clamp meters accuracy ?

[Hayden]

How good are clamp meters? I need to measure current to fine tune a rc car I was just wondering are they as accurate as an inline meter?

do they vary in accuracy if the wire isn’t in the middle of the clamp?

[EC8010]

I think you'll find they're for AC only, whereas a radio-controlled car is DC.

[cliffforrest]

And the lowest range on mine is 200A A/C, with a resolution of 100mA.

I doubt that it is better than 10% aacuracy.

EDIT: I found the leaflet

2% or reading + 5 digits (ie 500mA).

I don't think this is what you are looking for.

[theAnonymous1]

Originally posted by EC8010
I think you'll find they're for AC only, whereas a radio-controlled car is DC.

DC clamp meters are very common. They're not any more accurate than the AC variety though.

http://us.fluke.com/usen/products/LH...FlukeProducts)

I'm sure Hayden is trying to avoid having to cut the wire he wants to measure.

[phase_accurate]

RU able to exactly measure the DC resistance of the wire through which you want to measure the DC current ?
If yes you could use it as shunt resistor for this measurement if it has a reasonably high resistance and you have a DC voltmeter that is sufficiently sensitive.

Regards

Charles

[EC8010]

Originally posted by theAnonymous1
DC clamp meters are very common. They're not any more accurate than the AC variety though.

Thanks for that. I expect they're more expensive than the AC only ones. AC current probes for oscilloscopes aren't too bad, but when you want one that goes down to DC, whooee! The price goes up.

[Hayden]

I can remove the wire but I’m talking a brushless motor which is oscillated in excess of 1400watts
I also wanted to measure what power I’m drawing out of the battery.

My situation is ac/dc i think

[theAnonymous1]

Originally posted by Hayden
I can remove the wire but I’m talking a brushless motor which is oscillated in excess of 1400watts
I also wanted to measure what power I’m drawing out of the battery.

My situation is ac/dc i think

When you said "fine tune a RC car" I'm sure we all assumed relatively low current levels were to be measured. I think at 1400 watts the accuracy of a clamp meter should be acceptable. I guess it all depends on how "fine" your fine tuning needs to be.

You could also try a high current shunt.

http://www.rc-electronics-usa.com/current-shunt.html

[Hayden]

When you change things like motors or the gear ratio you sometimes need to dyno the car to see what the power/speed output and current draw/temperature so it can work efficient or not efficient for speed runs

It doesn’t have be “very” accurate maybe just 2% if that’s possible?

[theAnonymous1]

The choice is really yours.

Clamp meter:

Pros: Easy to use.

Cons: Not the best accuracy, expensive initial $investment$.

Current shunt:

Pros: Better accuracy possible than a clamp meter(need a good volt meter), less expensive than a clamp meter.

Cons: Must be in series with the load so requires disconnecting/cutting wires, accuracy can drift if the shunt heats up due to high currents.