Thank you Jim!

That’s really interesting… the same meter gives different behavior measuring 480VAC.

It’s a tough diagnosis. I’m trying to think what impact a marginal battery connection could have… the best hypothesis I can come up with is tenuous. It goes like this: The inputs to the ADC have a clamping path that dumps back to the batteries (there’s enough series resistance that the current involved is on the level of hundreds of microamps). It may be possible that there was a tenuous connection to the battery, and the overvoltage clamp did not function correctly, which was causing the overload and reset events that you witnessed the first time.

It’s hazy and tenuous but that’s all I can think of right now. I’ll let you know if I see the answer in a dream. I’m glad it’s working for you though, please let me know if you discover anything new.

Best
~James