Micro Cooling Fan actual speed

"Micro Cooling Fan" tachometer signal is generally output from the three-wire plug, three leads, yellow and black, respectively + 12V power and ground, another color of the line is the line speed signal output. It should be noted that some three-lead Lead is not a fan of the third speed signal output line, but the speed control signal line, through which the "dota2雷竞技预测 " input speed control signal. Some fan speed signal is not output from the fan's speed, but the speed multiples, such as 2 per revolution, four or six pulses, must be treated in order to form a true reflection of the fan speed signal. To identify the "Micro Cooling Fan" Speed is real or a multiple speed, tachometer can be used to measure the actual speed, and data were then compared.