In the thread "
TS100 doesn't function properly when earthed" users Rooster Cogburn and Gyro discuss the implication of a non-earthed PSU connected with a 3-prong cable. They use expressions like
This brick PSU is certainly not mains earth referenced and leaks plenty of AC like most SMPS units
or
I must have like a hundred devices here with cheap SMPS that each have ~50% mains VAC between their ground and mains earth.
or
the output floats to half mains voltage due to the EMC filter caps.
Could someone explain what is this AC leakage and how it can be detected?
If I had an oscilloscope (I don't), could I measure the voltage between mains earth and the -V of the 12V PSU output and see an oscillating wave with amplitude 120V (240V/2)?
What about probing earth and +V? Would I get an oscillating 108V wave (240V - 12V)?
If so, isn't that extremely dangerous? How could it be that Rooster has hundreds of such PSUs in his house?