Re: Practical resistor accuracy distribution

On Sat, 27 Apr 2024 14:24:43 -0700, John Larkin
<jjSNIPlarkin@highNONOlandtechnology.com> wrote:

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.

Yes, and calibration will wash all those strange-distribution woes
away.

Joe Gwinn