Messuring current into motor

[wolff2000]

Can anyone tell me how to measure the current going from the controller to the motor. I have a cheep-o digital VOM and when I hook it up in series (I know how to do it correctly) I get a current reading (about what I expect) but the motor only hums. It does not turnover? BTW Everything works fine without the ammeter hooked up
The controller is a pixie 7P and a GWS-A motor.
Thanks for any information!!!!

[Patrick del Castillo]

Wolf,

Sounds like your ammeter is adding too much resistance to the circuit. Plus, it won't really give you a good result anyway, most ammeters are designed to measure low frequency stuff.

Best way is to use a shunt resistor (.001 ohms or so) and an oscilloscope.

Anybody else have an easy way to do this?

Patrick

[wolff2000]

Look like I'm going to have to fork over a few bucks and buy a Astroflight Super Whatt Meter ........ $ 65.90
Oh well, I guess it's cheeper then a scope!
Thanks... J

[FoamCrusher]

Why not measure the current on the battery side of the ESC rather than between the ESC and the motor? On the power side of the ESC the drain is all pure DC and not pulsed.

Measure the current with the motor off so you can record the draw of the Rx, ESC and servos at rest, then crank up the motor and record that value. Subtract the first reading from the second and you should have the current consumed by the motor, minus a little for heat lost in the ESC, or am I missing something here?

If I am, aren't we still just usually concerned about how the batteries will hold up to a given prop/motor combination and not "pure" power comsumption of the motor and that should include all of the drain on the batteries?

FoamCrusher

[wolff2000]

Yeah, I came to the same (inexpensive) conclusion! Thanks!