I made this little device to check current of Christmas light circuits. It is made from a 30 amp ampmeter, 20 amp recepticle, 2 prong plug, short section of 12 AWG wire, cord grip, and small plastic project box. Its intended use is for checking individual lighting circuits. I do this for a couple of reasons. First being the fact that loads should be checked when using extension cords. I use a lot of extension cords. Secondly each channel of a Light O Rama can only have 8 amps of load per channel and 20 amps per bank of 8 channels.
This is the back of the ampmeter. It has a standard 20 amp recepticle and a household coverplate. The plug is a standard 2 prong plug. I choose this because I use a lot of SPT1 and SPT2 type zip cord for my lights. This allows me to plug into any of my extension cords.
Inside is some simple wiring. The cord comes in through the cord grip. The white wire of the cord is wired to the receptical neutral screw and the black is run to the ampmeter. Then another black wire is run from the other terminal of the ampmeter to the hot terminal of the recepticle. So to test a circut all I do is plug the one end in to the source and then plug the light circuit into the back . Then I get an analog reading of how much current is being used by the circuit.