Ferrite Inductor Tolerance
in [Design]
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From: John Larkin on 13 Jun 2010 14:56 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 $$$. >>> >>> Nobody needs to be that precise. Nobody here anyway. >> >> We buy 2% inductors and 1% capacitors to make LC clock oscillators in >> our digital delay generators. >> > >Once you get above 100uH though prices can go through the roof. True. The 2% parts we use are 1008 wire-on-ceramic things, 150 nH sort of stuff. Like most "air" core inductors, they have a positive TC in the 120 PPM ballpark. We do coarse compensation with NTC caps, fine with a temperature sensor, software, DAC, and a varicap. It's hard to buy surface-mount NTC caps in reasonable quantities. John
From: Archimedes' Lever on 13 Jun 2010 15:52 On Sun, 13 Jun 2010 07:57:09 -0700, Joerg <invalid(a)invalid.invalid> wrote: > >Environmentally and financially not very friendly unless you can sell >the excess for a reasonable price. There is nothing about coils that is bad for the environment, and I never said anything about disposing of the remaining pieces. The matching and culling also allows one to use an off target value, as long as value matching is used, and the balance can be set by adjusting the cap values if that is even needed. Sorry, but most of the values will be fine, and you are wrong... again... as usual.
From: Archimedes' Lever on 13 Jun 2010 15:53 On Sun, 13 Jun 2010 07:57:09 -0700, Joerg <invalid(a)invalid.invalid> wrote: >BlindBaby wrote: >> On Sat, 12 Jun 2010 16:33:11 -0700, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> John Larkin wrote: >>>> On Sat, 12 Jun 2010 15:34:24 -0700, Archimedes' Lever >>>> <OneBigLever(a)InfiniteSeries.Org> wrote: >>>> >>>>> On Sat, 12 Jun 2010 15:00:59 -0700, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> You can get 5% catalog inductors from Delevan, Miller, TDK and several >>>>>> others. If it needs to be more precise then you'd be off to boutique >>>>>> lines, meaning $$$. >>>>> 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. It woiuldn't be an ECO, you dump chump. It would be the original design spec.
From: Archimedes' Lever on 13 Jun 2010 15:59 On Sun, 13 Jun 2010 18:32:35 +0100, Ian Bell <ruffrecords(a)yahoo.com> wrote: >On 13/06/10 15:28, Tim Williams wrote: >> "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 >> > >Fractional Henry, yes. I never said I wanted 1%, I just wanted to know >what is the likely tolerance. Q or more than one is easy with inductors >even of several Henries. > >Cheers > >Ian Look up ANY typical parameters and see that there is so much slop aging, and drift in so many of them that your desired 'batch' of inductors would be hard to gather up. That is why a lot of such a custom value will be a 5x cost increase or more over normal product runs.
From: Archimedes' Lever on 13 Jun 2010 16:14
On Sun, 13 Jun 2010 20:44:25 +0200, Fred Bartoli <myname_with_a_dot_inbetween(a)free.fr> wrote: >I did use 1% inductors in "power" (was 50mW level) application a few >months ago. > 50mW! Oh boy! That *REAL* power... not! Were they >100mH, like the OP speaks of? |