The Collaborative International Dictionary of English v.0.48:

Electro-dynamometer \E*lec`tro-dy`na*mom"e*ter\, n.
   An instrument for measuring the strength of electro-dynamic
   currents.
   [1913 Webster]

WordNet (r) 3.0 (2006):

electrodynamometer
    n 1: measuring instrument that uses the interaction of the
         magnetic fields of two coils to measure current or voltage
         or power