  An experimental study is presented, about transitions between Non-Equilibrium
Steady States (NESS) in a dissipative medium. The core device is a small
rotating blade that imposes cycles of increasing and decreasing forcings to a
granular gas, shaken independently. The velocity of this blade is measured,
subject to the transitions imposed by the periodic torque variation. The
Hatano-Sasa equality, that generalises the second principle of thermodynamics
to NESS, is verified with a high accuracy (a few $10^{-3}$), at different
variation rates. Besides, it is observed that the fluctuating velocity at fixed
forcing follows a generalised Gumbel distribution. A rough evaluation of the
mean free path in the granular gas suggests that it might be a correlated
system, at least partially.
