Odp: [sdiy] really basic question .. tolerance

[Tim Ressel]

Roman,

Gee, maybe I am full of it and don't know how TCs
work. I ran numbers and it seemed to add. So like, can
anyone give us all a lesson on TC??

--Tim

--- Roman <modular at go2.pl> wrote:
> Well, I checked again, and it seems correct. I also
> did
> ran a couple (67 actually) of numbers to be
> absolutely
> sure and it works.
> 
> Anybody to confirm this?
> 
> Roman
> 
> Tim Ressel <madhun2001 at yahoo.com>:
> 
> >Roman,
> >
> >I think your formula for series resistors is
> >incorrect. I ran some numbers and it looks like the
> >TCs add for a series combination.
> >
> >--tim
> >
> >--- Roman Sowa <modular at go2.pl> wrote:
> >> for parallel:
> >> Tc = Tc1 * R2 / (R1+R2)   +   Tc2 * R1 / (R1+R2)
> >> Tc1 is tempco of R1 and Tc2 of R2
> >> 
> >> for series connection:
> >> Tc = Tc1 * R1 / (R1+R2)   +   Tc2 * R2 / (R1+R2)
> >> 
> >> Roman
> >> 
> >> ----- Original Message -----
> >> From: patchell <patchell at silcom.com>
> >> To: <synth-diy at dropmix.xs4all.nl>
> >> Sent: Sunday, January 19, 2003 3:58 AM
> >> Subject: Re: [sdiy] really basic question ..
> >> tolerance
> >> 
> >> 
> >> >     Heres one for you to think about.  You have
> a
> >> 10K resistor with a
> >> +100ppm./C
> >> > tempco and a 100K resistor with a +1000ppm/C
> >> tempco, you connect them together
> >> in
> >> > parrallel to make ~9K, what is the tempco of
> the
> >> resulting ~9K resistance?
> >> >
> >> >     Guess I should work this one out myself to
> see
> >> what the answer is...
> >> >
> >> >     Just a brain teaser I thought up on the
> spur
> >> of the moment...
> >> >
> >> > harrybissell wrote:
> >> >
> >> > > Tell ya what John...
> >> > >
> >> > > I'll buy your arguement that it can't be
> worse
> >> than the original
> >> tolerance...
> >> > >
> >> > > if you buy mine that its likely to be BETTER
> >> than the original tolerance...
> >> > >
> >> > > H^) harry
> >> > >
> >> > > John L Marshall wrote:
> >> > >
> >> > > > Tim or Harry or Peter,
> >> > > >
> >> > > > Please show me an example of two 1%
> resistors
> >> in series or parallel where
> >> > > > the tolerance exceeds 1%. I heard this rule
> >> many times but I can't see it.
> >> > > >
> >> > > > Complex circuits are another story. I can
> see
> >> how errors accumulate
> >> through
> >> > > > gain stages.
> >> > > >
> >> > > > I need empirical evidence to be convinced.
> >> > > >
> >> > > > Take care,
> >> > > > John
> >> > > > www.sound-photo.com
> >> > >
> >> >
> >>
>
>---------------------------------------------------------------------
> ------
> >> > > >
> >> > > > ----- Original Message -----
> >> > > > From: "Tim Ressel" <madhun2001 at yahoo.com>
> >> > > > To: "diysynth" <diy_list at analog-synth.de>;
> >> <synth-diy at dropmix.xs4all.nl>
> >> > > > Sent: Saturday, January 18, 2003 1:32 PM
> >> > > > Subject: Re: [sdiy] really basic question
> ..
> >> tolerance
> >> > > >
> >> > > > > Joerg,
> >> > > > >
> >> > > > > That is an optimistic way of looking at
> it.
> >> However
> >> > > > > the worse-case is still the sum. If I'm
> >> worrying about
> >> > > > > tolerances, I always look at worse-case.
> >> > > > >
> >> > > > > --tim
> >> > > > >
> >> > > > >
> >> > > > >
> >> > > > > --- diysynth <diy_list at analog-synth.de>
> >> wrote:
> >> > > > > > Hi all
> >> > > > > >
> >> > > > > > > tolerance are connected in series
> that
> >> the result
> >> > > > > > will be out of
> >> > > > > > tolerance?
> >> > > > > > >
> >> > > > > > > Add two 100k resistors 101k + 101k =
> >> 202k still 1%
> >> > > > > >
> >> > > > > > Sure ? I allways thought, the resulting
> >> tolerance
> >> > > > > > gets better with the
> >> > > > > > factor t_res=t_single/sqrt(n), where n
> is
> >> the number
> >> > > > > > of used resistors, and
> >> > > > > > t_single is the tolerance of the single
> >> resistor ?
> >> > > > > >
> >> > > > > > Joerg
> >> > > > > >
> >> > > > > >
> >> > > > >
> >> > > > >
> >> > > > >
> >>
> __________________________________________________
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> >> >
> >> > --
> >> >  -Jim
> >> >
> ------------------------------------------------
> >> > * Visit:http://www.silcom.com/~patchell/
> >> >
> *-----------------------------------------------
> >> > *I'm sure glad Merry Christmas comes just once
> a
> >> year
> >> > * -Yogi Yorgensen
> >> >
> ------------------------------------------------
> >> >
> >> >
> >> 
> >
> >
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> 


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