More testing on the Zoom of digital Filter Function
Here I test a LoPass Dig. Filter : Normal and Zoom
1 LoPass at 20Khz and sweep from 5-40Khz
2 LoPass at 20Khz and sweep from 5-40Khz Zoomed
3 LoPass at 8Khz and sweep from 5-40Khz Zoomed
From this, I conjecture that the FW is using the 5oous/div time base, with the Zoomed Data and therefore the Digital Filter function is incorrect by a factor of 200/500.
Therefore the Cutoff frequency becomes 2/5 of 20KHz=8KHz.
I conclude it is a Bug!!
In zoomed mode the filter slope should expand by the zoom factor (display division)