Hi all,
I've been playing with a 4 pin PWM controlled fan (Here's a
link to a specification for those interested).
The tachometer output signal is defined to output two pulses per revolution of the fan. I understand that there are small magnets attached to either side of the fan. A pulse is generated each time a small magnet passes a hall effect sensor.
Why are there two pulses per revolution and not just one?
TL;DRIn a 4 pin fan why does the tachometer output two pulses per revolution and not just one?