[Nut-upsuser] ups.test.result meaning

[Gene Heskett]

On Sunday 01 November 2020 09:02:56 Charles Lepple wrote:

> Gene,
>
> you might have missed this email, and I admit I wasn't very precise
> with my wording.

Yes, or at least I don't recall it, which at my age IS a possibility.
More below as needed.

> This particular UPS model is returning a fixed (in the sense of
> "constant") integer "24" (not 24.0) for both battery voltage and
> nominal battery voltage, likely because according to the vendor, some
> models do not have a battery voltage sensor (or, I suspect, it isn't
> accessible to the microprocessor that sends stats back over USB).
> Given the broken HID report descriptor that the UPS provides, NUT
> 2.7.2 scales "24" to "16.0". NUT 2.7.4 uses a heuristic to "fix" that
> value back to 24.0, but "garbage in, garbage out".
>
> Another way to look at it: if you had two 12V lead-acid batteries in
> series, and someone gave you many readings of 27.0V, 26.0V, 25.0V, and
> 24.0V over time, would you be suspicious that you weren't seeing, say,
> 26.5V at some point?

A bit odd, yes. Particularly since a 20 cent comparator and a kilobyte of 
machine code for a successive approximation routine is essentially 
public domain, published for a Z80 in about 1981, so such ability is 
essentially free.  All they have to do is make room on the pcb, and port 
that code to whatever micro they are using. I used it for quite a few 
readings in a transmitter controller in the 1981-1982 time frame that 
was essentially an ATS system without the label as that changed the 
Friendly Candy Commissions rules back then. It kept the logs on paper 
tape at the studio, adjusted the transmitter if it was not within 
tolerance, reporting the adjustment on the log printer, even started the 
air conditioner that fed the bottom of an early solid state Sparta FM 
transmitter as its finals weren't overly stable in a high altitude Cali 
summer in the high sierra's. All without any operator action.

That was now almost 40 years ago, and most of that code I wrote by 
looking up the next z-80 commands machine code in the programmers manual 
from Zilog. In that time frame an assembler wasn't affordable and needed 
more resources than a micro-professor kit board supplied. I even made my 
own 2716 programmer, eraseing them in the sunlight when I needed to 
reprogram them again. Now its part of linux and free for the 
downloading. And uv erasers are gone, replaced by better tech in the 
memory chips. There was no internet then.

> Rick's batteries may be low, but I would be surprised if he actually
> saw 16.0V on a multimeter.
>
> I wish we had a better way to flag these bogus values in NUT, but
> we're still collecting the data in order to programmatically figure
> out which models really do have a voltage sensor hooked up to USB, and
> which ones don't. For now, the next best thing is annotating the DDL
> entries from user-submitted data, like the link above.
>
> See also the output.voltage discussion below. The scaling issue isn't
> as bad, but it's rooted in the same USB HID descriptor (the decoder
> ring for the values the UPS sends back).
>
> > I think we even "fixed" that after NUT 2.7.2, before I realized that
> > many units are providing a bogus value:
> >
> > https://github.com/networkupstools/nut/commit/c8950dee9c91ce45d05d8f
> >220ea26891fb92329e
> >
> >>> output.voltage: 138.0
> >>
> >> too high by about 15 volts
> >
> > From the other CPS UPS thread on Monday:
> >> This is another known CyberPower issue, and fixing it properly
> >> requires making some changes deep in the core USB HID code (that
> >> would require a lot of testing on other vendors' equipment) for
> >> what is basically a cosmetic issue:
> >>
> >> https://github.com/networkupstools/nut/issues/439
> >
> > https://alioth-lists.debian.net/pipermail/nut-upsuser/2020-October/0
> >12126.html

Thanks for a cogent explanation Charles.

Sitting in your chair, the temptation to point those errors out in the 
logs, potentially giving the vendor an elbow in the ribs to fix their 
liars would be hard to resist. But thats just me being me. :)

Take care now.

Cheers, Gene Heskett
-- 
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