Speed is the number of "Micro Cooling Fan" fan rotations per minute, the unit is rpm. Fan speed is determined by the motor inside the coil turns, voltage, number of fan blades, angle, height, diameter and bearing systems. Fan speed and quality are not necessarily linked. Fan speed can be measured by the rotational speed of the internal signal can be measured externally. With the "Micro Cooling Fan" application and ambient temperature changes, and sometimes require different speed fan to meet demand. Some manufacturers specially designed adjustable fan speed cooling fan, manual and automatic modes. Manual is designed to allow users to use a low speed in the winter low-noise, high speed access to good cooling effect in the summer. Automatic Class thermostat "Micro Cooling Fan" in general with a thermostat sensor, according to the current working temperature control fan speed, temperature is high then increase speed, low temperature, then reduce speed in order to achieve a dynamic equilibrium, thereby so that the cooling effect of wind noise and maintain an optimal combination of points.