Determine magnetic permeability and inductance factor of a ferrite toroid core - 4.2 out of 5 based on 5 votes
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Calculating characteristics of an unknown ferrite toroid:

Often radio-enthusiast can found in his spare box some unknown ferrite toroid core. However, he doesn't know anything about its characteristics, he doesn't know the AL – the inductance factor or µ – the initial permeability of the core. So far as the magnetic flux is closed in the core and don't have an air gap, we can quite easy to estimate these values. We have to wind some turns on the core and to measure obtained inductance by using an LCR meter. The following calculator helps to determine characteristics of the toroid core. Here you can see the formulas that the calculator uses. You can download the cross-platform app Coil64 to determined the magnetic permeability of the toroid core offline.

On-line ferrite ring core inductor calculator
ferrite toroid calculator
Select units: 

N – Number of turns
L – Measured inductance
D1   – Outer diameter of ring
D2   – Inner diameter of ring
h   – Height of ring

µ – Initial magnetic permeability
AL – Inductance factor of the core [nH/N2]
Clear all

The Ring_permeability plugin in Coil32 software allows to solve the same problem.

If you determined the magnetic permeability of the toroid core, you can calculate the number of turns for required inductance with this core.


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