Ferrite Inductor Tolerance
in [Design]
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From: Joerg on 12 Jun 2010 19:33 John Larkin wrote: > On Sat, 12 Jun 2010 15:34:24 -0700, Archimedes' Lever > <OneBigLever(a)InfiniteSeries.Org> wrote: > >> On Sat, 12 Jun 2010 15:00:59 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> You can get 5% catalog inductors from Delevan, Miller, TDK and several >>> others. If it needs to be more precise then you'd be off to boutique >>> lines, meaning $$$. >> >> Nobody needs to be that precise. Nobody here anyway. > > We buy 2% inductors and 1% capacitors to make LC clock oscillators in > our digital delay generators. > Once you get above 100uH though prices can go through the roof. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: BlindBaby on 12 Jun 2010 20:20 On Sat, 12 Jun 2010 16:33:11 -0700, Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Sat, 12 Jun 2010 15:34:24 -0700, Archimedes' Lever >> <OneBigLever(a)InfiniteSeries.Org> wrote: >> >>> On Sat, 12 Jun 2010 15:00:59 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> You can get 5% catalog inductors from Delevan, Miller, TDK and several >>>> others. If it needs to be more precise then you'd be off to boutique >>>> lines, meaning $$$. >>> >>> Nobody needs to be that precise. Nobody here anyway. >> >> We buy 2% inductors and 1% capacitors to make LC clock oscillators in >> our digital delay generators. >> > >Once you get above 100uH though prices can go through the roof. Just the same... once you get up there, tight tolerance is of little importance. 5% is fine. You want precision? You buy 500 cheap, 5% coils, and use in-house matching and culling techniques to get the matched set that you desire at a far far cheaper overall cost.
From: Ian Bell on 13 Jun 2010 10:05 On 12/06/10 23:00, Joerg wrote: > Ian Bell wrote: >> On 12/06/10 16:07, John Larkin wrote: >>> On Sat, 12 Jun 2010 10:22:59 +0100, Ian Bell<ruffrecords(a)yahoo.com> >>> wrote: >>> >>>> When winding modest inductors of a few hundred milliHenries on a ferrite >>>> core, given Al and a number of turns, what is the typical tolerance on >>>> the actual value of inductance when these are made in quantity? >>>> >>>> Cheers >>>> >>>> Ian >>> >>> An ungapped ferrite core could be all over the place. 25% wouldn't >>> surprise me. They will vary with temperature, too. You can buy gapped >>> pot cores in tolerances around 2-5%, I think. Or use a pot core with a >>> slug adjuster if you need 1% or better. See the datasheets. >>> >>> Powder-type cores can be bought with better tolerances. >>> >>> The people who wind inductors commercially get the exact number of >>> turns every time. >>> >>> John >>> >> >> >> It seems to me there are quite a few factors that could affect the >> actual inductance achieved and perhaps the least of them is the accuracy >> in counting the number of turns. I would expect there to be some >> tolerance in the Al value of the ferrite, that its exact dimensions >> would have an effect along with how neatly or otherwise the turns are >> wound. I have absolutely no idea if these are the major factors nor of >> the likely size of the actual major factors affecting the actual >> inductance. I am just trying to get a feel for the likely tolerance of >> ready made inductors. >> >> The reason I ask is am am designing some passive audio filters and I >> know exactly what tolerance of resistance and capacitance I can obtain >> but not a clue about inductance. It is no good me using 1% capacitors >> and resistors if inductors normally fail to achieve 5%. >> > > You can get 5% catalog inductors from Delevan, Miller, TDK and several > others. If it needs to be more precise then you'd be off to boutique > lines, meaning $$$. > > Example: > > http://www.delevan.com/seriesPDFs/1782.pdf > Those devices seem to be in the sub milliHenry range, the one I need are in the humfreds of milliHenries. Cheers ian
From: Tim Williams on 13 Jun 2010 10:28 "Ian Bell" <ruffrecords(a)yahoo.com> wrote in message news:hv2ok0$3q3$1(a)localhost.localdomain... > Those devices seem to be in the sub milliHenry range, the one I need are > in the humfreds of milliHenries. Fractional henry? In 1% sizes? With Q more than 1? Ya, they call those op-amps. You don't have any choice now... Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: Joerg on 13 Jun 2010 10:57
BlindBaby wrote: > On Sat, 12 Jun 2010 16:33:11 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> John Larkin wrote: >>> On Sat, 12 Jun 2010 15:34:24 -0700, Archimedes' Lever >>> <OneBigLever(a)InfiniteSeries.Org> wrote: >>> >>>> On Sat, 12 Jun 2010 15:00:59 -0700, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> You can get 5% catalog inductors from Delevan, Miller, TDK and several >>>>> others. If it needs to be more precise then you'd be off to boutique >>>>> lines, meaning $$$. >>>> Nobody needs to be that precise. Nobody here anyway. >>> We buy 2% inductors and 1% capacitors to make LC clock oscillators in >>> our digital delay generators. >>> >> Once you get above 100uH though prices can go through the roof. > > Just the same... once you get up there, tight tolerance is of little > importance. 5% is fine. > How do you deduce that it's of little importance? Got a spy camera in every enterprise, worldwide? :-) > You want precision? You buy 500 cheap, 5% coils, and use in-house > matching and culling techniques to get the matched set that you desire at > a far far cheaper overall cost. Environmentally and financially not very friendly unless you can sell the excess for a reasonable price. Also, I found that when inductors were at minus 15%-20% then, usually, the whole series was. In fact sometimes over months. So no dice there, I would not sign the ECO for that. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |