The falling and rising motion are repeated more than once with a period that depends on the initial height difference h, on the acceleration due to gravity g and on the relationship between the radius of the wheel and the radius of its pivot. 

Maxwell’s pendulum consists of a wheel hanging by two wires which are wound in the same direction on an axis passing through its center of gravity. 

It slowly comes down (low kinetic translation energy).

If there were no friction, it would go up to the initial level of its fall. 

It rotates rapidly (high kinetic rotary energy).

After the wires have been unwound, the wheel goes on rotating rewinding the wires on its axis and coming back up. 

Once released, the wheel comes down under the action of its weight, but it is forced to rotate in order to unwind the two wires.

At the end of the fall the total kinetic energy, not considering the losses, has to be equal to the gravitational energy supplied at the beginning. 

Through the position sensor it possible to evaluate at which speed the wheel gets to at the end run the point and to perform accurate measurements.