If you add an air gap to a ferrite core, you can greatly tighten up the
tolerance, down to around 1%. This is commonly done with ferrite pot
cores, but i have also seen it done on ferrite toroids.
---
Rick Karlquist
N6RK
On 2025-11-03 18:19, Jim Lux wrote:
> yeah - the book by Snelling discusses all the variables.
> The Fair-rite catalog also goes into the mfr process.
> There's a reminder at the bottom of most of the pages that says "if you need
> better, call us, and we can talk"
> You can get better surface finish (less "flash" from the mold, for instance),
> better size tolerances, etc.
>
> But for the vast majority of applications - the designer just accounts for
> the variability and moves on. That ferrite lump around the keyboard cable?
> If it's off by 20% or even 50%, they'll still pass Part 15 and CISPR tests.
>
> On Mon, 3 Nov 2025 18:50:06 -0700, David Gilbert <ab7echo@gmail.com> wrote:
>
> Most of a lifetime ago I was a component engineer at Collins Radio, and
> one of the products I was responsible for was a small ferrite core. The
> manufacturer's rep explained the manufacturing process to me, which is
> basically like making a ceramic mug, and likened it to baking a cake.
> The process variables are many and significant, and even with automation
> the end result varies a lot.
>
> ChatGPT provided a summary of the potential process considerations:
>
> https://chatgpt.com/share/69095b41-ed34-8001-83ba-6c412e5e473e
>
> Dave AB7E
>
> On 11/3/2025 4:40 PM, Jim Lux wrote:
>
>> 20-25% is actually what Fair-rite gives as a tolerance for their cores (at
>> least for the EMI suppression family) - Chip beads are 25%
>> So if you've measured 20% variation, that's probably within spec.
> _______________________________________________
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
> _______________________________________________
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|