I am using the PPKII to supply a 1.8V supply for a circuit board in my measurement setup.
I have been battling a low-frequency oscillation at 0.5Hz at around 5mVpp, which is causing measurement variations in my setup.
I have now found that this LF oscillation is likely coming from my PC via the 5V USB connection - see below plot:
Above the blue curve is the 5V from the PC and the orange is the output 1.8V.
The oscillation amplitude is reduced about 50% from input voltage to output (app. same as the mean voltage difference).
Likely this is too low frequency for the internal filtering on PPKII to deal with it.
I have tried to use the PPKII in Amp meter configuration with a clean 1.8V input - but I still see a ripple from the PC connection (smaller effect but still there...)
Questions:
- Is there a way to use the second power port on the PPKII to run a clean power to the PPKII output driver circuits - thus removing this ripple while still being able to communicate over USB with the PC?
- Does anyone have other ideas for removing such a 0.5Hz ripple/oscillation from the PC connection? As mentioned using it in Amp meter mode does not solve the problem completely.
This does appear to be a limitation for using the PPKII for measurements over seconds or minutes. An option to provide a clean 5V to the internal circuits would be great.
Thanks for your help
