oh it’s an optical interface to a smart meter, not “optical meter”. Could not find the schematic or BoM for the $15 PiggyMeter board. How does this “set new standards for documentation”?

Exactly – I’ve seen people tell newbies fiddling with Arduinos that they need a $200 fluke to be safe when a $5 meter and $195 change for other things is by far the best answer for them.