Interesting – are the sample depth and sample rate on auto?

If so, it should switch itself to 4000Hz and 256 samples when you go to AC. If you have a manual sample rate set too low (say 125Hz) then the 60Hz in the wall will not give a good AC RMS reading.

Also – iOS or Android? If Android I recommend pulling the moosh.im/s/app-latest.apk
Once I get a few more results I’ll make it the default.