I'm not sure I agree with the conclusion that this is merely caused by UPS system control logic. That is an extreme amount of coordination across a lot of makes, models and configurations.

The FFT indicates this is a periodic signal, not a once a day or week thing. It's happening continuously all day every day. I don't know of any UPS systems that perform tests with this kind of regularity.

In any case, I refuse to believe an external sync signal is causing this. The more likely explanation is that the active elements are pulling each other to a common mode due to being physically coupled on the same grid. This is like how clocks on the same beam will synchronize.

https://en.wikipedia.org/wiki/Injection_locking

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0xbadcafebee 9 hours ago | parent | next [-]

The coordination is organic. Simply start with this assumption: "each device will check [something] every 60 seconds". Within a few years, all systems will be synced.

When the power goes out on the grid, everything is turned off at the same time. When the power comes back on, everything turns back on at the same time. Every machine that had a 60 second timer is now operating from the same starting time.

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the8472 a day ago | parent | prev [-]

The external sync here is NTP. Synchronized clocks + timer-scheduled actions → globally synchronized behavior

From the article:

> The origin of these current peaks was independently confirmed by the manufacturer to be periodic self-tests executed by the battery EMS, confirming our interpretation. Similar minute-scale diagnostic routines are also documented for other commercial UPS systems (cf. Supplementary Note 8).

https://www.snaptec.com.au/akkutec-4801-din-user-manual.pdf

> battery circuit testing 1 x per minute for 1 sec

https://adelsystem.com/hubfs/PDF%20DC-UPS/Instruction%20Manu...

> The battery testing is carried out automatically every 60 sec.

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ButlerianJihad a day ago | parent [-]

So, the two devices you refer to have no time-of-day clock, no network connection, no TCP/IP stack, and certainly no NTP clients.

Their testing on the enterprise-class equipment shows the difference that NTP makes, and with enterprise-class equipment comes wider deployment and more powerful models.

But most of the consumer units would not have this stuff. Surely, the manuals would describe how to set it up.

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mischanix a day ago | parent [-]

Counting mains power cycles is an adequate clock with a 0 of whenever it was last closed in. That 0 could conceivably be correlated to an hourly schedule if that process is automated. Not saying it’s common, but signals don’t have to come from the network.

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