In message <39F4E69E.3E6E13C0@nb.net>, Chris Eddy <ceddy@NB.NET> writes
>I know this subject has been thrashed somewhere back in history, but I
>cannot help it.  My electric company (Duquesne Light in Pittsburgh) is
>kicking my ass with the bill.  I am so spitting mad that I could
>co-generate.  $300+ per month when not even in the winter is
>rediculous.  So I have been pondering making some measurements so that I
>can identify where the electrons are all going.  I envision a small PIC
>based device with a current transformer that is put on each feeder in
>the breaker panel.  A simple serial bus to a PC, and voila, I am logging
>use on individual branches.
>
>My question is this.  Do I have to measure phase, via current and
>voltage, in order to get a usable value?  And if I do have to have both,
>I would prefer to use the CT for current and a galvanic field sense
>method to 'see' the voltage.  I would not get an accurate absolute
>voltage, but I would get an accurate phase lead/lag.  And if I have the
>phase angle and current, how would one then calculate the KVA's?  I once
>knew some of this stuff from school, but you know, don't use it and you
>loose it.

The UK Magazine Everyday and Practical Electronics (EPE) did a project
for this a few years ago using a PIC16C84, the actual sensing was done
using a hall effect transformer device. I built one, it works really
well!.
--

Nigel.

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