Dynamometer

The dynamometer controls the engine RPM and measures the output torque and RPM of the engine in steady state. The device is a DC generator that is driven by the engine. The electrical work of the generator is dissipated in a load resistance. The generator output is controlled by altering its magnetic field using a rheostat to control the current through the field windings on the generator. As the field is changed both the output voltage and current vary.

The output torque of the transparent engine is in mechanical equilibrium with the torque due to the electromagnetic interaction between the field coils and the rotor of the DC generator. This torque is measured using a strain gauge balance coupled to the field coils. The engine RPM is measured using both a mechanical tachometer and an electronic tachometer coupled to the output shaft of the engine.