Adafruit USB Isolator - 100mA Isolated Low/Full Speed USBHave some USB logic analyser, multimeter or oscilloscope and bumping up against the frustration of a shared earth ground? The Offspring (known for being electrical engineers) wisely sang "Ya gotta keep'em isolated!" Power and signal isolation improves common mode voltage, enhances noise rejection, and permits two circuits to operate at different voltage levels. This handy little low cost USB Isolator is exactly what you need to provide protection