how to test power supply

[missouri 69]

how can you know a power supply is putting out the amps it is supposed to be putting out??
I can check voltage, but how do you check to see if a power supply will supply the amps it says it will?
thanks
sam

 

[Beetle]

If you can get a "carbon pile" (very high power variable resistor used in automotive electrical repair and battery testing), this will be a big help.

Then you'll need a DC voltmeter and a DC ammeter (don't try this by switching one meter between two functions). Most DC ammeter functions in multimeters only go up to ten amperes or so. Beyond that you'd need either a DC clamp-on meter, or a shunt for the multimeter (and you'd use the multimeter on a millivolts scale).

 

[Switch Kit]

Great question 69 !! Good answer Beetle !! kind of a pain in the butt to do if you don't have the stuff on hand )-: but I have always kind of wondered the same thing with power supplies ? ......it's surely a lot easier to check to see if a amplifier is putting out .....I can't count how many times I've seen used power supplies at Ham/CB radio swap meets that always made me wonder if they were doing what they were supposed to be doing ?(like did somebody put to much on the supply and weaken it ?) ....for that reason alone ,unless I knew the person that was selling it , I more then likely wouldn't go there in the first place.

 

[Beetle]

Someone else suggested that you could gather a bunch of still-good car headlight bulbs, noting the power ratings of each, and keeping the voltage constant, loading the supply with these bulbs connected in parallel, adding the branch currents, until the supply voltage dropped out of spec. This, used with Mr. Ohm's Law, would give a good estimate of the supply's capacity.