To summarize, a PID Loop controls a process based on three questions: LetвЂ™s make the analogy little more interesting and now you are driving with your mom who still thinks you are a child and every time you push on the gas pedal, she concludes that you are going to continue pushing harder and end up dying in a car crash!! What she is doing is looking at your current action, predicting the future and asking you to take corrective action before the future happens. This ensures that your car reaches the posted speed faster and stays there. And that forms the basis of the second part of the PID loop called the Integral Control. You would continue doing so as long as your friend remembers that you are below the speed limit. You succumb to the nagging and slowly increase the force on the gas pedal. Now imagine you are driving with a friend whose sole purpose in life is to keep reminding you that you are below the speed limit. Of course, you would make small adjustments with your foot as you get closer to the speed limit, and thatвЂ™s where the real magic of PID happens. This is the Proportional Control in a PID loop. If you leave your foot in exactly the same position, then you will end up either speeding (overshooting) or going under the limit (undershooting). As you start closing in on the speed limit, you are going to ease back on the pedal. Of course, you could choose to not push hard but then it will take longer to get to that higher speed. The higher the posted speed, the harder you will step on the pedal. Imagine you are driving down a street and see an increase in the posted speed. The CV has to be changed by a larger amount during peak load compared to off-peak periods in order to change the PV by the same amount. Ideally the PV should change in a predictable fashion with a change in CV but in a real-world situation the load or demand will not be constant thereby altering the relation between CV and PV.

The target value for PV is the Setpoint (SP).

The parameter that reacts to a Control Variable change is the Process Variable (PV).The parameter that is controlled is the Control Variable (CV).For example, pump speed is controlled to maintain pressure, valve position is controlled to maintain flow, and fuel feed rate is controlled to maintain temperature. One parameter is controlled (varied) to maintain another parameter at a desired value. PID controllers can be applied whether you are pumping water, processing chemicals in a plant, or controlling temperature in a furnace. PID stands for Proportional-Integral-Derivative (PID) and consists of three parameters P, I, and D which control your process. This post provides an intuitive look at how a PID works before getting into the math. To successfully apply and tune these controllers, it is important to understand how they work, the math behind them, and the nuances of the specific implementation by various manufacturers. PID controllers work great when applied and configured correctly, and they are often viewed as a sort of magic box that can solve any process control problem. PID control is one of the most commonly used closed-loop control mechanisms in industrial control systems.

Control variable