Clamp on CT sensor

I've been doing some reading up and would like to build a project that non invasively measures the power of different devices (PC, fridge, TV etc)

I'm going to be using a arduino and a clamp on CT sensor. From **broken link removed** up about these sensors it looks like the clamp needs to put around the live or neutral wire only and not around the whole cable (live/neutral/earth) - that's not what I was expecting as its not quite invasive then?

Am i missing something? Do you get sensors that you can clip around the whole cable that will give you the current value?

In order to use a clamp meter, only one conductor is normally passed through the probe; if more than one conductor is passed through then the measurement would be the vector sum of the currents flowing in the conductors and would depend on the phase relationship of the currents. In particular if the clamp is closed around a two-conductor cable carrying power to equipment the same current flows down one conductor and up the other, with a net current of zero.

Click to expand...

The above quote was taken from here and "sums" it up nicely.

So to answer your question, no, the sensor is placed around a single conductor. Now, that single conductor can be looped through the clamp on sensor. For example if I loop a conductor carrying 5 amps through the C/T sensor 5 times the sensor would sense 25 amps.

Ron

Ron

Thanks for the info. All cleared up now.

Im going to order a current sensor and then use it with a inline plug.

if you put the CT about three cables, the result set would be the difference between the currents passing through each individual cable, normalmene zero.