What is the ADC input impedances? I’m seeing some loading effects on my measurements, and just want to quantify these.
The ADC+/- input impedance varies with input voltage due to the way the input circuitry works in the INA226 chip that is utilized for those pins. With a low input voltage the combined input impedance will consist mainly of the VBUS pin input impedance which is typically 830kOhm. With higher input voltages the input bias current will start to ramp up to 10uA per pin decreasing impedance down to slightly higher than 200kOhm at the high end. I did a quick sweep with both ADC inputs connected to the main output:
Compare this to the Sense+/- pins where the input impedance is a constant ~1MOhm per pin:
Ahh, that would explain the variation in the variation as well…
I didn’t think to connect the Otii to itself… Thanks for the prompt reply!