I have a rotation sensor (TACH) that returns two pulses per revolution.

I can connect this to a GPIO pin… but I don't know how to read a pulse width in.
Can anyone shed some light on this? I want to periodically update my screen… so if I measured it like 20 times a second it would be more than enough.

I am using the piGPIO routines if that's helpful. pigpio library

But I'm open to other options as well. I'm building a wind tunnel and need to know the rotational speed of the turbine to calculate wind speed.

Thanks,
Jerry