Hello Slobodan, Rob, Erik, Steve and all,

Sloboday is certainly correct in that I will need to add an inverter to one of the 4066. I will fix the schematic later today.

I stuck with the 4066 because I have it, easy to get world wide and it is super cheap (<$0.50 US).

I am leaving the 1 meg ohms resistors on the opamps for CMRR.

This method provides the most isolation I know of. It also provides the most convince I have ever heard of for measuring high AC voltage and AC current. It delivers 98% accuracy and is about standard as you are going to get.

The 12 MHz crystal is also going to stay. There is a timing issue which needs the 12 MHz crystal. Outputting the speed is not a real big issue. If the user needs faster speed he can put in a 24 MHz crystal and get 4800 baud.


The web site given does have the application I mentioned. Look for the below description.

http://www.atmel.com/dyn/produ...ily_id=604

Analog-to-Digital Conversion Utilizing the AT89CX051 MCU (6 pages, updated 12/97)
This Application Note describes how to build a low cost A/D converter with the Atmel 20-Pin Microcontrollers.

Again special thanks to Slobodan. I missed your point twice.

Regards,

Charles Bannister