At 11:20 AM 8/17/2009, Forrest W Christian wrote: >Measuring voltage is a bit tougher in my mind. I'd really like to keep >the AC voltage isolated from my circuits. We use a Hammond PCB-mount transformer for our units (10VA or so). It has a 110/220V primary wired for 220V and 12/24V secondary wired for 24V. We run the primary at half-voltage or less just to ensure that we are as far away from saturation errors as possible. Many (most?) of the power-generating stations we build instrumentation for have their voltage-sense lines come out as 120V 3-phase which is about 70V across each transformer primary. That's less than a third of the rated voltage rating of the primary and we get excellent accuracy. Sorry that I can't recall the transformer part number right now but I can look it up for you if you need. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist