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.