How to measure Amp?

Running current
Do solution 1 but don’t try to stall the motor.


Now here’s a thing. My $50 one and my $10 one BOTH have a 10A scale.

I hardly ever use them I just guessed they were for people who couldn’t be arsed to put in a series resistor and measure the PD across it.

What’s scarey is I am

What’s scarey is I am applying at Washington University to work on my PhD in computer science and to be a research assistant for a professor in robotics. That’s right Ill be teaching the young adults of tomorrow how to measure amps with their tongues. Actually I really was reading this thread because I had the same question. I pull motors from broken electronic equipment that peopl eI work with donate. Most of them dont have any markings so a good way to come up with voltage and amps that the motor can take is helpful.

Sometimes I can’t supress my inner child and I have t oleave stupid comments.

Yes, I know that Ohm’s law
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.

A note on Lego

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.

Scary thought

That is frightening. I used to be a “professor” (over here, “Professor” is a grade awarded to someone who’s an very eperienced lecturer and researcher) of Computer Architecture. (Can’t you tell?) It was back in the days when such posts were awarded on ability rather than on wether or not you had a PhD. I started my PhD: An Artifically Intelligent System for Closed Loop Control of a Refrigeration Plant. (Yawn.) My wife called it “A Clever Little Fridge.” I packed it in after one year, because the money was better in the Aerospace Sector.