I have a UPS battery backup that occasionally thinks there is a power issue and goes to battery and comes right back a second later. Nothing else in the house loses power. non-ups computers don't reboot. None of my VHS players start blinking, yet the UPS sends me an email telling me how lucky I am to have it because it saved the day......
I'd like to verify the UPS next time it trips out by running a continuous recording of the waveform of power going into the UPS, and then when I get that email I'll stop recording, and go back to the moment in question.
I have a 4CH USB scope and a pc I can dedicate to this task. If I have to I'll set it up to record for 59 minutes every hour to a new file, and delete all files older than a day. I want to catch this!
I'm pretty sure I can take care of the software part of this problem. But as for electrically connecting mains into a scope channel, I don't want to spend too much, and don't want to burn down the house. But mostly don't want to spend too much.
What's the cheapest way I could plausibly sample mains to a scope input without needing batteries, (since this will need to be running for weeks to months). I was reading something about using a resistive divider. essentially if you had a 100ft long space heater element and measured one foot from neutral you'd see 1% of the voltage.
I also saw one probe option in my price range (<$50 each), but it doesn't look any different than a normal probe so I was thinking this might just be a bunk listing on amazon. And I also don't know that "a probe" is what I need. I'm not going to sit down there and hold it all day. So I would be what, soldering a wire to the tip of it?
I imagine I'd take male and female nema 5-15 connectors and 12 inches of wire between them, with an extra wire to one of the hot lugs as my test point.
Would it work just as well to run the hot conductor through a toroid and wrap some turns of magnet wire around it and connect the ends of the magnet wire to a scope BNC port? Basically I'd be creating a CT then... I wouldn't think that could measure voltage. But the sine wave should show up in measuring current right? And it'd be a hell of a lot safer and wouldn't need the same isolation to avoid things blowing up....
I'd have to be absolutely confident in timing though. because the UPS going to battery would sure show up on that CT as a major deviation from the norm.
Maybe use a scope channel to probe an LED that I would blink a time-code in binary, visible on camera as well.
I'm also kind of curious to compare measurements from different times of day to see just how far off the frequency gets from 60hz exactly. Yeah. I could read about it. But I would enjoy being able to make an actual measurement myself!
What's the best way to go about this?