Identify the heat dissipation dc cooling fan is good or bad

Vibration measurement -- -- -- -- -- - the same specifications and speed of the fan, small vibration of dc cooling fans better, dc cooling fan, is a high-speed operation of parts, it must have some vibration, no one can guarantee no vibration, if there is a manufacturer to tell you, their products have no vibration, that is used to cheat ghost, never believe, the smaller the vibration is, the better, the smaller the vibration, the fan operation is more stable, the bearing and the smaller the wastage of the shaft core, also can reduce the volatilization of oil or ball bearing wear, life will be longer, of course.