What is the difference between a chassis dynamometer and a rotating hub?

　　Chassis dynamometer is a special metering device used to measure the output power, torque (or driving force) and vehicle speed (or driving wheel speed) of the driving wheels of automobiles. The general chassis dynamometer can be used to test the power of the car (maximum speed, maximum grade, 0~100Km/h acceleration time), the durability of the power transmission system, additional equipment, and can also help measure the economy and emissions of the car performance. The main parts of the chassis dynamometer are the roller mechanism, power absorption device, control and measurement system and auxiliary devices.

　　The rotating hub is generally referred to as the drum in the drum mechanism of the chassis dynamometer, but since the most commonly seen parts of the chassis dynamometer are rollers, non-professionals also refer to the chassis dynamometer as the "rotating hub".