Hey I'm already measuring current with an arduino and it's working great and it agrees with what my clamp meters read. Now I'll like to measure voltage but I'm having a hard time sourcing an AC-AC power supply in Mexico.
Will something like this: http://imagenes.steren.com.mx/_imgs/prod/zoom/TR06-500.JPG actually do the job? It's just a simple RAW 120AC->9AC transformer without any other circuit, is that everything that is required? (plus the scaling and offsetting circuit) or does the 9VAC power supply needs other properties?
Re: AC-AC Adapter
I cannot tell from just a photograph, but your description that it is a transformer with a 9 v output is what you need. You will find the voltage without a load is considerably greater than 9 V (normally it about 11 V) but this is not a problem with the input circuit and component values in Building Blocks. You must of course house it properly in either an insulated or an earthed metal enclosure to protect it and to assure the safety of anyone who might otherwise touch it.