bottle cap:

[pito]

ferrite, beer cap, cola tab, coin

[pito]

ground blanced ferrite

[pito]

The phase response of ferrite depends on how much hysteresis is in the BH curve:

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I forgot about it
ps.
it is inconvenient to quote selected/highlighted part of text, manually i need to delete from all text not relevant info

[Sergey_P]

Hi, Carl-NC
I once tried to describe the process of EMF generation based on magnetization and conductivity using formulas, but I can't find them now. However, I do remember that one differential is sufficient for magnetization, while two are required for conductivity. That is, the dependence of EMF on frequency is linear for magnetization, but quadratic for conductivity. In other words, as frequency increases, the vector directed away from the target shifts toward zero (the vertical axis in the figure).
his is precisely what your hodograph shows.

[Aziz]

Hi all,

I think, we have to talk about natural magnetite (hot rock, ferrite), it's own "relative good" conductivity, the "eddy current" caused losses (BH-curve gets horizontal wider and the area increases), the frequency dependency and forming micro domain capacitor effects, which increases it's conductivity further on high frequencies...

This is really interesting. The effects are really huge on high frequency (up to 100 kHz).

Just ask the AI.
Aziz

[Sergey_P]

Hi Aziz
The presented method for calculating detector elements contradicted a misunderstanding of the physics of inductive object detection. The background factor consists of artifacts from secondary processes during detection (hysteresis, etc.).