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How to measure Amp?

Could somebody explain in a very easy way (with a drawing of what goes to what) show how one measures how many amp a motor is taking?


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I usually just measure resistance of motor when it's not running. Then use Ohm's law to get approximate stall current.
I'm not sure that works with inductive loads! (Well, you DID say "approximate.")
Yes, I know that Ohm's law only applies to resistors :-), but this is just to get an idea of what to expect when doing the real measurement setup using ampere meter. It worked quite nicely for my lego 9V motors anyway.

I found the Lego motors (I presume you're into the NXT or RCX style motors rather than teh old circa 1980s ones?) to be massively efficient. Strange as it sounds, they don't behave like coils at all.

Have you ever hooked two of them back-to-back and turned the spindle of one? Of course it acts as a generator, but the "slave" motor turns with an almost 1:! ratio!!

I find that reasonably strange. 

 Hey Frits,

I think you can just use a clip-on meter. It simply clamps around the positive wire -it's inductive. Double check what you get, though -some will only work with AC. 

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