Capacitance measurements above 20KHz: helpful for measuring eddy current effects

[Mike Sulzer]

I think the main inductance has essentially lost its influence on the admittance above 30kHz.
But I could imagine that the effective permeability of the cores has some effect on the "transformer" coupling between coil partitions.

For 2H and 150pf the difference is about a factor of 10 at 30KHz. Suppose you want fo find the capacitance accurately enough with measurements centered at that frequency so that you can subtract its admittance from the total admittance to reveal the changes of the inductance with frequency in order to determine eddy current effects. Then you need to include the inductive reactance in the technique for the measurement of C to be sufficiently accurate. But the value of the inductive reactance does not have to be all the accurate since it is already a smallish effect. I still have to explain the technique I use to accomplish this.

[Helmholtz]

Yes, the admittance of 2H contributes around 10% at 30kHz.

But what I meant is that your measurements essentially show no difference in admittance at e.g. 40kHz though the cores should change inductance by 30% or more.
Makes me think that with given method and resolution, there's probably little chance to separate Eddy effects at that high frequencies.

What capacitance do calculate from the main impedance resonance of the coreless coil, using the L measured at 100Hz?