About: http://webisa.webdatacommons.org/56680846

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Ground is only 0v because you are comparing it to itself, so the difference should very well be 0v.Differential is a special case because it does not reference ground, it references another signal line.
http://www.w3.org/ns/prov#wasQuotedFrom	arduino.cc