Re: Re: Odp: [sdiy] really basic question .. tolerance

[Roman]

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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