I have an application where I need to monitor voltage and current of 
three phase power in datacenters .... typically in the US, we're talking 
120/208 Wye (120 each leg to ground , 208 leg to leg).  

The current is easy - three current transformers wired to an appropriate 
circuit to rectify, filter, and measure...  pretty standard 
engineering.   Plus, current transformers are available pretty cheaply.

Measuring voltage is a bit tougher in my mind.   I'd really like to keep 
the AC voltage isolated from my circuits.   I have lots of ideas on how 
to do this (build a second circuit, with a PIC which is interconnected 
with the line voltage, and sends a serial datastream out a optocoupled 
line, etc.), but all of them involve building something which attaches 
directly to the AC line (which means the possible need for UL listing, 
and the added dangers/liabilities of having a product which does so).

I guess I'm looking for a couple of things... first of all if there is 
something commerically available that I've missed that will measure line 
voltage and output it as some sort of isolated low voltage - similar to 
a current transformer.   Cost is definitely an object.

Secondly, if there isn't an option that way, any design ideas which are 
simple/effective for measuring this with a PIC would be useful.  Thanks.

-forrest
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