[sdiy] really basic question .. tolerance

[Tim Ressel]

Hey,

I don't mean to be a stick in the mud, but I have to
disagree. You are talking about probabilities. When I
put a trim pot in a circuit, I don't figure what the
mean error is going to be, I figure the worse case so
the trimpot will have enough range to compensate. And
yes, I have seen resistors on the ragged edge of
tolerance. This is why Spice has Monte Carlo stuff in
it.

I guess its all that time I spent at Agilent.
Precision is a disease that is spread my casual
designing...

--Tim



--- diysynth <diy_list at analog-synth.de> wrote:
> Hi all, hi Tim,
> 
> > Rules... We don't need no stinkin' rules!
> Oooh Yes we do....
> 
> 100 KOhm with 1 %
> 
> to simplify, we have (with 1% tolerance) 99, 100 and
> 101 KOhm.
> With 3 possibilities in a 2-combination :
> 9 Possible Combinations:
> 
> 99 + 99 = 198  instead of 200 (i.e. 1% error)
> 99 + 100 = 199 (0,5%)
> 99 + 101 =200 (0%)
> 100 + 99 = 199 (0,5%)
> 100 + 100 = 200 (0%)
> 100 + 101 = 201 (0,5%)
> 101 + 99 = 200 (0%)
> 101 + 100 = 201 (0,5%)
> 101 + 101 = 202 (1%)
> 
> so, we have a arithmetic mean of tolerances of :
> (1,0 + 0,5 + 0 + 0,5 + 0 +0,5 + 0 + 0,5 + 1) / 9 =
> 0,4444 %
> 
> That is, of course, better than 1%.
> This estimation doesnt take into account, that 1%
> tolerance means, that
> there is a gauss-distribution of the resistor values
> with a standard
> deviation around 100 KOhm of  (less than) 1 KOhm or
> so. Tis would increase
> this e-mail to some hundred lines.
> 
> Joerg
> 
> 
> 
> 
> 
> 
> 
> 
> 
> > clear now?
> sorry, no.
> 
> 
> 
> 


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