I thought the other day I would grab a couple of these cheap little LED volt & amp meters modules you see on eBay. 30V, 10A, red and blue LED displays. Funky little things. I felt I should take a look at them and see just what they are, what they do, how you use them, etc.
Now of course, true to form, the details on eBay are very sketchy about how to use them. This is all it has to say on the page I bought mine from about the wiring: