4) Access for charging internal batteries would compromise safety - just as having external access to the internal microSD card would be on the 121GW
How would access to the SD card compromise safety?
Ok, potential loop grounding issue if plugged into a computer USB port while measuring mains voltage at the same time. Or like three meters I own the simple solution is serial put data to usb via two infrared making it completely iscolated from the ground in the USB of the computer.
After all, it doesn’t need to be USB 3.1 Gen 2 sleeeds at 10Gbs data transfer, it is just little lines of text being stored. If the micro processor had a little extra code it might be able to complete one of the oldest tasks besides computers have dkne for years besides a calculator, and compress this into a zip file making it 1/100th of the original size for faster transfer speeds.
Update: I just saw the comment you made to those who missed the point. I didn’t miss it, but I do have a $20 meter in my hand that does this type of isolation made by Digitek, it’s the DT-4000ZC
if a $20 meter can do this, I’m sure the effort can be that much extra?