Testing the output of some UPSs from around the office. Checking out the results and finding avenues for further exploration.

Please just buy a pair of mains voltage diff probes. They're not expensive (around $500 each new, much less used) and they will eliminate the crazy connection scheme and give you true input -> output fidelity.

Please spend $300 on a differential probe https://www.micsig.com/DPA/

I hope nobody sees this article and tries to replicate the experiments as presented. You can get away with it when everything goes correctly, but a diff probe is good insurance.

Great to see LTT in this space, you're well positioned for it (access to a variety of hardware.) Would love to see a more developed experiment design.

Would love to see how the waveform changes over load -- perhaps test at 0, 10, 20, 40, 80% load.

Also, how does waveform vary as the battery depletes?

Another metric is how capacity varies with load. If a UPS gives me 1 hour @ 100w, will it give me 10 hours @ 10w? How long will it power an idling rpi5 (<1w)? How long will it give my workstation PC?

Please just buy a proper differential probe for stuff like this, you definitely don't need the R&SRT-ZHD mentioned in the article. Otherwise loved the article btw.