Thanks, I didn't know that the USB B port doesn't provide voltage (in fact I measured it and it doesn't have 5V). Patience, I will power the probe from a USB charger.
As for where to place the two probe tips, if I understand correctly, for example if we had a rectifier diode, I could put the probe tips on the two ends, both having a voltage?). In short, I would measure the voltage drop signal in the diode. It works like this? Thank you