I am confused about a problem I am having measuring the output of a full wave diode bridge rectifier driven by a function generator. I am only getting half of the output as if it where a half wave rectifier. This is only a problem when I hook up my o-scope.
This is just an experiment. I don't plan on driving any sort of real load.
Now the obvious answer here was that the both the generator and the scope where referenced to earth ground. I tried to solve this problem by floating the function generator through a 1:1 isolation transformer. I also used an adapter to prevent earth ground from being connected through. I confirmed there was no continuity between the ground shields of the BNC connectors of the generator and o-scope yet I got the same result.
At this point curiosity/frustration caused me to put caution to the wind and I tried to drive the rectifier directly through a toroidal transformer I had salvaged from some strip lighting that was rated for line voltage with 12V out. It worked as expected. I had both sides of the rectified signal.
So what is the difference between using this toroidal transformer and driving it from a function generator that I have floated using an isolation transformer.
I just ordered a caltest differential probe. I figure it will be a useful piece of gear to have one way or the other. Im hoping this might help to float the ground of the probe.
I cant seem to reproduce the problem today. So I guess the problem was between the chair and oscilloscope. Sorry...
Just for the sake of completeness this was the setup:
Wall -> Powerstat 3PN1168 Variac -> Triad N-59MG Isolation Transformer -> (adapter to lift earth ground) -> SDG2042X Waveform Generator -> Diode Rectifier
Wall -> Rigol DS2202A -> RP3300A 10x Probe -> Diode Rectifier.
Lifting the earth ground with an adapter is necessary. Perhaps I was somehow missing this yesterday in swapping between different configurations. It does add a significant amount of 60Hz noise to the output of the function generator regardless if the output is turned on or not.