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I want to measure the power coming out of a 120V outlet that can go up to 20 Amps. A standard household circuit is limited to 15 amps but this is a special situation where we're running our own temporary power grid off a generator. Specifically, the plugs are "NEMA 5-20P" where one of the blades can be slanted.

All the watt-meters I find online only support up to 1800W/15A since they're meant for home use. Usually, that'll be fine, but situations where we start drawing more than 15 amps is exactly when I want to know how much I'm using.

Any ideas on to build something that can measure current/power when it can go up to 20A? At this point off the shelf doesn't seem like an option so I figure I'll make to make my own and would love some tips.

Thanks!

Chris
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  • Unfortunately, "shopping" questions are off-topic here. Please [take our tour](//diy.stackexchange.com/tour) so you'll know how best to participate here. – Daniel Griscom Aug 09 '19 at 01:57
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    Can you get your paws on a clampmeter and plug adapter for same? – ThreePhaseEel Aug 09 '19 at 02:21
  • @DanielGriscom thanks! At this point, I figure I'll have to make my own meter, so I tweaked the question to reflect that and make it less about "shopping" =) – Chris Aug 09 '19 at 02:22
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    This is a dupe of https://diy.stackexchange.com/questions/131012/diy-ac-line-splitter, basically (can't VtC it any longer) – ThreePhaseEel Aug 09 '19 at 02:34
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    if you get a *current transformer* to make your own. *be warned* ... these devices are *EXTREMELY* dangerous. they can have *DEADLY* voltages. if you don't thoroughly understand how they work and are wired, don't mess with them. – Skaperen Aug 09 '19 at 03:27
  • 20 amp circuits are quite common and not the exception is residential in fact the required circuits in the kitchen, bath and laundry are all 20 amps, I wire more homes with 20 amp circuits more often than 15. If you want to check your current draw there are many meters under 100$ that can accurately measure in the +100 amp range including fluke meters. – Ed Beal Aug 09 '19 at 13:48
  • Possible duplicate of [DIY AC Line Splitter](https://diy.stackexchange.com/questions/131012/diy-ac-line-splitter) – JPhi1618 Aug 09 '19 at 18:02
  • Not a duplicate but as I said in a comment on that post a male female cord cap set and a clamp meter will allow a meter to be used to measure current. A clamp meter is needed to do this and most clamp meters have much higher ability’s than 20 amps. – Ed Beal Aug 10 '19 at 02:07
  • Kill-a-Watts will measure up to 20A, even though they will complain if current flow is over 15A. However they are not made with turned-neutral NEMA 5-20 plugs or sockets. – Harper - Reinstate Monica Aug 10 '19 at 05:00
  • I would be purchasing a professional tool like this [Fluke Clamp Multimeter](https://www.amazon.com/dp/B00AQKIEXY/ref=cm_sw_em_r_mt_dp_U_k4ywDbJV8A38Q). It's capable of up to 400 Amps. I think this is your best bet. – technogeek1995 Aug 18 '19 at 17:43

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