Hi all,
I have a little question concerning ferrite coils I'd like to ask you.
I'd like to make a inductor based on a ferrite cylinder, sort of rod you find in a AM radio.
But the question is: what is the permeability of the ferrite ?
I have 2 methods, but I don't know which one will provide the correct answer.
because they provide 2 different results.
All are expressed in metric system (sorry for that one)
Here's the first one:
where L is the measured inductance [H] and N the number of turns []
(quoting from
http://www.c-maxgroup.com/tech/antenna.php )
The second one is:
where L is the inductance [H], l the length of the rod [m], N the number of turn [] and S the section [m²]
(quoting from
http://fr.wikipedia.org/wiki/Bobine_(électricité) )
First of all, is there any mistake in any formula ?
Then, do I understand well when I say µeff = µr ?
Afterward, do I made any mistake transcripting ?
Calculation provides a µ=480
(*) for the first one and µ=200 for the second one.
What is quite annoying !
Any help would be greatly appreciated !
Thanks a lot !
Regards
Data: L= 71.9µH (measured), N=22, S is calculated with a diameter of 1.10^(-2)m
(*) mistake : 71.9µ/484=1.48µ !!!
So µeff is related to what ??