Electrical Questions? Ask an Electrician Online.
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Are you trying to test if / the amount of amperage running through the romex or are you just trying to determine if the circuit is "live".
There are testers that local home centers and electrical supply stores sell that actually light up and beep if current is flowing through the circuit, much the same as voltage pen testers detect voltage on a cable, basically it's a warning light just to test the line.
Actual measurement of amperage is done with a clamp on amp meter that is placed around an Individual wire in the cable as it's connected to the load to get an accurate reading of how much current is flowing, obviously you will have to have access to the wire itself so you will have to be at a point where the outer insulation of the cable has been removed and you can access the individual conductors. This is often accomplished at the electrical panel or at the equipment itself if possible.
I'd like to add that there are some multi meters that can measure amperage, but you actually have to put the meter's leads in series with the circuit or you risk blowing up your meter, if you are not familiar with electrical configurations and meters I do not suggest this approach.
The Non contact amperage tester that I am familiar with on the market is made by Extech, the Extech DVA30, this item can be pricy though depending on your current testing needs may not be the ideal choice due to cost.
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