How do you measure the voltage across an ungrounded component, while using an oscilloscope?

 

Is there a reason you can't ground one side of the power supply for this circuit?

 

Do not ground scope (of course if you are looking not at high frequency signal) ?

 

...or use two-channel scope and subtract channels...

 

Measure the voltage on the one side of the component, then the voltage on the other side and subtract the first from the second or vice versa (It just changes the sign).

 

...or use two-channel scope and subtract channels...

This is pretty much my "default" mode in the ham shack! I work with a lot of balanced R.F. circuitry. I'm surprised how few people know this function is even available on most scopes!

eric