From Newsgroup: sci.electronics.design

One of the UPSs was throwing caniptions, today -- constantly complaining
about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and
back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115lrbu$2581i$1@dont-email.me...

One of the UPSs was throwing caniptions, today -- constantly complaining about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps? https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M


--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On Thu, 13 Aug 2026 18:34:51 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

One of the UPSs was throwing caniptions, today -- constantly complaining >about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and >back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Hamonics maybe. Kill the fundamental with a notch or highpass filter.

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 8/13/2026 6:42 PM, Edward Rawde wrote:

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115lrbu$2581i$1@dont-email.me...

One of the UPSs was throwing caniptions, today -- constantly complaining
about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and
back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps? https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M

I don't know. What good will "knowing" this do me? Why does the UPS
get so upset? Is there some risk -- other than not being able to
deliver sufficient power to the load? If I had a 'scope on the line,
could I *tell* what was problematic??

Is it complaining about an unimportant problem?


--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115ls2e$25c5a$1@dont-email.me...

On 8/13/2026 6:42 PM, Edward Rawde wrote:

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115lrbu$2581i$1@dont-email.me...

One of the UPSs was throwing caniptions, today -- constantly complaining >>> about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and >>> back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps?
https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M

I don't know. What good will "knowing" this do me? Why does the UPS
get so upset?

I don't know. Ask the UPS :)

Is there some risk -- other than not being able to
deliver sufficient power to the load? If I had a 'scope on the line,
could I *tell* what was problematic??

My crystal ball is in for a service so I don't know.
But if the UPS is complaining about distortion then a
harmonic analysis of the line when it complains might be revealing.

Is it complaining about an unimportant problem?

Probably.
If you're a UPS then you'll want to make sure the customer knows that you're doing your job.





--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 8/13/2026 7:23 PM, Edward Rawde wrote:

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps?
https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M

I don't know. What good will "knowing" this do me? Why does the UPS
get so upset?

I don't know. Ask the UPS :)

It is (apparently) a catchall error that can mean low line, high line,
voltage spikes, dropouts, etc. "Mains don't look right"

Is there some risk -- other than not being able to
deliver sufficient power to the load? If I had a 'scope on the line,
could I *tell* what was problematic??

My crystal ball is in for a service so I don't know.
But if the UPS is complaining about distortion then a
harmonic analysis of the line when it complains might be revealing.

Or not. It would be nice if the error was more informative;
e.g., if a typical load wouldn't be bothered by the "distorted
input", then why react to it?

Is it complaining about an unimportant problem?

Probably.
If you're a UPS then you'll want to make sure the customer knows that you're doing your job.

It would be nice to be able to reassure yourself that it is doing its
job and not shitting the bed! (I had another UPS of the same make/model
die some years back)
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115luv5$264ik$1@dont-email.me...

On 8/13/2026 7:23 PM, Edward Rawde wrote:

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps?
https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M

I don't know. What good will "knowing" this do me? Why does the UPS
get so upset?

I don't know. Ask the UPS :)

It is (apparently) a catchall error that can mean low line, high line, voltage spikes, dropouts, etc. "Mains don't look right"

Then you'll probably never know what upset it.
I sometimes hear a click from the relay in the UPS attached to this computer. But not often. If there's a storm brewing nearby I might get a few clicks.

Why does a UPS need a relay anyway?
Can't today's technology just down convert the incoming power to 12V
and also up convert it back to line voltage?
What's the relay doing?

Is there some risk -- other than not being able to
deliver sufficient power to the load? If I had a 'scope on the line,
could I *tell* what was problematic??

My crystal ball is in for a service so I don't know.
But if the UPS is complaining about distortion then a
harmonic analysis of the line when it complains might be revealing.

Or not. It would be nice if the error was more informative;
e.g., if a typical load wouldn't be bothered by the "distorted
input", then why react to it?

Is it complaining about an unimportant problem?

Probably.
If you're a UPS then you'll want to make sure the customer knows that you're >> doing your job.

It would be nice to be able to reassure yourself that it is doing its
job and not shitting the bed! (I had another UPS of the same make/model
die some years back)

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On Thu, 13 Aug 2026 18:34:51 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

One of the UPSs was throwing caniptions, today -- constantly complaining >about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and >back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

Your unspecified model UPS probably has adjustable limits for how much distortion (i.e. harmonic) in can tolerate on the AC input. For
example:

"Adjusting Input Sensitivity on APC Smart-UPS SMT & SMX Series |
Schneider Electric"
<https://www.youtube.com/watch?v=PRJb1GDdskI> (1:12)

"Understanding the full implications of harmonic distortion" <https://www.ups.rehlko.co.uk/understanding-full-implications-harmonic-distortion/>

I run into distortion problems when utility power is switched to
generator backup power during power outages. The inverter generators,
which produce low distortion sine waves work the best. The modified
staircase approximations of a sine wave, produced by cheap commodity generators, are horrible.

Another source of distorted power line waveforms are non-linear loads.

"Understanding Total Harmonic Distortion" <https://powerquality.blog/2021/02/11/understanding-total-harmonic-distortion/> <https://powerquality.blog/wp-content/uploads/2021/02/understanding-total-harmonic-distortion.pdf>

"Analysis of Total Harmonic Distortion on the U.S. Electric Grid" <https://www.tingfire.com/blog/analysis-of-total-harmonic-distortion-on-the-u-s-electric-grid/>

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

There should be something here. I'm not familiar with todays power
line test equipment.

"Power quality meter THD" <https://www.google.com/search?q=power%20quality%20meter%20THD&udm=2>

"Clamp meter THD" <https://www.google.com/search?q=clamp%20meter%20THD&num=10&udm=2>

Incidentally, IEEE 519-2022 sets "voltage distortion limits" at 8% for
power lines under 1000v:
"Power quality - IEEE 519-2022" <https://comsys.se/en-us/our-adf-technology/power-quality-ieee-519-2022/>
--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272 AE6KS 831-336-2558

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 8/13/2026 7:50 PM, Edward Rawde wrote:

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115luv5$264ik$1@dont-email.me...

On 8/13/2026 7:23 PM, Edward Rawde wrote:

But, started thinking about what I could use (short of a scope) to >>>>>> detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps?
https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M

I don't know. What good will "knowing" this do me? Why does the UPS
get so upset?

I don't know. Ask the UPS :)

It is (apparently) a catchall error that can mean low line, high line,
voltage spikes, dropouts, etc. "Mains don't look right"

Then you'll probably never know what upset it.
I sometimes hear a click from the relay in the UPS attached to this computer. But not often. If there's a storm brewing nearby I might get a few clicks.

Why does a UPS need a relay anyway?
Can't today's technology just down convert the incoming power to 12V
and also up convert it back to line voltage?
What's the relay doing?

Depends on the UPS's topology. "Line interactive" tend to let the
mains through UNLESS there is a disturbance (low line, high line,
outage, "distorted input", etc.)

An "online" UPS rectifies the mains and uses that to charge the battery
as well as drive the inverter. ALL THE TIME. There is no "switching" involved. E.g., this is how POTS worked.

An "offline" UPS lets the mains flow to the output UNLESS there is
an outage -- in which case the inverter powers the load. This necessitates
a switch to select between power sources (mains or inverter out).

A line interactive UPS usually dynamically controls an (auto) transformer
to adjust for variations in sensed mains voltage. When things go
beyond its ability to compensate, the inverter is switched in to
carry the load. (switch == relay click) But, most of the time, the
load sees the mains directly, even thought the inverter is ready and
waiting. There is less control over the line but less effort to do so.

Online is the gold standard. But, it also does the most work as the inverter is ALWAYS powering the load -- so, throws off lots of heat, etc.

[The fans in my online UPSs run continuously; in the line interactive units, they only come on when the power has failed and the inverter is carrying the full load.]
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 8/13/2026 7:52 PM, Jeff Liebermann wrote:

On Thu, 13 Aug 2026 18:34:51 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:

One of the UPSs was throwing caniptions, today -- constantly complaining
about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and
back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

Your unspecified model UPS probably has adjustable limits for how much distortion (i.e. harmonic) in can tolerate on the AC input. For
example:

"Adjusting Input Sensitivity on APC Smart-UPS SMT & SMX Series |
Schneider Electric"
<https://www.youtube.com/watch?v=PRJb1GDdskI> (1:12)

Thes are in bogunits -- low, medium, high. No real way to look at
hard data and determine how that should affect your choice of
setting.

Given that the UPS *rarely* engages the inverter -- and, that the
lights in the room were "shimmering" -- I imagine there was *something*
going on with the mains.

"Understanding the full implications of harmonic distortion" <https://www.ups.rehlko.co.uk/understanding-full-implications-harmonic-distortion/>

I run into distortion problems when utility power is switched to
generator backup power during power outages. The inverter generators,
which produce low distortion sine waves work the best. The modified staircase approximations of a sine wave, produced by cheap commodity generators, are horrible.

We have some switching transients that happen, daily, at reasonably
predictable times. Not much you can do except wait for the click on,
click off, as the transient passes. I.e., a UPS that can carry the
load for "many seconds" is often all that is needed.

Another source of distorted power line waveforms are non-linear loads.

"Understanding Total Harmonic Distortion" <https://powerquality.blog/2021/02/11/understanding-total-harmonic-distortion/>
<https://powerquality.blog/wp-content/uploads/2021/02/understanding-total-harmonic-distortion.pdf>

"Analysis of Total Harmonic Distortion on the U.S. Electric Grid" <https://www.tingfire.com/blog/analysis-of-total-harmonic-distortion-on-the-u-s-electric-grid/>

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

There should be something here. I'm not familiar with todays power
line test equipment.

"Power quality meter THD" <https://www.google.com/search?q=power%20quality%20meter%20THD&udm=2>

"Clamp meter THD" <https://www.google.com/search?q=clamp%20meter%20THD&num=10&udm=2>

Incidentally, IEEE 519-2022 sets "voltage distortion limits" at 8% for
power lines under 1000v:
"Power quality - IEEE 519-2022" <https://comsys.se/en-us/our-adf-technology/power-quality-ieee-519-2022/>

But, what are the consequences of those disturbances?
Knowing your line quality is X doesn't really tell you much
(except that it is not *Y*!)

E.g., many devices rectify the line so the only significant
issue is an extreme voltage spike (that exceeds the rating
of some front-end component) *or* a significant dropout that
the bulk filter can't carry (at the present load).
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

Don Y <blockedofcourse@foo.invalid>wrote:

One of the UPSs was throwing caniptions, today -- constantly complaining >about "distorted input" (though I've never seen a formal definition of

what constitutes "distorted input") and switching to battery power -- and >back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Maybe use a resistor attenuator and record the mains
with a PC sound card?
There exists lots of software that then can replay and show the waveform,
and do all sorts of math on it.

Here one part of mains lead is ground, other live,
PCs are all grounded, use the live one :-)

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 14/08/2026 02:34, Don Y wrote:

One of the UPSs was throwing caniptions, today -- constantly complaining about "distorted input" (though I've never seen a formal definition of
what constitutes "distorted input") and switching to battery power -- and back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains.-a And, again, what might
constitute such irregularities!

Suggestions?

The one that upsets mine is when one of the three hot phases goes down
and instead of 240vac we get 87% of that. Everything being on switched
mode PSUs these days you don't notice until you try to boil a kettle!

In the good old days of CRTs the height and width would shrink (if it
worked at all). Incandescent lamps would be redder and dimmer too.

Easiest way is put a scope on it to see the actual mains waveform, or
perhaps on an old ac transformer output at a safer voltage.
--
Martin Brown

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 8/14/2026 2:57 AM, Martin Brown wrote:

The one that upsets mine is when one of the three hot phases goes down and instead of 240vac we get 87% of that. Everything being on switched mode PSUs these days you don't notice until you try to boil a kettle!

Here, the worry is an open neutral as few homes have truly balanced loads (especially when users can switch individual loads on and off)

In the good old days of CRTs the height and width would shrink (if it worked at
all). Incandescent lamps would be redder and dimmer too.

Easiest way is put a scope on it to see the actual mains waveform, or perhaps
on an old ac transformer output at a safer voltage.

But that still doesn't tell me what to look for or if I should care.
If the UPS gave better clues as to *why* it was "intervening on
my behalf" (instead of just complaining that the line was abnormal),
then I could decide if the condition was likely a transient or
might persist. In the latter case, I could elect to just power off
the powered device until things settled down a bit.

E.g., when I've lived places with overhead services, storms would
often cause momentary disruptions and fluctuations in power. Without
a UPS, it was wisest to just shut everything down and wait for the
storm to pass -- at which time, power would restabilize.

Here, services are below grade so disturbances tend to be more
network-wide. This time of year, likely related to excessive load
on the grid. Much harder to predict if that will come back under
control or fall apart, entirely.
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

Edward Rawde <invalid@invalid.invalid> wrote:

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115ls2e$25c5a$1@dont-email.me...

On 8/13/2026 6:42 PM, Edward Rawde wrote:

"Don Y" <blockedofcourse@foo.invalid> wrote in message news:115lrbu$2581i$1@dont-email.me...

One of the UPSs was throwing caniptions, today -- constantly complaining >>>> about "distorted input" (though I've never seen a formal definition of >>>> what constitutes "distorted input") and switching to battery power -- and >>>> back -- every couple of seconds.

I let it diddle with itself until the line, apparently, settled down.

But, started thinking about what I could use (short of a scope) to
detect irregularities in the mains. And, again, what might
constitute such irregularities!

Suggestions?

Something like this perhaps?
https://www.amazon.com/Taidacent-Harmonic-Distortion-Frequency-10Hz-1kHz/dp/B07KC6X51M

I don't know. What good will "knowing" this do me? Why does the UPS
get so upset?

I don't know. Ask the UPS :)

Probably better to ask the load 8-)

bob prohaska

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: sci.electronics.design

On 8/14/26 15:52, Don Y wrote:

On 8/14/2026 2:57 AM, Martin Brown wrote:

The one that upsets mine is when one of the three hot phases goes down
and instead of 240vac we get 87% of that. Everything being on switched
mode PSUs these days you don't notice until you try to boil a kettle!

Here, the worry is an open neutral as few homes have truly balanced loads (especially when users can switch individual loads on and off)

yep, it tends to make things go bang and that is a lot more annoying and permanent than not working very well

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