I have a circuit which generates an accurate pulse 500ms wide. I use the PicoScope 6 measurement function to measure the high pulse width between rulers. When the timebase is set to 100ms/div, I get sensible results:
Thanks for pointing this out, but I was already aware of it. The thing is, I'm seeing good accuracy at the lower sampling rate, and lousy accuracy at the higher sampling rate.
At 12.27KS/sec you'd expect to measure a 500ms interval to about 0.02% accuracy. At 2.5MS/sec, you'd obviously expect better accuracy, not worse.
Yes, if I change the slow sampling transition to 500ms/div, then the measurements are good at 200ms/div. So it appears there is a bug which only affects slow sampling mode - do you agree?
It does appear that when using the slow sampling mode the downsampled data that is used by the measurements engine is introducing inaccuracies, compared with the downsampled data retrieved directly from the scope when using faster timebases. I will pass the information on to the development team.
Can you send the text from Help->About, with the scope attached, so that we know the versions of S/W, F/W and H/W you have.
Thank you for the information. I tried with an identical setup and am seeing stable high pulse width values, with the same values in both modes.
When replicating the same sampling intervals as you, I did notice that the digital channels are enabled but not showing in your screenshots. Does the issue disappear if they are turned off.
Would it be possible for you to post the two psdata files, corresponding to the two pictures.
I re-ran it at 100ms/div (m_100ms_div.psdata) and 200ms/div (m_200ms_div.psdata). As before, the results were correct for 100ms/div but wrong for 200ms/div.
I turned off the digital channels and tried again at 200ms/div (m_200ms_div_digital_off.psdata). This does seem to fix the problem.
I've also attached settings.pssettings which will hopefully allow you to recreate the problem.