Some of you may recall my previous post about a ~20V potential between my electrical ground and my concrete slab. That’s still not resolved - it’s currently sitting just under 10V.

Today I have a new mystery - to me anyway…

I’m sitting at my desk and notice that I got a tingle from the outer shield/shell of a USB-C cable. I got my multi-meter and measured 65V from the cable to me with my bare feet on the slab! It drops to about 16V if I lift my feet off the floor. I immediately assumed the charging brick it’s plugged into was faulty, but just in case I took a more measurements and found that the another similar charger has a similar offset, the “ground” part of a TRS cable plugged into an amplifier is similar, the accessible metal shield part of a USB-A port on an ASUS ChromeBox is similar. I assume that’s not normal?

This is a new slab on grade build. Ground and neutral are properly bonded - I checked a few outlets and ground to neutral is ~0.3V.

Edit - I don’t think there is any safety risk - I measured 0.3μA current.