Resostor 10ohm is here. In reality we need to add ammeter on that place. With pot it needs to be calibrated. Max measuring current need to be 1mA. When is 1mA than is input siglal (from hall sensor) 10 000 rpm. When we have 3000 rpm on input,that is 20ms, current on 10ohm resistor will be 300uA,it is equal to 3000rpm. Write comment if you dont understand, I will try to help.
