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NNTP-Posting-Date: Sat, 27 Apr 2024 20:47:29 +0000
From: Joe Gwinn <joegwinn@comcast.net>
Newsgroups: sci.electronics.design
Subject: Re: Practical resistor accuracy distribution
Date: Sat, 27 Apr 2024 16:47:29 -0400
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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