[chbot] Earth issues

[Marshland Engineering]

Wow what a reply I got !!

For this discussion can we ignore the safety aspect. Besides, if you want
shocks, come and play with my eclectic fence. 10 times more shock than humble
mains. 

The discussion is about saving components on PC boards while under test. 

My Tenma rework station does not have the soldering iron tip earth to mains
ground. I was expecting this. 
MY Tenma power supply also does not have the negative connected to earth.  
I am working with a laptop so the USB ground would be floating.
My Rigol DS105E which when not earthed has a 90 volt AC on the probe earth
with respect to mains ground. I did not expect this. 

If the scope was not exhibiting the 90 v, my guess would have been a high
value resistor between equipment ground and mains ground to drain away any
buildup of static. 

Any suggestions on the Rigol's 90 v issue ?

Thanks Wallace.