[volt-nuts] current-nut question .. total waste of ones time type question

Brooke Clarke brooke at pacific.net
Tue Apr 29 20:08:23 EDT 2014

Hi Pete:

I did this may decades ago.

1) Do not use clamp on current probes, they have very poor accuracy at low currents.

2) Rather than using a current monitor on each circuit just use two current sensors, one on each input leg.

3) Current transformers MUST be terminated with some load resistance, i.e. they transform an input current into an 
output current which gets changed to an output voltage by the load resistor.  I put the load resistor close to the 
current transformer so that a break in the long cable would not cause a problem.

4) I plotted current use on an 8.5 x 11 paper in landscape mode. Each trace was offset from the prior trace by about 
1/4".  At night when not much is happening  you just have a bunch of straight lines, except for the frig which has a 
regular cycle. But if someone gets up at night you can tell.

Smart meters can provide data every  15 minutes, if they are in a network.  My smart meter gets read manually so no data.

Have Fun,

Brooke Clarke

Pete Lancashire wrote:
> Next spring I'm going be rewiring my house. And for 'fun' I want to drop a
> couple current sensors on the input side of the main panel.
> Being a beginner 'nut', I'm looking for more accuracy then needed.
> Voltage, Frequency, waveform will be taken care of later, but accurate
> current has be a bit flustered.
> I've been reading up on CT's Iron core and Ferrite, and on Rogowski coils.
> And the many new IC's on the market that take care of a lot of things.
> Has someone done this before ? And if so any experiences to share ?
> -pete
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