Re: How do I properly measure the current of power supply?

I hooked up 10W 10 ohm resistor, 55W 12V headlight bulb, and two 55W 12V headlight bulbs in parallel to check voltage and current.
Measurement of voltage and current of each load:
10W 10 ohm resistor, 11.58V, 1.17A
55W 12V headlight bulb, 10.09V, 3.75A
2x 55W 12V headlight bulb in parallel, the PSU went dead without blowing fuse. When I turned on the PSU, the fan gave a jerk motion then nothing happened.
I was going to use it for RAMPS 1.4 controller if it passed the 110W load test, but I'm planning to convert another ATX PSU.

Quote
dc42
If the PSU has two separate 12V outputs, connecting them together is a bad idea. One of the outputs is likely to regulate to a slightly higher voltage than the other, and will end up taking nearly all the load. If you are using RAMPS, then I suggest you use one output to power the heated bed (the 11A circuit), and the other output to power everything else (the 5A circuit).

How do I identify two positive 12V rails?