One final tweak, behind each of the AC and DC switches are some mechanical switches. These are operated by small cams on the back of the rotary mechanism. This of course is a convenient way to turn off the unit without needing to add any more switches.
With that along with a nice cable I'm calling this project done...
Attached is the schematic, consisting of number of common blocks, DC offset filter and bias, variable gain Op-Amp and a rectifier.
This is a "slightly" tweaked version from circuitlib.com the main change being R3 to work better with my particular meter movement.
The rest of the build was largely around laying out and building the circuit onto a PCB and making the brackets to mount it. The brackets where made from metal salvaged from a rice cooker that already had M4 threads tapped.
Power is supplied using the existing battery contacts, an old school braided power cable would really finish the look.
Tim Savage
