Abstract: A system is provided for measuring the rotational velocity of the rotor of an electric motor or generator having (i) a stator with a plurality of circumferentially spaced pole pieces, each pole piece having a corresponding armature winding, and (ii) a rotor with a plurality of circumferentially spaced magnet portions, the armature windings interacting with the magnetic field produced by the magnet portions. The system includes one or more voltage sensing coils. The or each voltage sensing coil is adapted to encircle a respective pole piece of the stator such that a time-varying electromotive force is induced in the voltage sensing coil as the magnet portions of the rotor pass by the pole piece. The system further includes is a detector for detecting the time-varying electromotive force induced in the or each voltage sensing coil, and determining the rotational velocity of the rotor from the time between peaks in the induced electromotive force.