Odp: [sdiy] really basic question .. tolerance

[Tim Ressel]

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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