How to Identify an Unknown Ferrite Core

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Do you have a ferrite core, but don’t know what it is? Follow along with Mike Arasim, Product Manager for Power and Inductive Applications at Fair-Rite Products as he identifies two unknown Fair-Rite EMI suppression beads using basic, inexpensive, readily available equipment in a very not temperature controlled environment.

Test equipment used: Keysight 1733C LCR Meter. Flir DM93 Digital Multimeter. Mitutoyo Absolute Digimatic 6” Caliper. 10 turns of 26awg solid wire.

Starring

Fair-Rite P/N 2673002402 as Sample #1
Fair-Rite P/N 2643002402 as Sample #2

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Thank you for this, Mike. Very useful. Now to sort through my not-so-small collection of toroid cores.
73, de W1MM

zerolabs

Thankyou Mike, that was educational. I have been a fan if Amidon/Fair-rite as a young boy. I am now 48 and continue to be.

bpcorner

Brilliant info. I've got a whole box of assorted ferrites that I'd use if only I knew the specs. But why don't the manufacturers just colour code them like they do with resistors and capacitors?

BritishBeachcomber

Mike thx for sharing. I know it's been a long time since this video was released but these days NANO VNAs have come down in price to the point they are quite affordable and can do the impedance measurement over quite wide frequencies directly.
I agree with many of the commenters cores should be marked somehow. I believe that Amidon color codes their cores or they used to.

Again Mike thx for sharing and giving us a tool/procedure to characterize cores.

pcrengnr

Thank you. Ferrites have been a big gap in my knowledge base. You are helping to solve that problem.

johnwest

Nagyon szépen kőszönöm a tájékoztatást, régota keresem

pumukli

Hi Mike, Core sample 1 (MnZn) O.D. 62.08mm; I.D. 36.01mm.; Ht 12.89mm. Sample 2 (NiZn) O.D. 61.52mm; I.D. 36.30mm.; Ht 12.72mm. Each toroid was wound with the same 0.8mm diam. X 125 cm. long solid Silver-Teflon conductor that passed through each aperture completely for ten turns, spaced generally evenly along the surface of the toroids. The F-R spreadsheet your company offers for an Excel download operates well, and returned an Init. Perm. of 172.

hymanlipschitzmd

Really good heads up on cores. Now I’m a little bit wiser. Thank you sir. 73 de GI8WFA.

DucatiMTS

Why the manufacturer doesn't mark them in any good way is bad practice.

KjartanAndersen

Very cool! Just the info I was searching for! Thanks & 73!

thomthumbe

When I drop ferrite cores on the floor I no longer need to identify them...
Thanks for the video.

sidewinderamm

f = 1/(2pi*((L*C)^0.5)). If you know your frequency, then use a series circuit with a potentiometer with your LC part of the circuit. You can dial in your pot so that the voltage drop is the same, that the value as the same. And you know the value of C, just plug and crank on your calculator, or spreadsheet.

jimparsons

Interesting on the beads. Are these actually useful as inductors or only as interference suppressors? I used a Fair-rite bead to make up a 10 uhy inductor using a General Radio standard inductor as a reference. (The standard inductor is a relatively large air core unit.) But there was no correlation to how they operated in a tuned circuit! The general radio unit resonated exactly as expected but the ferrite bead inductor was significantly off, (over 10%) even though they both read the same on the LCR meter.

glasslinger

Ham’s have two main questions about Ferrite cores…
1. what is the best mix for choking hf common mode currents?
2. what is the best mix for hf step up / down transformers (aka baluns)?
hf being 1.8-54mhz
these types and winding are all over the place on the internet.

richarde

Why ferrite cores are not part number laser marked to make it easier? 😂 I'm just thinking what a mess it would be if a worker drops 2 different boxes of ferrite cores....

mohamedlanjri