Measuring current at circuit breaker

[systemguy]

Hi all,

I have a labjack U6. I am trying to measure current running through individual circuit breakers in my house. My first thought was to buy some split core current transformers (digikey part #: 582-1004-ND) and clamp them to wire going into each breaker.

Any sense of whether this will work? I assume I can measure just one phase of the AC voltage and use an appropriate resistor to scale the voltage properly. Am I missing something?

I assume the max number of current transformers I get working with the U6 is 14, is that correct?


Thanks,
Mike

[LabJack Support]

Sounds reasonable. You would pass the CT output through a resistor to get a voltage signal. I wonder what happens if the resistor comes loose. There would not be anywhere for the current to flow, so the voltage would rise, and could it rise high enough to damage the LabJack analog input? The datasheet for your CT barely mentions that it will "develop signals up to 10.0 Vac", which would be fine, but not sure what the actual max is.

You need to acquire a waveform and do the desired math to get the information you want (such as RMS).

The proper way to measure energy is to collect a voltage and current waveform at the same time, multiply them point-by-point to get a power waveform, and then integrate that to get energy. Short of that, I would just assume voltage and measure current only.

Useful topics:

http://forums.labjack.com/index.php?showtopic=4274

http://forums.labjack.com/index.php?showtopic=4263