What purpose does ground clip serve on oscilloscope connected to isolation transformer

 

It provides a return path for the signal being measured by the oscilloscope.

 

Do you mean that you are powering the scope through an isolation transformer, or what you are measuring with the scope is being powered through an isolation transformer, or that there is an isolation transformer between the scope and what you are measuring?

 

Do you mean that you are powering the scope through an isolation transformer, or what you are measuring with the scope is being powered through an isolation transformer, or that there is an isolation transformer between the scope and what you are measuring?

As far as the ground clip is concerned it doesn't matter. Since a voltage can only exist between two points you need the ground clip for the 2nd point irrespective of it being connected to Earth ground or Pluto.

 

As far as the ground clip is concerned it doesn't matter. Since a voltage can only exist between two points you need the ground clip for the 2nd point irrespective of it being connected to Earth ground or Pluto.

I agree. I should have stated that this question wasn't directly related to the OP's specific query, but rather just to trying to visualize the setup they are talking about.

 

Without a ground clip, you will be fine if your circuit under test is connected to the same ground reference as your scope. If your scope is isolated and/or if you are testing a circuit that is isolated (battery or isolation transformer powered), then you will get a lot of noise because the ground clip will be an antenna to all emf. Your probe will also be more of an antenna than a probe because it has only one connection to the circuit.

 

Without a ground clip, you will be fine if your circuit under test is connected to the same ground reference as your scope. ........................

Not if the signal is high frequency (above about a MHz). Then you need the ground clip connected to the circuit ground close to where the probe is connected. to minimize ringing and distortion of the signal.

 

Not if the signal is high frequency (above about a MHz). Then you need the ground clip connected to the circuit ground close to where the probe is connected. to minimize ringing and distortion of the signal.

True, true, true. I just keep thinking about hobbyists and 555 timer frequencies on this site.