[sdiy] really basic question .. tolerance

[Peter Grenader]

<<> tolerance are connected in series that the result will be out of
tolerance?>>

<<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.>>

I haven't read all the replies in this string, so I can only respond to what
I said originally: 

Be careful of accumulative tolerances.

Meaning: the amount from the nominal value of each resistor will be summed
as well. I didn't mention anything about them suddenly being out of
tolerance.

I guess if you needed 1% and one of the two you used in series was a 20%,
depending on the summed value you could be headed for trouble.

P




> 
> 
> 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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> 
>