I did some tests with the current 7.6.1.20R1 firmware just to make sure prefixes and units are handled correctly. I could see prefixes ranging from pico to mega as expected, which should cover all practical use cases for this DSO. I did not see femto though, so this must have been on some other scope.
First I tried simulating high currents by using 100V DC with a 10k probe factor.
SDS1104X-E_Int_DC_MA
Channel settings are displayed in kA, while math, automatic and cursor measurements use MA as required.
With the 0.1x probe factor, the lowest setting can be 50uA/div, but standard deviation in the measurement statistics is in nA and on a fast timebase, the integral can be brought down to the pAs range.
SDS1104X-E_Int_Pulse_uA
After these tests, I am positive that units and prefixes shouldn’t be an issue with the custom probe factors – but we’d need the femto prefix, see below...
I’ve also spotted a potential improvement for math functons in general and the integral in particular: the range for the Scale parameter could be a little wider than it is now.
The 2nd example uses the maximum sensitivity, which is 500pAs/div for 0.1x probe factor. Even though this should just be enough for real world applications, I would still think that it wouldn’t hurt to be able to go down to 100pAs/div (equivalent to 1nAs/div for 1x probe factor).
For the new probe factors down to 1E-6, we have to go much lower and would need the femto prefix indeed:
Probe Factor min. Scale
1E+6 1 mA/div
1E+5 100 uA/div
1E+4 10 uA/div
1E+3 1 uA/div
1E+2 100 nA/div
1E+1 10 nA/div
1E0 1 nA/div
1E-1 100 pA/div
1E-2 10 pA/div
1E-3 1 pA/div
1E-4 100 fA/div
1E-5 10 fA/div
1E-6 1 fA/div
There is also an issue in the first example, where I’ve used the highest Scale of 200kAs/div and this is not enough to get the entire math trace on the screen. I’m not entirely sure how the maximum Scale is determined, yet generally it appears to work just fine - just not in that particular case, where maybe some hard upper limit comes into effect.
In order to demonstrate that the upper Scale range is usually wide enough, I’ve tried the most extreme situation by setting a -2A offset in the 500uA/div range (1x probe factor). The integral can be scaled to fit the screen just fine:
SDS1104X-E_Int_DC_Offset_1ms
I have also tried a 1s/div timebase setting, and the math Scale automatically changed to 5As/div, just as it should be.