I'm confused about the Vrms value of a clipped rectified sine:
The reason it's clipped and distorted, is because it's the output from a tiny transformer (0.7W), and the filter bank charges at the peaks of the waveform, pulling down the voltage.
Anyway, it measures as 3.88V peak, yet only has 1.39V RMS. I don't understand that. If it were a sine with the same peak of 3.88V, Vrms would be 2.74V. If anything, I expect Vrms to be higher than that (like driving an amplifier into clipping increases power to the load).
Can this really be the correct Vrms value?
The scope itself seems to behave OK; sines, quares, triangles with and without DC offset measure correctly. Edit: actually, it doesn't... It doesn't include DC offset in the Vrms value.