bug found? Hantek DSO5102P: different measures in AC vs DC coupling

[bdunham7]

And this is consistent across all channels?

[radiolistener]

And this is consistent across all channels?

yes, the behavior is exactly the same for both channels. Both have the same frequency response.

[DL2XY]

Your mains voltage is not a sine wave but a trapezoid.

Simulating the measurement with a clean trapezia clearly shoes the effect:
During the constant voltage phases the coupling capacitator is charging, in the transients this charge is transported to the other half-cycle resulting in overshoot.


 

[David Hess]

There are plenty of oscilloscopes which do not suffer from additional distortion when measuring distorted AC line waveforms.  With a single pole response, even the difference between 1x and 10x probe attenuation yielding 10 and 1 Hz cutoffs is not visible.