It’s generally accepted that tuning a PID controller requires some form of testing. Whether a step, bump, doublet, or pseudo random binary sequence, the test forces a change to the Controller Output (CO) which drives a response in the Process Variable (PV). The dynamic relationship between the CO and PV provides the basis for modeling a process’ behavior. In turn, the model is converted into tuning parameters corresponding with your controller. All of this is made possible by conducting a simple test. But what if it’s not that simple.