I am trying to galvanically isolate my electronics from the Mains and isolate Earth, so have placed an isolation step-down transformer (230:20) in between the Mains and my electronics.
If I measure from load (which is across the secondary) or the secondary terminal to primary terminal, I am seeing Voltage. The two terminals of the secondary show different voltages with respect to the two terminals of the primary, but both the secondary terminals show voltage with respect to both the primary terminals.
The above readings differ from multimeter to multimeter, some not showing any voltages at all. I am sticking to Fluke multimeter.
I guess this is capacitive coupling.These voltages do not disappear even when the secondary is loaded.
I got my transformer maker to make a transformer with shield in between and grounded the shield. Still the cross-voltage only worsened.
As the source of this voltage is capacitive coupling, I guess this will allow AC noise to be transmitted to the load.
I would like to know if it is possible at all to completely decouple this cross-voltage from the secondary and if yes, by what means ? Can this coupling convey primary side noise and fluctuation to secondary side ?
On the secondary side, I have a switching regulator supplying regulated voltage to an electronics instrument. I do not want secondary side to refer to Earth.
Thanks in advance.