Dynamometer: A device used to measure the power output of rotating machinery. In it’s simplest terms, a dynamometer is a power-absorbing brake, incorporating an accurate method of measuring how much torque (and horsepower) is being absorbed. Braking is accomplished through friction (usually a hydraulic absorber) or by an electric dynamo (converts energy to electricity). Modern computer-controlled dynamometers for high-performance automotive use have sophisticated speed controls that allow the operator to select the rpm point or range of speeds through which the torque is to be measured. Then the operator opens the throttle and the dynamometer applies the precise amount of load to maintain the chosen rpm points; horsepower is read out directly on a gauge and/or computer screen.