Thank you so much cattledog. Your advice has been very helpfull!
DrDiettrich: My potentiometer is very simple. It detects the angular position in a range between 0 - 1023.
I tranform the value found in the corresponds value in voltage. My pot is linked to the ground and
to the 5 V pins on the board so that the value found between 0 and 1023 corresponds to a value
between 0 and 5V. The angular position is equal to: alpha = (360*voltage_value_founded)/5V.
This alpha must be converted in rad. Once done this the value must be divided by the time to
capture the angular speed.
GoForSmoke: I have thought to use an Hall sensor but my project works with very low speeds values but thank
for the advise!