you measure the DC offset to the zero crossing points of the sine wave cycle
the zero crossing point of the AC sinewave is sitting at 6V on your CRO.
When measuring AC ripple on a power supply is the measurement from the Oscilloscope's zero Origin zero volts to the negative peak of the AC sinewave or to the zero crossing point of the AC sinewave? Neither, its the peak to peak voltage of the superimposed ripple waveform.
DC superimposed on a AC waveform is different than DC offset voltage? Just semantics, offset voltages normally refer to odd voltages at the input of opamps. DC superimposed on a AC waveform, would mean that some DC is added to a signal wave form for some purpose.
DC superimposed voltage means you measure the DC voltage from the zero origin to the negative peak of the cycle? no it is the zero crossing thing again.
Whats the difference between DC superimposed voltages VS DC offset voltages? see previous answer.
Frank