@indman:Sorry to report a minor bug in your portable s/w version, that you linked in reply#450.
In playing around, I noticed that with the probes shorted and sensitivity set to 5mV/div (Probe x1 setting), the CH1 trace had virtually no noise compared to CH2. By tying the probes together, I found that instead of 5mV/div it is actually selecting 500mV/div. This is duplicated on the other probe multiplier settings (eg. 5V instead of 50mV on probe X10 etc.).
One other thing I noticed is that I was getting voltage offsets at zero signal on various ranges, which I hadn't seen previously - even after Factory Reset and Self Cal. Then I remembered you saying that you had manually tuned your scope for maximum accuracy on voltage readings....
After some experimenting, I found that both \flash_text\flashmemory.txt and \configuration\com.owon.uppersoft.dso\pref.properties seem to be involved in storage of calibration data. Copying both files from my previous (camomille) installation restored the zero offsets.
I am not surprised that your portable snapshot would contain calibration data for your specific unit, what did surprise me is that Factory Reset and Self Cal didn't completely resolve it - curious. The good thing is that these two files appear to hold all of the relevant calibration data - I don't think anything gets stored in Flash on the unit.
I am still trying to figure out the difference between the 'Zero Amplitude' and [EDIT:
'Zero Offset' 'Zero Compensation'] tabs in the calibration screen. I suspect that one is for AC coupled and the other for DC but haven't established that yet.