How do I check Amp draw? - RC Groups
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Jun 20, 2002, 05:16 PM
Green Member
FX1SUB's Avatar

How do I check Amp draw?

I keep hearing how this motor combo draws x amount of amps and so on. Is there a website that explains all of this and how to check amps. I feel silly asking this since I already have three well flying planes, but I guess it's time to learn how the motor systems work. Hope I'm posting this in the right place...Thanks

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Jun 20, 2002, 05:42 PM
Dude, where's My Plane?
JasonJ's Avatar
You either need a watt meter or a multi meter. Very few multi meters can measue more than 30 Amps. If your stuff is smaller and draws less than 20 A, than a sears multi meter is fine, to measue current, you have to break the circuit and put the meter in series with the motor. There are some half decent low $ inductive meters out there that just clip around the wire and measure the strenght of the magnetic field to give current and are fairly accurate.
Most of the big advertisers here on the zone like hoby lobby sell watt meters for RC modeling though at a good price.
Jun 21, 2002, 10:09 PM
Sean in YVR (Vancouver)
YVR's Avatar
You want an Astroflight Whattmeter. If you're at all serious about electrics, you'll find it an invaluable tool for testing different setups (cells, props, motors). You can put whatever connectors you use on it and simply plug it in between your battery and esc. The display will give you amps and mah used. They come up occasionally in the For Sale forum, but they're always snapped up immediately. You won't know how you lived without it!

Sep 06, 2002, 02:13 PM
Registered User
I cannot seem to find any info telling the difference between Astroflight's Watt Meter and the Micro Watt Meter.
Anybody know what that is?

Sep 06, 2002, 04:21 PM
Trampling out the vintage
When I bought my Astro Wattmeter from Kirk at New Creations he said that the micro is for very small motors, such as used on indoor, and the regular Wattmeter is for parkflyers and up. Mine does a good job measuring current etc. to at least as small as the GWS A motors, which is as small as I go. I agree this thing is really needed if you are serious at all about electric flying. It is both fun and easy to use. I have a multimeter too and that is more of a pain to use.
Sep 06, 2002, 04:38 PM
Registered User
The micro watt meter measures 0 to 15 amps to 2 decimal places. I don't know the upper limit for the regular watt meter but it displays only to a single decimal place.

The advantage over a multi-meter is the watt meter displays amps, volts and watts at the same time.

The micro watt meter should be able to measure up to speed400 size except for the jst connectors supplied.

mike i.
Sep 06, 2002, 05:00 PM
Registered User
The great thing about the AstroFlight Whattmeter is the ability to see what the amps are pulling at different throttle settings. I use this along with the (60 * ah)/ Amps = Duration in Minutes to get an Idea of what i should set my timer to on my Tx for when to land

I also use it to charge batteries with capacities under 1ah due to the inacurate display by the 110D charger I use.

Its a great tool!