Distinction between "24V DC Cooling Fan" Powerful and silent type is not too strict, but the same size, the same voltage for computer fans, air pressure and noise will always be two irreconcilable contradictions. Fan speed is the number of revolutions per minute fan fan page, the unit is rpm. "24V DC Cooling Fan" motor speed is determined by the number of turns in the coil, voltage, number of fans fan page, inclination, height, diameter and fan bearing system. In the case of the fixed structure of the fan, DC fan (i.e., the use of a DC fan) with the speed of change of the operating voltage changes in synchronization. "24V DC Cooling Fan" can be performed by the rotational speed of the rotational speed of the internal signal measurement, can also be measured (external measurement is to measure the rotational speed of the fan with a special tachometer red line through the outside, the inside can be measured directly watching the BIOS, may also be look through the software. internal measurement error is relatively larger).