A dynamometer or dyno can be defined as a device that is used to measure torque and the rotational speed of a machine. This measured data can determine the brake power, speed and other parameters of the rotating machine or an engine. A dyno, apart from measuring torque and power, can also be used as a test-bed for different types of engine-related activities such as calibration of engine management controllers, deep investigation of combustion behavior and tribology.

A dynamometer can be classified into two types:

Power absorption dynamometer:

Power Absorption dynamometers measure and absorb the power output of the engine to which they are coupled. The power absorbed is usually dissipated as heat by some means.Examples of power absorption dynamometers are Prony brake dynamometer, Rope brake dynamometer, Eddy current dynamometer, Hydraulic dynamometer, etc.

Power transmission dynamometer:

In power transmission dynamometers the power is transmitted to the load coupled to the engine after it is indicated on some scale. These are also called torque meters.

Also Read: What Is Vernier Caliper ? Principle Of Working Of The Vernier Scale

Classification of absorption dynamometers

  • Prony brake dynamometer:

It is the simplest form of absorption type dynamometer. It has two wooden blocks that are placed on a pulley which is fixed on the shaft of the engine whose power is to be measured. The wooden blocks are clamped together with two sets of bolts and nuts. To control the speed of pulley, the pressure is adjusted over a pulley with the help of a helical spring present between the nut and the upper block.


A long lever is attached to the upper block which carries weight on its outer end. This weight placed on the lever balances the brake when unloaded. When the brake is to be applied, the suitable weight is loaded on the outer end of the lever and nuts are tightened till shaft of the engine runs at a constant speed. The movement because of the weight loaded on the outer end of lever balances the movement of frictional resistance between the pulley and wooden block. The power absorbed during friction is converted into heat which is why this dynamometer needs to be cooled down often.

The brake power formula is given by-

Brake power (bp) = 2π NT, where T = Weight applied (W) × distance (l)

  • Rope brake dynamometer: