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From: John Larkin <jjSNIPlarkin@highNONOlandtechnology.com>
Newsgroups: sci.electronics.design
Subject: Re: Practical resistor accuracy distribution
Date: Sat, 27 Apr 2024 14:24:43 -0700
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On Sat, 27 Apr 2024 16:47:29 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:

>On Fri, 26 Apr 2024 19:38:07 -0700, John Larkin
><jjSNIPlarkin@highNONOlandtechnology.com> wrote:
>
>>On Fri, 26 Apr 2024 20:16:48 -0400, Joe Gwinn <joegwinn@comcast.net>
>>wrote:
>>
>>>On Sat, 27 Apr 2024 00:54:41 +0200, Klaus Vestergaard Kragelund
>>><klauskvik@hotmail.com> wrote:
>>>
>>>>Hi
>>>>
>>>>I needed to look into distribution of accuracy of resistors.
>>>>
>>>>Vendors don't have any info, but luckily some nice people online have 
>>>>done measurements:
>>>>
>>>><https://www.eevblog.com/forum/projects/smd-resistor-distributions/>
>>>>
>>>><https://lambdafox.com/resistor-tolerances/>
>>>>
>>>The thing to be aware of is that resistor value distributions are
>>>often wildly non-Gaussian.  The classic example is where there are
>>>grades, say 1%, 5%, and 20%.  The 5% group will often have a hole that
>>>happens to match the 1% distribution perfectly.
>>>
>>>A lot of modern resistors are made with a relatively wide
>>>distribution, and then machine-sorted into bins.  In this case, many
>>>of the bins will have uniform distributions.  And so on.
>>>
>>>Joe Gwinn
>>
>>I suspect that they may laser trimmed and shipped, not binned.
>>
>>One batch on a reel could be very close to one another. 
>
>Also possible, and maybe a combination of both?
>
>But the fundamental point is that one must measure to be sure, unless
>one is a large enough customer that the manufacturer will simply tell
>you.
>
>Joe Gwinn

We just assume that all 1% resistors are within 1%.

We buy 0.1% and some 0.05% parts too. Since most of our products have
software-based calibration, we mostly care about resistor tempcos, not
so much tolerances.