Dynamometers

In order to measure the mechanical power transmitted by a shaft, it can be coupled to either:-

I) an impeller which, rotating within a water or oil-filled casing, causes mechanical energy to be converted to heat energy. The reaction force, on the casing can be measured by a load cell and when combined with the speed of the shaft, enables the shaft power to be calculated.

OR
ii) an armature which in rotating within the magnetic field of the stator-casing windings causes mechanical energy to be converted to electrical energy. The shaft power is calculated as described above.

OR
iii) a steel disc can be whirled between electric coils such that eddy-magnetic currents cause the mechanical energy to be converted to heat energy. The shaft power is calculated as described above.