Measuring ac amperage with multimeter

[ccdoggy]

So i got a Clamp multimeter (craftsman i think) for xmas, on the package it says it reads AC/DC Amperages. So i quickly take it out and try it out. I get my 1500watt space heater going and try and measure it's power cable, I do have it set on AC and zeroed out. but alas i get nothing. I take it to my car and it can measure the dc current no problem.

I took it back and got a new one and had them test it there but the same result, nothing showing when on AC. So i got a refund.


I i doing it wrong? After thinking about it for a bit can i only connect it to one of the ac wires, not both (would both effectively neutralize any reading?). Or am i doing it right and both were just broken?


I want this to work as i need to do some amperage testing for our house and i am more or less curious about stuff.

Thanks for the help.

[AKN]

Originally posted by ccdoggy
I i doing it wrong? After thinking about it for a bit can i only connect it to one of the ac wires, not both (would both effectively neutralize any reading?)

Hi ccdoggy,

Yes, you must have access to a single wire otherwise reading will be a summary of turn and return currents that go in opposite directions - zero reading. The same applies to DC measurements.

[ccdoggy]

Thanks so much for the reply, i posted this on another forum and got into an argument with someone about measuring amperages without placing the multimeter in series with the circuit.

So I need to go back and get that multimeter and then to also pick up a AC line separator which plugs into an outlet and thus allows me to read only one wire. Would that be correct?

Thanks again.

[Eva]

Correct. It will measure AC current that way.

Be aware that it may not measure any DC current at all with the clamp method, though, as this involves expensive hall effect sensors.

[ccdoggy]

Suprisingly it did, i measured my car's alternator's output and my mom's suv's output and it was good at measuring that.

Im going back right away to pick it up as it should be allot more expencive then it was at $99.99. It even measured capacitance too.

[AKN]

ccdoggy,
The "zero measuring" you have done so far on AC cables is also useful, that way you make sure all current goes through the power cable and not some other way.

[Pano]

Some of the clamp on ammeters have an adapter just for this purpose. You camp thru the adapter loop and plug what you want to measure into the other end.

Or better yet, get the "Kill-A-Watt" meter.



I've had one for years - works great.

Will give you:
Volts AC
Hertz
Watts
VA
Amps (up to 15)
Power factor
Kilowatt hours

All for about $25 US. They were $50 when they first came out. You can find them all over the web, including Amazon.com

A very handy gadget!