220V AC Cooling Fan of the tachometer signal

"220V AC Cooling Fan" is generally the speed signal from the three-pin configuration the output three leads are yellow and black + 12V the power and grounding line of another color is the speed signal output line. It should be noted that certain three-lead "220V AC Cooling Fan" third lead wires are not speed signal output line, but the speed control signal line, through which the input speed control signal to the fan motor. At present, the fan itself alarm monitor mode and the speed sensor are two types, the use of alarm sensors can give an alarm in the "220V AC Cooling Fan" speed is below a certain threshold value, and the output speed signal can be realized Real-time monitoring of fan speed.