RPM from hall effect sensor, peak detection?

[Edh95]

Hello,

I have a hall effect sensor picking up from a small magnet attached to a small fan, the input into the DAQ is in the below Imgur link and attached.

www.imgur.com/a/8TOpjs1

I can tell that I am getting roughly two rotations every 0.1seconds, so 20/second, 1200/min, however how can I get labvLab to detect and calculate this automatically over a period of one minute. Ideally I'm after something that would count how many times 2.5V is exceeded, then resetting at 2.45 so it can increment again after 2.5V is exceeded again, so that ultimately if the count in a minute period is lower than a setpoint I can trigger an output when the rpm is less than a certain setpoint if the fan slows down. (I can do this but I think)

After looking at previous threads I've seen peak detection recommended, however it looks more complicated than I'd have guessed, is this the only way, or is there a simpler, cruder solution?

Regards

Ed

[aputman]

Wire your signal up to the "Extract Single Tone Information" VI to get a frequency value.  Since you only get one pulse per revolution, multiply frequency by 60 to get an RPM value. 

[Edh95]

Thanks pal, I'm going to have a look tomorrow, appreciate it