If this works will I need to incorporate pulse-width modulation to ensure more accuracy on reaching my setpoint (my pumps flow rate is 13L/Min but I have installed a manual valve to restrict the flow as necessary)? I have attached the vi below. I have read up a bit on manual tuning and the Ziegler-Nichols method, but I have been reluctant to try these without a bit of advise 1st. I havnt tried to use this program with my hardware yet due to my lack of understanding of PID and tuning the controller. I have two DAQ assistants in my program - one configured as an analog input (this input is from a cistern arm turning a pot which will determine the level of my test tank), and the other is configured as a digital output driving a pump. I am wondering does anyone know the best way to work out my P, I and D values for my level control project? Basically I am using a subvi called simplePID which I found on the NI website.