Thanks for the reply, do you have a part number for the instrumentation Op-AMP? I prefer the full isolated method since the PLC will be switched between the 120VAC supply and battery backup, though I will have to study the circuits sensors, and controlled devices to see whether everything is isolated. The wires are in 30 feet of metallic conduit, there are 3 CAT-5's in one conduit, and 4 #12 stranded plus 10 #18 stranded (to controlled devices, automotive relays) in another. Planning to use the two of the #12's for indoor mounted battery charger, could use one of the other #12's for the ground, or maybe 1 or 2 of the CAT-5 twisted pairs.