The inductor (eddy current) dynamometer is a device used for measuring mechanical horsepower. The machine is fundamentally an electric generator and has a field member which produces a magnetic field through which the conductors on the armature are rotated as the dynamometer is driven by the prime mover under test. The conductors on the armature cut through the magnetic field and a current is generated. The generation of the current in the dynamometer produces a counter torque that opposes the torque of the prime mover driving the dynamometer. This counter torque is traditionally measured by an arm projecting from the dynamometer frame and acting on a scale or other transducer resulting in a reading of a force which, multiplied by the distance from the center of the dynamometer, gives the torque. Torque coupled with the speed of the dynamometer gives the horsepower according to well-known formulas.
Dynamometer design and determination of horsepower through use of a dynamometer has remained quite static for many years. The methods do not provide an instantaneous reading of the horsepower.