>> Use a small transformer from 120 VAC to 6 or 12 volts. Monitor the
>> output
>> of that instead of the 120VAC line.
>
> The output of the transformer that supplies the +5 VDC regulator should
> work, then.

Not unless one of the transformer terminals is at circuit ground. That
would be if you have either a center tapped transformer, or are doing only
half wave rectification.

> Will there be any phase difference between the primary and secondary
> side?  That is, will both cross zero at exactly the same moment?  I'd
> sort of assume yes, as, well, that's what transformers do...  This is a
> dual secondary, with the outputs connected in parallel for higher current.

I would not use a transformer that is driving a rectifier load if you need
high accuracy. Use a separate transformer, with a small load resistor (a
percent or two of rated current) for most accuracy.

Cheers,

Bob


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist