Ayrton shunt

The Ayrton shunt or universal shunt is an arrangement of switched resistors used to increase the current range of an ammeter or galvanometer . It is an improvement invented by William E. Ayrton <ref>{{cite web|url=http://www.merriam webster.com/dictionary/ayrton%20shunt|title=Ayrton over the classical arrangement, which requires a make-before-break switch to avoid damaging current surges through the meter movement when switching ranges. If the switch ever fails to make before break, the movement can be destroyed .