Power Supply Efficiency Testing

Aruffell

Aruffell

Aruffell

Soldato
Joined
29 Dec 2004
Posts
5,653
Location
Chatham, Kent
Just wondering how one would go about testing a power supplies efficiency.

I know how to stick a DMM's probed into the appropriate coloured pin on the atx 24 pin connector to test the rails.

Just wondering how to test efficiency.

Any ideas?

Thanks,

Andy
 
You'd need to plug a known load into the output of the power supply (like a 50W car headlight or something), and then measure the wattage input to the power supply. (Using one of those mains watt meters).

The input will be slightly higher than the (known) output.

PS. This is the most basic method possible, and will probably only test the efficiency of whichever rail you connect your load to. To do it properly you would need a special testing rig.
 
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To be fair, Engram your method isnt that bad for something that can be done at home. Best bet is to aim for a load somewhere within 40-60% of the PSU's maximum capacity. (several car headlights should do the trick for example).. But be carefull they get hot, and you can get a nasty burn :P

The 12v efficiency is most important as the majority of parts in modern PCs are running on the 12v rails anyway :).

Rather than guessing the load, it's probably better to measure it using a meter, just measure the voltage of the rail under load, and multiply by amps drawn, it will be the wattage on a DC rail :). Then compare with the plug in power meter's results.

The best PSU's aim to be 80%+ efficient from 10% load to 90% load so mid load efficiency is the easiest test without using professional testing kit.
 
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