Measurement technology

The twenty-fifth entry is l’anello di massa, and the trap is that both halves translate cleanly and the result is nonsense. La massa really is mass, the kilograms of a thing, everywhere except on a circuit diagram — and this list is a circuit diagram. There, la massa is the common reference conductor, the metal that every voltage is counted from: the chassis, the instrument case, the screen of a cable. English calls that « earth » on this side of the Atlantic and « ground » on the other, and the fault named here is the « earth loop », a second return path that turns the reference into an aerial and lays mains hum over the reading. So l’anello di massa is a loop of earth, not a ring of mass. Two habits follow from it. Collegare a massa is to earth something, and massa printed beside a terminal means what « GND » means beside an English one. And Italian keeps a second term, la messa a terra, for the protective earth that goes into the soil; in a laboratory the two are not used for each other.