Total Harmonic Distortion THD for the rectifier
this depends a lot how "good" this estimate needs to be. Here is a "rough &amp; dirty" method.


Put your scope in spectrum analyzer mode. Make sure you see all harmonics. 
Look where the highest harmonic is and that's still visibly sticking out over the noise floor.
Quadruple that frequency and use this as your sample rate. 
Sample your signal for a sizable portion. You want at least a 1000 cycles
Filter the signal with a steep notch filter at the line frequency
Throw away the first 50 cycles or so.
Divide the power of the filtered signal by the power of the unfiltered signal. That's your THD estimate